Don't pass zero to rsa_complete() as a param
When parsing a PKCS#1 RSAPrivateKey structure, all parameters are always
present. After importing them, we need to call rsa_complete() for the sake of
alternative implementations. That function interprets zero as a signal for
"this parameter was not provided". As that's never the case, we mustn't pass
any zero value to that function, so we need to explicitly check for it.
diff --git a/library/pkparse.c b/library/pkparse.c
index 7df30fe..7fb24e8 100644
--- a/library/pkparse.c
+++ b/library/pkparse.c
@@ -679,6 +679,32 @@
#if defined(MBEDTLS_RSA_C)
/*
+ * Wrapper around mbedtls_asn1_get_mpi() that rejects zero.
+ *
+ * The value zero is:
+ * - never a valid value for an RSA parameter
+ * - interpreted as "omitted, please reconstruct" by mbedtls_rsa_complete().
+ *
+ * Since values can't be omitted in PKCS#1, passing a zero value to
+ * rsa_complete() would be incorrect, so reject zero values early.
+ */
+static int asn1_get_nonzero_mpi( unsigned char **p,
+ const unsigned char *end,
+ mbedtls_mpi *X )
+{
+ int ret;
+
+ ret = mbedtls_asn1_get_mpi( p, end, X );
+ if( ret != 0 )
+ return( ret );
+
+ if( mbedtls_mpi_cmp_int( X, 0 ) == 0 )
+ return( MBEDTLS_ERR_PK_KEY_INVALID_FORMAT );
+
+ return( 0 );
+}
+
+/*
* Parse a PKCS#1 encoded private RSA key
*/
static int pk_parse_key_pkcs1_der( mbedtls_rsa_context *rsa,
@@ -730,44 +756,34 @@
}
/* Import N */
- if( ( ret = mbedtls_asn1_get_tag( &p, end, &len,
- MBEDTLS_ASN1_INTEGER ) ) != 0 ||
- ( ret = mbedtls_rsa_import_raw( rsa, p, len, NULL, 0, NULL, 0,
- NULL, 0, NULL, 0 ) ) != 0 )
+ if( ( ret = asn1_get_nonzero_mpi( &p, end, &T ) ) != 0 ||
+ ( ret = mbedtls_rsa_import( rsa, &T, NULL, NULL,
+ NULL, NULL ) ) != 0 )
goto cleanup;
- p += len;
/* Import E */
- if( ( ret = mbedtls_asn1_get_tag( &p, end, &len,
- MBEDTLS_ASN1_INTEGER ) ) != 0 ||
- ( ret = mbedtls_rsa_import_raw( rsa, NULL, 0, NULL, 0, NULL, 0,
- NULL, 0, p, len ) ) != 0 )
+ if( ( ret = asn1_get_nonzero_mpi( &p, end, &T ) ) != 0 ||
+ ( ret = mbedtls_rsa_import( rsa, NULL, NULL, NULL,
+ NULL, &T ) ) != 0 )
goto cleanup;
- p += len;
/* Import D */
- if( ( ret = mbedtls_asn1_get_tag( &p, end, &len,
- MBEDTLS_ASN1_INTEGER ) ) != 0 ||
- ( ret = mbedtls_rsa_import_raw( rsa, NULL, 0, NULL, 0, NULL, 0,
- p, len, NULL, 0 ) ) != 0 )
+ if( ( ret = asn1_get_nonzero_mpi( &p, end, &T ) ) != 0 ||
+ ( ret = mbedtls_rsa_import( rsa, NULL, NULL, NULL,
+ &T, NULL ) ) != 0 )
goto cleanup;
- p += len;
/* Import P */
- if( ( ret = mbedtls_asn1_get_tag( &p, end, &len,
- MBEDTLS_ASN1_INTEGER ) ) != 0 ||
- ( ret = mbedtls_rsa_import_raw( rsa, NULL, 0, p, len, NULL, 0,
- NULL, 0, NULL, 0 ) ) != 0 )
+ if( ( ret = asn1_get_nonzero_mpi( &p, end, &T ) ) != 0 ||
+ ( ret = mbedtls_rsa_import( rsa, NULL, &T, NULL,
+ NULL, NULL ) ) != 0 )
goto cleanup;
- p += len;
/* Import Q */
- if( ( ret = mbedtls_asn1_get_tag( &p, end, &len,
- MBEDTLS_ASN1_INTEGER ) ) != 0 ||
- ( ret = mbedtls_rsa_import_raw( rsa, NULL, 0, NULL, 0, p, len,
- NULL, 0, NULL, 0 ) ) != 0 )
+ if( ( ret = asn1_get_nonzero_mpi( &p, end, &T ) ) != 0 ||
+ ( ret = mbedtls_rsa_import( rsa, NULL, NULL, &T,
+ NULL, NULL ) ) != 0 )
goto cleanup;
- p += len;
#if !defined(MBEDTLS_RSA_NO_CRT)
/*
@@ -782,22 +798,25 @@
*/
/* Import DP */
- if( ( ret = mbedtls_asn1_get_mpi( &p, end, &rsa->DP ) ) != 0)
+ if( ( ret = asn1_get_nonzero_mpi( &p, end, &T ) ) != 0 ||
+ ( ret = mbedtls_mpi_copy( &rsa->DP, &T ) ) != 0 )
goto cleanup;
/* Import DQ */
- if( ( ret = mbedtls_asn1_get_mpi( &p, end, &rsa->DQ ) ) != 0)
+ if( ( ret = asn1_get_nonzero_mpi( &p, end, &T ) ) != 0 ||
+ ( ret = mbedtls_mpi_copy( &rsa->DQ, &T ) ) != 0 )
goto cleanup;
/* Import QP */
- if( ( ret = mbedtls_asn1_get_mpi( &p, end, &rsa->QP ) ) != 0)
+ if( ( ret = asn1_get_nonzero_mpi( &p, end, &T ) ) != 0 ||
+ ( ret = mbedtls_mpi_copy( &rsa->QP, &T ) ) != 0 )
goto cleanup;
#else
/* Verify existance of the CRT params */
- if( ( ret = mbedtls_asn1_get_mpi( &p, end, &T ) ) != 0 ||
- ( ret = mbedtls_asn1_get_mpi( &p, end, &T ) ) != 0 ||
- ( ret = mbedtls_asn1_get_mpi( &p, end, &T ) ) != 0 )
+ if( ( ret = asn1_get_nonzero_mpi( &p, end, &T ) ) != 0 ||
+ ( ret = asn1_get_nonzero_mpi( &p, end, &T ) ) != 0 ||
+ ( ret = asn1_get_nonzero_mpi( &p, end, &T ) ) != 0 )
goto cleanup;
#endif