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Merge pull request #10792 from nvxbug/ssl-context-load-alpn-bounds

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Reject out-of-bounds ALPN length in ssl_context_load
This commit is contained in:
Ronald Cron
2026-10-05 11:39:44 +00:00
committed by GitHub
parent c0748befd5 fbc06d7909
commit 6bdf4e15e2
4 changed files with 186 additions and 33 deletions
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ChangeLog.d/ssl-context-load-alpn-bounds.txt
+4
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@@ -0,0 +1,4 @@
Bugfix
* Reject serialized SSL contexts whose ALPN protocol length exceeds the
remaining serialized data, instead of reading past the end of the buffer
in mbedtls_ssl_context_load().
library/ssl_tls.c
+4
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@@ -5101,6 +5101,10 @@ static int ssl_context_load(mbedtls_ssl_context *ssl,
alpn_len = *p++;
if ((size_t) (end - p) < alpn_len) {
return MBEDTLS_ERR_SSL_BAD_INPUT_DATA;
}
if (alpn_len != 0 && ssl->conf->alpn_list != NULL) {
/* alpn_chosen should point to an item in the configured list */
for (cur = ssl->conf->alpn_list; *cur != NULL; cur++) {
tests/suites/test_suite_ssl.data
+11 -3
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@@ -3064,9 +3064,17 @@ 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_session_load_rejects_bad_serialized_data:MBEDTLS_SSL_VERSION_TLS1_3:MBEDTLS_SSL_IS_SERVER:TEST_TLS13_SESSION_LOAD_ALPN_NO_NUL
SSL context serialization rejects out-of-bounds DTLS CID length
depends_on:MBEDTLS_SSL_HANDSHAKE_WITH_CERT_ENABLED:MBEDTLS_SSL_PROTO_TLS1_2:MBEDTLS_SSL_PROTO_DTLS:MBEDTLS_SSL_DTLS_CONNECTION_ID:MBEDTLS_SSL_CONTEXT_SERIALIZATION:PSA_HAVE_ALG_SOME_RSA_SIGN:PSA_WANT_ECC_SECP_R1_384:PSA_WANT_ALG_SHA_256:MBEDTLS_CAN_HANDLE_RSA_TEST_KEY:TEST_GCM_OR_CHACHAPOLY_ENABLED
ssl_context_load_rejects_oob_cid_length:
SSL context serialization rejects out-of-bounds DTLS in_cid length
depends_on:MBEDTLS_SSL_DTLS_CONNECTION_ID
ssl_context_load_rejects_oob_length:TEST_SSL_CONTEXT_LOAD_OOB_IN_CID
SSL context serialization rejects out-of-bounds DTLS out_cid length
depends_on:MBEDTLS_SSL_DTLS_CONNECTION_ID
ssl_context_load_rejects_oob_length:TEST_SSL_CONTEXT_LOAD_OOB_OUT_CID
SSL context serialization rejects out-of-bounds ALPN length
depends_on:MBEDTLS_SSL_ALPN
ssl_context_load_rejects_oob_length:TEST_SSL_CONTEXT_LOAD_OOB_ALPN
TLS 1.2: Session serialization rejects out-of-bounds session ID length (client)
depends_on:MBEDTLS_SSL_PROTO_TLS1_2:MBEDTLS_SSL_CLI_C
tests/suites/test_suite_ssl.function
+167 -30
View File
@@ -32,6 +32,11 @@
#define TEST_TLS13_SESSION_LOAD_ALPN_NO_NUL 2
#define TEST_TLS12_SESSION_LOAD_OOB_ID_LEN 3
/* Corrupted length fields for ssl_context_load_rejects_oob_length */
#define TEST_SSL_CONTEXT_LOAD_OOB_IN_CID 0
#define TEST_SSL_CONTEXT_LOAD_OOB_OUT_CID 1
#define TEST_SSL_CONTEXT_LOAD_OOB_ALPN 2
#if defined(MBEDTLS_SSL_PROTO_TLS1_2) && \
defined(MBEDTLS_SSL_SESSION_TICKETS) && \
defined(MBEDTLS_SSL_CLI_C) && defined(MBEDTLS_SSL_SRV_C) && \
@@ -3038,22 +3043,45 @@ exit:
}
/* END_CASE */
/* BEGIN_CASE depends_on:MBEDTLS_SSL_HANDSHAKE_WITH_CERT_ENABLED:MBEDTLS_SSL_PROTO_TLS1_2:MBEDTLS_SSL_PROTO_DTLS:MBEDTLS_SSL_DTLS_CONNECTION_ID:MBEDTLS_SSL_CONTEXT_SERIALIZATION:PSA_HAVE_ALG_SOME_RSA_SIGN:PSA_WANT_ECC_SECP_R1_384:PSA_WANT_ALG_SHA_256:MBEDTLS_CAN_HANDLE_RSA_TEST_KEY:TEST_GCM_OR_CHACHAPOLY_ENABLED */
void ssl_context_load_rejects_oob_cid_length(void)
