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mbedtls/library/rsa.c
Janos Follath 6bcbc925bf Extend blinding to RSA result check 
Signed-off-by: Janos Follath <janos.follath@arm.com>
2024-01-22 15:33:19 +00:00

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/*
* The RSA public-key cryptosystem
*
* Copyright The Mbed TLS Contributors
* SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later
*/
/*
* 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 "bignum_core.h"
#include "rsa_alt_helpers.h"
#include "mbedtls/oid.h"
#include "mbedtls/platform_util.h"
#include "mbedtls/error.h"
#include "constant_time_internal.h"
#include "mbedtls/constant_time.h"
#include "md_psa.h"
#include <string.h>
#if defined(MBEDTLS_PKCS1_V15) && !defined(__OpenBSD__) && !defined(__NetBSD__)
#include <stdlib.h>
#endif
#include "mbedtls/platform.h"
#if defined(MBEDTLS_PKCS1_V15) && defined(MBEDTLS_RSA_C) && !defined(MBEDTLS_RSA_ALT)
/** This function performs the unpadding part of a PKCS#1 v1.5 decryption
* operation (EME-PKCS1-v1_5 decoding).
*
* \note The return value from this function is a sensitive value
* (this is unusual). #MBEDTLS_ERR_RSA_OUTPUT_TOO_LARGE shouldn't happen
* in a well-written application, but 0 vs #MBEDTLS_ERR_RSA_INVALID_PADDING
* is often a situation that an attacker can provoke and leaking which
* one is the result is precisely the information the attacker wants.
*
* \param input The input buffer which is the payload inside PKCS#1v1.5
* encryption padding, called the "encoded message EM"
* by the terminology.
* \param ilen The length of the payload in the \p input buffer.
* \param output The buffer for the payload, called "message M" by the
* PKCS#1 terminology. This must be a writable buffer of
* length \p output_max_len bytes.
* \param olen The address at which to store the length of
* the payload. This must not be \c NULL.
* \param output_max_len The length in bytes of the output buffer \p output.
*
* \return \c 0 on success.
* \return #MBEDTLS_ERR_RSA_OUTPUT_TOO_LARGE
* The output buffer is too small for the unpadded payload.
* \return #MBEDTLS_ERR_RSA_INVALID_PADDING
* The input doesn't contain properly formatted padding.
*/
static int mbedtls_ct_rsaes_pkcs1_v15_unpadding(unsigned char *input,
size_t ilen,
unsigned char *output,
size_t output_max_len,
size_t *olen)
{
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
size_t i, plaintext_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;
mbedtls_ct_condition_t bad;
mbedtls_ct_condition_t pad_done;
size_t plaintext_size = 0;
mbedtls_ct_condition_t output_too_large;
plaintext_max_size = (output_max_len > ilen - 11) ? ilen - 11
: output_max_len;
/* Check and get padding length in constant time and constant
* memory trace. The first byte must be 0. */
bad = mbedtls_ct_bool(input[0]);
/* Decode EME-PKCS1-v1_5 padding: 0x00 || 0x02 || PS || 0x00
* where PS must be at least 8 nonzero bytes. */
bad = mbedtls_ct_bool_or(bad, mbedtls_ct_uint_ne(input[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. */
pad_done = MBEDTLS_CT_FALSE;
for (i = 2; i < ilen; i++) {
mbedtls_ct_condition_t found = mbedtls_ct_uint_eq(input[i], 0);
pad_done = mbedtls_ct_bool_or(pad_done, found);
pad_count += mbedtls_ct_uint_if_else_0(mbedtls_ct_bool_not(pad_done), 1);
}
/* If pad_done is still zero, there's no data, only unfinished padding. */
bad = mbedtls_ct_bool_or(bad, mbedtls_ct_bool_not(pad_done));
/* There must be at least 8 bytes of padding. */
