gsm0808: Add utils for Encryption Information
The planned support for true A over IP requires the encoding of
the an Encryption Information element (see also BSS_MAP_MSG_CIPHER_MODE_CMD).
This commt adds encoding/decoding functionality and tests for
the element mentioned above, however, it is not yet actively used.
Change-Id: I8262050a9d9fd3f17462cfbb046c6e034dccc6fb
diff --git a/src/gsm/gsm0808_utils.c b/src/gsm/gsm0808_utils.c
index ef0f943..1915605 100644
--- a/src/gsm/gsm0808_utils.c
+++ b/src/gsm/gsm0808_utils.c
@@ -33,6 +33,7 @@
#define CHANNEL_TYPE_ELEMENT_MAXLEN 11
#define CHANNEL_TYPE_ELEMENT_MINLEN 3
+#define ENCRYPT_INFO_ELEMENT_MINLEN 1
/* Encode AoIP transport address element */
uint8_t gsm0808_enc_aoip_trasp_addr(struct msgb *msg,
@@ -379,3 +380,73 @@
return (int)(elem - old_elem);
}
+
+/* Encode Encryption Information element */
+uint8_t gsm0808_enc_encrypt_info(struct msgb *msg,
+ const struct gsm0808_encrypt_info *ei)
+{
+ unsigned int i;
+ uint8_t perm_algo = 0;
+ uint8_t *ptr;
+ uint8_t *old_tail;
+ uint8_t *tlv_len;
+
+ OSMO_ASSERT(msg);
+ OSMO_ASSERT(ei);
+ OSMO_ASSERT(ei->key_len <= ARRAY_SIZE(ei->key));
+ OSMO_ASSERT(ei->perm_algo_len <= ENCRY_INFO_PERM_ALGO_MAXLEN);
+
+ msgb_put_u8(msg, GSM0808_IE_ENCRYPTION_INFORMATION);
+ tlv_len = msgb_put(msg, 1);
+ old_tail = msg->tail;
+
+ for (i = 0; i < ei->perm_algo_len; i++) {
+ /* Note: gsm_08_08.h defines the permitted algorithms
+ * as an enum which ranges from 0x01 to 0x08 */
+ OSMO_ASSERT(ei->perm_algo[i] != 0);
+ OSMO_ASSERT(ei->perm_algo[i] <= ENCRY_INFO_PERM_ALGO_MAXLEN);
+ perm_algo |= (1 << (ei->perm_algo[i] - 1));
+ }
+
+ msgb_put_u8(msg, perm_algo);
+ ptr = msgb_put(msg, ei->key_len);
+ memcpy(ptr, ei->key, ei->key_len);
+
+ *tlv_len = (uint8_t) (msg->tail - old_tail);
+ return *tlv_len + 2;
+}
+
+/* Decode Encryption Information element */
+int gsm0808_dec_encrypt_info(struct gsm0808_encrypt_info *ei,
+ const uint8_t *elem, uint8_t len)
+{
+ uint8_t perm_algo;
+ unsigned int i;
+ unsigned int perm_algo_len = 0;
+ const uint8_t *old_elem = elem;
+
+ OSMO_ASSERT(ei);
+ if (!elem)
+ return -EINVAL;
+ if (len <= 0)
+ return -EINVAL;
+
+ memset(ei, 0, sizeof(*ei));
+
+ perm_algo = *elem;
+ elem++;
+
+ for (i = 0; i < ENCRY_INFO_PERM_ALGO_MAXLEN; i++) {
+ if (perm_algo & (1 << i)) {
+ ei->perm_algo[perm_algo_len] = i + 1;
+ perm_algo_len++;
+ }
+ }
+ ei->perm_algo_len = perm_algo_len;
+
+ ei->key_len = len - 1;
+ memcpy(ei->key, elem, ei->key_len);
+ elem+=ei->key_len;
+
+ return (int)(elem - old_elem);
+}