/* BEGIN_CASE depends_on:MBEDTLS_SSL_HANDSHAKE_WITH_CERT_ENABLED:MBEDTLS_SSL_PROTO_TLS1_2:MBEDTLS_SSL_PROTO_DTLS:MBEDTLS_SSL_CONTEXT_SERIALIZATION:PSA_HAVE_ALG_SOME_RSA_SIGN:PSA_WANT_ECC_SECP_R1_384:PSA_WANT_ALG_SHA_256:MBEDTLS_CAN_HANDLE_RSA_TEST_KEY:TEST_GCM_OR_CHACHAPOLY_ENABLED */
void ssl_context_load_rejects_oob_length(int field)
{
/* Sentinel CID so we can find its location inside the serialized buffer. */
#if defined(MBEDTLS_SSL_DTLS_CONNECTION_ID)
/* Sentinel CIDs so we can find their location inside the serialized
* buffer. The server's own CID is serialized as in_cid and the client's
* as out_cid; they have different lengths so that the two fields can be
* told apart. */
const unsigned char server_cid[] = {
0xAB, 0xCD, 0xEF, 0x12, 0x34, 0x56, 0x78, 0x9A
};
const unsigned char client_cid[] = {
0x9A, 0x78, 0x56, 0x34, 0x12, 0xEF, 0xCD, 0xAB
0x9A, 0x78, 0x56, 0x34, 0x12, 0xEF,
0xCD, 0xAB, 0x10, 0x32, 0x54, 0x76
};
#endif
#if defined(MBEDTLS_SSL_ALPN)
/* The negotiated protocol (alpn[0]) is the last field in the serialized
* context, so exactly strlen(alpn[0]) bytes remain after its length byte.
* On load, ssl_context_load() only memcmp()s configured protocols whose
* strlen() equals the length byte, so the corrupted length has to match a
* configured protocol to reach the memcmp(): alpn[1] is one character
* longer than alpn[0], which makes the corrupted length point exactly one
* byte past the end of the serialized data. It shares alpn[0]'s prefix so
* that all in-bounds bytes match and the memcmp() cannot stop before
* reading past the end of the buffer. */
const char negotiated[] = "alpnsentinel";
const char *alpn[] = { negotiated, "alpnsentinel2", NULL };
#endif
mbedtls_test_handshake_test_options options;
mbedtls_test_ssl_endpoint client_ep, server_ep;
unsigned char *context_buf = NULL;
size_t context_buf_len, i;
unsigned char *cid_len_p = NULL;
unsigned char *load_buf = NULL;
size_t context_buf_len, load_len, field_off, i;
const unsigned char *sentinel = NULL;
size_t sentinel_len = 0;
unsigned char corrupt_len = 0;
unsigned char *len_p = NULL;
memset(&client_ep, 0, sizeof(client_ep));
memset(&server_ep, 0, sizeof(server_ep));
@@ -3069,23 +3097,82 @@ void ssl_context_load_rejects_oob_cid_length(void)
TEST_EQUAL(mbedtls_test_ssl_endpoint_init(
&server_ep, MBEDTLS_SSL_IS_SERVER, &options), 0);
/* Configure CID with unique patterns so we can locate the length byte in
* the serialized context. Both peers must agree on the CID length via
* conf_cid() before set_cid() will accept the value. */
TEST_EQUAL(mbedtls_ssl_conf_cid(&client_ep.conf, sizeof(client_cid),
MBEDTLS_SSL_UNEXPECTED_CID_FAIL), 0);
TEST_EQUAL(mbedtls_ssl_conf_cid(&server_ep.conf, sizeof(server_cid),
MBEDTLS_SSL_UNEXPECTED_CID_FAIL), 0);
TEST_EQUAL(mbedtls_ssl_set_cid(&client_ep.ssl, MBEDTLS_SSL_CID_ENABLED,
client_cid, sizeof(client_cid)), 0);
TEST_EQUAL(mbedtls_ssl_set_cid(&server_ep.ssl, MBEDTLS_SSL_CID_ENABLED,
server_cid, sizeof(server_cid)), 0);
switch (field) {
#if defined(MBEDTLS_SSL_DTLS_CONNECTION_ID)
case TEST_SSL_CONTEXT_LOAD_OOB_IN_CID:
case TEST_SSL_CONTEXT_LOAD_OOB_OUT_CID:
/* Each peer's own CID has to fit in MBEDTLS_SSL_CID_IN_LEN_MAX and
* its peer's CID in MBEDTLS_SSL_CID_OUT_LEN_MAX. */
TEST_ASSUME(MBEDTLS_SSL_CID_IN_LEN_MAX >= sizeof(server_cid) &&
MBEDTLS_SSL_CID_IN_LEN_MAX >= sizeof(client_cid));
TEST_ASSUME(MBEDTLS_SSL_CID_OUT_LEN_MAX >= sizeof(server_cid) &&
MBEDTLS_SSL_CID_OUT_LEN_MAX >= sizeof(client_cid));
/* Configure CID with unique patterns so we can locate the length
