Add ESP decryption (unused)

Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>

gnutls-esp.c

@@ -109,8 +109,8 @@ int setup_esp_keys(struct openconnect_info *vpninfo)
 		return -EINVAL;
 	}
 
-	ret = gnutls_rnd(GNUTLS_RND_NONCE, &vpninfo->esp_in.secrets,
-			 sizeof(vpninfo->esp_in.secrets));
+	ret = gnutls_rnd(GNUTLS_RND_NONCE, &vpninfo->esp_in.spi,
+			 sizeof(vpninfo->esp_in.secrets) + sizeof(vpninfo->esp_in.spi));
 	if (ret) {
 		vpn_progress(vpninfo, PRG_ERR,
 			     _("Failed to generate random keys for ESP: %s\n"),
@@ -131,3 +131,65 @@ int setup_esp_keys(struct openconnect_info *vpninfo)
 	vpninfo->dtls_state = DTLS_SECRET;
 	return 0;
 }
+
+
+int decrypt_and_queue_esp_packet(struct openconnect_info *vpninfo, unsigned char *esp, int len)
+{
+	struct pkt *pkt;
+	unsigned char hmac_buf[20];
+	const int ivsize = 16; /* We don't support anything different... yet. */
+
+	if (len < 20 + ivsize)
+		return -EINVAL;
+
+	if (memcmp(esp, vpninfo->esp_in.spi, 4)) {
+		vpn_progress(vpninfo, PRG_DEBUG,
+			     _("Received ESP packet with invalid SPI %02x%02x%02x%02x\n"),
+			     esp[0], esp[1], esp[2], esp[3]);
+		return -EINVAL;
+	}
+
+	/* XXX: Implement seq checking. Record the highest seq# received, and keep
+	   a small bitmap covering a sliding window just before that, so out-of-order
+	   packets can be accepted within reason but each packet only once. */
+
+	gnutls_hmac(vpninfo->esp_in.hmac, esp, len - 12);
+	gnutls_hmac_output(vpninfo->esp_in.hmac, hmac_buf);
+	if (memcmp(hmac_buf, esp + len - 12, 12)) {
+		vpn_progress(vpninfo, PRG_DEBUG,
+			     _("Received ESP packet with invalid HMAC\n"));
+		return -EINVAL;
+	}
+
+	gnutls_cipher_set_iv(vpninfo->esp_in.cipher, esp + 8, ivsize);
+
+	len -= 20 + ivsize;
+
+	pkt = malloc(sizeof(struct pkt) + len);
+	if (!pkt)
+		return -ENOMEM;
+
+	if (gnutls_cipher_decrypt2(vpninfo->esp_in.cipher,
+				   pkt->data + 8 + ivsize, len,
+				   pkt->data, len)) {
+		printf("decrypt fail\n");
+		return -EINVAL;
+	}
+
+	if (pkt->data[len - 1] != 0x04 && pkt->data[len - 1] != 0x29) {
+		/* 0x05 is LZO compressed. */
+		vpn_progress(vpninfo, PRG_ERR,
+			     _("Received ESP packet with unrecognised payload type %02x\n"),
+			     pkt->data[len-1]);
+		return -EINVAL;
+	}
+	if (len <= 2 + pkt->data[len - 2]) {
+		printf("Invalid padding length %02x in ESP\n",
+		       pkt->data[len - 2]);
+		return -EINVAL;
+	}
+	pkt->len = len - 2 + pkt->data[len - 2];
+
+	queue_packet(&vpninfo->incoming_queue, pkt);
+	return 0;
+}

openconnect-internal.h

@@ -751,6 +751,7 @@ int load_pkcs11_certificate(struct openconnect_info *vpninfo);
 /* gnutls-esp.c */
 int setup_esp_keys(struct openconnect_info *vpninfo);
 void destroy_esp_ciphers(struct esp *esp);
+int decrypt_and_queue_esp_packet(struct openconnect_info *vpninfo, unsigned char *esp, int len);
 
 /* {gnutls,openssl}.c */
 int ssl_nonblock_read(struct openconnect_info *vpninfo, void *buf, int maxlen);