bad = mbedtls_ct_bool_or(bad, mbedtls_ct_uint_gt(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 = mbedtls_ct_uint_if(
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 = mbedtls_ct_uint_gt(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 = mbedtls_ct_error_if(
bad,
MBEDTLS_ERR_RSA_INVALID_PADDING,
mbedtls_ct_error_if_else_0(output_too_large, MBEDTLS_ERR_RSA_OUTPUT_TOO_LARGE)
);
/* 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. */
mbedtls_ct_zeroize_if(mbedtls_ct_bool_or(bad, output_too_large), input + 11, ilen - 11);
/* 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 = mbedtls_ct_uint_if(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. */
mbedtls_ct_memmove_left(input + 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, input + 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;
return ret;
}
#endif /* MBEDTLS_PKCS1_V15 && MBEDTLS_RSA_C && ! MBEDTLS_RSA_ALT */
#if !defined(MBEDTLS_RSA_ALT)
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;
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;
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;
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;
/* 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;
/* 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;
/* 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)
{
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 defined(MBEDTLS_PKCS1_V21)
if ((padding == MBEDTLS_RSA_PKCS_V21) &&
(hash_id != MBEDTLS_MD_NONE)) {
/* Just make sure this hash is supported in this build. */
if (mbedtls_md_info_from_type(hash_id) == NULL) {
return MBEDTLS_ERR_RSA_INVALID_PADDING;
}
}
#endif /* MBEDTLS_PKCS1_V21 */
ctx->padding = padding;
ctx->hash_id = hash_id;
return 0;
}
/*
* Get padding mode of initialized RSA context
*/
int mbedtls_rsa_get_padding_mode(const mbedtls_rsa_context *ctx)
{
return ctx->padding;
}
/*
* Get hash identifier of mbedtls_md_type_t type
*/
int mbedtls_rsa_get_md_alg(const mbedtls_rsa_context *ctx)
{
return ctx->hash_id;
}
/*
* 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;
/*
* 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 (exponent < 3 || nbits % 2 != 0) {
ret = MBEDTLS_ERR_RSA_BAD_INPUT_DATA;
goto cleanup;
}
if (nbits < MBEDTLS_RSA_GEN_KEY_MIN_BITS) {
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)
{
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)
{
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)
{
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;
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;
}
/*
* Unblind
* T = T * Vf mod N
*/
int rsa_unblind(mbedtls_mpi* T, mbedtls_mpi* Vf, mbedtls_mpi* N)
{
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
const mbedtls_mpi_uint mm = mbedtls_mpi_core_montmul_init(N->p);
const size_t nlimbs = N->n;
const size_t tlimbs = mbedtls_mpi_core_montmul_working_limbs(nlimbs);
mbedtls_mpi RR, M_T;
mbedtls_mpi_init(&RR);
mbedtls_mpi_init(&M_T);
MBEDTLS_MPI_CHK(mbedtls_mpi_core_get_mont_r2_unsafe(&RR, N));
MBEDTLS_MPI_CHK(mbedtls_mpi_grow(&M_T, tlimbs));
MBEDTLS_MPI_CHK(mbedtls_mpi_grow(T, nlimbs));
MBEDTLS_MPI_CHK(mbedtls_mpi_grow(Vf, nlimbs));
// T = T * R mod N
mbedtls_mpi_core_to_mont_rep(T->p, T->p, N->p, nlimbs, mm, RR.p, M_T.p);
// T = T * Vf mod N
mbedtls_mpi_core_montmul(T->p, T->p, Vf->p, nlimbs, N->p, nlimbs, mm, M_T.p);
cleanup:
mbedtls_mpi_free(&RR);
mbedtls_mpi_free(&M_T);
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 average.
*
* For example with 28 byte blinding to achieve 2 collisions the adversary has
* to make 2^112 observations on average.
