Get rid of large stack buffers in PSA sign wrapper
This commit is contained in:
Manuel Pégourié-Gonnard
parent
2f2b396b7a
commit
d8454bc515
1 changed files with 101 additions and 79 deletions
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@ -761,88 +761,13 @@ static int pk_opaque_can_do( mbedtls_pk_type_t type )
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type == MBEDTLS_PK_ECDSA );
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}
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/* Like mbedtls_asn1_write_mpi, but from a buffer */
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static int asn1_write_mpibuf( unsigned char **p, unsigned char *start,
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const unsigned char *src, size_t slen )
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/* translate PSA errors to best PK approximation */
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static int pk_err_from_psa( psa_status_t status )
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{
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int ret;
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size_t len = 0;
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if( (size_t)( *p - start ) < slen )
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return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL );
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len = slen;
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*p -= len;
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memcpy( *p, src, len );
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if( **p & 0x80 )
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{
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if( *p - start < 1 )
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return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL );
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*--(*p) = 0x00;
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len += 1;
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}
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MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( p, start, len ) );
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MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( p, start, MBEDTLS_ASN1_INTEGER ) );
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return( (int) len );
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}
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/* Transcode signature from PSA format to ASN.1 sequence.
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* See ecdsa_signature_to_asn1 in ecdsa.c.
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*
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* [in] sig: the signature in PSA format
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* [in/out] sig_len: signature length pre- and post-transcoding
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* [out] dst: the signature in ASN.1 format
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*/
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static int pk_ecdsa_sig_asn1_from_psa( const unsigned char *sig, size_t *sig_len,
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unsigned char *dst )
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{
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int ret;
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unsigned char buf[MBEDTLS_ECDSA_MAX_LEN];
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unsigned char *p = buf + sizeof( buf );
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size_t len = 0;
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const size_t mpi_len = *sig_len / 2;
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MBEDTLS_ASN1_CHK_ADD( len, asn1_write_mpibuf( &p, buf, sig + mpi_len, mpi_len ) );
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MBEDTLS_ASN1_CHK_ADD( len, asn1_write_mpibuf( &p, buf, sig, mpi_len ) );
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MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( &p, buf, len ) );
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MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( &p, buf,
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MBEDTLS_ASN1_CONSTRUCTED | MBEDTLS_ASN1_SEQUENCE ) );
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memcpy( dst, p, len );
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*sig_len = len;
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return( 0 );
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}
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static int pk_opaque_sign_wrap( void *ctx, mbedtls_md_type_t md_alg,
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const unsigned char *hash, size_t hash_len,
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unsigned char *sig, size_t *sig_len,
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int (*f_rng)(void *, unsigned char *, size_t), void *p_rng )
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{
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const psa_key_slot_t *key = (const psa_key_slot_t *) ctx;
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psa_status_t status;
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psa_algorithm_t alg = PSA_ALG_ECDSA( mbedtls_psa_translate_md( md_alg ) );
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/* PSA needs a buffer of know size */
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unsigned char buf[2 * MBEDTLS_ECP_MAX_BYTES];
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const size_t buf_len = sizeof( buf );
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/* PSA has its own RNG */
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(void) f_rng;
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(void) p_rng;
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status = psa_asymmetric_sign( *key, alg, hash, hash_len,
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buf, buf_len, sig_len );
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/* translate errors to best approximation */
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switch( status )
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{
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case PSA_SUCCESS:
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break; /* don't return now */
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return( 0 );
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case PSA_ERROR_NOT_SUPPORTED:
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return( MBEDTLS_ERR_PK_FEATURE_UNAVAILABLE );
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case PSA_ERROR_INSUFFICIENT_MEMORY:
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@ -858,12 +783,109 @@ static int pk_opaque_sign_wrap( void *ctx, mbedtls_md_type_t md_alg,
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default: /* should never happen */
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return( MBEDTLS_ERR_PK_HW_ACCEL_FAILED );
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}
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}
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pk_ecdsa_sig_asn1_from_psa( buf, sig_len, sig );
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/*
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* Like mbedtls_asn1_write_mpi(), but from a buffer.
