/* * The RSA public-key cryptosystem * * Copyright The Mbed TLS Contributors * SPDX-License-Identifier: Apache-2.0 * * Licensed under the Apache License, Version 2.0 (the "License"); you may * not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ /* * The following sources were referenced in the design of this implementation * of the RSA algorithm: * * [1] A method for obtaining digital signatures and public-key cryptosystems * R Rivest, A Shamir, and L Adleman * http://people.csail.mit.edu/rivest/pubs.html#RSA78 * * [2] Handbook of Applied Cryptography - 1997, Chapter 8 * Menezes, van Oorschot and Vanstone * * [3] Malware Guard Extension: Using SGX to Conceal Cache Attacks * Michael Schwarz, Samuel Weiser, Daniel Gruss, Clémentine Maurice and * Stefan Mangard * https://arxiv.org/abs/1702.08719v2 * */ #include "common.h" #if defined(MBEDTLS_RSA_C) #include "mbedtls/rsa.h" #include "rsa_alt_helpers.h" #include "mbedtls/oid.h" #include "mbedtls/platform_util.h" #include "mbedtls/error.h" #include #if defined(MBEDTLS_PKCS1_V21) #include "mbedtls/md.h" #endif #if defined(MBEDTLS_PKCS1_V15) && !defined(__OpenBSD__) && !defined(__NetBSD__) #include #endif #if defined(MBEDTLS_PLATFORM_C) #include "mbedtls/platform.h" #else #include #define mbedtls_printf printf #define mbedtls_calloc calloc #define mbedtls_free free #endif #if !defined(MBEDTLS_RSA_ALT) /* Parameter validation macros */ #define RSA_VALIDATE_RET( cond ) \ MBEDTLS_INTERNAL_VALIDATE_RET( cond, MBEDTLS_ERR_RSA_BAD_INPUT_DATA ) #define RSA_VALIDATE( cond ) \ MBEDTLS_INTERNAL_VALIDATE( cond ) #if defined(MBEDTLS_PKCS1_V15) /* constant-time buffer comparison */ static inline int mbedtls_safer_memcmp( const void *a, const void *b, size_t n ) { size_t i; const unsigned char *A = (const unsigned char *) a; const unsigned char *B = (const unsigned char *) b; unsigned char diff = 0; for( i = 0; i < n; i++ ) diff |= A[i] ^ B[i]; return( diff ); } #endif /* MBEDTLS_PKCS1_V15 */ int mbedtls_rsa_import( mbedtls_rsa_context *ctx, const mbedtls_mpi *N, const mbedtls_mpi *P, const mbedtls_mpi *Q, const mbedtls_mpi *D, const mbedtls_mpi *E ) { int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; RSA_VALIDATE_RET( ctx != NULL ); if( ( N != NULL && ( ret = mbedtls_mpi_copy( &ctx->N, N ) ) != 0 ) || ( P != NULL && ( ret = mbedtls_mpi_copy( &ctx->P, P ) ) != 0 ) || ( Q != NULL && ( ret = mbedtls_mpi_copy( &ctx->Q, Q ) ) != 0 ) || ( D != NULL && ( ret = mbedtls_mpi_copy( &ctx->D, D ) ) != 0 ) || ( E != NULL && ( ret = mbedtls_mpi_copy( &ctx->E, E ) ) != 0 ) ) { return( MBEDTLS_ERROR_ADD( MBEDTLS_ERR_RSA_BAD_INPUT_DATA, ret ) ); } if( N != NULL ) ctx->len = mbedtls_mpi_size( &ctx->N ); return( 0 ); } int mbedtls_rsa_import_raw( mbedtls_rsa_context *ctx, unsigned char const *N, size_t N_len, unsigned char const *P, size_t P_len, unsigned char const *Q, size_t Q_len, unsigned char const *D, size_t D_len, unsigned char const *E, size_t E_len ) { int ret = 0; RSA_VALIDATE_RET( ctx != NULL ); if( N != NULL ) { MBEDTLS_MPI_CHK( mbedtls_mpi_read_binary( &ctx->N, N, N_len ) ); ctx->len = mbedtls_mpi_size( &ctx->N ); } if( P != NULL ) MBEDTLS_MPI_CHK( mbedtls_mpi_read_binary( &ctx->P, P, P_len ) ); if( Q != NULL ) MBEDTLS_MPI_CHK( mbedtls_mpi_read_binary( &ctx->Q, Q, Q_len ) ); if( D != NULL ) MBEDTLS_MPI_CHK( mbedtls_mpi_read_binary( &ctx->D, D, D_len ) ); if( E != NULL ) MBEDTLS_MPI_CHK( mbedtls_mpi_read_binary( &ctx->E, E, E_len ) ); cleanup: if( ret != 0 ) return( MBEDTLS_ERROR_ADD( MBEDTLS_ERR_RSA_BAD_INPUT_DATA, ret ) ); return( 0 ); } /* * Checks whether the context fields are set in such a way * that the RSA primitives will be able to execute without error. * It does *not* make guarantees for consistency of the parameters. */ static int rsa_check_context( mbedtls_rsa_context const *ctx, int is_priv, int blinding_needed ) { #if !defined(MBEDTLS_RSA_NO_CRT) /* blinding_needed is only used for NO_CRT to decide whether * P,Q need to be present or not. */ ((void) blinding_needed); #endif if( ctx->len != mbedtls_mpi_size( &ctx->N ) || ctx->len > MBEDTLS_MPI_MAX_SIZE ) { return( MBEDTLS_ERR_RSA_BAD_INPUT_DATA ); } /* * 1. Modular exponentiation needs positive, odd moduli. */ /* Modular exponentiation wrt. N is always used for * RSA public key operations. */ if( mbedtls_mpi_cmp_int( &ctx->N, 0 ) <= 0 || mbedtls_mpi_get_bit( &ctx->N, 0 ) == 0 ) { return( MBEDTLS_ERR_RSA_BAD_INPUT_DATA ); } #if !defined(MBEDTLS_RSA_NO_CRT) /* Modular exponentiation for P and Q is only * used for private key operations and if CRT * is used. */ if( is_priv && ( mbedtls_mpi_cmp_int( &ctx->P, 0 ) <= 0 || mbedtls_mpi_get_bit( &ctx->P, 0 ) == 0 || mbedtls_mpi_cmp_int( &ctx->Q, 0 ) <= 0 || mbedtls_mpi_get_bit( &ctx->Q, 0 ) == 0 ) ) { return( MBEDTLS_ERR_RSA_BAD_INPUT_DATA ); } #endif /* !MBEDTLS_RSA_NO_CRT */ /* * 2. Exponents must be positive */ /* Always need E for public key operations */ if( mbedtls_mpi_cmp_int( &ctx->E, 0 ) <= 0 ) return( MBEDTLS_ERR_RSA_BAD_INPUT_DATA ); #if defined(MBEDTLS_RSA_NO_CRT) /* For private key operations, use D or DP & DQ * as (unblinded) exponents. */ if( is_priv && mbedtls_mpi_cmp_int( &ctx->D, 0 ) <= 0 ) return( MBEDTLS_ERR_RSA_BAD_INPUT_DATA ); #else if( is_priv && ( mbedtls_mpi_cmp_int( &ctx->DP, 0 ) <= 0 || mbedtls_mpi_cmp_int( &ctx->DQ, 0 ) <= 0 ) ) { return( MBEDTLS_ERR_RSA_BAD_INPUT_DATA ); } #endif /* MBEDTLS_RSA_NO_CRT */ /* Blinding shouldn't make exponents negative either, * so check that P, Q >= 1 if that hasn't yet been * done as part of 1. */ #if defined(MBEDTLS_RSA_NO_CRT) if( is_priv && blinding_needed && ( mbedtls_mpi_cmp_int( &ctx->P, 0 ) <= 0 || mbedtls_mpi_cmp_int( &ctx->Q, 0 ) <= 0 ) ) { return( MBEDTLS_ERR_RSA_BAD_INPUT_DATA ); } #endif /* It wouldn't lead to an error if it wasn't satisfied, * but check for QP >= 1 nonetheless. */ #if !defined(MBEDTLS_RSA_NO_CRT) if( is_priv && mbedtls_mpi_cmp_int( &ctx->QP, 0 ) <= 0 ) { return( MBEDTLS_ERR_RSA_BAD_INPUT_DATA ); } #endif return( 0 ); } int mbedtls_rsa_complete( mbedtls_rsa_context *ctx ) { int ret = 0; int have_N, have_P, have_Q, have_D, have_E; #if !defined(MBEDTLS_RSA_NO_CRT) int have_DP, have_DQ, have_QP; #endif int n_missing, pq_missing, d_missing, is_pub, is_priv; RSA_VALIDATE_RET( ctx != NULL ); have_N = ( mbedtls_mpi_cmp_int( &ctx->N, 0 ) != 0 ); have_P = ( mbedtls_mpi_cmp_int( &ctx->P, 0 ) != 0 ); have_Q = ( mbedtls_mpi_cmp_int( &ctx->Q, 0 ) != 0 ); have_D = ( mbedtls_mpi_cmp_int( &ctx->D, 0 ) != 0 ); have_E = ( mbedtls_mpi_cmp_int( &ctx->E, 0 ) != 0 ); #if !defined(MBEDTLS_RSA_NO_CRT) have_DP = ( mbedtls_mpi_cmp_int( &ctx->DP, 0 ) != 0 ); have_DQ = ( mbedtls_mpi_cmp_int( &ctx->DQ, 0 ) != 0 ); have_QP = ( mbedtls_mpi_cmp_int( &ctx->QP, 0 ) != 0 ); #endif /* * Check whether provided parameters are enough * to deduce all others. The following incomplete * parameter sets for private keys are supported: * * (1) P, Q missing. * (2) D and potentially N missing. * */ n_missing = have_P && have_Q && have_D && have_E; pq_missing = have_N && !have_P && !have_Q && have_D && have_E; d_missing = have_P && have_Q && !have_D && have_E; is_pub = have_N && !have_P && !have_Q && !have_D && have_E; /* These three alternatives are mutually exclusive */ is_priv = n_missing || pq_missing || d_missing; if( !is_priv && !is_pub ) return( MBEDTLS_ERR_RSA_BAD_INPUT_DATA ); /* * Step 1: Deduce N if P, Q are provided. */ if( !have_N && have_P && have_Q ) { if( ( ret = mbedtls_mpi_mul_mpi( &ctx->N, &ctx->P, &ctx->Q ) ) != 0 ) { return( MBEDTLS_ERROR_ADD( MBEDTLS_ERR_RSA_BAD_INPUT_DATA, ret ) ); } ctx->len = mbedtls_mpi_size( &ctx->N ); } /* * Step 2: Deduce and verify all remaining core parameters. */ if( pq_missing ) { ret = mbedtls_rsa_deduce_primes( &ctx->N, &ctx->E, &ctx->D, &ctx->P, &ctx->Q ); if( ret != 0 ) return( MBEDTLS_ERROR_ADD( MBEDTLS_ERR_RSA_BAD_INPUT_DATA, ret ) ); } else if( d_missing ) { if( ( ret = mbedtls_rsa_deduce_private_exponent( &ctx->P, &ctx->Q, &ctx->E, &ctx->D ) ) != 0 ) { return( MBEDTLS_ERROR_ADD( MBEDTLS_ERR_RSA_BAD_INPUT_DATA, ret ) ); } } /* * Step 3: Deduce all additional parameters specific * to our current RSA implementation. */ #if !defined(MBEDTLS_RSA_NO_CRT) if( is_priv && ! ( have_DP && have_DQ && have_QP ) ) { ret = mbedtls_rsa_deduce_crt( &ctx->P, &ctx->Q, &ctx->D, &ctx->DP, &ctx->DQ, &ctx->QP ); if( ret != 0 ) return( MBEDTLS_ERROR_ADD( MBEDTLS_ERR_RSA_BAD_INPUT_DATA, ret ) ); } #endif /* MBEDTLS_RSA_NO_CRT */ /* * Step 3: Basic sanity checks */ return( rsa_check_context( ctx, is_priv, 1 ) ); } int mbedtls_rsa_export_raw( const mbedtls_rsa_context *ctx, unsigned char *N, size_t N_len, unsigned char *P, size_t P_len, unsigned char *Q, size_t Q_len, unsigned char *D, size_t D_len, unsigned char *E, size_t E_len ) { int ret = 0; int is_priv; RSA_VALIDATE_RET( ctx != NULL ); /* Check if key is private or public */ is_priv = mbedtls_mpi_cmp_int( &ctx->N, 0 ) != 0 && mbedtls_mpi_cmp_int( &ctx->P, 0 ) != 0 && mbedtls_mpi_cmp_int( &ctx->Q, 0 ) != 0 && mbedtls_mpi_cmp_int( &ctx->D, 0 ) != 0 && mbedtls_mpi_cmp_int( &ctx->E, 0 ) != 0; if( !is_priv ) { /* If we're trying to export private parameters for a public key, * something must be wrong. */ if( P != NULL || Q != NULL || D != NULL ) return( MBEDTLS_ERR_RSA_BAD_INPUT_DATA ); } if( N != NULL ) MBEDTLS_MPI_CHK( mbedtls_mpi_write_binary( &ctx->N, N, N_len ) ); if( P != NULL ) MBEDTLS_MPI_CHK( mbedtls_mpi_write_binary( &ctx->P, P, P_len ) ); if( Q != NULL ) MBEDTLS_MPI_CHK( mbedtls_mpi_write_binary( &ctx->Q, Q, Q_len ) ); if( D != NULL ) MBEDTLS_MPI_CHK( mbedtls_mpi_write_binary( &ctx->D, D, D_len ) ); if( E != NULL ) MBEDTLS_MPI_CHK( mbedtls_mpi_write_binary( &ctx->E, E, E_len ) ); cleanup: return( ret ); } int mbedtls_rsa_export( const mbedtls_rsa_context *ctx, mbedtls_mpi *N, mbedtls_mpi *P, mbedtls_mpi *Q, mbedtls_mpi *D, mbedtls_mpi *E ) { int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; int is_priv; RSA_VALIDATE_RET( ctx != NULL ); /* Check if key is private or public */ is_priv = mbedtls_mpi_cmp_int( &ctx->N, 0 ) != 0 && mbedtls_mpi_cmp_int( &ctx->P, 0 ) != 0 && mbedtls_mpi_cmp_int( &ctx->Q, 0 ) != 0 && mbedtls_mpi_cmp_int( &ctx->D, 0 ) != 0 && mbedtls_mpi_cmp_int( &ctx->E, 0 ) != 0; if( !is_priv ) { /* If we're trying to export private parameters for a public key, * something must be wrong. */ if( P != NULL || Q != NULL || D != NULL ) return( MBEDTLS_ERR_RSA_BAD_INPUT_DATA ); } /* Export all requested core parameters. */ if( ( N != NULL && ( ret = mbedtls_mpi_copy( N, &ctx->N ) ) != 0 ) || ( P != NULL && ( ret = mbedtls_mpi_copy( P, &ctx->P ) ) != 0 ) || ( Q != NULL && ( ret = mbedtls_mpi_copy( Q, &ctx->Q ) ) != 0 ) || ( D != NULL && ( ret = mbedtls_mpi_copy( D, &ctx->D ) ) != 0 ) || ( E != NULL && ( ret = mbedtls_mpi_copy( E, &ctx->E ) ) != 0 ) ) { return( ret ); } return( 0 ); } /* * Export CRT parameters * This must also be implemented if CRT is not used, for being able to * write DER encoded RSA keys. The helper function mbedtls_rsa_deduce_crt * can be used in this case. */ int mbedtls_rsa_export_crt( const mbedtls_rsa_context *ctx, mbedtls_mpi *DP, mbedtls_mpi *DQ, mbedtls_mpi *QP ) { int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; int is_priv; RSA_VALIDATE_RET( ctx != NULL ); /* Check if key is private or public */ is_priv = mbedtls_mpi_cmp_int( &ctx->N, 0 ) != 0 && mbedtls_mpi_cmp_int( &ctx->P, 0 ) != 0 && mbedtls_mpi_cmp_int( &ctx->Q, 0 ) != 0 && mbedtls_mpi_cmp_int( &ctx->D, 0 ) != 0 && mbedtls_mpi_cmp_int( &ctx->E, 0 ) != 0; if( !is_priv ) return( MBEDTLS_ERR_RSA_BAD_INPUT_DATA ); #if !defined(MBEDTLS_RSA_NO_CRT) /* Export all requested blinding parameters. */ if( ( DP != NULL && ( ret = mbedtls_mpi_copy( DP, &ctx->DP ) ) != 0 ) || ( DQ != NULL && ( ret = mbedtls_mpi_copy( DQ, &ctx->DQ ) ) != 0 ) || ( QP != NULL && ( ret = mbedtls_mpi_copy( QP, &ctx->QP ) ) != 0 ) ) { return( MBEDTLS_ERROR_ADD( MBEDTLS_ERR_RSA_BAD_INPUT_DATA, ret ) ); } #else if( ( ret = mbedtls_rsa_deduce_crt( &ctx->P, &ctx->Q, &ctx->D, DP, DQ, QP ) ) != 0 ) { return( MBEDTLS_ERROR_ADD( MBEDTLS_ERR_RSA_BAD_INPUT_DATA, ret ) ); } #endif return( 0 ); } /* * Initialize an RSA context */ void mbedtls_rsa_init( mbedtls_rsa_context *ctx ) { RSA_VALIDATE( ctx != NULL ); memset( ctx, 0, sizeof( mbedtls_rsa_context ) ); ctx->padding = MBEDTLS_RSA_PKCS_V15; ctx->hash_id = MBEDTLS_MD_NONE; #if defined(MBEDTLS_THREADING_C) /* Set ctx->ver to nonzero to indicate that the mutex has been * initialized and will need to be freed. */ ctx->ver = 1; mbedtls_mutex_init( &ctx->mutex ); #endif } /* * Set padding for an existing RSA context */ int mbedtls_rsa_set_padding( mbedtls_rsa_context *ctx, int padding, mbedtls_md_type_t hash_id ) { switch( padding ) { #if defined(MBEDTLS_PKCS1_V15) case MBEDTLS_RSA_PKCS_V15: break; #endif #if defined(MBEDTLS_PKCS1_V21) case MBEDTLS_RSA_PKCS_V21: break; #endif default: return( MBEDTLS_ERR_RSA_INVALID_PADDING ); } if( ( padding == MBEDTLS_RSA_PKCS_V21 ) && ( hash_id != MBEDTLS_MD_NONE ) ) { const mbedtls_md_info_t *md_info; md_info = mbedtls_md_info_from_type( hash_id ); if( md_info == NULL ) return( MBEDTLS_ERR_RSA_INVALID_PADDING ); } ctx->padding = padding; ctx->hash_id = hash_id; return( 0 ); } /* * Get length in bytes of RSA modulus */ size_t mbedtls_rsa_get_len( const mbedtls_rsa_context *ctx ) { return( ctx->len ); } #if defined(MBEDTLS_GENPRIME) /* * Generate an RSA keypair * * This generation method follows the RSA key pair generation procedure of * FIPS 186-4 if 2^16 < exponent < 2^256 and nbits = 2048 or nbits = 3072. */ int mbedtls_rsa_gen_key( mbedtls_rsa_context *ctx, int (*f_rng)(void *, unsigned char *, size_t), void *p_rng, unsigned int nbits, int exponent ) { int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; mbedtls_mpi H, G, L; int prime_quality = 0; RSA_VALIDATE_RET( ctx != NULL ); RSA_VALIDATE_RET( f_rng != NULL ); /* * If the modulus is 1024 bit long or shorter, then the security strength of * the RSA algorithm is less than or equal to 80 bits and therefore an error * rate of 2^-80 is sufficient. */ if( nbits > 1024 ) prime_quality = MBEDTLS_MPI_GEN_PRIME_FLAG_LOW_ERR; mbedtls_mpi_init( &H ); mbedtls_mpi_init( &G ); mbedtls_mpi_init( &L ); if( nbits < 128 || exponent < 3 || nbits % 2 != 0 ) { ret = MBEDTLS_ERR_RSA_BAD_INPUT_DATA; goto cleanup; } /* * find primes P and Q with Q < P so that: * 1. |P-Q| > 2^( nbits / 2 - 100 ) * 2. GCD( E, (P-1)*(Q-1) ) == 1 * 3. E^-1 mod LCM(P-1, Q-1) > 2^( nbits / 2 ) */ MBEDTLS_MPI_CHK( mbedtls_mpi_lset( &ctx->E, exponent ) ); do { MBEDTLS_MPI_CHK( mbedtls_mpi_gen_prime( &ctx->P, nbits >> 1, prime_quality, f_rng, p_rng ) ); MBEDTLS_MPI_CHK( mbedtls_mpi_gen_prime( &ctx->Q, nbits >> 1, prime_quality, f_rng, p_rng ) ); /* make sure the difference between p and q is not too small (FIPS 186-4 §B.3.3 step 5.4) */ MBEDTLS_MPI_CHK( mbedtls_mpi_sub_mpi( &H, &ctx->P, &ctx->Q ) ); if( mbedtls_mpi_bitlen( &H ) <= ( ( nbits >= 200 ) ? ( ( nbits >> 1 ) - 99 ) : 0 ) ) continue; /* not required by any standards, but some users rely on the fact that P > Q */ if( H.s < 0 ) mbedtls_mpi_swap( &ctx->P, &ctx->Q ); /* Temporarily replace P,Q by P-1, Q-1 */ MBEDTLS_MPI_CHK( mbedtls_mpi_sub_int( &ctx->P, &ctx->P, 1 ) ); MBEDTLS_MPI_CHK( mbedtls_mpi_sub_int( &ctx->Q, &ctx->Q, 1 ) ); MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( &H, &ctx->P, &ctx->Q ) ); /* check GCD( E, (P-1)*(Q-1) ) == 1 (FIPS 186-4 §B.3.1 criterion 2(a)) */ MBEDTLS_MPI_CHK( mbedtls_mpi_gcd( &G, &ctx->E, &H ) ); if( mbedtls_mpi_cmp_int( &G, 1 ) != 0 ) continue; /* compute smallest possible D = E^-1 mod LCM(P-1, Q-1) (FIPS 186-4 §B.3.1 criterion 3(b)) */ MBEDTLS_MPI_CHK( mbedtls_mpi_gcd( &G, &ctx->P, &ctx->Q ) ); MBEDTLS_MPI_CHK( mbedtls_mpi_div_mpi( &L, NULL, &H, &G ) ); MBEDTLS_MPI_CHK( mbedtls_mpi_inv_mod( &ctx->D, &ctx->E, &L ) ); if( mbedtls_mpi_bitlen( &ctx->D ) <= ( ( nbits + 1 ) / 2 ) ) // (FIPS 186-4 §B.3.1 criterion 3(a)) continue; break; } while( 1 ); /* Restore P,Q */ MBEDTLS_MPI_CHK( mbedtls_mpi_add_int( &ctx->P, &ctx->P, 1 ) ); MBEDTLS_MPI_CHK( mbedtls_mpi_add_int( &ctx->Q, &ctx->Q, 1 ) ); MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( &ctx->N, &ctx->P, &ctx->Q ) ); ctx->len = mbedtls_mpi_size( &ctx->N ); #if !defined(MBEDTLS_RSA_NO_CRT) /* * DP = D mod (P - 1) * DQ = D mod (Q - 1) * QP = Q^-1 mod P */ MBEDTLS_MPI_CHK( mbedtls_rsa_deduce_crt( &ctx->P, &ctx->Q, &ctx->D, &ctx->DP, &ctx->DQ, &ctx->QP ) ); #endif /* MBEDTLS_RSA_NO_CRT */ /* Double-check */ MBEDTLS_MPI_CHK( mbedtls_rsa_check_privkey( ctx ) ); cleanup: mbedtls_mpi_free( &H ); mbedtls_mpi_free( &G ); mbedtls_mpi_free( &L ); if( ret != 0 ) { mbedtls_rsa_free( ctx ); if( ( -ret & ~0x7f ) == 0 ) ret = MBEDTLS_ERROR_ADD( MBEDTLS_ERR_RSA_KEY_GEN_FAILED, ret ); return( ret ); } return( 0 ); } #endif /* MBEDTLS_GENPRIME */ /* * Check a public RSA key */ int mbedtls_rsa_check_pubkey( const mbedtls_rsa_context *ctx ) { RSA_VALIDATE_RET( ctx != NULL ); if( rsa_check_context( ctx, 0 /* public */, 0 /* no blinding */ ) != 0 ) return( MBEDTLS_ERR_RSA_KEY_CHECK_FAILED ); if( mbedtls_mpi_bitlen( &ctx->N ) < 128 ) { return( MBEDTLS_ERR_RSA_KEY_CHECK_FAILED ); } if( mbedtls_mpi_get_bit( &ctx->E, 0 ) == 0 || mbedtls_mpi_bitlen( &ctx->E ) < 2 || mbedtls_mpi_cmp_mpi( &ctx->E, &ctx->N ) >= 0 ) { return( MBEDTLS_ERR_RSA_KEY_CHECK_FAILED ); } return( 0 ); } /* * Check for the consistency of all fields in an RSA private key context */ int mbedtls_rsa_check_privkey( const mbedtls_rsa_context *ctx ) { RSA_VALIDATE_RET( ctx != NULL ); if( mbedtls_rsa_check_pubkey( ctx ) != 0 || rsa_check_context( ctx, 1 /* private */, 1 /* blinding */ ) != 0 ) { return( MBEDTLS_ERR_RSA_KEY_CHECK_FAILED ); } if( mbedtls_rsa_validate_params( &ctx->N, &ctx->P, &ctx->Q, &ctx->D, &ctx->E, NULL, NULL ) != 0 ) { return( MBEDTLS_ERR_RSA_KEY_CHECK_FAILED ); } #if !defined(MBEDTLS_RSA_NO_CRT) else if( mbedtls_rsa_validate_crt( &ctx->P, &ctx->Q, &ctx->D, &ctx->DP, &ctx->DQ, &ctx->QP ) != 0 ) { return( MBEDTLS_ERR_RSA_KEY_CHECK_FAILED ); } #endif return( 0 ); } /* * Check if contexts holding a public and private key match */ int mbedtls_rsa_check_pub_priv( const mbedtls_rsa_context *pub, const mbedtls_rsa_context *prv ) { RSA_VALIDATE_RET( pub != NULL ); RSA_VALIDATE_RET( prv != NULL ); if( mbedtls_rsa_check_pubkey( pub ) != 0 || mbedtls_rsa_check_privkey( prv ) != 0 ) { return( MBEDTLS_ERR_RSA_KEY_CHECK_FAILED ); } if( mbedtls_mpi_cmp_mpi( &pub->N, &prv->N ) != 0 || mbedtls_mpi_cmp_mpi( &pub->E, &prv->E ) != 0 ) { return( MBEDTLS_ERR_RSA_KEY_CHECK_FAILED ); } return( 0 ); } /* * Do an RSA public key operation */ int mbedtls_rsa_public( mbedtls_rsa_context *ctx, const unsigned char *input, unsigned char *output ) { int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; size_t olen; mbedtls_mpi T; RSA_VALIDATE_RET( ctx != NULL ); RSA_VALIDATE_RET( input != NULL ); RSA_VALIDATE_RET( output != NULL ); if( rsa_check_context( ctx, 0 /* public */, 0 /* no blinding */ ) ) return( MBEDTLS_ERR_RSA_BAD_INPUT_DATA ); mbedtls_mpi_init( &T ); #if defined(MBEDTLS_THREADING_C) if( ( ret = mbedtls_mutex_lock( &ctx->mutex ) ) != 0 ) return( ret ); #endif MBEDTLS_MPI_CHK( mbedtls_mpi_read_binary( &T, input, ctx->len ) ); if( mbedtls_mpi_cmp_mpi( &T, &ctx->N ) >= 0 ) { ret = MBEDTLS_ERR_MPI_BAD_INPUT_DATA; goto cleanup; } olen = ctx->len; MBEDTLS_MPI_CHK( mbedtls_mpi_exp_mod( &T, &T, &ctx->E, &ctx->N, &ctx->RN ) ); MBEDTLS_MPI_CHK( mbedtls_mpi_write_binary( &T, output, olen ) ); cleanup: #if defined(MBEDTLS_THREADING_C) if( mbedtls_mutex_unlock( &ctx->mutex ) != 0 ) return( MBEDTLS_ERR_THREADING_MUTEX_ERROR ); #endif mbedtls_mpi_free( &T ); if( ret != 0 ) return( MBEDTLS_ERROR_ADD( MBEDTLS_ERR_RSA_PUBLIC_FAILED, ret ) ); return( 0 ); } /* * Generate or update blinding values, see section 10 of: * KOCHER, Paul C. Timing attacks on implementations of Diffie-Hellman, RSA, * DSS, and other systems. In : Advances in Cryptology-CRYPTO'96. Springer * Berlin Heidelberg, 1996. p. 104-113. */ static int rsa_prepare_blinding( mbedtls_rsa_context *ctx, int (*f_rng)(void *, unsigned char *, size_t), void *p_rng ) { int ret, count = 0; mbedtls_mpi R; mbedtls_mpi_init( &R ); if( ctx->Vf.p != NULL ) { /* We already have blinding values, just update them by squaring */ MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( &ctx->Vi, &ctx->Vi, &ctx->Vi ) ); MBEDTLS_MPI_CHK( mbedtls_mpi_mod_mpi( &ctx->Vi, &ctx->Vi, &ctx->N ) ); MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( &ctx->Vf, &ctx->Vf, &ctx->Vf ) ); MBEDTLS_MPI_CHK( mbedtls_mpi_mod_mpi( &ctx->Vf, &ctx->Vf, &ctx->N ) ); goto cleanup; } /* Unblinding value: Vf = random number, invertible mod N */ do { if( count++ > 10 ) { ret = MBEDTLS_ERR_RSA_RNG_FAILED; goto cleanup; } MBEDTLS_MPI_CHK( mbedtls_mpi_fill_random( &ctx->Vf, ctx->len - 1, f_rng, p_rng ) ); /* Compute Vf^-1 as R * (R Vf)^-1 to avoid leaks from inv_mod. */ MBEDTLS_MPI_CHK( mbedtls_mpi_fill_random( &R, ctx->len - 1, f_rng, p_rng ) ); MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( &ctx->Vi, &ctx->Vf, &R ) ); MBEDTLS_MPI_CHK( mbedtls_mpi_mod_mpi( &ctx->Vi, &ctx->Vi, &ctx->N ) ); /* At this point, Vi is invertible mod N if and only if both Vf and R * are invertible mod N. If one of them isn't, we don't need to know * which one, we just loop and choose new values for both of them. * (Each iteration succeeds with overwhelming probability.) */ ret = mbedtls_mpi_inv_mod( &ctx->Vi, &ctx->Vi, &ctx->N ); if( ret != 0 && ret != MBEDTLS_ERR_MPI_NOT_ACCEPTABLE ) goto cleanup; } while( ret == MBEDTLS_ERR_MPI_NOT_ACCEPTABLE ); /* Finish the computation of Vf^-1 = R * (R Vf)^-1 */ MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( &ctx->Vi, &ctx->Vi, &R ) ); MBEDTLS_MPI_CHK( mbedtls_mpi_mod_mpi( &ctx->Vi, &ctx->Vi, &ctx->N ) ); /* Blinding value: Vi = Vf^(-e) mod N * (Vi already contains Vf^-1 at this point) */ MBEDTLS_MPI_CHK( mbedtls_mpi_exp_mod( &ctx->Vi, &ctx->Vi, &ctx->E, &ctx->N, &ctx->RN ) ); cleanup: mbedtls_mpi_free( &R ); return( ret ); } /* * Exponent blinding supposed to prevent side-channel attacks using multiple * traces of measurements to recover the RSA key. The more collisions are there, * the more bits of the key can be recovered. See [3]. * * Collecting n collisions with m bit long blinding value requires 2^(m-m/n) * observations on avarage. * * For example with 28 byte blinding to achieve 2 collisions the adversary has * to make 2^112 observations on avarage. * * (With the currently (as of 2017 April) known best algorithms breaking 2048 * bit RSA requires approximately as much time as trying out 2^112 random keys. * Thus in this sense with 28 byte blinding the security is not reduced by * side-channel attacks like the one in [3]) * * This countermeasure does not help if the key recovery is possible with a * single trace. */ #define RSA_EXPONENT_BLINDING 28 /* * Do an RSA private key operation */ int mbedtls_rsa_private( mbedtls_rsa_context *ctx, int (*f_rng)(void *, unsigned char *, size_t), void *p_rng, const unsigned char *input, unsigned char *output ) { int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; size_t olen; /* Temporary holding the result */ mbedtls_mpi T; /* Temporaries holding P-1, Q-1 and the * exponent blinding factor, respectively. */ mbedtls_mpi P1, Q1, R; #if !defined(MBEDTLS_RSA_NO_CRT) /* Temporaries holding the results mod p resp. mod q. */ mbedtls_mpi TP, TQ; /* Temporaries holding the blinded exponents for * the mod p resp. mod q computation (if used). */ mbedtls_mpi DP_blind, DQ_blind; /* Pointers to actual exponents to be used - either the unblinded * or the blinded ones, depending on the presence of a PRNG. */ mbedtls_mpi *DP = &ctx->DP; mbedtls_mpi *DQ = &ctx->DQ; #else /* Temporary holding the blinded exponent (if used). */ mbedtls_mpi D_blind; /* Pointer to actual exponent to be used - either the unblinded * or the blinded one, depending on the presence of a PRNG. */ mbedtls_mpi *D = &ctx->D; #endif /* MBEDTLS_RSA_NO_CRT */ /* Temporaries holding the initial input and the double * checked result; should be the same in the end. */ mbedtls_mpi I, C; RSA_VALIDATE_RET( ctx != NULL ); RSA_VALIDATE_RET( input != NULL ); RSA_VALIDATE_RET( output != NULL ); if( f_rng == NULL ) return( MBEDTLS_ERR_RSA_BAD_INPUT_DATA ); if( rsa_check_context( ctx, 1 /* private key checks */, 1 /* blinding on */ ) != 0 ) { return( MBEDTLS_ERR_RSA_BAD_INPUT_DATA ); } #if defined(MBEDTLS_THREADING_C) if( ( ret = mbedtls_mutex_lock( &ctx->mutex ) ) != 0 ) return( ret ); #endif /* MPI Initialization */ mbedtls_mpi_init( &T ); mbedtls_mpi_init( &P1 ); mbedtls_mpi_init( &Q1 ); mbedtls_mpi_init( &R ); #if defined(MBEDTLS_RSA_NO_CRT) mbedtls_mpi_init( &D_blind ); #else mbedtls_mpi_init( &DP_blind ); mbedtls_mpi_init( &DQ_blind ); #endif #if !defined(MBEDTLS_RSA_NO_CRT) mbedtls_mpi_init( &TP ); mbedtls_mpi_init( &TQ ); #endif mbedtls_mpi_init( &I ); mbedtls_mpi_init( &C ); /* End of MPI initialization */ MBEDTLS_MPI_CHK( mbedtls_mpi_read_binary( &T, input, ctx->len ) ); if( mbedtls_mpi_cmp_mpi( &T, &ctx->N ) >= 0 ) { ret = MBEDTLS_ERR_MPI_BAD_INPUT_DATA; goto cleanup; } MBEDTLS_MPI_CHK( mbedtls_mpi_copy( &I, &T ) ); /* * Blinding * T = T * Vi mod N */ MBEDTLS_MPI_CHK( rsa_prepare_blinding( ctx, f_rng, p_rng ) ); MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( &T, &T, &ctx->Vi ) ); MBEDTLS_MPI_CHK( mbedtls_mpi_mod_mpi( &T, &T, &ctx->N ) ); /* * Exponent blinding */ MBEDTLS_MPI_CHK( mbedtls_mpi_sub_int( &P1, &ctx->P, 1 ) ); MBEDTLS_MPI_CHK( mbedtls_mpi_sub_int( &Q1, &ctx->Q, 1 ) ); #if defined(MBEDTLS_RSA_NO_CRT) /* * D_blind = ( P - 1 ) * ( Q - 1 ) * R + D */ MBEDTLS_MPI_CHK( mbedtls_mpi_fill_random( &R, RSA_EXPONENT_BLINDING, f_rng, p_rng ) ); MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( &D_blind, &P1, &Q1 ) ); MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( &D_blind, &D_blind, &R ) ); MBEDTLS_MPI_CHK( mbedtls_mpi_add_mpi( &D_blind, &D_blind, &ctx->D ) ); D = &D_blind; #else /* * DP_blind = ( P - 1 ) * R + DP */ MBEDTLS_MPI_CHK( mbedtls_mpi_fill_random( &R, RSA_EXPONENT_BLINDING, f_rng, p_rng ) ); MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( &DP_blind, &P1, &R ) ); MBEDTLS_MPI_CHK( mbedtls_mpi_add_mpi( &DP_blind, &DP_blind, &ctx->DP ) ); DP = &DP_blind; /* * DQ_blind = ( Q - 1 ) * R + DQ */ MBEDTLS_MPI_CHK( mbedtls_mpi_fill_random( &R, RSA_EXPONENT_BLINDING, f_rng, p_rng ) ); MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( &DQ_blind, &Q1, &R ) ); MBEDTLS_MPI_CHK( mbedtls_mpi_add_mpi( &DQ_blind, &DQ_blind, &ctx->DQ ) ); DQ = &DQ_blind; #endif /* MBEDTLS_RSA_NO_CRT */ #if defined(MBEDTLS_RSA_NO_CRT) MBEDTLS_MPI_CHK( mbedtls_mpi_exp_mod( &T, &T, D, &ctx->N, &ctx->RN ) ); #else /* * Faster decryption using the CRT * * TP = input ^ dP mod P * TQ = input ^ dQ mod Q */ MBEDTLS_MPI_CHK( mbedtls_mpi_exp_mod( &TP, &T, DP, &ctx->P, &ctx->RP ) ); MBEDTLS_MPI_CHK( mbedtls_mpi_exp_mod( &TQ, &T, DQ, &ctx->Q, &ctx->RQ ) ); /* * T = (TP - TQ) * (Q^-1 mod P) mod P */ MBEDTLS_MPI_CHK( mbedtls_mpi_sub_mpi( &T, &TP, &TQ ) ); MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( &TP, &T, &ctx->QP ) ); MBEDTLS_MPI_CHK( mbedtls_mpi_mod_mpi( &T, &TP, &ctx->P ) ); /* * T = TQ + T * Q */ MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( &TP, &T, &ctx->Q ) ); MBEDTLS_MPI_CHK( mbedtls_mpi_add_mpi( &T, &TQ, &TP ) ); #endif /* MBEDTLS_RSA_NO_CRT */ /* * Unblind * T = T * Vf mod N */ MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( &T, &T, &ctx->Vf ) ); MBEDTLS_MPI_CHK( mbedtls_mpi_mod_mpi( &T, &T, &ctx->N ) ); /* Verify the result to prevent glitching attacks. */ MBEDTLS_MPI_CHK( mbedtls_mpi_exp_mod( &C, &T, &ctx->E, &ctx->N, &ctx->RN ) ); if( mbedtls_mpi_cmp_mpi( &C, &I ) != 0 ) { ret = MBEDTLS_ERR_RSA_VERIFY_FAILED; goto cleanup; } olen = ctx->len; MBEDTLS_MPI_CHK( mbedtls_mpi_write_binary( &T, output, olen ) ); cleanup: #if defined(MBEDTLS_THREADING_C) if( mbedtls_mutex_unlock( &ctx->mutex ) != 0 ) return( MBEDTLS_ERR_THREADING_MUTEX_ERROR ); #endif mbedtls_mpi_free( &P1 ); mbedtls_mpi_free( &Q1 ); mbedtls_mpi_free( &R ); #if defined(MBEDTLS_RSA_NO_CRT) mbedtls_mpi_free( &D_blind ); #else mbedtls_mpi_free( &DP_blind ); mbedtls_mpi_free( &DQ_blind ); #endif mbedtls_mpi_free( &T ); #if !defined(MBEDTLS_RSA_NO_CRT) mbedtls_mpi_free( &TP ); mbedtls_mpi_free( &TQ ); #endif mbedtls_mpi_free( &C ); mbedtls_mpi_free( &I ); if( ret != 0 && ret >= -0x007f ) return( MBEDTLS_ERROR_ADD( MBEDTLS_ERR_RSA_PRIVATE_FAILED, ret ) ); return( ret ); } #if defined(MBEDTLS_PKCS1_V21) /** * Generate and apply the MGF1 operation (from PKCS#1 v2.1) to a buffer. * * \param dst buffer to mask * \param dlen length of destination buffer * \param src source of the mask generation * \param slen length of the source buffer * \param md_ctx message digest context to use */ static int mgf_mask( unsigned char *dst, size_t dlen, unsigned char *src, size_t slen, mbedtls_md_context_t *md_ctx ) { unsigned char mask[MBEDTLS_MD_MAX_SIZE]; unsigned char counter[4]; unsigned char *p; unsigned int hlen; size_t i, use_len; int ret = 0; memset( mask, 0, MBEDTLS_MD_MAX_SIZE ); memset( counter, 0, 4 ); hlen = mbedtls_md_get_size( md_ctx->md_info ); /* Generate and apply dbMask */ p = dst; while( dlen > 0 ) { use_len = hlen; if( dlen < hlen ) use_len = dlen; if( ( ret = mbedtls_md_starts( md_ctx ) ) != 0 ) goto exit; if( ( ret = mbedtls_md_update( md_ctx, src, slen ) ) != 0 ) goto exit; if( ( ret = mbedtls_md_update( md_ctx, counter, 4 ) ) != 0 ) goto exit; if( ( ret = mbedtls_md_finish( md_ctx, mask ) ) != 0 ) goto exit; for( i = 0; i < use_len; ++i ) *p++ ^= mask[i]; counter[3]++; dlen -= use_len; } exit: mbedtls_platform_zeroize( mask, sizeof( mask ) ); return( ret ); } #endif /* MBEDTLS_PKCS1_V21 */ #if defined(MBEDTLS_PKCS1_V21) /* * Implementation of the PKCS#1 v2.1 RSAES-OAEP-ENCRYPT function */ int mbedtls_rsa_rsaes_oaep_encrypt( mbedtls_rsa_context *ctx, int (*f_rng)(void *, unsigned char *, size_t), void *p_rng, const unsigned char *label, size_t label_len, size_t ilen, const unsigned char *input, unsigned char *output ) { size_t olen; int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; unsigned char *p = output; unsigned int hlen; const mbedtls_md_info_t *md_info; mbedtls_md_context_t md_ctx; RSA_VALIDATE_RET( ctx != NULL ); RSA_VALIDATE_RET( output != NULL ); RSA_VALIDATE_RET( ilen == 0 || input != NULL ); RSA_VALIDATE_RET( label_len == 0 || label != NULL ); if( f_rng == NULL ) return( MBEDTLS_ERR_RSA_BAD_INPUT_DATA ); md_info = mbedtls_md_info_from_type( (mbedtls_md_type_t) ctx->hash_id ); if( md_info == NULL ) return( MBEDTLS_ERR_RSA_BAD_INPUT_DATA ); olen = ctx->len; hlen = mbedtls_md_get_size( md_info ); /* first comparison checks for overflow */ if( ilen + 2 * hlen + 2 < ilen || olen < ilen + 2 * hlen + 2 ) return( MBEDTLS_ERR_RSA_BAD_INPUT_DATA ); memset( output, 0, olen ); *p++ = 0; /* Generate a random octet string seed */ if( ( ret = f_rng( p_rng, p, hlen ) ) != 0 ) return( MBEDTLS_ERROR_ADD( MBEDTLS_ERR_RSA_RNG_FAILED, ret ) ); p += hlen; /* Construct DB */ if( ( ret = mbedtls_md( md_info, label, label_len, p ) ) != 0 ) return( ret ); p += hlen; p += olen - 2 * hlen - 2 - ilen; *p++ = 1; if( ilen != 0 ) memcpy( p, input, ilen ); mbedtls_md_init( &md_ctx ); if( ( ret = mbedtls_md_setup( &md_ctx, md_info, 0 ) ) != 0 ) goto exit; /* maskedDB: Apply dbMask to DB */ if( ( ret = mgf_mask( output + hlen + 1, olen - hlen - 1, output + 1, hlen, &md_ctx ) ) != 0 ) goto exit; /* maskedSeed: Apply seedMask to seed */ if( ( ret = mgf_mask( output + 1, hlen, output + hlen + 1, olen - hlen - 1, &md_ctx ) ) != 0 ) goto exit; exit: mbedtls_md_free( &md_ctx ); if( ret != 0 ) return( ret ); return( mbedtls_rsa_public( ctx, output, output ) ); } #endif /* MBEDTLS_PKCS1_V21 */ #if defined(MBEDTLS_PKCS1_V15) /* * Implementation of the PKCS#1 v2.1 RSAES-PKCS1-V1_5-ENCRYPT function */ int mbedtls_rsa_rsaes_pkcs1_v15_encrypt( mbedtls_rsa_context *ctx, int (*f_rng)(void *, unsigned char *, size_t), void *p_rng, size_t ilen, const unsigned char *input, unsigned char *output ) { size_t nb_pad, olen; int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; unsigned char *p = output; RSA_VALIDATE_RET( ctx != NULL ); RSA_VALIDATE_RET( output != NULL ); RSA_VALIDATE_RET( ilen == 0 || input != NULL ); olen = ctx->len; /* first comparison checks for overflow */ if( ilen + 11 < ilen || olen < ilen + 11 ) return( MBEDTLS_ERR_RSA_BAD_INPUT_DATA ); nb_pad = olen - 3 - ilen; *p++ = 0; if( f_rng == NULL ) return( MBEDTLS_ERR_RSA_BAD_INPUT_DATA ); *p++ = MBEDTLS_RSA_CRYPT; while( nb_pad-- > 0 ) { int rng_dl = 100; do { ret = f_rng( p_rng, p, 1 ); } while( *p == 0 && --rng_dl && ret == 0 ); /* Check if RNG failed to generate data */ if( rng_dl == 0 || ret != 0 ) return( MBEDTLS_ERROR_ADD( MBEDTLS_ERR_RSA_RNG_FAILED, ret ) ); p++; } *p++ = 0; if( ilen != 0 ) memcpy( p, input, ilen ); return( mbedtls_rsa_public( ctx, output, output ) ); } #endif /* MBEDTLS_PKCS1_V15 */ /* * Add the message padding, then do an RSA operation */ int mbedtls_rsa_pkcs1_encrypt( mbedtls_rsa_context *ctx, int (*f_rng)(void *, unsigned char *, size_t), void *p_rng, size_t ilen, const unsigned char *input, unsigned char *output ) { RSA_VALIDATE_RET( ctx != NULL ); RSA_VALIDATE_RET( output != NULL ); RSA_VALIDATE_RET( ilen == 0 || input != NULL ); switch( ctx->padding ) { #if defined(MBEDTLS_PKCS1_V15) case MBEDTLS_RSA_PKCS_V15: return mbedtls_rsa_rsaes_pkcs1_v15_encrypt( ctx, f_rng, p_rng, ilen, input, output ); #endif #if defined(MBEDTLS_PKCS1_V21) case MBEDTLS_RSA_PKCS_V21: return mbedtls_rsa_rsaes_oaep_encrypt( ctx, f_rng, p_rng, NULL, 0, ilen, input, output ); #endif default: return( MBEDTLS_ERR_RSA_INVALID_PADDING ); } } #if defined(MBEDTLS_PKCS1_V21) /* * Implementation of the PKCS#1 v2.1 RSAES-OAEP-DECRYPT function */ int mbedtls_rsa_rsaes_oaep_decrypt( mbedtls_rsa_context *ctx, int (*f_rng)(void *, unsigned char *, size_t), void *p_rng, const unsigned char *label, size_t label_len, size_t *olen, const unsigned char *input, unsigned char *output, size_t output_max_len ) { int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; size_t ilen, i, pad_len; unsigned char *p, bad, pad_done; unsigned char buf[MBEDTLS_MPI_MAX_SIZE]; unsigned char lhash[MBEDTLS_MD_MAX_SIZE]; unsigned int hlen; const mbedtls_md_info_t *md_info; mbedtls_md_context_t md_ctx; RSA_VALIDATE_RET( ctx != NULL ); RSA_VALIDATE_RET( output_max_len == 0 || output != NULL ); RSA_VALIDATE_RET( label_len == 0 || label != NULL ); RSA_VALIDATE_RET( input != NULL ); RSA_VALIDATE_RET( olen != NULL ); /* * Parameters sanity checks */ if( ctx->padding != MBEDTLS_RSA_PKCS_V21 ) return( MBEDTLS_ERR_RSA_BAD_INPUT_DATA ); ilen = ctx->len; if( ilen < 16 || ilen > sizeof( buf ) ) return( MBEDTLS_ERR_RSA_BAD_INPUT_DATA ); md_info = mbedtls_md_info_from_type( (mbedtls_md_type_t) ctx->hash_id ); if( md_info == NULL ) return( MBEDTLS_ERR_RSA_BAD_INPUT_DATA ); hlen = mbedtls_md_get_size( md_info ); // checking for integer underflow if( 2 * hlen + 2 > ilen ) return( MBEDTLS_ERR_RSA_BAD_INPUT_DATA ); /* * RSA operation */ ret = mbedtls_rsa_private( ctx, f_rng, p_rng, input, buf ); if( ret != 0 ) goto cleanup; /* * Unmask data and generate lHash */ mbedtls_md_init( &md_ctx ); if( ( ret = mbedtls_md_setup( &md_ctx, md_info, 0 ) ) != 0 ) { mbedtls_md_free( &md_ctx ); goto cleanup; } /* seed: Apply seedMask to maskedSeed */ if( ( ret = mgf_mask( buf + 1, hlen, buf + hlen + 1, ilen - hlen - 1, &md_ctx ) ) != 0 || /* DB: Apply dbMask to maskedDB */ ( ret = mgf_mask( buf + hlen + 1, ilen - hlen - 1, buf + 1, hlen, &md_ctx ) ) != 0 ) { mbedtls_md_free( &md_ctx ); goto cleanup; } mbedtls_md_free( &md_ctx ); /* Generate lHash */ if( ( ret = mbedtls_md( md_info, label, label_len, lhash ) ) != 0 ) goto cleanup; /* * Check contents, in "constant-time" */ p = buf; bad = 0; bad |= *p++; /* First byte must be 0 */ p += hlen; /* Skip seed */ /* Check lHash */ for( i = 0; i < hlen; i++ ) bad |= lhash[i] ^ *p++; /* Get zero-padding len, but always read till end of buffer * (minus one, for the 01 byte) */ pad_len = 0; pad_done = 0; for( i = 0; i < ilen - 2 * hlen - 2; i++ ) { pad_done |= p[i]; pad_len += ((pad_done | (unsigned char)-pad_done) >> 7) ^ 1; } p += pad_len; bad |= *p++ ^ 0x01; /* * The only information "leaked" is whether the padding was correct or not * (eg, no data is copied if it was not correct). This meets the * recommendations in PKCS#1 v2.2: an opponent cannot distinguish between * the different error conditions. */ if( bad != 0 ) { ret = MBEDTLS_ERR_RSA_INVALID_PADDING; goto cleanup; } if( ilen - ( p - buf ) > output_max_len ) { ret = MBEDTLS_ERR_RSA_OUTPUT_TOO_LARGE; goto cleanup; } *olen = ilen - (p - buf); if( *olen != 0 ) memcpy( output, p, *olen ); ret = 0; cleanup: mbedtls_platform_zeroize( buf, sizeof( buf ) ); mbedtls_platform_zeroize( lhash, sizeof( lhash ) ); return( ret ); } #endif /* MBEDTLS_PKCS1_V21 */ #if defined(MBEDTLS_PKCS1_V15) /** Turn zero-or-nonzero into zero-or-all-bits-one, without branches. * * \param value The value to analyze. * \return Zero if \p value is zero, otherwise all-bits-one. */ static unsigned all_or_nothing_int( unsigned value ) { /* MSVC has a warning about unary minus on unsigned, but this is * well-defined and precisely what we want to do here */ #if defined(_MSC_VER) #pragma warning( push ) #pragma warning( disable : 4146 ) #endif return( - ( ( value | - value ) >> ( sizeof( value ) * 8 - 1 ) ) ); #if defined(_MSC_VER) #pragma warning( pop ) #endif } /** Check whether a size is out of bounds, without branches. * * This is equivalent to `size > max`, but is likely to be compiled to * to code using bitwise operation rather than a branch. * * \param size Size to check. * \param max Maximum desired value for \p size. * \return \c 0 if `size <= max`. * \return \c 1 if `size > max`. */ static unsigned size_greater_than( size_t size, size_t max ) { /* Return the sign bit (1 for negative) of (max - size). */ return( ( max - size ) >> ( sizeof( size_t ) * 8 - 1 ) ); } /** Choose between two integer values, without branches. * * This is equivalent to `cond ? if1 : if0`, but is likely to be compiled * to code using bitwise operation rather than a branch. * * \param cond Condition to test. * \param if1 Value to use if \p cond is nonzero. * \param if0 Value to use if \p cond is zero. * \return \c if1 if \p cond is nonzero, otherwise \c if0. */ static unsigned if_int( unsigned cond, unsigned if1, unsigned if0 ) { unsigned mask = all_or_nothing_int( cond ); return( ( mask & if1 ) | (~mask & if0 ) ); } /** Shift some data towards the left inside a buffer without leaking * the length of the data through side channels. * * `mem_move_to_left(start, total, offset)` is functionally equivalent to * ``` * memmove(start, start + offset, total - offset); * memset(start + offset, 0, total - offset); * ``` * but it strives to use a memory access pattern (and thus total timing) * that does not depend on \p offset. This timing independence comes at * the expense of performance. * * \param start Pointer to the start of the buffer. * \param total Total size of the buffer. * \param offset Offset from which to copy \p total - \p offset bytes. */ static void mem_move_to_left( void *start, size_t total, size_t offset ) { volatile unsigned char *buf = start; size_t i, n; if( total == 0 ) return; for( i = 0; i < total; i++ ) { unsigned no_op = size_greater_than( total - offset, i ); /* The first `total - offset` passes are a no-op. The last * `offset` passes shift the data one byte to the left and * zero out the last byte. */ for( n = 0; n < total - 1; n++ ) { unsigned char current = buf[n]; unsigned char next = buf[n+1]; buf[n] = if_int( no_op, current, next ); } buf[total-1] = if_int( no_op, buf[total-1], 0 ); } } /* * Implementation of the PKCS#1 v2.1 RSAES-PKCS1-V1_5-DECRYPT function */ int mbedtls_rsa_rsaes_pkcs1_v15_decrypt( mbedtls_rsa_context *ctx, int (*f_rng)(void *, unsigned char *, size_t), void *p_rng, size_t *olen, const unsigned char *input, unsigned char *output, size_t output_max_len ) { int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; size_t ilen, i, plaintext_max_size; unsigned char buf[MBEDTLS_MPI_MAX_SIZE]; /* The following variables take sensitive values: their value must * not leak into the observable behavior of the function other than * the designated outputs (output, olen, return value). Otherwise * this would open the execution of the function to * side-channel-based variants of the Bleichenbacher padding oracle * attack. Potential side channels include overall timing, memory * access patterns (especially visible to an adversary who has access * to a shared memory cache), and branches (especially visible to * an adversary who has access to a shared code cache or to a shared * branch predictor). */ size_t pad_count = 0; unsigned bad = 0; unsigned char pad_done = 0; size_t plaintext_size = 0; unsigned output_too_large; RSA_VALIDATE_RET( ctx != NULL ); RSA_VALIDATE_RET( output_max_len == 0 || output != NULL ); RSA_VALIDATE_RET( input != NULL ); RSA_VALIDATE_RET( olen != NULL ); ilen = ctx->len; plaintext_max_size = ( output_max_len > ilen - 11 ? ilen - 11 : output_max_len ); if( ctx->padding != MBEDTLS_RSA_PKCS_V15 ) return( MBEDTLS_ERR_RSA_BAD_INPUT_DATA ); if( ilen < 16 || ilen > sizeof( buf ) ) return( MBEDTLS_ERR_RSA_BAD_INPUT_DATA ); ret = mbedtls_rsa_private( ctx, f_rng, p_rng, input, buf ); if( ret != 0 ) goto cleanup; /* Check and get padding length in constant time and constant * memory trace. The first byte must be 0. */ bad |= buf[0]; /* Decode EME-PKCS1-v1_5 padding: 0x00 || 0x02 || PS || 0x00 * where PS must be at least 8 nonzero bytes. */ bad |= buf[1] ^ MBEDTLS_RSA_CRYPT; /* Read the whole buffer. Set pad_done to nonzero if we find * the 0x00 byte and remember the padding length in pad_count. */ for( i = 2; i < ilen; i++ ) { pad_done |= ((buf[i] | (unsigned char)-buf[i]) >> 7) ^ 1; pad_count += ((pad_done | (unsigned char)-pad_done) >> 7) ^ 1; } /* If pad_done is still zero, there's no data, only unfinished padding. */ bad |= if_int( pad_done, 0, 1 ); /* There must be at least 8 bytes of padding. */ bad |= size_greater_than( 8, pad_count ); /* If the padding is valid, set plaintext_size to the number of * remaining bytes after stripping the padding. If the padding * is invalid, avoid leaking this fact through the size of the * output: use the maximum message size that fits in the output * buffer. Do it without branches to avoid leaking the padding * validity through timing. RSA keys are small enough that all the * size_t values involved fit in unsigned int. */ plaintext_size = if_int( bad, (unsigned) plaintext_max_size, (unsigned) ( ilen - pad_count - 3 ) ); /* Set output_too_large to 0 if the plaintext fits in the output * buffer and to 1 otherwise. */ output_too_large = size_greater_than( plaintext_size, plaintext_max_size ); /* Set ret without branches to avoid timing attacks. Return: * - INVALID_PADDING if the padding is bad (bad != 0). * - OUTPUT_TOO_LARGE if the padding is good but the decrypted * plaintext does not fit in the output buffer. * - 0 if the padding is