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Fail closed in the lwIP packet filter glue #108

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d39d266
F-2438 - https://fenrir.wolfssl.com/finding/2438 - Deny lwIP packets …
aidangarske Oct 22, 2026
1e73174
F-3866 - https://fenrir.wolfssl.com/finding/3866 - Deny lwIP packets …
aidangarske Oct 22, 2026
9b71bb4
F-10500 - https://fenrir.wolfssl.com/finding/10500 - Set the close-wa…
aidangarske Oct 22, 2026
be804b7
F-3864 - https://fenrir.wolfssl.com/finding/3864 - Clear the lwIP ICM…
aidangarske Oct 22, 2026
7c76225
F-3868 - https://fenrir.wolfssl.com/finding/3868 - Install the lwIP f…
aidangarske Oct 22, 2026
dc2b5cc
F-4762 - https://fenrir.wolfssl.com/finding/4762 - Only clear lwIP fi…
aidangarske Oct 22, 2026
3687f4c
F-5004 - https://fenrir.wolfssl.com/finding/5004 - Publish the STM32 …
aidangarske Oct 22, 2026
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5 changes: 4 additions & 1 deletion examples/STM32-LWIP/README.md
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Original file line number Diff line number Diff line change
Expand Up @@ -68,7 +68,10 @@ In `StartDefaultTask()`:
```c
/* USER CODE BEGIN 5 */
printf("Sentry init\n");
sentry_init();
if (sentry_init() != 0) {
printf("Sentry init failed, all traffic will be denied\n");
Error_Handler();
}
printf("Echo init\n");
echo_init();
printf("Ping init\n");
Expand Down
231 changes: 146 additions & 85 deletions examples/STM32-LWIP/Src/sentry.c
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Original file line number Diff line number Diff line change
Expand Up @@ -135,109 +135,144 @@ static wolfsentry_errcode_t test_action(
int sentry_init(void)
{
wolfsentry_errcode_t ret;
wolfsentry_errcode_t fini_ret;
wolfsentry_ent_id_t id;
struct wolfsentry_context *ctx = NULL;
struct wolfsentry_eventconfig config = { 0 };
char err_buf[512];
struct wolfsentry_json_process_state *jps;
struct wolfsentry_json_process_state *jps = NULL;

config.route_private_data_size = 32;
config.route_private_data_alignment = 16;
ret = wolfsentry_init(wolfsentry_build_settings,
WOLFSENTRY_CONTEXT_ARGS_OUT_EX4(NULL /* hpi */, NULL /* thread */), &config,
&wolfsentry);
&ctx);

if (ret < 0)
{
printf("unable to initialize wolfSentry, " WOLFSENTRY_ERROR_FMT "\n",
WOLFSENTRY_ERROR_FMT_ARGS(ret));
return ret;
}

/* Insert the possible actions into wolfSentry */
wolfsentry_action_insert( WOLFSENTRY_CONTEXT_ARGS_OUT_EX4(wolfsentry, NULL),
ret = wolfsentry_action_insert(WOLFSENTRY_CONTEXT_ARGS_OUT_EX4(ctx, NULL),
"handle-insert",
WOLFSENTRY_LENGTH_NULL_TERMINATED,
WOLFSENTRY_ACTION_FLAG_NONE,
test_action,
NULL,
&id);

wolfsentry_action_insert(
WOLFSENTRY_CONTEXT_ARGS_OUT_EX4(wolfsentry, NULL),
"handle-delete",
WOLFSENTRY_LENGTH_NULL_TERMINATED,
WOLFSENTRY_ACTION_FLAG_NONE,
test_action,
