Skip to content

Harden CONNECT credential handling compliance #572

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
embhorn merged 1 commit into from
Aug 12, 2026
Merged

Harden CONNECT credential handling compliance #572

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
17 changes: 14 additions & 3 deletions src/mqtt_packet.c
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -1259,9 +1259,20 @@ int MqttEncode_Connect(byte *tx_buf, int tx_buf_len, MqttConnect *mc_connect)
mc_connect->protocol_level = MQTT_CONNECT_PROTOCOL_LEVEL;
}

/* [MQTT-3.1.2-22]: If the User Name Flag is set to 0, the Password Flag
* MUST be set to 0 */
if (mc_connect->password != NULL && mc_connect->username == NULL) {
/* Reject protocol levels this build cannot encode. */
#ifdef WOLFMQTT_V5
if (mc_connect->protocol_level != MQTT_CONNECT_PROTOCOL_LEVEL_4 &&
mc_connect->protocol_level != MQTT_CONNECT_PROTOCOL_LEVEL_5) {
#else
if (mc_connect->protocol_level != MQTT_CONNECT_PROTOCOL_LEVEL_4) {
#endif
return MQTT_TRACE_ERROR(MQTT_CODE_ERROR_BAD_ARG);
}

/* [MQTT-3.1.2-22]: MQTT v3.1.1 requires User Name when Password is set.
* MQTT v5 section 3.1.2.9 permits Password without User Name. */
if (mc_connect->protocol_level == MQTT_CONNECT_PROTOCOL_LEVEL_4 &&
mc_connect->password != NULL && mc_connect->username == NULL) {
return MQTT_TRACE_ERROR(MQTT_CODE_ERROR_BAD_ARG);
}

Expand Down
93 changes: 93 additions & 0 deletions tests/test_mqtt_packet.c
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -2265,12 +2265,98 @@ TEST(encode_connect_password_without_username)

XMEMSET(&conn, 0, sizeof(conn));
conn.client_id = "test_client";
conn.protocol_level = MQTT_CONNECT_PROTOCOL_LEVEL_4;
Comment thread
aidangarske marked this conversation as resolved.
Comment thread
aidangarske marked this conversation as resolved.
conn.username = NULL;
conn.password = "secret";
rc = MqttEncode_Connect(tx_buf, (int)sizeof(tx_buf), &conn);
ASSERT_EQ(MQTT_CODE_ERROR_BAD_ARG, rc);
}

TEST(encode_connect_default_password_without_username)
{
byte tx_buf[256];
MqttConnect conn;
int rc;

XMEMSET(&conn, 0, sizeof(conn));
conn.client_id = "test_client";
conn.password = "secret";
rc = MqttEncode_Connect(tx_buf, (int)sizeof(tx_buf), &conn);
#ifdef WOLFMQTT_V5
ASSERT_TRUE(rc > 0);
ASSERT_EQ(MQTT_CONNECT_PROTOCOL_LEVEL_5, conn.protocol_level);
#else
ASSERT_EQ(MQTT_CODE_ERROR_BAD_ARG, rc);
ASSERT_EQ(MQTT_CONNECT_PROTOCOL_LEVEL_4, conn.protocol_level);
#endif
}

TEST(encode_connect_unsupported_protocol_level)
{
byte tx_buf[256];
MqttConnect conn;
int rc;

XMEMSET(&conn, 0, sizeof(conn));
conn.client_id = "test_client";
conn.protocol_level = 3;
conn.username = "user";
conn.password = "secret";
rc = MqttEncode_Connect(tx_buf, (int)sizeof(tx_buf), &conn);
ASSERT_EQ(MQTT_CODE_ERROR_BAD_ARG, rc);

conn.protocol_level = MQTT_CONNECT_PROTOCOL_LEVEL_5 + 1;
rc = MqttEncode_Connect(tx_buf, (int)sizeof(tx_buf), &conn);
ASSERT_EQ(MQTT_CODE_ERROR_BAD_ARG, rc);
}

#ifdef WOLFMQTT_V5
/* MQTT v5 permits the Password Flag without the User Name Flag.
* [MQTT-3.1.2-22] is scoped to MQTT 3.1.1; v5 section 3.1.2.9
* explicitly removes that restriction. */
TEST(encode_connect_v5_password_without_username)
{
byte tx_buf[256];
static const byte expected[] = {
/* Fixed header: CONNECT, Remaining Length 32. */
0x10, 0x20,
/* Variable header: MQTT, level 5, Password flag, keepalive 0,
* Properties Length 0. */
0x00, 0x04, 'M', 'Q', 'T', 'T', 0x05, 0x40, 0x00, 0x00, 0x00,
/* Payload: Client Identifier "test_client", Password "secret". */
0x00, 0x0B, 't', 'e', 's', 't', '_', 'c', 'l', 'i', 'e', 'n', 't',
0x00, 0x06, 's', 'e', 'c', 'r', 'e', 't'
};
MqttConnect conn;
int rc;

XMEMSET(&conn, 0, sizeof(conn));
conn.client_id = "test_client";
conn.protocol_level = MQTT_CONNECT_PROTOCOL_LEVEL_5;
conn.password = "secret";
rc = MqttEncode_Connect(tx_buf, (int)sizeof(tx_buf), &conn);
ASSERT_EQ((int)sizeof(expected), rc);
ASSERT_MEM_EQ(expected, tx_buf, sizeof(expected));
}
#else
/* A build without v5 support cannot encode the v5 CONNECT Properties
* Length field, so it must reject an application-selected v5 level. */
TEST(encode_connect_v5_unsupported)
{
byte tx_buf[256];
MqttConnect conn;
int rc;

XMEMSET(&conn, 0, sizeof(conn));
conn.client_id = "test_client";
conn.protocol_level = MQTT_CONNECT_PROTOCOL_LEVEL_5;
conn.username = "user";
conn.password = "secret";
rc = MqttEncode_Connect(tx_buf, (int)sizeof(tx_buf), &conn);
ASSERT_EQ(MQTT_CODE_ERROR_BAD_ARG, rc);
Comment thread
aidangarske marked this conversation as resolved.
Comment thread
aidangarske marked this conversation as resolved.
}
#endif

TEST(encode_connect_username_and_password)
{
byte tx_buf[256];
Expand Down Expand Up @@ -5438,6 +5524,13 @@ void run_mqtt_packet_tests(void)

/* MqttEncode_Connect */
RUN_TEST(encode_connect_password_without_username);
RUN_TEST(encode_connect_default_password_without_username);
RUN_TEST(encode_connect_unsupported_protocol_level);
#ifdef WOLFMQTT_V5
RUN_TEST(encode_connect_v5_password_without_username);
#else
RUN_TEST(encode_connect_v5_unsupported);
#endif
RUN_TEST(encode_connect_username_and_password);
RUN_TEST(encode_connect_binary_password_accepted);
RUN_TEST(encode_connect_invalid_utf8_clientid_rejected);
Expand Down
Loading