iwinfo: Query hostapd for 'ssid2'

DAWN is reporting invalid results because it can't find the SSID of the
running networks. Reported by Elwin Huang in
https://github.com/berlin-open-wireless-lab/DAWN/issues/247#issuecomment-3327148254

It needs to be parsed like wpa_config_parse_string() does.

Signed-off-by: David Woodhouse <dwmw2@infradead.org>

1 files changed, 90 insertions, 0 deletions

diff --git a/iwinfo_nl80211.c b/iwinfo_nl80211.c
index cd801af..813678a 100644
--- a/iwinfo_nl80211.c
+++ b/iwinfo_nl80211.c
@@ -1299,6 +1299,87 @@ static int nl80211_get_ssid_bssid_cb(struct nl_msg *msg, void *arg)
 	}
 }
 
+/*
+ * This matches the behaviour of hostapd's wpa_config_parse_string
+ *
+ * (double quoted string, hexdump, printf-escaped string)
+ * ssid2="test"
+ * ssid2=74657374
+ * ssid2=P"hello\nthere"
+ */
+static int parse_ssid2(const char *value, char *buf, size_t buflen)
+{
+	const char *pos;
+	size_t len, i;
+
+	if (*value == '"') {
+		value++;
+		pos = strrchr(value, '"');
+		if (!pos || pos[1] != '\0')
+			return -1;
+		len = pos - value;
+		if (len >= buflen)
+			len = buflen - 1;
+		memcpy(buf, value, len);
+		buf[len] = '\0';
+		return 0;
+	} else if (*value == 'P' && value[1] == '"') {
+		value += 2;
+		pos = strrchr(value, '"');
+		if (!pos || pos[1] != '\0')
+			return -1;
+		len = 0;
+		while (*value && value < pos && len < buflen - 1) {
+			if (*value == '\\' && value + 1 < pos) {
+				value++;
+				if (*value == 'x' && value + 2 < pos) {
+					char hex[3] = {value[1], value[2], 0};
+					buf[len++] = strtol(hex, NULL, 16);
+					value += 3;
+				} else if (*value >= '0' && *value <= '7' && value + 2 < pos &&
+					   value[1] >= '0' && value[1] <= '7' &&
+					   value[2] >= '0' && value[2] <= '7') {
+					buf[len++] = ((value[0] - '0') << 6) |
+						     ((value[1] - '0') << 3) |
+						     (value[2] - '0');
+					value += 3;
+				} else {
+					switch (*value) {
+					case 'n': buf[len++] = '\n'; break;
+					case 'r': buf[len++] = '\r'; break;
+					case 't': buf[len++] = '\t'; break;
+					case '\\': buf[len++] = '\\'; break;
+					case '"': buf[len++] = '"'; break;
+					default: buf[len++] = *value; break;
+					}
+					value++;
+				}
+			} else {
+				buf[len++] = *value++;
+			}
+		}
+		buf[len] = '\0';
+		return 0;
+	} else {
+		len = strlen(value);
+		if (len & 1)
+			return -1;
+		len /= 2;
+		if (len >= buflen)
+			len = buflen - 1;
+		for (i = 0; i < len; i++) {
+			char hex[3] = {value[i*2], value[i*2+1], 0};
+			char *end;
+			long val = strtol(hex, &end, 16);
+			if (*end)
+				return -1;
+			buf[i] = val;
+		}
+		buf[len] = '\0';
+		return 0;
+	}
+}
+
 static int nl80211_get_ssid(const char *ifname, char *buf)
 {
 	char *res;
@@ -1316,6 +1397,15 @@ static int nl80211_get_ssid(const char *ifname, char *buf)
 		nl80211_hostapd_query(ifname, "ssid", sb.ssid,
 		                      IWINFO_ESSID_MAX_SIZE + 1);
 
+	if (sb.ssid[0] == 0) {
+		/* ssid2 can be quoted, printf-encoded, or hex; needs parsing.
+		 * Buffer sized for printf encoding (\xHH = 4 chars per byte) plus P"" wrapper. */
+		char ssid2_raw[IWINFO_ESSID_MAX_SIZE * 4 + 3];
+		ssid2_raw[0] = 0;
+		if (nl80211_hostapd_query(ifname, "ssid2", ssid2_raw, sizeof(ssid2_raw)))
+			parse_ssid2(ssid2_raw, (char *)sb.ssid, IWINFO_ESSID_MAX_SIZE + 1);
+	}
+
 	/* failed, try to obtain Mesh ID */
 	if (sb.ssid[0] == 0)
 		iwinfo_ubus_query(res ? res : ifname, "mesh_id",