Hello,
I upgraded from OpenSSL version v1.0.2 to v1.0.2e and started observing issues
in SSL negotiations randomly.
I observed that as part of v1.0.2e, while processing CLIENT_HELLO message in
t1_lib.c, extra checks for checking return value of HMAC_Update() have been
added while decrypting the ticket IE.
Following is the code flow:
ssl3_get_client_hello()
|-ssl_get_prev_session
|-tls1_process_ticket
|-tls_decrypt_ticket
|-HMAC_Update --------> Check for this function to return a value
has been added as part of OpenSSL v1.0.2e.
|-EVP_DigestUpdate
|-ctx->update(ctx, data, count)
The update function in EVP_MD_CTX has a return type void.
Thus, HMAC_Update function end up checking for random values. When the value is
greater than 0, SSL negotiations are successful but for other values, the
failure is percolated to the calling functions which typically lead to
ssl3_accept() failures in my case.
Following is the reference to the issue in GitHub:
https://github.com/openssl/openssl/issues/607
As part of the fix, I suggest removing the check for checking the return type
of HMAC_Update function in tls_decrypt_ticket().
Please find attached patch for the same.
Thanks and regards
Neha Chatrath
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Thank You.
diff -ur openssl-1.0.2f/ssl/t1_lib.c openssl-1.0.2f_work/ssl/t1_lib.c
--- openssl-1.0.2f/ssl/t1_lib.c 2016-01-28 08:56:08.000000000 -0500
+++ openssl-1.0.2f_work/ssl/t1_lib.c 2016-02-01 19:58:57.000000000 -0500
@@ -3401,8 +3401,8 @@
}
eticklen -= mlen;
/* Check HMAC of encrypted ticket */
- if (HMAC_Update(&hctx, etick, eticklen) <= 0
- || HMAC_Final(&hctx, tick_hmac, NULL) <= 0) {
+ HMAC_Update(&hctx, etick, eticklen);
+ if (HMAC_Final(&hctx, tick_hmac, NULL) <= 0) {
goto err;
}
HMAC_CTX_cleanup(&hctx);
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