*
* (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;
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;
}
/*
* 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));
MBEDTLS_MPI_CHK(mbedtls_mpi_copy(&I, &T));
/*
* 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 */
/* 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;
}
/*
* Unblind
* T = T * Vf mod N
*/
MBEDTLS_MPI_CHK(rsa_unblind(&T, &ctx->Vf, &ctx->N));
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_alg message digest to use
*/
static int mgf_mask(unsigned char *dst, size_t dlen, unsigned char *src,
size_t slen, mbedtls_md_type_t md_alg)
{
unsigned char counter[4];
unsigned char *p;
unsigned int hlen;
size_t i, use_len;
unsigned char mask[MBEDTLS_MD_MAX_SIZE];
int ret = 0;
const mbedtls_md_info_t *md_info;
mbedtls_md_context_t md_ctx;
mbedtls_md_init(&md_ctx);
md_info = mbedtls_md_info_from_type(md_alg);
if (md_info == NULL) {
return MBEDTLS_ERR_RSA_BAD_INPUT_DATA;
}
mbedtls_md_init(&md_ctx);
if ((ret = mbedtls_md_setup(&md_ctx, md_info, 0)) != 0) {
goto exit;
}
hlen = mbedtls_md_get_size(md_info);
memset(mask, 0, sizeof(mask));
memset(counter, 0, 4);
/* 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));
mbedtls_md_free(&md_ctx);
return ret;
}
/**
* Generate Hash(M') as in RFC 8017 page 43 points 5 and 6.
*
* \param hash the input hash
* \param hlen length of the input hash
* \param salt the input salt
* \param slen length of the input salt
* \param out the output buffer - must be large enough for \p md_alg
* \param md_alg message digest to use
*/
static int hash_mprime(const unsigned char *hash, size_t hlen,
const unsigned char *salt, size_t slen,
unsigned char *out, mbedtls_md_type_t md_alg)
{
const unsigned char zeros[8] = { 0, 0, 0, 0, 0, 0, 0, 0 };
mbedtls_md_context_t md_ctx;
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
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;
}
mbedtls_md_init(&md_ctx);
if ((ret = mbedtls_md_setup(&md_ctx, md_info, 0)) != 0) {
goto exit;
}
if ((ret = mbedtls_md_starts(&md_ctx)) != 0) {
goto exit;
}
if ((ret = mbedtls_md_update(&md_ctx, zeros, sizeof(zeros))) != 0) {
goto exit;
}
if ((ret = mbedtls_md_update(&md_ctx, hash, hlen)) != 0) {
goto exit;
}
if ((ret = mbedtls_md_update(&md_ctx, salt, slen)) != 0) {
goto exit;
}
if ((ret = mbedtls_md_finish(&md_ctx, out)) != 0) {
goto exit;
}
exit:
mbedtls_md_free(&md_ctx);
return ret;
}
/**
* Compute a hash.
*
* \param md_alg algorithm to use
* \param input input message to hash
* \param ilen input length
* \param output the output buffer - must be large enough for \p md_alg
*/
static int compute_hash(mbedtls_md_type_t md_alg,
const unsigned char *input, size_t ilen,
unsigned char *output)
{
const mbedtls_md_info_t *md_info;
md_info = mbedtls_md_info_from_type(md_alg);
if (md_info == NULL) {
return MBEDTLS_ERR_RSA_BAD_INPUT_DATA;
}
return mbedtls_md(md_info, input, ilen, output);
}
#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;
if (f_rng == NULL) {
return MBEDTLS_ERR_RSA_BAD_INPUT_DATA;
}
hlen = mbedtls_md_get_size_from_type((mbedtls_md_type_t) ctx->hash_id);
if (hlen == 0) {
return MBEDTLS_ERR_RSA_BAD_INPUT_DATA;
}
olen = ctx->len;
/* 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 */
ret = compute_hash((mbedtls_md_type_t) ctx->hash_id, label, label_len, p);
if (ret != 0) {
return ret;
}
p += hlen;
p += olen - 2 * hlen - 2 - ilen;
*p++ = 1;
if (ilen != 0) {
memcpy(p, input, ilen);
}
/* maskedDB: Apply dbMask to DB */
if ((ret = mgf_mask(output + hlen + 1, olen - hlen - 1, output + 1, hlen,
