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Buffer overflow vulnerabilities in the Zephyr Bluetooth subsystem

High
ceolin published GHSA-rgx6-3w4j-gf5j Sep 26, 2023

Package

Zephyr

Affected versions

<= 3.4.0

Patched versions

None

Description

Summary

I spotted a few buffer overflow vulnerabilities at the following locations in the Zephyr Bluetooth subsystem source code:
https://github.com/zephyrproject-rtos/zephyr/blob/main/subsys/bluetooth/audio/tbs.c
https://github.com/zephyrproject-rtos/zephyr/blob/main/subsys/bluetooth/audio/shell/mcc.c
https://github.com/zephyrproject-rtos/zephyr/blob/main/subsys/bluetooth/audio/shell/media_controller.c
https://github.com/zephyrproject-rtos/zephyr/blob/main/subsys/bluetooth/host/conn.c
https://github.com/zephyrproject-rtos/zephyr/blob/main/subsys/bluetooth/mesh/beacon.c
https://github.com/zephyrproject-rtos/zephyr/blob/main/subsys/bluetooth/mesh/prov_device.c
https://github.com/zephyrproject-rtos/zephyr/blob/main/subsys/bluetooth/mesh/provisioner.c
https://github.com/zephyrproject-rtos/zephyr/blob/main/subsys/bluetooth/mesh/shell/rpr.c

Details

Static buffer overflows in /subsys/bluetooth/audio/tbs.c:

int bt_tbs_remote_incoming(uint8_t bearer_index, const char *to,
			   const char *from, const char *friendly_name)
{
	struct tbs_service_inst *inst;
	struct bt_tbs_call *call = NULL;
	size_t local_uri_ind_len;
	size_t remote_uri_ind_len;
	size_t friend_name_ind_len;
...
	inst = &svc_insts[bearer_index];
...
	if (friendly_name) {
		inst->friendly_name.call_index = call->index;
		(void)strcpy(inst->friendly_name.uri, friendly_name); /* VULN */
		friend_name_ind_len = strlen(from) + 1;
...
	if (IS_ENABLED(CONFIG_BT_GTBS)) {
...
		if (friendly_name) {
			gtbs_inst.friendly_name.call_index = call->index;
			(void)strcpy(gtbs_inst.friendly_name.uri, friendly_name); /* VULN */
			friend_name_ind_len = strlen(from) + 1;
...

Stack-based buffer overflow in /subsys/bluetooth/audio/shell/mcc.c:

#ifdef CONFIG_BT_MCC_OTS
static int cmd_mcc_send_search_raw(const struct shell *sh, size_t argc,
				   char *argv[])
{
	int result;
	struct mpl_search search;

	search.len = strlen(argv[1]);
	memcpy(search.search, argv[1], search.len); /* VULN */
	LOG_DBG("Search string: %s", argv[1]);

	result = bt_mcc_send_search(default_conn, &search);
	if (result) {
		shell_print(sh, "Fail: %d", result);
	}
	return result;
}

Stack-based buffer overflow in /subsys/bluetooth/audio/shell/media_controller.c:

#ifdef CONFIG_BT_OTS
static int cmd_media_set_search(const struct shell *sh, size_t argc, char *argv[])
{
	/* TODO: Currently takes the raw search as input - add parameters
	 * and build the search item here
	 */

	struct mpl_search search;
	int err;

	search.len = strlen(argv[1]);
	memcpy(search.search, argv[1], search.len); /* VULN */
	LOG_DBG("Search string: %s", argv[1]);

	err = media_proxy_ctrl_send_search(current_player, &search);
	if (err) {
		shell_error(ctx_shell, "Search send failed (%d)", err);
	}

	return err;
}

Heap-based buffer overflow in /subsys/bluetooth/host/conn.c:

#if defined(CONFIG_BT_SMP)
...
int bt_conn_le_start_encryption(struct bt_conn *conn, uint8_t rand[8],
				uint8_t ediv[2], const uint8_t *ltk, size_t len)
{
	struct bt_hci_cp_le_start_encryption *cp;
	struct net_buf *buf;

	buf = bt_hci_cmd_create(BT_HCI_OP_LE_START_ENCRYPTION, sizeof(*cp));
	if (!buf) {
		return -ENOBUFS;
	}

	cp = net_buf_add(buf, sizeof(*cp));
	cp->handle = sys_cpu_to_le16(conn->handle);
	memcpy(&cp->rand, rand, sizeof(cp->rand));
	memcpy(&cp->ediv, ediv, sizeof(cp->ediv));

	memcpy(cp->ltk, ltk, len); /* VULN */
	if (len < sizeof(cp->ltk)) {
		(void)memset(cp->ltk + len, 0, sizeof(cp->ltk) - len);
	}

	return bt_hci_cmd_send_sync(BT_HCI_OP_LE_START_ENCRYPTION, buf, NULL);
}

Ineffective size check due to assert and buffer overflow in /subsys/bluetooth/mesh/beacon.c:

void bt_mesh_beacon_priv_random_get(uint8_t *random, size_t size)
{
	__ASSERT(size <= sizeof(priv_random.val), "Invalid random value size %u", size);
	memcpy(random, priv_random.val, size); /* VULN */
}