* bytes in the serialized context. On each peer the length passed
* to conf_cid() must match the one passed to set_cid(). */
TEST_EQUAL(mbedtls_ssl_conf_cid(
&client_ep.conf, sizeof(client_cid),
MBEDTLS_SSL_UNEXPECTED_CID_FAIL), 0);
TEST_EQUAL(mbedtls_ssl_conf_cid(
&server_ep.conf, sizeof(server_cid),
MBEDTLS_SSL_UNEXPECTED_CID_FAIL), 0);
TEST_EQUAL(mbedtls_ssl_set_cid(
&client_ep.ssl, MBEDTLS_SSL_CID_ENABLED,
client_cid, sizeof(client_cid)), 0);
TEST_EQUAL(mbedtls_ssl_set_cid(
&server_ep.ssl, MBEDTLS_SSL_CID_ENABLED,
server_cid, sizeof(server_cid)), 0);
/* The corrupted length is the smallest one that overflows the
* in_cid or out_cid array in the SSL transform, so the size check
* on that array, not the in-buffer bounds check before it, is
* what must reject it. The loaded data gets the field grown to
* this many bytes (see the construction of load_buf below) so
* that the in-buffer bounds check indeed passes. A one-byte
* serialized length cannot overflow a 255-byte CID array. */
if (field == TEST_SSL_CONTEXT_LOAD_OOB_IN_CID) {
TEST_ASSUME(MBEDTLS_SSL_CID_IN_LEN_MAX < 255);
sentinel = server_cid;
sentinel_len = sizeof(server_cid);
corrupt_len = (unsigned char) (MBEDTLS_SSL_CID_IN_LEN_MAX + 1);
} else {
TEST_ASSUME(MBEDTLS_SSL_CID_OUT_LEN_MAX < 255);
sentinel = client_cid;
sentinel_len = sizeof(client_cid);
corrupt_len = (unsigned char) (MBEDTLS_SSL_CID_OUT_LEN_MAX + 1);
}
break;
#endif
#if defined(MBEDTLS_SSL_ALPN)
case TEST_SSL_CONTEXT_LOAD_OOB_ALPN:
/* Offer the same protocol list on both peers so alpn[0] is
* negotiated and serialized into the context. */
TEST_EQUAL(mbedtls_ssl_conf_alpn_protocols(&client_ep.conf, alpn),
0);
TEST_EQUAL(mbedtls_ssl_conf_alpn_protocols(&server_ep.conf, alpn),
0);
sentinel = (const unsigned char *) negotiated;
sentinel_len = strlen(negotiated);
/* One byte past the end of the serialized data; see the
* declaration of alpn[] above. */
corrupt_len = (unsigned char) strlen(alpn[1]);
break;
#endif
default:
TEST_ASSERT(0);
}
TEST_EQUAL(mbedtls_test_ssl_dtls_join_endpoints(&client_ep, &server_ep), 0);
TEST_ASSERT(mbedtls_test_ssl_perform_connection(&options, &client_ep,
&server_ep));
#if defined(MBEDTLS_SSL_ALPN)
if (field == TEST_SSL_CONTEXT_LOAD_OOB_ALPN) {
TEST_ASSERT(server_ep.ssl.alpn_chosen != NULL);
TEST_EQUAL(strcmp(server_ep.ssl.alpn_chosen, negotiated), 0);
}
#endif
/* Serialize the post-handshake server context. */
TEST_EQUAL(mbedtls_ssl_context_save(&server_ep.ssl, NULL, 0,
&context_buf_len),
@@ -3094,29 +3181,78 @@ void ssl_context_load_rejects_oob_cid_length(void)
TEST_EQUAL(mbedtls_ssl_context_save(&server_ep.ssl, context_buf,
context_buf_len, &context_buf_len), 0);
/* The serialized format writes [in_cid_len][in_cid bytes]; locate the
* length byte by searching for our sentinel CID. */
for (i = 1; i + sizeof(server_cid) <= context_buf_len; i++) {
if (context_buf[i - 1] == (unsigned char) sizeof(server_cid) &&
memcmp(context_buf + i, server_cid, sizeof(server_cid)) == 0) {
cid_len_p = context_buf + i - 1;
/* Double-check that the serialized data loads cleanly before it gets
* corrupted. */
mbedtls_ssl_free(&server_ep.ssl);
mbedtls_ssl_init(&server_ep.ssl);
TEST_EQUAL(mbedtls_ssl_setup(&server_ep.ssl, &server_ep.conf), 0);
TEST_EQUAL(mbedtls_ssl_context_load(&server_ep.ssl, context_buf,
context_buf_len), 0);
/* Both fields are serialized as [length byte][data bytes]; locate the
* length byte by searching for the sentinel data. */