correct. */ ret = - (int) if_int( bad, - MBEDTLS_ERR_RSA_INVALID_PADDING, if_int( output_too_large, - MBEDTLS_ERR_RSA_OUTPUT_TOO_LARGE, 0 ) ); /* If the padding is bad or the plaintext is too large, zero the * data that we're about to copy to the output buffer. * We need to copy the same amount of data * from the same buffer whether the padding is good or not to * avoid leaking the padding validity through overall timing or * through memory or cache access patterns. */ bad = all_or_nothing_int( bad | output_too_large ); for( i = 11; i < ilen; i++ ) buf[i] &= ~bad; /* If the plaintext is too large, truncate it to the buffer size. * Copy anyway to avoid revealing the length through timing, because * revealing the length is as bad as revealing the padding validity * for a Bleichenbacher attack. */ plaintext_size = if_int( output_too_large, (unsigned) plaintext_max_size, (unsigned) plaintext_size ); /* Move the plaintext to the leftmost position where it can start in * the working buffer, i.e. make it start plaintext_max_size from * the end of the buffer. Do this with a memory access trace that * does not depend on the plaintext size. After this move, the * starting location of the plaintext is no longer sensitive * information. */ mem_move_to_left( buf + ilen - plaintext_max_size, plaintext_max_size, plaintext_max_size - plaintext_size ); /* Finally copy the decrypted plaintext plus trailing zeros into the output * buffer. If output_max_len is 0, then output may be an invalid pointer * and the result of memcpy() would be undefined; prevent undefined * behavior making sure to depend only on output_max_len (the size of the * user-provided output buffer), which is independent from plaintext * length, validity of padding, success of the decryption, and other * secrets. */ if( output_max_len != 0 ) memcpy( output, buf + ilen - plaintext_max_size, plaintext_max_size ); /* Report the amount of data we copied to the output buffer. In case * of errors (bad padding or output too large), the value of *olen * when this function returns is not specified. Making it equivalent * to the good case limits the risks of leaking the padding validity. */ *olen = plaintext_size; cleanup: mbedtls_platform_zeroize( buf, sizeof( buf ) ); return( ret ); } #endif /* MBEDTLS_PKCS1_V15 */ /* * Do an RSA operation, then remove the message padding */ int mbedtls_rsa_pkcs1_decrypt( mbedtls_rsa_context *ctx, int (*f_rng)(void *, unsigned char *, size_t), void *p_rng, size_t *olen, const unsigned char *input, unsigned char *output, size_t output_max_len) { RSA_VALIDATE_RET( ctx != NULL ); RSA_VALIDATE_RET( output_max_len == 0 || output != NULL ); RSA_VALIDATE_RET( input != NULL ); RSA_VALIDATE_RET( olen != NULL ); switch( ctx->padding ) { #if defined(MBEDTLS_PKCS1_V15) case MBEDTLS_RSA_PKCS_V15: return mbedtls_rsa_rsaes_pkcs1_v15_decrypt( ctx, f_rng, p_rng, olen, input, output, output_max_len ); #endif #if defined(MBEDTLS_PKCS1_V21) case MBEDTLS_RSA_PKCS_V21: return mbedtls_rsa_rsaes_oaep_decrypt( ctx, f_rng, p_rng, NULL, 0, olen, input, output, output_max_len ); #endif default: return( MBEDTLS_ERR_RSA_INVALID_PADDING ); } } #if defined(MBEDTLS_PKCS1_V21) static int rsa_rsassa_pss_sign( mbedtls_rsa_context *ctx, int (*f_rng)(void *, unsigned char *, size_t), void *p_rng, mbedtls_md_type_t md_alg, unsigned int hashlen, const unsigned char *hash, int saltlen, unsigned char *sig ) { size_t olen; unsigned char *p = sig; unsigned char *salt = NULL; size_t slen, min_slen, hlen, offset = 0; int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; size_t msb; const mbedtls_md_info_t *md_info; mbedtls_md_context_t md_ctx; RSA_VALIDATE_RET( ctx != NULL ); RSA_VALIDATE_RET( ( md_alg == MBEDTLS_MD_NONE && hashlen == 0 ) || hash != NULL ); RSA_VALIDATE_RET( sig != NULL ); if( ctx->padding != MBEDTLS_RSA_PKCS_V21 ) return( MBEDTLS_ERR_RSA_BAD_INPUT_DATA ); if( f_rng == NULL ) return( MBEDTLS_ERR_RSA_BAD_INPUT_DATA ); olen = ctx->len; if( md_alg != MBEDTLS_MD_NONE ) { /* Gather length of hash to sign */ md_info = mbedtls_md_info_from_type( md_alg ); if( md_info == NULL ) return( MBEDTLS_ERR_RSA_BAD_INPUT_DATA ); hashlen = mbedtls_md_get_size( md_info ); } md_info = mbedtls_md_info_from_type( (mbedtls_md_type_t) ctx->hash_id ); if( md_info == NULL ) return( MBEDTLS_ERR_RSA_BAD_INPUT_DATA ); hlen = mbedtls_md_get_size( md_info ); if (saltlen == MBEDTLS_RSA_SALT_LEN_ANY) { /* Calculate the largest possible salt length, up to the hash size. * Normally this is the hash length, which is the maximum salt length * according to FIPS 185-4 §5.5 (e) and common practice. If there is not * enough room, use the maximum salt length that fits. The constraint is * that the hash length plus the salt length plus 2 bytes must be at most * the key length. This complies with FIPS 186-4 §5.5 (e) and RFC 8017 * (PKCS#1 v2.2) §9.1.1 step 3. */ min_slen = hlen - 2; if( olen < hlen + min_slen + 2 ) return( MBEDTLS_ERR_RSA_BAD_INPUT_DATA ); else if( olen >= hlen + hlen + 2 ) slen = hlen; else slen = olen - hlen - 2; } else if ( (saltlen < 0) || (saltlen + hlen + 2 > olen) ) { return( MBEDTLS_ERR_RSA_BAD_INPUT_DATA ); } else { slen = (size_t) saltlen; } memset( sig, 0, olen ); /* Note: EMSA-PSS encoding is over the length of N - 1 bits */ msb = mbedtls_mpi_bitlen( &ctx->N ) - 1; p += olen - hlen - slen - 2; *p++ = 0x01; /* Generate salt of length slen in place in the encoded message */ salt = p; if( ( ret = f_rng( p_rng, salt, slen ) ) != 0 ) return( MBEDTLS_ERROR_ADD( MBEDTLS_ERR_RSA_RNG_FAILED, ret ) ); p += slen; mbedtls_md_init( &md_ctx ); if( ( ret = mbedtls_md_setup( &md_ctx, md_info, 0 ) ) != 0 ) goto exit; /* Generate H = Hash( M' ) */ if( ( ret = mbedtls_md_starts( &md_ctx ) ) != 0 ) goto exit; if( ( ret = mbedtls_md_update( &md_ctx, p, 8 ) ) != 0 ) goto exit; if( ( ret = mbedtls_md_update( &md_ctx, hash, hashlen ) ) != 0 ) goto exit; if( ( ret = mbedtls_md_update( &md_ctx, salt, slen ) ) != 0 ) goto exit; if( ( ret = mbedtls_md_finish( &md_ctx, p ) ) != 0 ) goto exit; /* Compensate for boundary condition when applying mask */ if( msb % 8 == 0 ) offset = 1; /* maskedDB: Apply dbMask to DB */ if( ( ret = mgf_mask( sig + offset, olen - hlen - 1 - offset, p, hlen, &md_ctx ) ) != 0 ) goto exit; msb = mbedtls_mpi_bitlen( &ctx->N ) - 1; sig[0] &= 0xFF >> ( olen * 8 - msb ); p += hlen; *p++ = 0xBC; exit: mbedtls_md_free( &md_ctx ); if( ret != 0 ) return( ret ); return mbedtls_rsa_private( ctx, f_rng, p_rng, sig, sig ); } /* * Implementation of the PKCS#1 v2.1 RSASSA-PSS-SIGN function with * the option to pass in the salt length. */ int mbedtls_rsa_rsassa_pss_sign_ext( mbedtls_rsa_context *ctx, int (*f_rng)(void *, unsigned char *, size_t), void *p_rng, mbedtls_md_type_t md_alg, unsigned int hashlen, const unsigned char *hash, int saltlen, unsigned char *sig ) { return rsa_rsassa_pss_sign( ctx, f_rng, p_rng, md_alg, hashlen, hash, saltlen, sig ); } /* * Implementation of the PKCS#1 v2.1 RSASSA-PSS-SIGN function */ int mbedtls_rsa_rsassa_pss_sign( mbedtls_rsa_context *ctx, int (*f_rng)(void *, unsigned char *, size_t), void *p_rng, mbedtls_md_type_t md_alg, unsigned int hashlen, const unsigned char *hash, unsigned char *sig ) { return rsa_rsassa_pss_sign( ctx, f_rng, p_rng, md_alg, hashlen, hash, MBEDTLS_RSA_SALT_LEN_ANY, sig ); } #endif /* MBEDTLS_PKCS1_V21 */ #if defined(MBEDTLS_PKCS1_V15) /* * Implementation of the PKCS#1 v2.1 RSASSA-PKCS1-V1_5-SIGN function */ /* Construct a PKCS v1.5 encoding of a hashed message * * This is used both for signature generation and verification. * * Parameters: * - md_alg: Identifies the hash algorithm used to generate the given hash; * MBEDTLS_MD_NONE if raw data is signed. * - hashlen: Length of hash in case hashlen is MBEDTLS_MD_NONE. * - hash: Buffer containing the hashed message or the raw data. * - dst_len: Length of the encoded message. * - dst: Buffer to hold the encoded message. * * Assumptions: * - hash has size hashlen if md_alg == MBEDTLS_MD_NONE. * - hash has size corresponding to md_alg if md_alg != MBEDTLS_MD_NONE. * - dst points to a buffer of size at least dst_len. * */ static int rsa_rsassa_pkcs1_v15_encode( mbedtls_md_type_t md_alg, unsigned int hashlen, const unsigned char *hash, size_t dst_len, unsigned char *dst ) { size_t oid_size = 0; size_t nb_pad = dst_len; unsigned char *p = dst; const char *oid = NULL; /* Are we signing hashed or raw data? */ if( md_alg != MBEDTLS_MD_NONE ) { const mbedtls_md_info_t *md_info = mbedtls_md_info_from_type( md_alg ); if( md_info == NULL ) return( MBEDTLS_ERR_RSA_BAD_INPUT_DATA ); if( mbedtls_oid_get_oid_by_md( md_alg, &oid, &oid_size ) != 0 ) return( MBEDTLS_ERR_RSA_BAD_INPUT_DATA ); hashlen = mbedtls_md_get_size( md_info ); /* Double-check that 8 + hashlen + oid_size can be used as a * 1-byte ASN.1 length encoding and that there's no overflow. */ if( 8 + hashlen + oid_size >= 0x80 || 10 + hashlen < hashlen || 10 + hashlen + oid_size < 10 + hashlen ) return( MBEDTLS_ERR_RSA_BAD_INPUT_DATA ); /* * Static bounds check: * - Need 10 bytes for five tag-length pairs. * (Insist on 1-byte length encodings to protect against variants of * Bleichenbacher's forgery attack against lax PKCS#1v1.5 verification) * - Need hashlen bytes for hash * - Need oid_size bytes for hash alg OID. */ if( nb_pad < 10 + hashlen + oid_size ) return( MBEDTLS_ERR_RSA_BAD_INPUT_DATA ); nb_pad -= 10 + hashlen + oid_size; } else { if( nb_pad < hashlen ) return( MBEDTLS_ERR_RSA_BAD_INPUT_DATA ); nb_pad -= hashlen; } /* Need space for signature header and padding delimiter (3 bytes), * and 8 bytes for the minimal padding */ if( nb_pad < 3 + 8 ) return( MBEDTLS_ERR_RSA_BAD_INPUT_DATA ); nb_pad -= 3; /* Now nb_pad is the amount of memory to be filled * with padding, and at least 8 bytes long. */ /* Write signature header and padding */ *p++ = 0; *p++ = MBEDTLS_RSA_SIGN; memset( p, 0xFF, nb_pad ); p += nb_pad; *p++ = 0; /* Are we signing raw data? */ if( md_alg == MBEDTLS_MD_NONE ) { memcpy( p, hash, hashlen ); return( 0 ); } /* Signing hashed data, add corresponding ASN.1 structure * * DigestInfo ::= SEQUENCE { * digestAlgorithm DigestAlgorithmIdentifier, * digest Digest } * DigestAlgorithmIdentifier ::= AlgorithmIdentifier * Digest ::= OCTET STRING * * Schematic: * TAG-SEQ + LEN [ TAG-SEQ + LEN [ TAG-OID + LEN [ OID ] * TAG-NULL + LEN [ NULL ] ] * TAG-OCTET + LEN [ HASH ] ] */ *p++ = MBEDTLS_ASN1_SEQUENCE | MBEDTLS_ASN1_CONSTRUCTED; *p++ = (unsigned char)( 0x08 + oid_size + hashlen ); *p++ = MBEDTLS_ASN1_SEQUENCE | MBEDTLS_ASN1_CONSTRUCTED; *p++ = (unsigned char)( 0x04 + oid_size ); *p++ = MBEDTLS_ASN1_OID; *p++ = (unsigned char) oid_size; memcpy( p, oid, oid_size ); p += oid_size; *p++ = MBEDTLS_ASN1_NULL; *p++ = 0x00; *p++ = MBEDTLS_ASN1_OCTET_STRING; *p++ = (unsigned char) hashlen; memcpy( p, hash, hashlen ); p += hashlen; /* Just a sanity-check, should be automatic * after the initial bounds check. */ if( p != dst + dst_len ) { mbedtls_platform_zeroize( dst, dst_len ); return( MBEDTLS_ERR_RSA_BAD_INPUT_DATA ); } return( 0 ); } /* * Do an RSA operation to sign the message digest */ int mbedtls_rsa_rsassa_pkcs1_v15_sign( mbedtls_rsa_context *ctx, int (*f_rng)(void *, unsigned char *, size_t), void *p_rng, mbedtls_md_type_t md_alg, unsigned int hashlen, const unsigned char *hash, unsigned char *sig ) { int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; unsigned char *sig_try = NULL, *verif = NULL; RSA_VALIDATE_RET( ctx != NULL ); RSA_VALIDATE_RET( ( md_alg == MBEDTLS_MD_NONE && hashlen == 0 ) || hash != NULL ); RSA_VALIDATE_RET( sig != NULL ); if( ctx->padding != MBEDTLS_RSA_PKCS_V15 ) return( MBEDTLS_ERR_RSA_BAD_INPUT_DATA ); /* * Prepare PKCS1-v1.5 encoding (padding and hash identifier) */ if( ( ret = rsa_rsassa_pkcs1_v15_encode( md_alg, hashlen, hash, ctx->len, sig ) ) != 0 ) return( ret ); /* Private key operation * * In order to prevent Lenstra's attack, make the signature in a * temporary buffer and check it before returning it. */ sig_try = mbedtls_calloc( 1, ctx->len ); if( sig_try == NULL ) return( MBEDTLS_ERR_MPI_ALLOC_FAILED ); verif = mbedtls_calloc( 1, ctx->len ); if( verif == NULL ) { mbedtls_free( sig_try ); return( MBEDTLS_ERR_MPI_ALLOC_FAILED ); } MBEDTLS_MPI_CHK( mbedtls_rsa_private( ctx, f_rng, p_rng, sig, sig_try ) ); MBEDTLS_MPI_CHK( mbedtls_rsa_public( ctx, sig_try, verif ) ); if( mbedtls_safer_memcmp( verif, sig, ctx->len ) != 0 ) { ret = MBEDTLS_ERR_RSA_PRIVATE_FAILED; goto cleanup; } memcpy( sig, sig_try, ctx->len ); cleanup: mbedtls_free( sig_try ); mbedtls_free( verif ); return( ret ); } #endif /* MBEDTLS_PKCS1_V15 */ /* * Do an RSA operation to sign the message digest */ int mbedtls_rsa_pkcs1_sign( mbedtls_rsa_context *ctx, int (*f_rng)(void *, unsigned char *, size_t), void *p_rng, mbedtls_md_type_t md_alg, unsigned int hashlen, const unsigned char *hash, unsigned char *sig ) { RSA_VALIDATE_RET( ctx != NULL ); RSA_VALIDATE_RET( ( md_alg == MBEDTLS_MD_NONE && hashlen == 0 ) || hash != NULL ); RSA_VALIDATE_RET( sig != NULL ); switch( ctx->padding ) { #if defined(MBEDTLS_PKCS1_V15) case MBEDTLS_RSA_PKCS_V15: return mbedtls_rsa_rsassa_pkcs1_v15_sign( ctx, f_rng, p_rng, md_alg, hashlen, hash, sig ); #endif #if defined(MBEDTLS_PKCS1_V21) case MBEDTLS_RSA_PKCS_V21: return mbedtls_rsa_rsassa_pss_sign( ctx, f_rng, p_rng, md_alg, hashlen, hash, sig ); #endif default: return( MBEDTLS_ERR_RSA_INVALID_PADDING ); } } #if defined(MBEDTLS_PKCS1_V21) /* * Implementation of the PKCS#1 v2.1 RSASSA-PSS-VERIFY function */ int mbedtls_rsa_rsassa_pss_verify_ext( mbedtls_rsa_context *ctx, mbedtls_md_type_t md_alg, unsigned int hashlen, const unsigned char *hash, mbedtls_md_type_t mgf1_hash_id, int expected_salt_len, const unsigned char *sig ) { int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; size_t siglen; unsigned char *p; unsigned char *hash_start; unsigned char result[MBEDTLS_MD_MAX_SIZE]; unsigned char zeros[8]; unsigned int hlen; size_t observed_salt_len, msb; const mbedtls_md_info_t *md_info; mbedtls_md_context_t md_ctx; unsigned char buf[MBEDTLS_MPI_MAX_SIZE]; RSA_VALIDATE_RET( ctx != NULL ); RSA_VALIDATE_RET( sig != NULL ); RSA_VALIDATE_RET( ( md_alg == MBEDTLS_MD_NONE && hashlen == 0 ) || hash != NULL ); siglen = ctx->len; if( siglen < 16 || siglen > sizeof( buf ) ) return( MBEDTLS_ERR_RSA_BAD_INPUT_DATA ); ret = mbedtls_rsa_public( ctx, sig, buf ); if( ret != 0 ) return( ret ); p = buf; if( buf[siglen - 1] != 0xBC ) return( MBEDTLS_ERR_RSA_INVALID_PADDING ); if( md_alg != MBEDTLS_MD_NONE ) { /* Gather length of hash to sign */ md_info = mbedtls_md_info_from_type( md_alg ); if( md_info == NULL ) return( MBEDTLS_ERR_RSA_BAD_INPUT_DATA ); hashlen = mbedtls_md_get_size( md_info ); } md_info = mbedtls_md_info_from_type( mgf1_hash_id ); if( md_info == NULL ) return( MBEDTLS_ERR_RSA_BAD_INPUT_DATA ); hlen = mbedtls_md_get_size( md_info ); memset( zeros, 0, 8 ); /* * Note: EMSA-PSS verification is over the length of N - 1 bits */ msb = mbedtls_mpi_bitlen( &ctx->N ) - 1; if( buf[0] >> ( 8 - siglen * 8 + msb ) ) return( MBEDTLS_ERR_RSA_BAD_INPUT_DATA ); /* Compensate for boundary condition when applying mask */ if( msb % 8 == 0 ) { p++; siglen -= 1; } if( siglen < hlen + 2 ) return( MBEDTLS_ERR_RSA_BAD_INPUT_DATA ); hash_start = p + siglen - hlen - 1; mbedtls_md_init( &md_ctx ); if( ( ret = mbedtls_md_setup( &md_ctx, md_info, 0 ) ) != 0 ) goto exit; ret = mgf_mask( p, siglen - hlen - 1, hash_start, hlen, &md_ctx ); if( ret != 0 ) goto exit; buf[0] &= 0xFF >> ( siglen * 8 - msb ); while( p < hash_start - 1 && *p == 0 ) p++; if( *p++ != 0x01 ) { ret = MBEDTLS_ERR_RSA_INVALID_PADDING; goto exit; } observed_salt_len = hash_start - p; if( expected_salt_len != MBEDTLS_RSA_SALT_LEN_ANY && observed_salt_len != (size_t) expected_salt_len ) { ret = MBEDTLS_ERR_RSA_INVALID_PADDING; goto exit; } /* * Generate H = Hash( M' ) */ ret = mbedtls_md_starts( &md_ctx ); if ( ret != 0 ) goto exit; ret = mbedtls_md_update( &md_ctx, zeros, 8 ); if ( ret != 0 ) goto exit; ret = mbedtls_md_update( &md_ctx, hash, hashlen ); if ( ret != 0 ) goto exit; ret = mbedtls_md_update( &md_ctx, p, observed_salt_len ); if ( ret != 0 ) goto exit; ret = mbedtls_md_finish( &md_ctx, result ); if ( ret != 0 ) goto exit; if( memcmp( hash_start, result, hlen ) != 0 ) { ret = MBEDTLS_ERR_RSA_VERIFY_FAILED; goto exit; } exit: mbedtls_md_free( &md_ctx ); return( ret ); } /* * Simplified PKCS#1 v2.1 RSASSA-PSS-VERIFY function */ int mbedtls_rsa_rsassa_pss_verify( mbedtls_rsa_context *ctx, mbedtls_md_type_t md_alg, unsigned int hashlen, const unsigned char *hash, const unsigned char *sig ) { mbedtls_md_type_t mgf1_hash_id; RSA_VALIDATE_RET( ctx != NULL ); RSA_VALIDATE_RET( sig != NULL ); RSA_VALIDATE_RET( ( md_alg == MBEDTLS_MD_NONE && hashlen == 0 ) || hash != NULL ); mgf1_hash_id = ( ctx->hash_id != MBEDTLS_MD_NONE ) ? (mbedtls_md_type_t) ctx->hash_id : md_alg; return( mbedtls_rsa_rsassa_pss_verify_ext( ctx, md_alg, hashlen, hash, mgf1_hash_id, MBEDTLS_RSA_SALT_LEN_ANY, sig ) ); } #endif /* MBEDTLS_PKCS1_V21 */ #if defined(MBEDTLS_PKCS1_V15) /* * Implementation of the PKCS#1 v2.1 RSASSA-PKCS1-v1_5-VERIFY function */ int mbedtls_rsa_rsassa_pkcs1_v15_verify( mbedtls_rsa_context *ctx, mbedtls_md_type_t md_alg, unsigned int