Static buffer overflow in /subsys/bluetooth/mesh/prov_device.c (conf_size could be 32 and not 16):

static void prov_confirm(const uint8_t *data)
{
	uint8_t conf_size = bt_mesh_prov_auth_size_get();

	LOG_DBG("Remote Confirm: %s", bt_hex(data, conf_size));

	memcpy(bt_mesh_prov_link.conf, data, conf_size); /* VULN */
	notify_input_complete();

	send_confirm();
}

Static buffer overflow in /subsys/bluetooth/mesh/provisioner.c (conf_size could be 32 and not 16):

static void prov_confirm(const uint8_t *data)
{
	uint8_t conf_size = bt_mesh_prov_auth_size_get();

	LOG_DBG("Remote Confirm: %s", bt_hex(data, conf_size));

	if (!memcmp(data, bt_mesh_prov_link.conf, conf_size)) {
		LOG_ERR("Confirm value is identical to ours, rejecting.");
		prov_fail(PROV_ERR_CFM_FAILED);
		return;
	}

	memcpy(bt_mesh_prov_link.conf, data, conf_size); /* VULN */

	send_random();
}

Stack-based buffer overflow in /subsys/bluetooth/mesh/shell/rpr.c:

static void rpr_scan_report(struct bt_mesh_rpr_cli *cli,
			    const struct bt_mesh_rpr_node *srv,
			    struct bt_mesh_rpr_unprov *unprov,
			    struct net_buf_simple *adv_data)
{
	char uuid_hex_str[32 + 1];

	bin2hex(unprov->uuid, 16, uuid_hex_str, sizeof(uuid_hex_str));

	shell_print(bt_mesh_shell_ctx_shell,
		    "Server 0x%04x:\n"
		    "\tuuid:   %s\n"
		    "\tOOB:    0x%04x",
		    srv->addr, uuid_hex_str, unprov->oob);

	while (adv_data && adv_data->len > 2) {
		uint8_t len, type;
		uint8_t data[31];

		len = net_buf_simple_pull_u8(adv_data) - 1;
		type = net_buf_simple_pull_u8(adv_data);
		memcpy(data, net_buf_simple_pull_mem(adv_data, len), len); /* VULN */
		data[len] = '\0';

		if (type == BT_DATA_URI) {
			shell_print(bt_mesh_shell_ctx_shell, "\tURI:    \"\\x%02x%s\"",
				    data[0], &data[1]);
		} else if (type == BT_DATA_NAME_COMPLETE) {
			shell_print(bt_mesh_shell_ctx_shell, "\tName:   \"%s\"", data);
		} else {
			char string[64 + 1];

			bin2hex(data, len, string, sizeof(string));
			shell_print(bt_mesh_shell_ctx_shell, "\t0x%02x:  %s", type, string);
		}
	}
}

PoC

I haven't tried to reproduce these potential vulnerabilities against a live install of the Zephyr OS.

Impact

If the unchecked inputs above are attacker-controlled and cross a security boundary, the impact of the buffer overflow vulnerabilities could range from denial of service to arbitrary code execution.

Patches

This has been fixed in:

For more information

If you have any questions or comments about this advisory:

embargo: 2023-08-19

Severity

High

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Adjacent
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Changed
Confidentiality
Low
Integrity
Low
Availability
Low

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:L

CVE ID

CVE-2023-4264

Weaknesses

Buffer Copy without Checking Size of Input ('Classic Buffer Overflow')

The product copies an input buffer to an output buffer without verifying that the size of the input buffer is less than the size of the output buffer, leading to a buffer overflow. Learn more on MITRE.

Stack-based Buffer Overflow

A stack-based buffer overflow condition is a condition where the buffer being overwritten is allocated on the stack (i.e., is a local variable or, rarely, a parameter to a function). Learn more on MITRE.

Heap-based Buffer Overflow

A heap overflow condition is a buffer overflow, where the buffer that can be overwritten is allocated in the heap portion of memory, generally meaning that the buffer was allocated using a routine such as malloc(). Learn more on MITRE.

Credits