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*
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* p: pointer to the end of the output buffer
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* start: start of the output buffer, and also of the mpi to write at the end
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* n_len: length ot the mpi to read from start
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*/
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static int asn1_write_mpibuf( unsigned char **p, unsigned char *start,
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size_t n_len )
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{
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int ret;
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size_t len = 0;
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if( (size_t)( *p - start ) < n_len )
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return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL );
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len = n_len;
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*p -= len;
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memmove( *p, start, len );
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/* if the msb is 1, ASN.1 requires that we prepend a 0.
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* we're never called with n_len == 0, so we can always read back a byte */
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if( **p & 0x80 )
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{
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if( *p - start < 1 )
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return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL );
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*--(*p) = 0x00;
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len += 1;
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}
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MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( p, start, len ) );
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MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( p, start,
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MBEDTLS_ASN1_INTEGER ) );
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return( (int) len );
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}
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/* Transcode signature from PSA format to ASN.1 sequence.
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* See ecdsa_signature_to_asn1 in ecdsa.c, but with byte buffers instead of
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* MPIs, and in-place.
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*
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* [in/out] sig: the signature pre- and post-transcoding
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* [in/out] sig_len: signature length pre- and post-transcoding
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* [int] buf_len: the available size the in/out buffer
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*/
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static int pk_ecdsa_sig_asn1_from_psa( unsigned char *sig, size_t *sig_len,
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size_t buf_len )
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{
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int ret;
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size_t len = 0;
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const size_t rs_len = *sig_len / 2;
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unsigned char *p = sig + buf_len;
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MBEDTLS_ASN1_CHK_ADD( len, asn1_write_mpibuf( &p, sig + rs_len, rs_len ) );
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MBEDTLS_ASN1_CHK_ADD( len, asn1_write_mpibuf( &p, sig, rs_len ) );
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MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( &p, sig, len ) );
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MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( &p, sig,
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MBEDTLS_ASN1_CONSTRUCTED | MBEDTLS_ASN1_SEQUENCE ) );
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memmove( sig, p, len );
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*sig_len = len;
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return( 0 );
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}
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static int pk_opaque_sign_wrap( void *ctx, mbedtls_md_type_t md_alg,
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const unsigned char *hash, size_t hash_len,
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unsigned char *sig, size_t *sig_len,
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int (*f_rng)(void *, unsigned char *, size_t), void *p_rng )
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{
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const psa_key_slot_t *key = (const psa_key_slot_t *) ctx;
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psa_algorithm_t alg = PSA_ALG_ECDSA( mbedtls_psa_translate_md( md_alg ) );
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size_t bits, buf_len;
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psa_status_t status;
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/* PSA has its own RNG */
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(void) f_rng;
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(void) p_rng;
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/* PSA needs an output buffer of known size, but our API doesn't provide
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* that information. Assume that the buffer is large enough for a
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* maximal-length signature with that key (otherwise the application is
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* buggy anyway). */
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status = psa_get_key_information( *key, NULL, &bits );
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if( status != PSA_SUCCESS )
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return( pk_err_from_psa( status ) );
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buf_len = MBEDTLS_ECDSA_MAX_SIG_LEN( bits );
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/* make the signature */
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status = psa_asymmetric_sign( *key, alg, hash, hash_len,
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sig, buf_len, sig_len );
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if( status != PSA_SUCCESS )
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return( pk_err_from_psa( status ) );
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/* transcode it to ASN.1 sequence */
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return( pk_ecdsa_sig_asn1_from_psa( sig, sig_len, buf_len ) );
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}
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const mbedtls_pk_info_t mbedtls_pk_opaque_info = {
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MBEDTLS_PK_OPAQUE,
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"Opaque",
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