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https://github.com/M66B/NetGuard.git
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Added SNI decoding
This commit is contained in:
M66B
parent
27cfbe8aba
commit
78a0feb5a6
4 changed files with 202 additions and 0 deletions
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@ -9,6 +9,7 @@ add_library( netguard
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src/main/jni/netguard/tcp.c
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src/main/jni/netguard/udp.c
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src/main/jni/netguard/icmp.c
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src/main/jni/netguard/tls.c
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src/main/jni/netguard/dns.c
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src/main/jni/netguard/dhcp.c
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src/main/jni/netguard/pcap.c
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@ -292,6 +292,20 @@ void handle_ip(const struct arguments *args,
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uid = get_uid_q(args, version, protocol, source, sport, dest, dport);
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}
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// Get server name
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if (protocol == IPPROTO_TCP) {
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const struct tcphdr *tcphdr = (struct tcphdr *) payload;
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const uint8_t tcpoptlen = (uint8_t) ((tcphdr->doff - 5) * 4);
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const uint8_t *data = payload + sizeof(struct tcphdr) + tcpoptlen;
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const uint16_t datalen = (const uint16_t) (length - (data - pkt));
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char server_name[TLS_SNI_LENGTH + 1];
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if (get_sni(data, datalen, server_name)) {
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log_android(ANDROID_LOG_INFO, "TLS server name: %s", server_name);
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dns_resolved(args, server_name, server_name, dest, -1);
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}
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}
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log_android(ANDROID_LOG_DEBUG,
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"Packet v%d %s/%u > %s/%u proto %d flags %s uid %d",
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version, source, sport, dest, dport, protocol, flags, uid);
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@ -253,6 +253,18 @@ typedef struct pcaprec_hdr_s {
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#define LINKTYPE_RAW 101
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// TLS
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#define TLS_SNI_LENGTH 255
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#define TLS_HANDSHAKE_RECORD 22
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#define TLS_MESSAGE_CLIENTHELLO 1
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#define TLS_EXTENSION_TYPE_SERVER_NAME 0
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int get_sni(
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const uint8_t *data,
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const uint16_t datalen,
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char *server_name);
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// DNS
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#define DNS_QCLASS_IN 1
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175
app/src/main/jni/netguard/tls.c
Normal file
175
app/src/main/jni/netguard/tls.c
Normal file
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@ -0,0 +1,175 @@
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/*
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This file is part of NetGuard.
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NetGuard is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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NetGuard is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with NetGuard. If not, see <http://www.gnu.org/licenses/>.
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Copyright 2015-2019 by Marcel Bokhorst (M66B)
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*/
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#include "netguard.h"
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int get_sni(
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const uint8_t *data,
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const uint16_t datalen,
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char *server_name) {
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if (datalen < 6) {
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log_android(ANDROID_LOG_DEBUG, "TLS header too short");
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return 0;
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}
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uint8_t content_type = (uint8_t) data[0];
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uint8_t major_version = (uint8_t) data[1];
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uint8_t minor_version = (uint8_t) data[2];
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uint16_t content_length = ((uint16_t) data[3] << 8) | data[4];
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uint8_t message_type = (uint8_t) data[5];
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// https://www.rfc-editor.org/rfc/rfc5246#section-7.4.1.2
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if (content_type != TLS_HANDSHAKE_RECORD ||
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major_version < 0x03 ||
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5 + content_length != datalen ||
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message_type != TLS_MESSAGE_CLIENTHELLO) {
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log_android(ANDROID_LOG_DEBUG, "TLS content %d version %d length %d/%d type %d",
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content_type, major_version, 5 + content_length, datalen, message_type);
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return 0;
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}
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log_android(ANDROID_LOG_DEBUG, "TLS client hello version %d.%d",
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major_version, minor_version);
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uint8_t index = 6 + // header above
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3 + // client hello length
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2 + // client hello protocol version
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32; // random value
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// Session ID
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if (index >= datalen) {
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log_android(ANDROID_LOG_WARN, "TLS session ID %d/%d", index, datalen);
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return 0;
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}
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log_android(ANDROID_LOG_DEBUG, "TLS hello version %d.%d",
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data[9], data[10]);
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uint8_t session_len = data[index];
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index += 1 + session_len;