(mbedtls_md_type_t) ctx->hash_id)) != 0) {
return ret;
}
/* maskedSeed: Apply seedMask to seed */
if ((ret = mgf_mask(output + 1, hlen, output + hlen + 1, olen - hlen - 1,
(mbedtls_md_type_t) ctx->hash_id)) != 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;
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)
{
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;
mbedtls_ct_condition_t bad, in_padding;
unsigned char buf[MBEDTLS_MPI_MAX_SIZE];
unsigned char lhash[MBEDTLS_MD_MAX_SIZE];
unsigned int hlen;
/*
* 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;
}
hlen = mbedtls_md_get_size_from_type((mbedtls_md_type_t) ctx->hash_id);
if (hlen == 0) {
return MBEDTLS_ERR_RSA_BAD_INPUT_DATA;
}
// 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
*/
/* seed: Apply seedMask to maskedSeed */
if ((ret = mgf_mask(buf + 1, hlen, buf + hlen + 1, ilen - hlen - 1,
(mbedtls_md_type_t) ctx->hash_id)) != 0 ||
/* DB: Apply dbMask to maskedDB */
(ret = mgf_mask(buf + hlen + 1, ilen - hlen - 1, buf + 1, hlen,
(mbedtls_md_type_t) ctx->hash_id)) != 0) {
goto cleanup;
}
/* Generate lHash */
ret = compute_hash((mbedtls_md_type_t) ctx->hash_id,
label, label_len, lhash);
if (ret != 0) {
goto cleanup;
}
/*
* Check contents, in "constant-time"
*/
p = buf;
bad = mbedtls_ct_bool(*p++); /* First byte must be 0 */
p += hlen; /* Skip seed */
/* Check lHash */
bad = mbedtls_ct_bool_or(bad, mbedtls_ct_bool(mbedtls_ct_memcmp(lhash, p, hlen)));
p += hlen;
/* Get zero-padding len, but always read till end of buffer
* (minus one, for the 01 byte) */
pad_len = 0;
in_padding = MBEDTLS_CT_TRUE;
for (i = 0; i < ilen - 2 * hlen - 2; i++) {
in_padding = mbedtls_ct_bool_and(in_padding, mbedtls_ct_uint_eq(p[i], 0));
pad_len += mbedtls_ct_uint_if_else_0(in_padding, 1);
}
p += pad_len;
bad = mbedtls_ct_bool_or(bad, mbedtls_ct_uint_ne(*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 != MBEDTLS_CT_FALSE) {
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)
/*
* 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;
unsigned char buf[MBEDTLS_MPI_MAX_SIZE];
ilen = ctx->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;
}
ret = mbedtls_ct_rsaes_pkcs1_v15_unpadding(buf, ilen,
output, output_max_len, olen);
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)
{
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;
if ((md_alg != MBEDTLS_MD_NONE || hashlen != 0) && hash == NULL) {
return MBEDTLS_ERR_RSA_BAD_INPUT_DATA;
}
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 */
size_t exp_hashlen = mbedtls_md_get_size_from_type(md_alg);
if (exp_hashlen == 0) {
return MBEDTLS_ERR_RSA_BAD_INPUT_DATA;
}
if (hashlen != exp_hashlen) {
return MBEDTLS_ERR_RSA_BAD_INPUT_DATA;
}
}
hlen = mbedtls_md_get_size_from_type((mbedtls_md_type_t) ctx->hash_id);
if (hlen == 0) {
return MBEDTLS_ERR_RSA_BAD_INPUT_DATA;
}
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;
/* Generate H = Hash( M' ) */
ret = hash_mprime(hash, hashlen, salt, slen, p, (mbedtls_md_type_t) ctx->hash_id);
if (ret != 0) {
return ret;
}
/* Compensate for boundary condition when applying mask */
if (msb % 8 == 0) {
offset = 1;
}
/* maskedDB: Apply dbMask to DB */
ret = mgf_mask(sig + offset, olen - hlen - 1 - offset, p, hlen,
(mbedtls_md_type_t) ctx->hash_id);
if (ret != 0) {
return ret;
}
msb = mbedtls_mpi_bitlen(&ctx->N) - 1;
sig[0] &= 0xFF >> (olen * 8 - msb);
p += hlen;
*p++ = 0xBC;
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. Must match md_alg if that's not 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.
