pk_wrap: reuse a static buffer for signature extraction
Use a buffer left over after importing a key to hold an extracted signature.
diff --git a/library/pk_wrap.c b/library/pk_wrap.c
index e33ea3f..46ffe4e 100644
--- a/library/pk_wrap.c
+++ b/library/pk_wrap.c
@@ -519,8 +519,8 @@
/*
* Convert a signature from an ASN.1 sequence of two integers
- * to a raw {r,s} buffer. Note: upon a successful call, the caller
- * takes ownership of the sig->p buffer.
+ * to a raw {r,s} buffer. Note: the provided sig buffer should be at least
+ * twice as big as int_size.
*/
static int extract_ecdsa_sig( unsigned char **p, const unsigned char *end,
mbedtls_asn1_buf *sig, size_t int_size )
@@ -532,9 +532,8 @@
return( MBEDTLS_ERR_ASN1_OUT_OF_DATA );
}
- sig->p = mbedtls_calloc( 2, int_size );
if( sig->p == NULL )
- return( MBEDTLS_ERR_ASN1_ALLOC_FAILED );
+ return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL );
sig->tag = **p;
@@ -561,8 +560,6 @@
return( 0 );
cleanup:
- mbedtls_free( sig->p );
- sig->p = NULL;
sig->len = 0;
sig->tag = 0;
return( ret );
@@ -640,12 +637,13 @@
mbedtls_pk_context key;
mbedtls_asn1_buf signature;
int key_len;
- const int buf_len = 30 + 2 * MBEDTLS_ECP_MAX_BYTES; // Equivalent of ECP_PUB_DER_MAX_BYTES
+ const unsigned buf_len = 30 + 2 * MBEDTLS_ECP_MAX_BYTES; // Equivalent of ECP_PUB_DER_MAX_BYTES
unsigned char buf[buf_len];
unsigned char *p = (unsigned char*) sig;
mbedtls_pk_info_t pk_info = mbedtls_eckey_info;
psa_algorithm_t psa_sig_md = mbedtls_psa_translate_md( md_alg );
psa_ecc_curve_t curve = mbedtls_ecc_group_to_psa ( ( (mbedtls_ecdsa_context *) ctx )->grp.id );
+ size_t signature_part_size = ( ( (mbedtls_ecdsa_context *) ctx ) ->grp.nbits + 7 ) / 8;
if( curve == 0 )
return( MBEDTLS_ERR_PK_BAD_INPUT_DATA );
@@ -660,22 +658,12 @@
psa_type = PSA_KEY_TYPE_ECC_PUBLIC_KEY( curve );
- if( ( ret = extract_ecdsa_sig( &p, p + sig_len, &signature,
- ( ( (mbedtls_ecdsa_context *) ctx )->grp.nbits + 7) / 8 ) ) != 0 )
- return( ret );
-
key_len = mbedtls_pk_write_pubkey_der( &key, buf, buf_len );
if( key_len <= 0 )
- {
- mbedtls_free( signature.p );
return( MBEDTLS_ERR_PK_BAD_INPUT_DATA );
- }
if( ( ret = mbedtls_psa_get_free_key_slot( &key_slot ) ) != PSA_SUCCESS )
- {
- mbedtls_free( signature.p );
return( mbedtls_psa_err_translate_pk( ret ) );
- }
psa_key_policy_init( &policy );
psa_key_policy_set_usage( &policy, PSA_KEY_USAGE_VERIFY, psa_sig_md );
@@ -692,6 +680,20 @@
goto cleanup;
}
+ /* Reuse the buffer of an already imported key */
+ if( 2 * signature_part_size > buf_len )
+ {
+ ret = MBEDTLS_ERR_PK_BAD_INPUT_DATA;
+ goto cleanup;
+ }
+ signature.p = buf;
+
+ if( ( ret = extract_ecdsa_sig( &p, p + sig_len, &signature,
+ signature_part_size ) ) != 0 )
+ {
+ goto cleanup;
+ }
+
if( psa_asymmetric_verify( key_slot, psa_sig_md,
hash, hash_len,
signature.p, signature.len )
@@ -704,7 +706,6 @@
cleanup:
psa_destroy_key( key_slot );
- mbedtls_free( signature.p );
return( ret );
}
#else /* MBEDTLS_USE_PSA_CRYPTO */