From f7a5e7f3a7d05c7d558abd2f56f86e4c201be48b Mon Sep 17 00:00:00 2001 From: Alexander Sosedkin Date: Mon, 20 Apr 2026 16:36:08 +0200 Subject: [PATCH 7/8] tests/mini-dtls-fragments: #1839 mismatching message_seq Signed-off-by: Alexander Sosedkin Upstream-Status: Backport [https://gitlab.com/gnutls/gnutls/-/commit/a2b41be83a1a3529c551ccf54958da91a656550e] CVE: CVE-2026-33846 Signed-off-by: Pritam Srichandan Sahoo --- tests/mini-dtls-fragments.c | 54 ++++++++++++++++++++++++++++++++----- 1 file changed, 47 insertions(+), 7 deletions(-) diff --git a/tests/mini-dtls-fragments.c b/tests/mini-dtls-fragments.c index 93490bac2..499a92a92 100644 --- a/tests/mini-dtls-fragments.c +++ b/tests/mini-dtls-fragments.c @@ -165,7 +165,7 @@ static uint64_t read_u48(const uint8_t *p) return seq; } -static void test(gnutls_push_func client_push) +static void test(gnutls_push_func client_push, bool expect_success) { gnutls_session_t client, server; gnutls_certificate_credentials_t ccred, scred; @@ -218,12 +218,22 @@ static void test(gnutls_push_func client_push) sr = gnutls_handshake(server); if (!sr || gnutls_error_is_fatal(sr)) sdone = true; + + if (c2s.head == c2s.tail && s2c.head == s2c.tail) + break; /* speed the test up */ } - if (cr) - fail("client: %s\n", gnutls_strerror(cr)); - if (sr) - fail("server: %s\n", gnutls_strerror(sr)); + if (expect_success) { + if (cr) + fail("client: %s\n", gnutls_strerror(cr)); + if (sr) + fail("server: %s\n", gnutls_strerror(sr)); + + } else { + if (cr == 0 && sr == 0) + fail("handshake unexpectedly succeeded: %s / %s\n", + gnutls_strerror(cr), gnutls_strerror(sr)); + } success("OK\n"); @@ -421,14 +431,44 @@ static ssize_t client_push_split_hello(gnutls_transport_ptr_t tr, const void *b, return l; } +static ssize_t client_push_split_hello_bad_seq(gnutls_transport_ptr_t tr, + const void *b, size_t l) +{ + /* gnutls wasn't matching on message_seq on merging, see #1839 */ + static int seq_offset = 0; /* for renumbering follow-up epoch0 ones */ + + const uint8_t *data = (const uint8_t *)b; + uint8_t *frag1, *frag2; + size_t frag1_len, frag2_len; + + /* Pass through anything that isn't an epoch0 ClientHello with body */ + if (l < 13 + 12 + 1 || /* too short for DTLS record header */ + data[0] != 22 || /* not a handshake record */ + data[3] != 0 || data[4] != 0 || /* not epoch 0 */ + data[13] != 1) /* not ClientHello */ + return queue_put_renumbered(&c2s, b, l, seq_offset); + + /* epoch0 Client Hello: special treatment of splitting into fragments */ + split_client_hello(data, l, &frag1, &frag1_len, &frag2, &frag2_len); + queue_put(&c2s, frag1, frag1_len); + frag2[18]++; /* WRONG, message_seq mismatch must be rejected, #1839 */ + queue_put(&c2s, frag2, frag2_len); + free(frag1); + free(frag2); + seq_offset++; + return l; +} + void doit(void) { global_init(); - test(client_push_normal); + test(client_push_normal, true); success("malicious reassembly bug exploitation (#1816):\n"); test_malicious1816(); success("split client hello smoke-test\n"); - test(client_push_split_hello); + test(client_push_split_hello, true); + success("split client hello smoke-test and mangle sequence number\n"); + test(client_push_split_hello_bad_seq, false); gnutls_global_deinit(); } -- 2.53.0