Signed-off-by: Arne Schwabe <a...@rfc2549.org>
---
src/openvpn/crypto.h | 16 +---------------
src/openvpn/crypto_mbedtls.c | 20 ++++++++++++++++++++
src/openvpn/crypto_openssl.c | 5 +++++
3 files changed, 26 insertions(+), 15 deletions(-)
diff --git a/src/openvpn/crypto.h b/src/openvpn/crypto.h
index 18a86ceb..dadf0a90 100644
--- a/src/openvpn/crypto.h
+++ b/src/openvpn/crypto.h
@@ -528,21 +528,7 @@ void crypto_read_openvpn_key(const struct key_type
*key_type,
* As memcmp(), but constant-time.
* Returns 0 when data is equal, non-zero otherwise.
*/
-static inline int
-memcmp_constant_time(const void *a, const void *b, size_t size)
-{
- const uint8_t *a1 = a;
- const uint8_t *b1 = b;
- int ret = 0;
- size_t i;
-
- for (i = 0; i < size; i++)
- {
- ret |= *a1++ ^ *b1++;
- }
-
- return ret;
-}
+int memcmp_constant_time(const void *a, const void *b, size_t size);
static inline bool
key_ctx_bi_defined(const struct key_ctx_bi *key)
diff --git a/src/openvpn/crypto_mbedtls.c b/src/openvpn/crypto_mbedtls.c
index 3e77fa9e..1f6a23f8 100644
--- a/src/openvpn/crypto_mbedtls.c
+++ b/src/openvpn/crypto_mbedtls.c
@@ -972,4 +972,24 @@ hmac_ctx_final(mbedtls_md_context_t *ctx, uint8_t *dst)
ASSERT(0 == mbedtls_md_hmac_finish(ctx, dst));
}
+int
+memcmp_constant_time(const void *a, const void *b, size_t size)
+{
+ /* mbed TLS has a no const time memcmp function.
+ * Adapt the function mbedtls_safer_memcmp that mbedtls
+ * internally uses as it considers that to be safe. */
+ volatile const unsigned char *A = (volatile const unsigned char *)a;
+ volatile const unsigned char *B = (volatile const unsigned char *)b;
+ volatile unsigned char diff = 0;
+
+ for (size_t i = 0; i < size; i++)
+ {
+ /* this conversion was introduced by mbedTLS to suppress a IAR
+ * compiler warning. We keep it as it is. */
+ unsigned char x = A[i], y = B[i];
+ diff |= x ^ y;
+ }
+
+ return diff;
+}
#endif /* ENABLE_CRYPTO_MBEDTLS */
diff --git a/src/openvpn/crypto_openssl.c b/src/openvpn/crypto_openssl.c
index a81dcfd8..9e7ea0ff 100644
--- a/src/openvpn/crypto_openssl.c
+++ b/src/openvpn/crypto_openssl.c
@@ -1066,4 +1066,9 @@ hmac_ctx_final(HMAC_CTX *ctx, uint8_t *dst)
HMAC_Final(ctx, dst, &in_hmac_len);
}
+int
+memcmp_constant_time(const void *a, const void *b, size_t size)
+{
+ return CRYPTO_memcmp(a, b, size);
+}
#endif /* ENABLE_CRYPTO_OPENSSL */
--
2.26.0
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