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net2pcap.c
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net2pcap.c
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/*
* net2pcap --- an auditable packet capture tool
* see http://www.secdev.org/projects/net2pcap.html
* for more informations
*
* Copyright (C) 2003-2013 Philippe Biondi <phil@secdev.org>
* Nicolas Bareil <nico@chdir.org>
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public License
* version 2 as published by the Free Software Foundation.
*
* 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
* Lesser General Public License for more details.
*/
#define IDENT "##PACKAGE_NAME -- ## PACKAGE_URL\n"
#define _FILE_OFFSET_BITS 64
#include "config.h"
#include <sys/types.h>
#include <sys/socket.h>
#include <netpacket/packet.h>
#include <net/if.h>
#include <net/if_arp.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#include <netinet/if_ether.h>
#include <getopt.h>
#include <stdio.h>
#include <ctype.h>
#include <errno.h>
#include <sys/time.h>
#include <sys/select.h>
#include <sys/signalfd.h>
#include <sys/types.h>
#include <pwd.h>
#include <grp.h>
#include <signal.h>
#include <stdlib.h>
#if HAVE_SECCOMP_H
# include <seccomp.h>
#endif
#include <syslog.h>
#include <string.h>
#include <unistd.h>
#ifndef O_LARGEFILE /* needed for SECCOMP rule */
# define O_LARGEFILE 00100000
#endif
#define MAX(a,b) (a > b ? a : b)
#define DEFAULT_SNAPLEN 65535
#define MAX_LEN_ERRORMSG 2048
#if __BYTE_ORDER == __BIG_ENDIAN
# define NATIVE2COMPAT(x) (sizeof(struct timeval) != 8 ? (uint32_t)(x >> 32) : (x))
#else
# define NATIVE2COMPAT(x) ((uint32_t)(x))
#endif
int daemonize = 0;
#define ERROR(x...) do{LOG(LOG_ERR, "ERROR: " x);exit(EXIT_FAILURE);}while(0)
#define LOG(prio,x...) do{if(daemonize > 1) syslog(prio, x); \
else fprintf(stderr,"net2pcap: " x);} while(0)
void PERROR(char *err) {
char errormsg[MAX_LEN_ERRORMSG];
strerror_r(errno, errormsg, MAX_LEN_ERRORMSG);
LOG(LOG_CRIT, "%s: %s\n", err, errormsg);
exit(EXIT_FAILURE);
}
#define CRATIONMASK (S_IRUSR|S_IWUSR)
struct timeval_compat {
uint32_t tv_sec; /* seconds */
uint32_t tv_usec; /* microseconds */
};
/* From pcap.h */
struct pcap_file_header {
uint32_t magic;
uint16_t version_major;
uint16_t version_minor;
int32_t thiszone; /* gmt to local correction */
uint32_t sigfigs; /* accuracy of timestamps */
uint32_t snaplen; /* max length saved portion of each pkt */
uint32_t linktype; /* data link type (LINKTYPE_*) */
};
struct pcap_pkthdr {
struct timeval_compat ts; /* time stamp using 32 bits fields */
uint32_t caplen; /* length of portion present */
uint32_t len; /* length this packet (off wire) */
};
/* mmmh.. what about big endian platforms ? */
#define PCAP_MAGIC 0xa1b2c3d4
#define PCAP_VERSION_MAJOR 2
#define PCAP_VERSION_MINOR 4