for (i = 1; i + sentinel_len <= context_buf_len; i++) {
if (context_buf[i - 1] == (unsigned char) sentinel_len &&
memcmp(context_buf + i, sentinel, sentinel_len) == 0) {
len_p = context_buf + i - 1;
break;
}
}
TEST_ASSERT(cid_len_p != NULL);
TEST_ASSERT(len_p != NULL);
/* Corrupt the length to the smallest value strictly greater than
* sizeof(in_cid), so we exercise the new bounds check rather than the
* pre-existing buffer-size check that would also trip on huge values. */
*cid_len_p = (unsigned char) (MBEDTLS_SSL_CID_IN_LEN_MAX + 1);
field_off = (size_t) (len_p + 1 - context_buf);
if (field == TEST_SSL_CONTEXT_LOAD_OOB_IN_CID ||
field == TEST_SSL_CONTEXT_LOAD_OOB_OUT_CID) {
/* The CID fields sit in the middle of the serialized data, so a
* corrupted length cannot reach past the end of the buffer. Instead
* grow the field itself: keep its bytes, pad it to corrupt_len bytes
* and append the untouched rest of the serialized data, so that the
* in-buffer bounds check passes and the size check on the CID array
* is reached. */
load_len = context_buf_len + corrupt_len - sentinel_len;
TEST_CALLOC(load_buf, load_len);
memcpy(load_buf, context_buf, field_off + sentinel_len);
memset(load_buf + field_off + sentinel_len, 0xA5,
(size_t) corrupt_len - sentinel_len);
memcpy(load_buf + field_off + corrupt_len,
context_buf + field_off + sentinel_len,
context_buf_len - field_off - sentinel_len);
/* Double-check that corrupt_len bytes of field data plus the next
* byte are present, which is the most the in-buffer bounds checks
* require (the in_cid one also accounts for the out_cid length
* byte). */
TEST_ASSERT(load_len - field_off >= (size_t) corrupt_len + 1);
} else {
/* The ALPN field is the last one saved, so the buffer already ends
* right after it and the corrupted length reaches exactly one byte
* past the end. Load from a tightly allocated copy, so that reading
* even one byte past the end of the data overruns the allocation and
* gets caught by ASan or Valgrind. */
TEST_EQUAL((size_t) corrupt_len, context_buf_len - field_off + 1);
load_len = context_buf_len;
TEST_CALLOC(load_buf, load_len);
memcpy(load_buf, context_buf, load_len);
}
load_buf[field_off - 1] = corrupt_len;
/* Reinitialise the server SSL context so we can load into a fresh one. */
mbedtls_ssl_free(&server_ep.ssl);
mbedtls_ssl_init(&server_ep.ssl);
TEST_EQUAL(mbedtls_ssl_setup(&server_ep.ssl, &server_ep.conf), 0);
TEST_EQUAL(mbedtls_ssl_context_load(&server_ep.ssl, context_buf,
context_buf_len),
/* How a regression is caught differs between the two cases. In the ALPN
* case, without the bounds check the load still fails, because the
* out-of-bounds bytes are unlikely to match a configured protocol; what
* the missing check leaks is the out-of-bounds read in memcmp() itself,
* so that case catches a regression only when the test suite runs under
* ASan or Valgrind. In the CID cases, without the size check the
* memcpy() overflows the in_cid or out_cid array inside the SSL
* transform (which stays within the enclosing struct, invisible to
* ASan), the rest of the data then parses correctly aligned and the
* load succeeds, so the check below catches a regression on its own. */
TEST_EQUAL(mbedtls_ssl_context_load(&server_ep.ssl, load_buf, load_len),
MBEDTLS_ERR_SSL_BAD_INPUT_DATA);
exit:
@@ -3124,6 +3260,7 @@ exit:
mbedtls_test_ssl_endpoint_free(&server_ep);
mbedtls_test_free_handshake_options(&options);
mbedtls_free(context_buf);
mbedtls_free(load_buf);
MD_OR_USE_PSA_DONE();
}
/* END_CASE */