NULL,
&id);

wolfsentry_action_insert(
WOLFSENTRY_CONTEXT_ARGS_OUT_EX4(wolfsentry, NULL),
"handle-match",
WOLFSENTRY_LENGTH_NULL_TERMINATED,
WOLFSENTRY_ACTION_FLAG_NONE,
test_action,
NULL,
&id);

wolfsentry_action_insert(
WOLFSENTRY_CONTEXT_ARGS_OUT_EX4(wolfsentry, NULL),
"notify-on-match",
WOLFSENTRY_LENGTH_NULL_TERMINATED,
WOLFSENTRY_ACTION_FLAG_NONE,
test_action,
NULL,
&id);

wolfsentry_action_insert(
WOLFSENTRY_CONTEXT_ARGS_OUT_EX4(wolfsentry, NULL),
"handle-connect",
WOLFSENTRY_LENGTH_NULL_TERMINATED,
WOLFSENTRY_ACTION_FLAG_NONE,
test_action,
NULL,
&id);

wolfsentry_action_insert(
WOLFSENTRY_CONTEXT_ARGS_OUT_EX4(wolfsentry, NULL),
"handle-connect2",
WOLFSENTRY_LENGTH_NULL_TERMINATED,
WOLFSENTRY_ACTION_FLAG_NONE,
test_action,
NULL,
&id);
if (ret >= 0)
ret = wolfsentry_action_insert(
WOLFSENTRY_CONTEXT_ARGS_OUT_EX4(ctx, NULL),
"handle-delete",
WOLFSENTRY_LENGTH_NULL_TERMINATED,
WOLFSENTRY_ACTION_FLAG_NONE,
test_action,
NULL,
&id);

if (ret >= 0)
ret = wolfsentry_action_insert(
WOLFSENTRY_CONTEXT_ARGS_OUT_EX4(ctx, NULL),
"handle-match",
WOLFSENTRY_LENGTH_NULL_TERMINATED,
WOLFSENTRY_ACTION_FLAG_NONE,
test_action,
NULL,
&id);

if (ret >= 0)
ret = wolfsentry_action_insert(
WOLFSENTRY_CONTEXT_ARGS_OUT_EX4(ctx, NULL),
"notify-on-match",
WOLFSENTRY_LENGTH_NULL_TERMINATED,
WOLFSENTRY_ACTION_FLAG_NONE,
test_action,
NULL,
&id);

if (ret >= 0)
ret = wolfsentry_action_insert(
WOLFSENTRY_CONTEXT_ARGS_OUT_EX4(ctx, NULL),
"handle-connect",
WOLFSENTRY_LENGTH_NULL_TERMINATED,
WOLFSENTRY_ACTION_FLAG_NONE,
test_action,
NULL,
&id);

if (ret >= 0)
ret = wolfsentry_action_insert(
WOLFSENTRY_CONTEXT_ARGS_OUT_EX4(ctx, NULL),
"handle-connect2",
WOLFSENTRY_LENGTH_NULL_TERMINATED,
WOLFSENTRY_ACTION_FLAG_NONE,
test_action,
NULL,
&id);

if (ret < 0)
{
printf("unable to insert wolfSentry actions, " WOLFSENTRY_ERROR_FMT "\n",
WOLFSENTRY_ERROR_FMT_ARGS(ret));
}

/* Initalize the wolfSentry JSON parser */
if ((ret = wolfsentry_config_json_init(
WOLFSENTRY_CONTEXT_ARGS_OUT_EX4(wolfsentry, NULL),
WOLFSENTRY_CONFIG_LOAD_FLAG_NONE,
&jps)) < 0)
if (ret >= 0)
{
printf("error while initializing wolfSentry config parser, "
WOLFSENTRY_ERROR_FMT "\n", WOLFSENTRY_ERROR_FMT_ARGS(ret));
ret = wolfsentry_config_json_init(
WOLFSENTRY_CONTEXT_ARGS_OUT_EX4(ctx, NULL),
WOLFSENTRY_CONFIG_LOAD_FLAG_NONE,
&jps);
if (ret < 0)
{
printf("error while initializing wolfSentry config parser, "
WOLFSENTRY_ERROR_FMT "\n", WOLFSENTRY_ERROR_FMT_ARGS(ret));
}
}

/* wolfSentry uses a streaming reader/parser for the config file */
/* Send the read data into the JSON parser */
ret = wolfsentry_config_json_feed(jps,
(const unsigned char *)wolfsentry_config_data,
strlen(wolfsentry_config_data), err_buf, sizeof err_buf);

if (ret < 0)
{
printf("error while loading wolfSentry config data, "
WOLFSENTRY_ERROR_FMT ", msg: %s\n",
