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Add sanity checks for the mbedtls_pk_sign output size

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mbedtls_pk_sign does not take the size of its output buffer as a
parameter. We guarantee that MBEDTLS_PK_SIGNATURE_MAX_SIZE is enough.
For RSA and ECDSA signatures made in software, this is ensured by the
way MBEDTLS_PK_SIGNATURE_MAX_SIZE is defined at compile time. For
signatures made through RSA-alt and PSA, this is not guaranteed
robustly at compile time, but we can test it at runtime, so do that.
This commit is contained in:
Gilles Peskine 2019-11-05 17:31:36 +01:00
parent b22a24b23f
commit f48d6f2320
1 changed files with 4 additions and 0 deletions
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4
library/pk_wrap.c
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@ -774,6 +774,8 @@ static int rsa_alt_sign_wrap( void *ctx, mbedtls_md_type_t md_alg,
#endif /* SIZE_MAX > UINT_MAX */
*sig_len = rsa_alt->key_len_func( rsa_alt->key );
if( *sig_len > MBEDTLS_PK_SIGNATURE_MAX_SIZE )
return( MBEDTLS_ERR_PK_BAD_INPUT_DATA );
return( rsa_alt->sign_func( rsa_alt->key, f_rng, p_rng, MBEDTLS_RSA_PRIVATE,
md_alg, (unsigned int) hash_len, hash, sig ) );
@ -1017,6 +1019,8 @@ static int pk_opaque_sign_wrap( void *ctx, mbedtls_md_type_t md_alg,
return( mbedtls_psa_err_translate_pk( status ) );
buf_len = MBEDTLS_ECDSA_MAX_SIG_LEN( psa_get_key_bits( &attributes ) );
psa_reset_key_attributes( &attributes );
if( *sig_len > MBEDTLS_PK_SIGNATURE_MAX_SIZE )
return( MBEDTLS_ERR_PK_BAD_INPUT_DATA );
/* make the signature */
status = psa_asymmetric_sign( *key, alg, hash, hash_len,