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Add output size parameter to signature functions

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The functions mbedtls_pk_sign(), mbedtls_pk_sign_restartable(),
mbedtls_ecdsa_write_signature() and mbedtls_ecdsa_write_signature_restartable()
now take an extra parameter indicating the size of the output buffer for the
signature.

No change to RSA because for RSA, the output size is trivial to calculate.

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
This commit is contained in:
Gilles Peskine
2021-06-22 00:09:00 +02:00
parent 1fed4b8324
commit f00f152444
19 changed files with 131 additions and 81 deletions
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15
library/ecdsa.c
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@ -648,7 +648,8 @@ int mbedtls_ecdsa_verify( mbedtls_ecp_group *grp,
* Convert a signature (given by context) to ASN.1
*/
static int ecdsa_signature_to_asn1( const mbedtls_mpi *r, const mbedtls_mpi *s,
unsigned char *sig, size_t *slen )
unsigned char *sig, size_t sig_size,
size_t *slen )
{
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
unsigned char buf[MBEDTLS_ECDSA_MAX_LEN] = {0};
@ -662,6 +663,9 @@ static int ecdsa_signature_to_asn1( const mbedtls_mpi *r, const mbedtls_mpi *s,
MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( &p, buf,
MBEDTLS_ASN1_CONSTRUCTED | MBEDTLS_ASN1_SEQUENCE ) );
if( len > sig_size )
return( MBEDTLS_ERR_ECP_BUFFER_TOO_SMALL );
memcpy( sig, p, len );
*slen = len;
@ -674,7 +678,7 @@ static int ecdsa_signature_to_asn1( const mbedtls_mpi *r, const mbedtls_mpi *s,
int mbedtls_ecdsa_write_signature_restartable( mbedtls_ecdsa_context *ctx,
mbedtls_md_type_t md_alg,
const unsigned char *hash, size_t hlen,
unsigned char *sig, size_t *slen,
unsigned char *sig, size_t sig_size, size_t *slen,
int (*f_rng)(void *, unsigned char *, size_t),
void *p_rng,
mbedtls_ecdsa_restart_ctx *rs_ctx )
@ -712,7 +716,7 @@ int mbedtls_ecdsa_write_signature_restartable( mbedtls_ecdsa_context *ctx,
#endif /* MBEDTLS_ECDSA_SIGN_ALT */
#endif /* MBEDTLS_ECDSA_DETERMINISTIC */
MBEDTLS_MPI_CHK( ecdsa_signature_to_asn1( &r, &s, sig, slen ) );
MBEDTLS_MPI_CHK( ecdsa_signature_to_asn1( &r, &s, sig, sig_size, slen ) );
cleanup:
mbedtls_mpi_free( &r );
@ -727,7 +731,7 @@ cleanup:
int mbedtls_ecdsa_write_signature( mbedtls_ecdsa_context *ctx,
mbedtls_md_type_t md_alg,
const unsigned char *hash, size_t hlen,
unsigned char *sig, size_t *slen,
unsigned char *sig, size_t sig_size, size_t *slen,
int (*f_rng)(void *, unsigned char *, size_t),
void *p_rng )
{
@ -736,7 +740,8 @@ int mbedtls_ecdsa_write_signature( mbedtls_ecdsa_context *ctx,
ECDSA_VALIDATE_RET( sig != NULL );
ECDSA_VALIDATE_RET( slen != NULL );
return( mbedtls_ecdsa_write_signature_restartable(
ctx, md_alg, hash, hlen, sig, slen, f_rng, p_rng, NULL ) );
ctx, md_alg, hash, hlen, sig, sig_size, slen,
f_rng, p_rng, NULL ) );
}
/*