SIM/USIM: Add function to get the MNC length from the SIM/USIM

The EF-AD (administrative data) file may contain information about the
length of the MNC (2 or 3 digits) in the IMSI. This can be used to
construct the realm according to 3GPP TS 23.003 during EAP-SIM or
EAP-AKA authentication.

Signed-hostap: Simon Baatz <gmbnomis@gmail.com>

src/utils/pcsc_funcs.c

@@ -1023,6 +1023,61 @@ int scard_get_imsi(struct scard_data *scard, char *imsi, size_t *len)
 }
 
 
+/**
+ * scard_get_mnc_len - Read length of MNC in the IMSI from SIM/USIM card
+ * @scard: Pointer to private data from scard_init()
+ * Returns: length (>0) on success, -1 if administrative data file cannot be
+ * selected, -2 if administrative data file selection returns invalid result
+ * code, -3 if parsing FSP template file fails (USIM only), -4 if length of
+ * the file is unexpected, -5 if reading file fails, -6 if MNC length is not
+ * in range (i.e. 2 or 3), -7 if MNC length is not available.
+ *
+ */
+int scard_get_mnc_len(struct scard_data *scard)
+{
+	unsigned char buf[100];
+	size_t blen;
+	int file_size;
+
+	wpa_printf(MSG_DEBUG, "SCARD: reading MNC len from (GSM) EF-AD");
+	blen = sizeof(buf);
+	if (scard_select_file(scard, SCARD_FILE_GSM_EF_AD, buf, &blen))
+		return -1;
+	if (blen < 4) {
+		wpa_printf(MSG_WARNING, "SCARD: too short (GSM) EF-AD "
+			   "header (len=%ld)", (long) blen);
+		return -2;
+	}
+
+	if (scard->sim_type == SCARD_GSM_SIM) {
+		file_size = (buf[2] << 8) | buf[3];
+	} else {
+		if (scard_parse_fsp_templ(buf, blen, NULL, &file_size))
+			return -3;
+	}
+	if (file_size == 3) {
+		wpa_printf(MSG_DEBUG, "SCARD: MNC length not available");
+		return -7;
+	}
+	if (file_size < 4 || file_size > sizeof(buf)) {
+		wpa_printf(MSG_DEBUG, "SCARD: invalid file length=%ld",
+			   (long) file_size);
+		return -4;
+	}
+
+	if (scard_read_file(scard, buf, file_size))
+		return -5;
+	buf[3] = buf[3] & 0x0f; /* upper nibble reserved for future use  */
+	if (buf[3] < 2 || buf[3] > 3) {
+		wpa_printf(MSG_DEBUG, "SCARD: invalid MNC length=%ld",
+			   (long) buf[3]);
+		return -6;
+	}
+	wpa_printf(MSG_DEBUG, "SCARD: MNC length=%ld", (long) buf[3]);
+	return buf[3];
+}
+
+
 /**
  * scard_gsm_auth - Run GSM authentication command on SIM card
  * @scard: Pointer to private data from scard_init()

src/utils/pcsc_funcs.h

@@ -26,6 +26,7 @@
 #define SCARD_FILE_GSM_DF	0x7F20
 #define SCARD_FILE_UMTS_DF	0x7F50
 #define SCARD_FILE_GSM_EF_IMSI	0x6F07
+#define SCARD_FILE_GSM_EF_AD	0x6FAD
 #define SCARD_FILE_EF_DIR	0x2F00
 #define SCARD_FILE_EF_ICCID	0x2FE2
 #define SCARD_FILE_EF_CK	0x6FE1
@@ -47,6 +48,7 @@ void scard_deinit(struct scard_data *scard);
 
 int scard_set_pin(struct scard_data *scard, const char *pin);
 int scard_get_imsi(struct scard_data *scard, char *imsi, size_t *len);
+int scard_get_mnc_len(struct scard_data *scard);
 int scard_gsm_auth(struct scard_data *scard, const unsigned char *_rand,
 		   unsigned char *sres, unsigned char *kc);
 int scard_umts_auth(struct scard_data *scard, const unsigned char *_rand,