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// Cipher suites
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if (index + 1 >= datalen) {
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log_android(ANDROID_LOG_WARN, "TLS cipher suites %d/%d", index + 1, datalen);
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return 0;
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}
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uint16_t suites_len = ((uint16_t) data[index] << 8) | data[index + 1];
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index += 2 + suites_len;
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// Compression method
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if (index >= datalen) {
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log_android(ANDROID_LOG_WARN, "TLS compression %d/%d", index, datalen);
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return 0;
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}
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uint8_t compression_len = data[index];
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index += 1 + compression_len;
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// Extensions length
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if (index + 1 >= datalen) {
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log_android(ANDROID_LOG_WARN, "TLS extensions %d/%d", index + 1, datalen);
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return 0;
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}
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uint16_t edatalen = ((uint16_t) data[index] << 8) | data[index + 1];
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index += 2;
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if (edatalen == 0 || index + edatalen != datalen) {
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log_android(ANDROID_LOG_WARN, "TLS extensions(2) len=%d %d/%d",
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edatalen, index + edatalen, datalen);
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return 0;
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}
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uint16_t eindex = 0;
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const uint8_t *edata = data + index;
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while (eindex < edatalen) {
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if (eindex + 1 >= edatalen) {
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log_android(ANDROID_LOG_WARN, "TLS ext_type %d/%d", eindex + 1, edatalen);
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return 0;
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}
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uint16_t ext_type = ((uint16_t) edata[eindex] << 8) | edata[eindex + 1];
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eindex += 2;
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log_android(ANDROID_LOG_DEBUG, "TLS ext_type=%d", ext_type);
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if (eindex + 1 >= edatalen) {
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log_android(ANDROID_LOG_WARN, "TLS ext_len %d/%d", eindex + 1, edatalen);
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return 0;
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}
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uint16_t ext_len = ((uint16_t) edata[eindex] << 8) | edata[eindex + 1];
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eindex += 2;
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if (eindex + ext_len > edatalen) {
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log_android(ANDROID_LOG_WARN, "TLS ext_len(2) %d/%d", eindex + ext_len, edatalen);
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return 0;
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}
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// https://datatracker.ietf.org/doc/html/rfc6066
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if (ext_type == TLS_EXTENSION_TYPE_SERVER_NAME) {
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if (eindex + 1 >= edatalen) {
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log_android(ANDROID_LOG_WARN, "TLS sni_len %d/%d", eindex + 1, edatalen);
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return 0;
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}
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uint16_t sni_len = ((uint16_t) edata[eindex] << 8) | edata[eindex + 1];
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eindex += 2;
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log_android(ANDROID_LOG_DEBUG, "TLS sni_len=%d", sni_len);
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if (eindex + sni_len >= edatalen) {
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log_android(ANDROID_LOG_WARN, "TLS sni_len(2) len=%d %d/%d",
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sni_len, eindex + sni_len, edatalen);
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return 0;
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}
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if (eindex >= edatalen) {
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log_android(ANDROID_LOG_WARN, "TLS sni_type %d/%d", eindex, edatalen);
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return 0;
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}
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uint8_t sni_type = edata[eindex++];
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if (sni_type != 0) {
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log_android(ANDROID_LOG_WARN, "TLS sni_type=%d", sni_type);
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return 0;
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}
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if (eindex + 1 >= edatalen) {
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log_android(ANDROID_LOG_WARN, "TLS name_len %d/%d", eindex + 1, edatalen);
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return 0;
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}
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uint16_t name_len = ((uint16_t) edata[eindex] << 8) | edata[eindex + 1];
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eindex += 2;
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if (eindex + name_len >= edatalen) {
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log_android(ANDROID_LOG_WARN, "TLS name_len(2) len=%d %d/%d",
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name_len, eindex + name_len, edatalen);
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return 0;
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}
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if (name_len >= TLS_SNI_LENGTH) {
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log_android(ANDROID_LOG_WARN, "TLS name_len(3) %d/%d",
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name_len, TLS_SNI_LENGTH);
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return 0;
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}
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memcpy(server_name, edata + eindex, name_len);
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server_name[name_len] = 0;
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return 1;
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}
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eindex += ext_len;
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}
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return 0;
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}
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