From 3ab4fce1a064d22c95eb4baf741b7372df106cdf Mon Sep 17 00:00:00 2001 From: Nadav0077 <18245584+Nadav0077@users.noreply.github.com> Date: Sat, 25 Apr 2026 15:19:30 +0300 Subject: [PATCH] Harden TLS 1.3 serialized session loading Signed-off-by: Nadav0077 <18245584+Nadav0077@users.noreply.github.com> --- ChangeLog.d/tls13-session-load-hardening.txt | 3 + library/ssl_tls.c | 24 +++++-- tests/suites/test_suite_ssl.data | 12 ++++ tests/suites/test_suite_ssl.function | 68 ++++++++++++++++++++ 4 files changed, 102 insertions(+), 5 deletions(-) create mode 100644 ChangeLog.d/tls13-session-load-hardening.txt diff --git a/ChangeLog.d/tls13-session-load-hardening.txt b/ChangeLog.d/tls13-session-load-hardening.txt new file mode 100644 index 0000000000..d56e14cfac --- /dev/null +++ b/ChangeLog.d/tls13-session-load-hardening.txt @@ -0,0 +1,3 @@ +Bugfix + * Reject malformed TLS 1.3 serialized sessions instead of accepting + unterminated strings or extra trailing data. diff --git a/library/ssl_tls.c b/library/ssl_tls.c index e8a44f834c..8b4f64bc96 100644 --- a/library/ssl_tls.c +++ b/library/ssl_tls.c @@ -3573,6 +3573,7 @@ static int ssl_tls13_session_load(mbedtls_ssl_session *session, { const unsigned char *p = buf; const unsigned char *end = buf + len; + int ret; if (end - p < 6) { return MBEDTLS_ERR_SSL_BAD_INPUT_DATA; @@ -3634,7 +3635,12 @@ static int ssl_tls13_session_load(mbedtls_ssl_session *session, } if (alpn_len > 0) { - int ret = mbedtls_ssl_session_set_ticket_alpn(session, (char *) p); + if (p[alpn_len - 1] != '\0' || + memchr(p, '\0', alpn_len - 1) != NULL) { + return MBEDTLS_ERR_SSL_BAD_INPUT_DATA; + } + + ret = mbedtls_ssl_session_set_ticket_alpn(session, (char *) p); if (ret != 0) { return ret; } @@ -3659,11 +3665,15 @@ static int ssl_tls13_session_load(mbedtls_ssl_session *session, return MBEDTLS_ERR_SSL_BAD_INPUT_DATA; } if (hostname_len > 0) { - session->hostname = mbedtls_calloc(1, hostname_len); - if (session->hostname == NULL) { - return MBEDTLS_ERR_SSL_ALLOC_FAILED; + if (p[hostname_len - 1] != '\0' || + memchr(p, '\0', hostname_len - 1) != NULL) { + return MBEDTLS_ERR_SSL_BAD_INPUT_DATA; + } + + ret = mbedtls_ssl_session_set_hostname(session, (const char *) p); + if (ret != 0) { + return ret; } - memcpy(session->hostname, p, hostname_len); p += hostname_len; } #endif /* MBEDTLS_SSL_SERVER_NAME_INDICATION */ @@ -3701,6 +3711,10 @@ static int ssl_tls13_session_load(mbedtls_ssl_session *session, } #endif /* MBEDTLS_SSL_CLI_C */ + if (p != end) { + return MBEDTLS_ERR_SSL_BAD_INPUT_DATA; + } + return 0; } diff --git a/tests/suites/test_suite_ssl.data b/tests/suites/test_suite_ssl.data index 881d502ed5..fd90f0606e 100644 --- a/tests/suites/test_suite_ssl.data +++ b/tests/suites/test_suite_ssl.data @@ -3028,6 +3028,18 @@ TLS 1.3: SRV: Session serialization, load buffer size depends_on:MBEDTLS_SSL_PROTO_TLS1_3:MBEDTLS_SSL_SESSION_TICKETS:MBEDTLS_SSL_SRV_C