Add backtrace-based error path testing mechanism

The new TEST_FAIL and GET_FAIL control interface commands can be used
similarly to the earlier TEST_ALLOC_FAIL/GET_ALLOC_FAIL design. The new
version is more generic framework allowing any function to be annotated
for failure testing with the TEST_FAIL() macro. This mechanism is only
available in builds with CONFIG_WPA_TRACE_BFD=y and
CONFIG_TESTING_OPTIONS=y. For other builds, the TEST_FAIL() macro is
defined to return 0 to allow the compiler to remove the test code from
normal production builds.

As the first test site, allow os_get_random() to be marked for failing
based on call backtrace.

Signed-off-by: Jouni Malinen <j@w1.fi>

hostapd/ctrl_iface.c

@@ -1746,6 +1746,45 @@ static int hostapd_ctrl_get_alloc_fail(struct hostapd_data *hapd,
 #endif /* WPA_TRACE_BFD */
 }
 
+
+static int hostapd_ctrl_test_fail(struct hostapd_data *hapd, char *cmd)
+{
+#ifdef WPA_TRACE_BFD
+	extern char wpa_trace_test_fail_func[256];
+	extern unsigned int wpa_trace_test_fail_after;
+	char *pos;
+
+	wpa_trace_test_fail_after = atoi(cmd);
+	pos = os_strchr(cmd, ':');
+	if (pos) {
+		pos++;
+		os_strlcpy(wpa_trace_test_fail_func, pos,
+			   sizeof(wpa_trace_test_fail_func));
+	} else {
+		wpa_trace_test_fail_after = 0;
+	}
+
+	return 0;
+#else /* WPA_TRACE_BFD */
+	return -1;
+#endif /* WPA_TRACE_BFD */
+}
+
+
+static int hostapd_ctrl_get_fail(struct hostapd_data *hapd,
+				 char *buf, size_t buflen)
+{
+#ifdef WPA_TRACE_BFD
+	extern char wpa_trace_test_fail_func[256];
+	extern unsigned int wpa_trace_test_fail_after;
+
+	return os_snprintf(buf, buflen, "%u:%s", wpa_trace_test_fail_after,
+			   wpa_trace_test_fail_func);
+#else /* WPA_TRACE_BFD */
+	return -1;
+#endif /* WPA_TRACE_BFD */
+}
+
 #endif /* CONFIG_TESTING_OPTIONS */
 
 
@@ -2079,6 +2118,11 @@ static void hostapd_ctrl_iface_receive(int sock, void *eloop_ctx,
 	} else if (os_strcmp(buf, "GET_ALLOC_FAIL") == 0) {
 		reply_len = hostapd_ctrl_get_alloc_fail(hapd, reply,
 							reply_size);
+	} else if (os_strncmp(buf, "TEST_FAIL ", 10) == 0) {
+		if (hostapd_ctrl_test_fail(hapd, buf + 10) < 0)
+			reply_len = -1;
+	} else if (os_strcmp(buf, "GET_FAIL") == 0) {
+		reply_len = hostapd_ctrl_get_fail(hapd, reply, reply_size);
 #endif /* CONFIG_TESTING_OPTIONS */
 	} else if (os_strncmp(buf, "CHAN_SWITCH ", 12) == 0) {
 		if (hostapd_ctrl_iface_chan_switch(hapd->iface, buf + 12))

src/utils/os.h

@@ -646,4 +646,12 @@ int os_exec(const char *program, const char *arg, int wait_completion);
 #define strcpy OS_DO_NOT_USE_strcpy
 #endif /* OS_REJECT_C_LIB_FUNCTIONS */
 
+
+#if defined(WPA_TRACE_BFD) && defined(CONFIG_TESTING_OPTIONS)
+#define TEST_FAIL() testing_test_fail()
+int testing_test_fail(void);
+#else
+#define TEST_FAIL() 0
+#endif
+
 #endif /* OS_H */

src/utils/os_unix.c

@@ -226,6 +226,9 @@ int os_get_random(unsigned char *buf, size_t len)
 	FILE *f;
 	size_t rc;
 
+	if (TEST_FAIL())
+		return -1;
+
 	f = fopen("/dev/urandom", "rb");
 	if (f == NULL) {
 		printf("Could not open /dev/urandom.\n");
@@ -548,6 +551,78 @@ static int testing_fail_alloc(void)
 	return 0;
 }
 
