nettrace dns and sni

3 files changed, 213 insertions, 0 deletions

diff --git a/src/fnettrace-dns/Makefile.in b/src/fnettrace-dns/Makefile.in
new file mode 100644
index 000000000..6c11e5bc8
--- /dev/null
+++ b/src/fnettrace-dns/Makefile.in
@@ -0,0 +1,17 @@
+.PHONY: all
+all: fnettrace-dns
+
+include ../common.mk
+
+%.o : %.c $(H_FILE_LIST)
+        $(CC) $(CFLAGS) $(EXTRA_CFLAGS) $(INCLUDE) -c $< -o $@
+
+fnettrace-dns: $(OBJS)
+        $(CC)  $(LDFLAGS) -o $@ $(OBJS) $(LIBS) $(EXTRA_LDFLAGS)
+
+.PHONY: clean
+clean:; rm -fr *.o fnettrace-dns *.gcov *.gcda *.gcno *.plist
+
+.PHONY: distclean
+distclean: clean
+        rm -fr Makefile
diff --git a/src/fnettrace-dns/fnettrace_dns.h b/src/fnettrace-dns/fnettrace_dns.h
new file mode 100644
index 000000000..db2e1a668
--- /dev/null
+++ b/src/fnettrace-dns/fnettrace_dns.h
@@ -0,0 +1,34 @@
+/*
+ * Copyright (C) 2014-2022 Firejail Authors
+ *
+ * This file is part of firejail project
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+*/
+#ifndef FNETTRACE_DNS_H
+#define FNETTRACE_DNS_H
+
+#include "../include/common.h"
+#include <unistd.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <netinet/in.h>
+#include <time.h>
+#include <stdarg.h>
+#include <fcntl.h>
+#include <sys/mman.h>
+
+#endif
\ No newline at end of file
diff --git a/src/fnettrace-dns/main.c b/src/fnettrace-dns/main.c
new file mode 100644
index 000000000..0281b5157
--- /dev/null
+++ b/src/fnettrace-dns/main.c
@@ -0,0 +1,162 @@
+/*
+ * Copyright (C) 2014-2022 Firejail Authors
+ *
+ * This file is part of firejail project
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+*/
+#include "fnettrace_dns.h"
+#include <sys/ioctl.h>
+#include <time.h>
+#include <linux/filter.h>
+#include <linux/if_ether.h>
+#define MAX_BUF_SIZE (64 * 1024)
+
+// pkt - start of DNS layer
+void print_dns(uint32_t ip_src, unsigned char *pkt) {
+        assert(pkt);
+
+        char ip[30];
+        sprintf(ip, "%d.%d.%d.%d", PRINT_IP(ip_src));
+        time_t seconds = time(NULL);
+        struct tm *t = localtime(&seconds);
+
+        // expecting a single question count
+        if (pkt[4] != 0 || pkt[5] != 1)
+                goto errout;
+
+        // check cname
+        unsigned char *ptr = pkt + 12;
+        int len = 0;
+        while (*ptr != 0 && len < 255) {        // 255 is the maximum length of a domain name including multiple '.'
+                if (*ptr > 63)  // the name left of a '.' is 63 length maximum
+                        goto errout;
+
+                int delta = *ptr + 1;
+                *ptr = '.';
+                len += delta;;
+                ptr += delta;
+        }
+
+        printf("%02d:%02d:%02d  %15s  %s\n", t->tm_hour, t->tm_min, t->tm_sec, ip, pkt + 12 + 1);
+        return;
+
+errout:
+        printf("%02d:%02d:%02d  %15s  Error: invalid DNS packet\n", t->tm_hour, t->tm_min, t->tm_sec, ip);
+}
+
+// https://www.kernel.org/doc/html/latest/networking/filter.html
+static void custom_bpf(int sock) {
+        struct sock_filter code[] = {
+                //  sudo tcpdump ip and udp and src port 53 -dd
+                { 0x28, 0, 0, 0x0000000c },
+                { 0x15, 0, 8, 0x00000800 },
+                { 0x30, 0, 0, 0x00000017 },
+                { 0x15, 0, 6, 0x00000011 },
+                { 0x28, 0, 0, 0x00000014 },
+                { 0x45, 4, 0, 0x00001fff },
+                { 0xb1, 0, 0, 0x0000000e },
+                { 0x48, 0, 0, 0x0000000e },
+                { 0x15, 0, 1, 0x00000035 },
+                { 0x6, 0, 0, 0x00040000 },
+                { 0x6, 0, 0, 0x00000000 },
+        };
+
+        struct sock_fprog bpf = {
+                .len = (unsigned short) sizeof(code) / sizeof(code[0]),
+                .filter = code,
+        };
+
+        int rv = setsockopt(sock, SOL_SOCKET, SO_ATTACH_FILTER, &bpf, sizeof(bpf));
+        if (rv < 0) {
+                fprintf(stderr, "Error: cannot attach BPF filter\n");
+                exit(1);
+        }
+}
+
+static void run_trace(void) {
+        // grab all Ethernet packets and use a custom BPF filter to get only UDP from source port 53
+        int s = socket(PF_PACKET, SOCK_RAW, htons(ETH_P_ALL));
+        if (s < 0)
+                errExit("socket");
+        custom_bpf(s);
+
+        unsigned char buf[MAX_BUF_SIZE];
+        while (1) {
+                fd_set rfds;
+                FD_ZERO(&rfds);
+                FD_SET(s, &rfds);
+                struct timeval tv;
+                tv.tv_sec = 1;
+                tv.tv_usec = 0;
+                int rv = select(s + 1, &rfds, NULL, NULL, &tv);
+                if (rv < 0)
+                        errExit("select");
+                else if (rv == 0)
+                        continue;
+                unsigned bytes = recvfrom(s, buf, MAX_BUF_SIZE, 0, NULL, NULL);
+
+                if (bytes >= (14 + 20 + 8)) { // size of  MAC + IP + UDP headers
+                        uint8_t ip_hlen = (buf[14] & 0x0f) * 4;
+                        uint16_t port_src;
+                        memcpy(&port_src, buf + 14 + ip_hlen, 2);
+                        port_src = ntohs(port_src);
+                        uint8_t protocol = buf[14 + 9];
+                        uint32_t ip_src;
+                        memcpy(&ip_src, buf + 14 + 12, 4);
+                        ip_src = ntohl(ip_src);
+
+                        // if DNS packet, extract the query
+                        if (port_src == 53 && protocol == 0x11) // UDP protocol
+                                print_dns(ip_src, buf + 14 + ip_hlen + 8); // IP and UDP header len
+                }
+        }
+
+        close(s);
+}
+
+
+static void usage(void) {
+        printf("Usage: fnettrace-dns [OPTIONS]\n");
+        printf("Options:\n");
+        printf("   --help, -? - this help screen\n");
+        printf("\n");
+}
+
+int main(int argc, char **argv) {
+        int i;
+
+        for (i = 1; i < argc; i++) {
+                if (strcmp(argv[i], "--help") == 0 || strcmp(argv[i], "-?") == 0) {
+                        usage();
+                        return 0;
+                }
+                else {
+                        fprintf(stderr, "Error: invalid argument\n");
+                        return 1;
+                }
+        }
+
+        if (getuid() != 0) {
+                fprintf(stderr, "Error: you need to be root to run this program\n");
+                return 1;
+        }
+
+        time_t now = time(NULL);
+        printf("DNS trace for %s\n", ctime(&now));
+        run_trace();
+
+        return 0;
+}