WOLFSENTRY_ERROR_FMT_ARGS(ret), err_buf);
}

/* Clean up the JSON parser */
if ((ret = wolfsentry_config_json_fini(&jps, err_buf, sizeof err_buf)) < 0)
if (ret >= 0)
{
printf("error while loading wolfSentry config data, "
WOLFSENTRY_ERROR_FMT ", msg: %s\n",
WOLFSENTRY_ERROR_FMT_ARGS(ret), err_buf);
ret = wolfsentry_config_json_feed(jps,
(const unsigned char *)wolfsentry_config_data,
strlen(wolfsentry_config_data), err_buf, sizeof err_buf);
if (ret < 0)
{
printf("error while loading wolfSentry config data, "
WOLFSENTRY_ERROR_FMT ", msg: %s\n",
WOLFSENTRY_ERROR_FMT_ARGS(ret), err_buf);
}
}

/* Clean up the JSON parser. This commits the parsed config. */
if (jps != NULL)
{
fini_ret = wolfsentry_config_json_fini(&jps, err_buf, sizeof err_buf);
if (fini_ret < 0)
{
printf("error while loading wolfSentry config data, "
WOLFSENTRY_ERROR_FMT ", msg: %s\n",
WOLFSENTRY_ERROR_FMT_ARGS(fini_ret), err_buf);
if (ret >= 0)
ret = fini_ret;
}
}

if (ret < 0)
{
(void)wolfsentry_shutdown(WOLFSENTRY_CONTEXT_ARGS_OUT_EX4(&ctx, NULL));
return ret;
}

/* Publish the context only once the policy is committed, so a concurrent
* packet filter never dispatches against an empty route table. */
WOLFSENTRY_ATOMIC_STORE(wolfsentry, ctx);

return 0;
}

Expand All @@ -247,14 +282,19 @@ int sentry_init(void)
int sentry_action(ip_addr_t *local_ip, ip_addr_t *remote_ip, uint16_t local_port, uint16_t remote_port, sentry_action_type action)
{
wolfsentry_errcode_t ret;
wolfsentry_action_res_t action_results;
wolfsentry_action_res_t action_results = WOLFSENTRY_ACTION_RES_NONE;
/* Note that sa.addr is 0 bytes, addr_buf essentially enlarges this to the correct size */
struct {
struct wolfsentry_sockaddr sa;
byte addr_buf[4];
} remote, local;
u32_t remoteip = remote_ip->addr;
u32_t localip = local_ip->addr;
struct wolfsentry_context *ctx = WOLFSENTRY_ATOMIC_LOAD(wolfsentry);

/* Fail closed until initialization has published a configured context */
if (ctx == NULL)
return -1;

/* Connect will increment the connection count in wolfSentry, disconnect
* will decrement it */
Expand Down Expand Up @@ -289,7 +329,7 @@ int sentry_action(ip_addr_t *local_ip, ip_addr_t *remote_ip, uint16_t local_port

/* Send the details of this to wolfSentry and get the result */
ret = wolfsentry_route_event_dispatch_with_inited_result(
WOLFSENTRY_CONTEXT_ARGS_OUT_EX4(wolfsentry, NULL),
WOLFSENTRY_CONTEXT_ARGS_OUT_EX4(ctx, NULL),
&remote.sa,
&local.sa,
WOLFSENTRY_ROUTE_FLAG_DIRECTION_IN,
Expand All @@ -304,11 +344,14 @@ int sentry_action(ip_addr_t *local_ip, ip_addr_t *remote_ip, uint16_t local_port
WOLFSENTRY_ERROR_FMT_ARGS(ret));
fflush(stdout);

/* Fail closed: a dispatch error denies the connection */
if (ret < 0) {
return -1;
}

/* Check the result, if it contains "reject" then notify the caller */
if (WOLFSENTRY_ERROR_DECODE_ERROR_CODE(ret) >= 0) {