+
+char wpa_trace_test_fail_func[256] = { 0 };
+unsigned int wpa_trace_test_fail_after;
+
+int testing_test_fail(void)
+{
+	const char *func[WPA_TRACE_LEN];
+	size_t i, res, len;
+	char *pos, *next;
+	int match;
+
+	if (!wpa_trace_test_fail_after)
+		return 0;
+
+	res = wpa_trace_calling_func(func, WPA_TRACE_LEN);
+	i = 0;
+	if (i < res && os_strcmp(func[i], __func__) == 0)
+		i++;
+
+	pos = wpa_trace_test_fail_func;
+
+	match = 0;
+	while (i < res) {
+		int allow_skip = 1;
+		int maybe = 0;
+
+		if (*pos == '=') {
+			allow_skip = 0;
+			pos++;
+		} else if (*pos == '?') {
+			maybe = 1;
+			pos++;
+		}
+		next = os_strchr(pos, ';');
+		if (next)
+			len = next - pos;
+		else
+			len = os_strlen(pos);
+		if (os_memcmp(pos, func[i], len) != 0) {
+			if (maybe && next) {
+				pos = next + 1;
+				continue;
+			}
+			if (allow_skip) {
+				i++;
+				continue;
+			}
+			return 0;
+		}
+		if (!next) {
+			match = 1;
+			break;
+		}
+		pos = next + 1;
+		i++;
+	}
+	if (!match)
+		return 0;
+
+	wpa_trace_test_fail_after--;
+	if (wpa_trace_test_fail_after == 0) {
+		wpa_printf(MSG_INFO, "TESTING: fail at %s",
+			   wpa_trace_test_fail_func);
+		for (i = 0; i < res; i++)
+			wpa_printf(MSG_INFO, "backtrace[%d] = %s",
+				   (int) i, func[i]);
+		return 1;
+	}
+
+	return 0;
+}
+
 #else
 
 static inline int testing_fail_alloc(void)

wpa_supplicant/ctrl_iface.c

@@ -7562,6 +7562,44 @@ static int wpas_ctrl_get_alloc_fail(struct wpa_supplicant *wpa_s,
 #endif /* WPA_TRACE_BFD */
 }
 
+
+static int wpas_ctrl_test_fail(struct wpa_supplicant *wpa_s, char *cmd)
+{
+#ifdef WPA_TRACE_BFD
+	extern char wpa_trace_test_fail_func[256];
+	extern unsigned int wpa_trace_test_fail_after;
+	char *pos;
+
+	wpa_trace_test_fail_after = atoi(cmd);
+	pos = os_strchr(cmd, ':');
+	if (pos) {
+		pos++;
+		os_strlcpy(wpa_trace_test_fail_func, pos,
+			   sizeof(wpa_trace_test_fail_func));
+	} else {
+		wpa_trace_test_fail_after = 0;
+	}
+	return 0;
+#else /* WPA_TRACE_BFD */
+	return -1;
+#endif /* WPA_TRACE_BFD */
+}
+
+
+static int wpas_ctrl_get_fail(struct wpa_supplicant *wpa_s,
+				    char *buf, size_t buflen)
+{
+#ifdef WPA_TRACE_BFD
+	extern char wpa_trace_test_fail_func[256];
+	extern unsigned int wpa_trace_test_fail_after;
+
+	return os_snprintf(buf, buflen, "%u:%s", wpa_trace_test_fail_after,
+			   wpa_trace_test_fail_func);
+#else /* WPA_TRACE_BFD */
+	return -1;
+#endif /* WPA_TRACE_BFD */
+}
+
 #endif /* CONFIG_TESTING_OPTIONS */
 
 
@@ -8579,6 +8617,11 @@ char * wpa_supplicant_ctrl_iface_process(struct wpa_supplicant *wpa_s,
 			reply_len = -1;
 	} else if (os_strcmp(buf, "GET_ALLOC_FAIL") == 0) {
 		reply_len = wpas_ctrl_get_alloc_fail(wpa_s, reply, reply_size);
+	} else if (os_strncmp(buf, "TEST_FAIL ", 10) == 0) {
+		if (wpas_ctrl_test_fail(wpa_s, buf + 10) < 0)
+			reply_len = -1;
+	} else if (os_strcmp(buf, "GET_FAIL") == 0) {
+		reply_len = wpas_ctrl_get_fail(wpa_s, reply, reply_size);
 #endif /* CONFIG_TESTING_OPTIONS */
 	} else if (os_strncmp(buf, "VENDOR_ELEM_ADD ", 16) == 0) {
 		if (wpas_ctrl_vendor_elem_add(wpa_s, buf + 16) < 0)