hashlen, const unsigned char *hash, const unsigned char *sig ) { int ret = 0; size_t sig_len; unsigned char *encoded = NULL, *encoded_expected = NULL; RSA_VALIDATE_RET( ctx != NULL ); RSA_VALIDATE_RET( sig != NULL ); RSA_VALIDATE_RET( ( md_alg == MBEDTLS_MD_NONE && hashlen == 0 ) || hash != NULL ); sig_len = ctx->len; /* * Prepare expected PKCS1 v1.5 encoding of hash. */ if( ( encoded = mbedtls_calloc( 1, sig_len ) ) == NULL || ( encoded_expected = mbedtls_calloc( 1, sig_len ) ) == NULL ) { ret = MBEDTLS_ERR_MPI_ALLOC_FAILED; goto cleanup; } if( ( ret = rsa_rsassa_pkcs1_v15_encode( md_alg, hashlen, hash, sig_len, encoded_expected ) ) != 0 ) goto cleanup; /* * Apply RSA primitive to get what should be PKCS1 encoded hash. */ ret = mbedtls_rsa_public( ctx, sig, encoded ); if( ret != 0 ) goto cleanup; /* * Compare */ if( ( ret = mbedtls_safer_memcmp( encoded, encoded_expected, sig_len ) ) != 0 ) { ret = MBEDTLS_ERR_RSA_VERIFY_FAILED; goto cleanup; } cleanup: if( encoded != NULL ) { mbedtls_platform_zeroize( encoded, sig_len ); mbedtls_free( encoded ); } if( encoded_expected != NULL ) { mbedtls_platform_zeroize( encoded_expected, sig_len ); mbedtls_free( encoded_expected ); } return( ret ); } #endif /* MBEDTLS_PKCS1_V15 */ /* * Do an RSA operation and check the message digest */ int mbedtls_rsa_pkcs1_verify( mbedtls_rsa_context *ctx, mbedtls_md_type_t md_alg, unsigned int hashlen, const unsigned char *hash, const unsigned char *sig ) { RSA_VALIDATE_RET( ctx != NULL ); RSA_VALIDATE_RET( sig != NULL ); RSA_VALIDATE_RET( ( md_alg == MBEDTLS_MD_NONE && hashlen == 0 ) || hash != NULL ); switch( ctx->padding ) { #if defined(MBEDTLS_PKCS1_V15) case MBEDTLS_RSA_PKCS_V15: return mbedtls_rsa_rsassa_pkcs1_v15_verify( ctx, md_alg, hashlen, hash, sig ); #endif #if defined(MBEDTLS_PKCS1_V21) case MBEDTLS_RSA_PKCS_V21: return mbedtls_rsa_rsassa_pss_verify( ctx, md_alg, hashlen, hash, sig ); #endif default: return( MBEDTLS_ERR_RSA_INVALID_PADDING ); } } /* * Copy the components of an RSA key */ int mbedtls_rsa_copy( mbedtls_rsa_context *dst, const mbedtls_rsa_context *src ) { int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; RSA_VALIDATE_RET( dst != NULL ); RSA_VALIDATE_RET( src != NULL ); dst->len = src->len; MBEDTLS_MPI_CHK( mbedtls_mpi_copy( &dst->N, &src->N ) ); MBEDTLS_MPI_CHK( mbedtls_mpi_copy( &dst->E, &src->E ) ); MBEDTLS_MPI_CHK( mbedtls_mpi_copy( &dst->D, &src->D ) ); MBEDTLS_MPI_CHK( mbedtls_mpi_copy( &dst->P, &src->P ) ); MBEDTLS_MPI_CHK( mbedtls_mpi_copy( &dst->Q, &src->Q ) ); #if !defined(MBEDTLS_RSA_NO_CRT) MBEDTLS_MPI_CHK( mbedtls_mpi_copy( &dst->DP, &src->DP ) ); MBEDTLS_MPI_CHK( mbedtls_mpi_copy( &dst->DQ, &src->DQ ) ); MBEDTLS_MPI_CHK( mbedtls_mpi_copy( &dst->QP, &src->QP ) ); MBEDTLS_MPI_CHK( mbedtls_mpi_copy( &dst->RP, &src->RP ) ); MBEDTLS_MPI_CHK( mbedtls_mpi_copy( &dst->RQ, &src->RQ ) ); #endif MBEDTLS_MPI_CHK( mbedtls_mpi_copy( &dst->RN, &src->RN ) ); MBEDTLS_MPI_CHK( mbedtls_mpi_copy( &dst->Vi, &src->Vi ) ); MBEDTLS_MPI_CHK( mbedtls_mpi_copy( &dst->Vf, &src->Vf ) ); dst->padding = src->padding; dst->hash_id = src->hash_id; cleanup: if( ret != 0 ) mbedtls_rsa_free( dst ); return( ret ); } /* * Free the components of an RSA key */ void mbedtls_rsa_free( mbedtls_rsa_context *ctx ) { if( ctx == NULL ) return; mbedtls_mpi_free( &ctx->Vi ); mbedtls_mpi_free( &ctx->Vf ); mbedtls_mpi_free( &ctx->RN ); mbedtls_mpi_free( &ctx->D ); mbedtls_mpi_free( &ctx->Q ); mbedtls_mpi_free( &ctx->P ); mbedtls_mpi_free( &ctx->E ); mbedtls_mpi_free( &ctx->N ); #if !defined(MBEDTLS_RSA_NO_CRT) mbedtls_mpi_free( &ctx->RQ ); mbedtls_mpi_free( &ctx->RP ); mbedtls_mpi_free( &ctx->QP ); mbedtls_mpi_free( &ctx->DQ ); mbedtls_mpi_free( &ctx->DP ); #endif /* MBEDTLS_RSA_NO_CRT */ #if defined(MBEDTLS_THREADING_C) /* Free the mutex, but only if it hasn't been freed already. */ if( ctx->ver != 0 ) { mbedtls_mutex_free( &ctx->mutex ); ctx->ver = 0; } #endif } #endif /* !MBEDTLS_RSA_ALT */ #if defined(MBEDTLS_SELF_TEST) #include "mbedtls/sha1.h" /* * Example RSA-1024 keypair, for test purposes */ #define KEY_LEN 128 #define RSA_N "9292758453063D803DD603D5E777D788" \ "8ED1D5BF35786190FA2F23EBC0848AEA" \ "DDA92CA6C3D80B32C4D109BE0F36D6AE" \ "7130B9CED7ACDF54CFC7555AC14EEBAB" \ "93A89813FBF3C4F8066D2D800F7C38A8" \ "1AE31942917403FF4946B0A83D3D3E05" \ "EE57C6F5F5606FB5D4BC6CD34EE0801A" \ "5E94BB77B07507233A0BC7BAC8F90F79" #define RSA_E "10001" #define RSA_D "24BF6185468786FDD303083D25E64EFC" \ "66CA472BC44D253102F8B4A9D3BFA750" \ "91386C0077937FE33FA3252D28855837" \ "AE1B484A8A9A45F7EE8C0C634F99E8CD" \ "DF79C5CE07EE72C7F123142198164234" \ "CABB724CF78B8173B9F880FC86322407" \ "AF1FEDFDDE2BEB674CA15F3E81A1521E" \ "071513A1E85B5DFA031F21ECAE91A34D" #define RSA_P "C36D0EB7FCD285223CFB5AABA5BDA3D8" \ "2C01CAD19EA484A87EA4377637E75500" \ "FCB2005C5C7DD6EC4AC023CDA285D796" \ "C3D9E75E1EFC42488BB4F1D13AC30A57" #define RSA_Q "C000DF51A7C77AE8D7C7370C1FF55B69" \ "E211C2B9E5DB1ED0BF61D0D9899620F4" \ "910E4168387E3C30AA1E00C339A79508" \ "8452DD96A9A5EA5D9DCA68DA636032AF" #define PT_LEN 24 #define RSA_PT "\xAA\xBB\xCC\x03\x02\x01\x00\xFF\xFF\xFF\xFF\xFF" \ "\x11\x22\x33\x0A\x0B\x0C\xCC\xDD\xDD\xDD\xDD\xDD" #if defined(MBEDTLS_PKCS1_V15) static int myrand( void *rng_state, unsigned char *output, size_t len ) { #if !defined(__OpenBSD__) && !defined(__NetBSD__) size_t i; if( rng_state != NULL ) rng_state = NULL; for( i = 0; i < len; ++i ) output[i] = rand(); #else if( rng_state != NULL ) rng_state = NULL; arc4random_buf( output, len ); #endif /* !OpenBSD && !NetBSD */ return( 0 ); } #endif /* MBEDTLS_PKCS1_V15 */ /* * Checkup routine */ int mbedtls_rsa_self_test( int verbose ) { int ret = 0; #if defined(MBEDTLS_PKCS1_V15) size_t len; mbedtls_rsa_context rsa; unsigned char rsa_plaintext[PT_LEN]; unsigned char rsa_decrypted[PT_LEN]; unsigned char rsa_ciphertext[KEY_LEN]; #if defined(MBEDTLS_SHA1_C) unsigned char sha1sum[20]; #endif mbedtls_mpi K; mbedtls_mpi_init( &K ); mbedtls_rsa_init( &rsa ); MBEDTLS_MPI_CHK( mbedtls_mpi_read_string( &K, 16, RSA_N ) ); MBEDTLS_MPI_CHK( mbedtls_rsa_import( &rsa, &K, NULL, NULL, NULL, NULL ) ); MBEDTLS_MPI_CHK( mbedtls_mpi_read_string( &K, 16, RSA_P ) ); MBEDTLS_MPI_CHK( mbedtls_rsa_import( &rsa, NULL, &K, NULL, NULL, NULL ) ); MBEDTLS_MPI_CHK( mbedtls_mpi_read_string( &K, 16, RSA_Q ) ); MBEDTLS_MPI_CHK( mbedtls_rsa_import( &rsa, NULL, NULL, &K, NULL, NULL ) ); MBEDTLS_MPI_CHK( mbedtls_mpi_read_string( &K, 16, RSA_D ) ); MBEDTLS_MPI_CHK( mbedtls_rsa_import( &rsa, NULL, NULL, NULL, &K, NULL ) ); MBEDTLS_MPI_CHK( mbedtls_mpi_read_string( &K, 16, RSA_E ) ); MBEDTLS_MPI_CHK( mbedtls_rsa_import( &rsa, NULL, NULL, NULL, NULL, &K ) ); MBEDTLS_MPI_CHK( mbedtls_rsa_complete( &rsa ) ); if( verbose != 0 ) mbedtls_printf( " RSA key validation: " ); if( mbedtls_rsa_check_pubkey( &rsa ) != 0 || mbedtls_rsa_check_privkey( &rsa ) != 0 ) { if( verbose != 0 ) mbedtls_printf( "failed\n" ); ret = 1; goto cleanup; } if( verbose != 0 ) mbedtls_printf( "passed\n PKCS#1 encryption : " ); memcpy( rsa_plaintext, RSA_PT, PT_LEN ); if( mbedtls_rsa_pkcs1_encrypt( &rsa, myrand, NULL, PT_LEN, rsa_plaintext, rsa_ciphertext ) != 0 ) { if( verbose != 0 ) mbedtls_printf( "failed\n" ); ret = 1; goto cleanup; } if( verbose != 0 ) mbedtls_printf( "passed\n PKCS#1 decryption : " ); if( mbedtls_rsa_pkcs1_decrypt( &rsa, myrand, NULL, &len, rsa_ciphertext, rsa_decrypted, sizeof(rsa_decrypted) ) != 0 ) { if( verbose != 0 ) mbedtls_printf( "failed\n" ); ret = 1; goto cleanup; } if( memcmp( rsa_decrypted, rsa_plaintext, len ) != 0 ) { if( verbose != 0 ) mbedtls_printf( "failed\n" ); ret = 1; goto cleanup; } if( verbose != 0 ) mbedtls_printf( "passed\n" ); #if defined(MBEDTLS_SHA1_C) if( verbose != 0 ) mbedtls_printf( " PKCS#1 data sign : " ); if( mbedtls_sha1( rsa_plaintext, PT_LEN, sha1sum ) != 0 ) { if( verbose != 0 ) mbedtls_printf( "failed\n" ); return( 1 ); } if( mbedtls_rsa_pkcs1_sign( &rsa, myrand, NULL, MBEDTLS_MD_SHA1, 0, sha1sum, rsa_ciphertext ) != 0 ) { if( verbose != 0 ) mbedtls_printf( "failed\n" ); ret = 1; goto cleanup; } if( verbose != 0 ) mbedtls_printf( "passed\n PKCS#1 sig. verify: " ); if( mbedtls_rsa_pkcs1_verify( &rsa, MBEDTLS_MD_SHA1, 0, sha1sum, rsa_ciphertext ) != 0 ) { if( verbose != 0 ) mbedtls_printf( "failed\n" ); ret = 1; goto cleanup; } if( verbose != 0 ) mbedtls_printf( "passed\n" ); #endif /* MBEDTLS_SHA1_C */ if( verbose != 0 ) mbedtls_printf( "\n" ); cleanup: mbedtls_mpi_free( &K ); mbedtls_rsa_free( &rsa ); #else /* MBEDTLS_PKCS1_V15 */ ((void) verbose); #endif /* MBEDTLS_PKCS1_V15 */ return( ret ); } #endif /* MBEDTLS_SELF_TEST */ #endif /* MBEDTLS_RSA_C */