mbedtls_ecdsa_raw_to_der and mbedtls_ecdsa_der_to_raw: reject bits==0
Cleanly reject bits == 0 when calling mbedtls_ecdsa_raw_to_der() and
mbedtls_ecdsa_der_to_raw(). This can plausibly happen when bits is
user-provided data that the calling application doesn't check.
Before this patch, there was typically-benign undefined behavior, such as
adding 0 to a null pointer or calling memcpy on a null pointer with a size
of 0.
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
diff --git a/library/psa_util.c b/library/psa_util.c
index 679d00e..014e648 100644
--- a/library/psa_util.c
+++ b/library/psa_util.c
@@ -440,6 +440,9 @@
unsigned char *p = der + der_size;
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
+ if (bits == 0) {
+ return MBEDTLS_ERR_ASN1_INVALID_DATA;
+ }
if (raw_len != (2 * coordinate_len)) {
return MBEDTLS_ERR_ASN1_INVALID_DATA;
}
@@ -559,6 +562,9 @@
size_t coordinate_size = PSA_BITS_TO_BYTES(bits);
int ret;
+ if (bits == 0) {
+ return MBEDTLS_ERR_ASN1_INVALID_DATA;
+ }
/* The output raw buffer should be at least twice the size of a raw
* coordinate in order to store r and s. */
if (raw_size < coordinate_size * 2) {