ssl_serialize_session_load_buf_size:0:"":MBEDTLS_SSL_IS_SERVER:MBEDTLS_SSL_VERSION_TLS1_3 +TLS 1.3: Session serialization rejects trailing data +depends_on:MBEDTLS_SSL_PROTO_TLS1_3:MBEDTLS_SSL_SESSION_TICKETS:MBEDTLS_SSL_CLI_C +ssl_tls13_session_load_rejects_bad_serialized_data:MBEDTLS_SSL_IS_CLIENT:0 + +TLS 1.3: Session serialization rejects hostname without terminator +depends_on:MBEDTLS_SSL_PROTO_TLS1_3:MBEDTLS_SSL_SESSION_TICKETS:MBEDTLS_SSL_CLI_C:MBEDTLS_SSL_SERVER_NAME_INDICATION +ssl_tls13_session_load_rejects_bad_serialized_data:MBEDTLS_SSL_IS_CLIENT:1 + +TLS 1.3: Session serialization rejects ALPN without terminator +depends_on:MBEDTLS_SSL_PROTO_TLS1_3:MBEDTLS_SSL_SESSION_TICKETS:MBEDTLS_SSL_SRV_C:MBEDTLS_SSL_EARLY_DATA:MBEDTLS_SSL_ALPN +ssl_tls13_session_load_rejects_bad_serialized_data:MBEDTLS_SSL_IS_SERVER:2 + Test configuration of EC groups through mbedtls_ssl_conf_groups() conf_group: diff --git a/tests/suites/test_suite_ssl.function b/tests/suites/test_suite_ssl.function index 39457c9047..af63d6dbca 100644 --- a/tests/suites/test_suite_ssl.function +++ b/tests/suites/test_suite_ssl.function @@ -2733,6 +2733,74 @@ exit: } /* END_CASE */ +/* BEGIN_CASE depends_on:MBEDTLS_SSL_PROTO_TLS1_3:MBEDTLS_SSL_SESSION_TICKETS */ +void ssl_tls13_session_load_rejects_bad_serialized_data(int endpoint_type, + int mutation) +{ + mbedtls_ssl_session session, restored; + unsigned char *buf = NULL; + size_t len, bad_len, i; + unsigned char *field = NULL; + const unsigned char hostname[] = "hostname example"; + const unsigned char alpn[] = "ALPNExample"; + const unsigned char *string_to_corrupt = NULL; + size_t string_len = 0; + + mbedtls_ssl_session_init(&session); + mbedtls_ssl_session_init(&restored); + USE_PSA_INIT(); + + TEST_EQUAL(mbedtls_test_ssl_tls13_populate_session( + &session, 42, endpoint_type), 0); + + TEST_EQUAL(mbedtls_ssl_session_save(&session, NULL, 0, &len), + MBEDTLS_ERR_SSL_BUFFER_TOO_SMALL); + TEST_CALLOC(buf, len + 1); + TEST_EQUAL(mbedtls_ssl_session_save(&session, buf, len, &len), 0); + + bad_len = len; + switch (mutation) { + case 0: + bad_len = len + 1; + buf[len] = 0; + break; + + case 1: + string_to_corrupt = hostname; + string_len = sizeof(hostname); + break; + + case 2: + string_to_corrupt = alpn; + string_len = sizeof(alpn); + break; + + default: + TEST_ASSERT(0); + } + + if (string_to_corrupt != NULL) { + for (i = 0; i + string_len <= len; i++) { + if (memcmp(buf + i, string_to_corrupt, string_len) == 0) { + field = buf + i; + break; + } + } + TEST_ASSERT(field != NULL); + field[string_len - 1] = 'X'; + } + + TEST_EQUAL(mbedtls_ssl_session_load(&restored, buf, bad_len), + MBEDTLS_ERR_SSL_BAD_INPUT_DATA); + +exit: + mbedtls_ssl_session_free(&session); + mbedtls_ssl_session_free(&restored); + mbedtls_free(buf); + USE_PSA_DONE(); +} +/* END_CASE */ + /* BEGIN_CASE */ void ssl_session_serialize_version_check(int corrupt_major, int corrupt_minor,