if (WOLFSENTRY_MASKIN_BITS(action_results, WOLFSENTRY_ACTION_RES_REJECT)) {
return -1;
}
if (WOLFSENTRY_MASKIN_BITS(action_results, WOLFSENTRY_ACTION_RES_REJECT)) {
return -1;
}

return 0;
Expand All @@ -324,6 +367,11 @@ int sentry_action_ping(const ip_addr_t *addr, u8_t type)
struct wolfsentry_sockaddr sa;
byte addr_buf[4];
} remote;
struct wolfsentry_context *ctx = WOLFSENTRY_ATOMIC_LOAD(wolfsentry);

/* Fail closed until initialization has published a configured context */
if (ctx == NULL)
return -1;

/* ICMP protocol check. The ICMP packet type is the port number for this
* check */
Expand All @@ -335,7 +383,7 @@ int sentry_action_ping(const ip_addr_t *addr, u8_t type)
memcpy(remote.sa.addr, &addr->addr, 4);

ret = wolfsentry_route_event_dispatch(
WOLFSENTRY_CONTEXT_ARGS_OUT_EX4(wolfsentry, NULL),
WOLFSENTRY_CONTEXT_ARGS_OUT_EX4(ctx, NULL),
&remote.sa,
&remote.sa, /* Reuse for now */
WOLFSENTRY_ROUTE_FLAG_DIRECTION_IN,
Expand All @@ -348,10 +396,14 @@ int sentry_action_ping(const ip_addr_t *addr, u8_t type)
printf("PING Sentry action returned " WOLFSENTRY_ERROR_FMT "\n",
WOLFSENTRY_ERROR_FMT_ARGS(ret));
fflush(stdout);
if (WOLFSENTRY_ERROR_DECODE_ERROR_CODE(ret) >= 0) {
if (WOLFSENTRY_MASKIN_BITS(action_results, WOLFSENTRY_ACTION_RES_REJECT)) {
return -1;
}

/* Fail closed: a dispatch error denies the packet */
if (ret < 0) {
return -1;
}

if (WOLFSENTRY_MASKIN_BITS(action_results, WOLFSENTRY_ACTION_RES_REJECT)) {
return -1;
}

return 0;
Expand All @@ -367,6 +419,11 @@ int sentry_action_mac(struct eth_addr *addr)
struct wolfsentry_sockaddr sa;
byte addr_buf[6];
} remote;
struct wolfsentry_context *ctx = WOLFSENTRY_ATOMIC_LOAD(wolfsentry);

/* Fail closed until initialization has published a configured context */
if (ctx == NULL)
return -1;

/* We only really care about the data and length, the family is AF_LINK */
remote.sa.sa_family = WOLFSENTRY_AF_LINK;
Expand All @@ -376,7 +433,7 @@ int sentry_action_mac(struct eth_addr *addr)
memcpy(remote.sa.addr, &addr->addr, 6);

ret = wolfsentry_route_event_dispatch(
WOLFSENTRY_CONTEXT_ARGS_OUT_EX4(wolfsentry, NULL),
WOLFSENTRY_CONTEXT_ARGS_OUT_EX4(ctx, NULL),
&remote.sa,
&remote.sa, /* Reuse for now */
WOLFSENTRY_ROUTE_FLAG_DIRECTION_IN,
Expand All @@ -390,10 +447,14 @@ int sentry_action_mac(struct eth_addr *addr)
printf("MAC Sentry action returned " WOLFSENTRY_ERROR_FMT "\n",
WOLFSENTRY_ERROR_FMT_ARGS(ret));
fflush(stdout);
if (WOLFSENTRY_ERROR_DECODE_ERROR_CODE(ret) >= 0) {
if (WOLFSENTRY_MASKIN_BITS(action_results, WOLFSENTRY_ACTION_RES_REJECT)) {
return -1;
}

/* Fail closed: a dispatch error denies the frame */
if (ret < 0) {
return -1;
}

if (WOLFSENTRY_MASKIN_BITS(action_results, WOLFSENTRY_ACTION_RES_REJECT)) {
return -1;
}

return 0;
Expand Down
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