* - 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) {
unsigned char md_size = mbedtls_md_get_size_from_type(md_alg);
if (md_size == 0) {
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;
}
if (hashlen != md_size) {
return MBEDTLS_ERR_RSA_BAD_INPUT_DATA;
}
/* 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;
if ((md_alg != MBEDTLS_MD_NONE || hashlen != 0) && hash == NULL) {
return MBEDTLS_ERR_RSA_BAD_INPUT_DATA;
}
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_ct_memcmp(verif, sig, ctx->len) != 0) {
ret = MBEDTLS_ERR_RSA_PRIVATE_FAILED;
goto cleanup;
}
memcpy(sig, sig_try, ctx->len);
cleanup:
mbedtls_zeroize_and_free(sig_try, ctx->len);
mbedtls_zeroize_and_free(verif, ctx->len);
if (ret != 0) {
memset(sig, '!', ctx->len);
}
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)
{
if ((md_alg != MBEDTLS_MD_NONE || hashlen != 0) && hash == NULL) {
return MBEDTLS_ERR_RSA_BAD_INPUT_DATA;
}
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 int hlen;
size_t observed_salt_len, msb;
unsigned char buf[MBEDTLS_MPI_MAX_SIZE] = { 0 };
if ((md_alg != MBEDTLS_MD_NONE || hashlen != 0) && hash == NULL) {
return MBEDTLS_ERR_RSA_BAD_INPUT_DATA;
}
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 */
size_t exp_hashlen = mbedtls_md_get_size_from_type(md_alg);
if (exp_hashlen == 0) {
return MBEDTLS_ERR_RSA_BAD_INPUT_DATA;
}
if (hashlen != exp_hashlen) {
return MBEDTLS_ERR_RSA_BAD_INPUT_DATA;
}
}
hlen = mbedtls_md_get_size_from_type(mgf1_hash_id);
if (hlen == 0) {
return MBEDTLS_ERR_RSA_BAD_INPUT_DATA;
}
/*
* 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;
ret = mgf_mask(p, siglen - hlen - 1, hash_start, hlen, mgf1_hash_id);
if (ret != 0) {
return ret;
}
buf[0] &= 0xFF >> (siglen * 8 - msb);
while (p < hash_start - 1 && *p == 0) {
p++;
}
if (*p++ != 0x01) {
return MBEDTLS_ERR_RSA_INVALID_PADDING;
}
observed_salt_len = hash_start - p;
if (expected_salt_len != MBEDTLS_RSA_SALT_LEN_ANY &&
observed_salt_len != (size_t) expected_salt_len) {
return MBEDTLS_ERR_RSA_INVALID_PADDING;
}
/*
* Generate H = Hash( M' )
*/
ret = hash_mprime(hash, hashlen, p, observed_salt_len,
result, mgf1_hash_id);
if (ret != 0) {
return ret;
}
if (memcmp(hash_start, result, hlen) != 0) {
return MBEDTLS_ERR_RSA_VERIFY_FAILED;
}
return 0;
}
/*
* 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;
if ((md_alg != MBEDTLS_MD_NONE || hashlen != 0) && hash == NULL) {
return MBEDTLS_ERR_RSA_BAD_INPUT_DATA;
}
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;
if ((md_alg != MBEDTLS_MD_NONE || hashlen != 0) && hash == NULL) {
return MBEDTLS_ERR_RSA_BAD_INPUT_DATA;
}
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_ct_memcmp(encoded, encoded_expected,
sig_len)) != 0) {
ret = MBEDTLS_ERR_RSA_VERIFY_FAILED;
goto cleanup;
}
cleanup:
if (encoded != NULL) {
mbedtls_zeroize_and_free(encoded, sig_len);
}
if (encoded_expected != NULL) {
mbedtls_zeroize_and_free(encoded_expected, sig_len);
}
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)
{
if ((md_alg != MBEDTLS_MD_NONE || hashlen != 0) && hash == NULL) {
return MBEDTLS_ERR_RSA_BAD_INPUT_DATA;
}
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;
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/md.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_MD_CAN_SHA1)
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_MD_CAN_SHA1)
if (verbose != 0) {
mbedtls_printf(" PKCS#1 data sign : ");
}
if (mbedtls_md(mbedtls_md_info_from_type(MBEDTLS_MD_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, 20,
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, 20,
sha1sum, rsa_ciphertext) != 0) {
if (verbose != 0) {
mbedtls_printf("failed\n");
}
ret = 1;
goto cleanup;
}
if (verbose != 0) {
mbedtls_printf("passed\n");
}
#endif /* MBEDTLS_MD_CAN_SHA1 */
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 */
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