[Openvpn-devel] [PATCH 1/5] Fix unaligned access in auth-token

[Arne Schwabe]

The undefined behaviour USAN clang checker found this. The optimiser
of clang/gcc will optimise the memcpy away in the auth_token case and output
excactly the same assembly on amd64/arm64 but it is still better to not rely
on undefined behaviour.

Signed-off-by: Arne Schwabe <a...@rfc2549.org>
---
 src/openvpn/auth_token.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/src/openvpn/auth_token.c b/src/openvpn/auth_token.c
index 7b963a9c5..e4486eb08 100644
--- a/src/openvpn/auth_token.c
+++ b/src/openvpn/auth_token.c
@@ -324,8 +324,14 @@ verify_auth_token(struct user_pass *up, struct tls_multi 
*multi,
     const uint8_t *tstamp_initial = sessid + AUTH_TOKEN_SESSION_ID_LEN;
     const uint8_t *tstamp = tstamp_initial + sizeof(int64_t);
 
-    uint64_t timestamp = ntohll(*((uint64_t *) (tstamp)));
-    uint64_t timestamp_initial = ntohll(*((uint64_t *) (tstamp_initial)));
+    /* tstamp, tstamp_initial might not be aligned to an uint64, use memcpy
+     * to avoid unaligned access */
+    uint64_t timestamp = 0, timestamp_initial = 0;
+    memcpy(&timestamp, tstamp, sizeof(uint64_t));
+    timestamp = ntohll(timestamp);
+
+    memcpy(&timestamp_initial, tstamp_initial, sizeof(uint64_t));
+    timestamp_initial = ntohll(timestamp_initial);
 
     hmac_ctx_t *ctx = multi->opt.auth_token_key.hmac;
     if (check_hmac_token(ctx, b64decoded, up->username))
-- 
2.37.1 (Apple Git-137.1)



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