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Added sppecific test cases for mbedtls_rsa_rsassa_pss_sign_ext()

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- all positibe test cases were sampled from the CAVP test suite
  (SigGenPSS_186-2.txt, SigGenPSS_186-3.txt)
  Only kept one representative for each triple (modlen, sha, saltlen)
- two extra test cases were added to cover the maximum salt length
  (slen=olen-slen-2 and slen=(olen-slen-2)-1)
- in rsa.c, the salt intermediate buffer was too small to cover cases
  where slen > hlen. So reworked the code to generate the salt in the
  encoded message directly. This has the advantage to remove a memcpy
  and a memset.

Signed-off-by: Cédric Meuter <cedric.meuter@gmail.com>
This commit is contained in:
Cédric Meuter
2020-04-30 11:57:04 +02:00
parent a05cbecc90
commit 668a78d952
3 changed files with 164 additions and 8 deletions
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15
library/rsa.c
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@ -1799,7 +1799,7 @@ static int rsa_rsassa_pss_sign( mbedtls_rsa_context *ctx,
{
size_t olen;
unsigned char *p = sig;
unsigned char salt[MBEDTLS_MD_MAX_SIZE];
unsigned char *salt = NULL;
size_t slen, min_slen, hlen, offset = 0;
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
size_t msb;
@ -1867,15 +1867,16 @@ static int rsa_rsassa_pss_sign( mbedtls_rsa_context *ctx,
memset( sig, 0, olen );
/* Generate salt of length slen */
if( ( ret = f_rng( p_rng, salt, slen ) ) != 0 )
return( MBEDTLS_ERR_RSA_RNG_FAILED + ret );
/* 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;
memcpy( p, salt, slen );
/* Generate salt of length slen in place in the encoded message */
salt = p;
if( ( ret = f_rng( p_rng, salt, slen ) ) != 0 )
return( MBEDTLS_ERR_RSA_RNG_FAILED + ret );
p += slen;
mbedtls_md_init( &md_ctx );
@ -1909,8 +1910,6 @@ static int rsa_rsassa_pss_sign( mbedtls_rsa_context *ctx,
p += hlen;
*p++ = 0xBC;
mbedtls_platform_zeroize( salt, sizeof( salt ) );
exit:
mbedtls_md_free( &md_ctx );