/* made from pcap-linux.c and bpf/net/bpf.h */
#ifndef ARPHRD_IEEE80211_PRISM /* From Linux 2.4.18 */
#define ARPHRD_IEEE80211_PRISM 802
#endif
#define LINKTYPE_NULL 0
#define LINKTYPE_ETHERNET 1 /* also for 100Mb and up */
#define LINKTYPE_EXP_ETHERNET 2 /* 3Mb experimental Ethernet */
#define LINKTYPE_AX25 3
#define LINKTYPE_PRONET 4
#define LINKTYPE_CHAOS 5
#define LINKTYPE_TOKEN_RING 6 /* DLT_IEEE802 is used for Token Ring */
#define LINKTYPE_ARCNET 7
#define LINKTYPE_SLIP 8
#define LINKTYPE_PPP 9
#define LINKTYPE_FDDI 10
#define LINKTYPE_PPP_HDLC 50 /* PPP in HDLC-like framing */
#define LINKTYPE_PPP_ETHER 51 /* NetBSD PPP-over-Ethernet */
#define LINKTYPE_ATM_RFC1483 100 /* LLC/SNAP-encapsulated ATM */
#define LINKTYPE_RAW 101 /* raw IP */
#define LINKTYPE_SLIP_BSDOS 102 /* BSD/OS SLIP BPF header */
#define LINKTYPE_PPP_BSDOS 103 /* BSD/OS PPP BPF header */
#define LINKTYPE_C_HDLC 104 /* Cisco HDLC */
#define LINKTYPE_IEEE802_11 105 /* IEEE 802.11 (wireless) */
#define LINKTYPE_ATM_CLIP 106 /* Linux Classical IP over ATM */
#define LINKTYPE_LOOP 108 /* OpenBSD loopback */
#define LINKTYPE_LINUX_SLL 113 /* Linux cooked socket capture */
#define LINKTYPE_LTALK 114 /* Apple LocalTalk hardware */
#define LINKTYPE_ECONET 115 /* Acorn Econet */
#define LINKTYPE_CISCO_IOS 118 /* For Cisco-internal use */
#define LINKTYPE_PRISM_HEADER 119 /* 802.11+Prism II monitor mode */
#define LINKTYPE_AIRONET_HEADER 120 /* FreeBSD Aironet driver stuff */
int pcap_map[] = { ARPHRD_ETHER, LINKTYPE_ETHERNET,
ARPHRD_METRICOM, LINKTYPE_ETHERNET,
ARPHRD_LOOPBACK, LINKTYPE_ETHERNET,
ARPHRD_EETHER, LINKTYPE_EXP_ETHERNET,
ARPHRD_AX25, LINKTYPE_AX25,
ARPHRD_PRONET, LINKTYPE_PRONET,
ARPHRD_CHAOS, LINKTYPE_CHAOS,
ARPHRD_IEEE802_TR, LINKTYPE_TOKEN_RING,
ARPHRD_IEEE802, LINKTYPE_TOKEN_RING,
ARPHRD_ARCNET, LINKTYPE_ARCNET,
ARPHRD_FDDI, LINKTYPE_FDDI,
ARPHRD_ATM, LINKTYPE_LINUX_SLL,
ARPHRD_IEEE80211, LINKTYPE_IEEE802_11,
ARPHRD_IEEE80211_PRISM, LINKTYPE_PRISM_HEADER,
ARPHRD_PPP, LINKTYPE_RAW,
ARPHRD_HDLC, LINKTYPE_C_HDLC,
ARPHRD_TUNNEL, LINKTYPE_RAW,
ARPHRD_SIT, LINKTYPE_RAW,
ARPHRD_CSLIP, LINKTYPE_RAW,
ARPHRD_SLIP6, LINKTYPE_RAW,
ARPHRD_CSLIP6,LINKTYPE_RAW,
ARPHRD_ADAPT, LINKTYPE_RAW,
ARPHRD_SLIP, LINKTYPE_RAW,
ARPHRD_RAWHDLC, LINKTYPE_RAW,
ARPHRD_LOCALTLK, LINKTYPE_LTALK,
0, 0};
int arphdr_to_linktype(int arphdr)
{
int *p;
for (p = pcap_map; *p; p += 2)
if (*p == arphdr)
return *(p+1);
return -1;
}
void usage(void)
{
fprintf(stderr, IDENT
"Usage: net2pcap -i interface [-pdx] [-f capfile] [-t ethertype] [-s snaplen] [-r newroot]\n"
"\t-p : doesn't set promiscuous mode\n"
"\t-d : daemon mode (background + uses syslog)\n"
"\t-x : hexdumps every packet on output (if not daemon)\n"
"\t-u : drop priviledges to UID\n"
"\t-g : drop priviledges to GID\n"
"\t-r : chroot into newroot\n"
"\t snaplen defaults to %d\n"
"\t capfile defaults to net2pcap.cap\n"
"\t ethertype defaults to ETH_P_ALL (sniff all)\n",
DEFAULT_SNAPLEN);
exit(EXIT_FAILURE);
}
/* Hexdump functions */
int sane(unsigned char x)
{
return ((x >= 0x20) && (x < 0x80));
}
void hexdump(void *buf, int len)
{
unsigned char *b = buf;
int i,j;
for (i=0; i < (len+15)/16*16; i++) {
if (i < len) printf("%02x ",b[i]); else printf(" ");
if (i%8 == 7) printf(" ");
if (i%16 == 15) {
for (j=i-15; (j < i) && (j < len); j++)
printf("%c", sane(b[j]) ? b[j] : '.');
printf("\n");
}
}
}
/* xwrite(): wrapper handling partial writes */
void xwrite(int fd, void *buf, size_t len) {
ssize_t ret;
size_t remaining = len;
do {
ret = write(fd, buf, remaining);
if (ret == -1) {
if (errno == EAGAIN || errno == EINTR)
continue;
else
PERROR("write(buf)");
}
remaining -= ret;
buf += ret;
} while (remaining > 0);
}
int only_digits(char *s) {
char c;
int nondigit_found = 0;
while (c = *s++) {
if (! isdigit(c)) {
nondigit_found = 1;
}
}
return !nondigit_found;
}
int term_received = 0, hup_received = 0;
int main(int argc, char *argv[])
{
int s, l, sigfd;
int ptype = ETH_P_ALL;
char *iff = NULL;
char *newroot = NULL;
char *fcap = "net2pcap.cap";
int promisc = 1;
int ifidx = 0;
char c;
void *buf;
size_t snaplen = DEFAULT_SNAPLEN;
int f;
struct sockaddr_ll sll;
struct pcap_file_header hdr;
struct pcap_pkthdr phdr;
struct passwd *user_entry;
struct group *group_entry;
struct timeval native_tv;
struct timezone tz;
struct signalfd_siginfo sigfdinfo;
sigset_t mask;
int xdump = 0;
unsigned long long int pktnb = 0;
int linktype;
uid_t uid = 0;
gid_t gid = 0;
fd_set readset;
#if HAVE_SECCOMP_H
scmp_filter_ctx ctx;
#endif
sigemptyset(&mask);
sigaddset(&mask, SIGINT);
sigaddset(&mask, SIGTERM);
sigaddset(&mask, SIGQUIT);
sigaddset(&mask, SIGHUP);
if (sigprocmask(SIG_BLOCK, &mask, NULL) == -1)
PERROR("sigprocmask()");
sigfd = signalfd(-1, &mask, 0);
if (sigfd == -1)
PERROR("signalfd()");
/* Get options */
while ((c = getopt(argc, argv, "dxhi:f:t:r:s:pu:g:")) != -1) {
switch(c) {
case 'h':
usage();
case 'i':
iff = optarg;
break;
case 'f':
fcap = optarg;
break;
case 't':
ptype = strtoul(optarg, NULL, 0);
break;
case 'p':
promisc = 0;
break;
case 'r':
newroot = optarg;
break;
case 's':
errno = 0;
snaplen = strtoul(optarg, NULL,0);
if (errno)
PERROR("invalid snaplen");
break;
case 'd':
daemonize = 1;
break;
case 'u':
errno = 0;
if (only_digits(optarg)) {
uid = strtoul(optarg, NULL, 0);
if (errno) {
PERROR("Invalid uid");
}
} else {
errno = 0;
user_entry = getpwnam(optarg);
if (user_entry == NULL) {
if (errno) {
PERROR("getpwent()");
} else {
ERROR("Username not found\n");
}
}
uid = user_entry->pw_uid;
}
break;
case 'g':
errno = 0;
if (only_digits(optarg)) {
gid = strtoul(optarg, NULL, 0);
if (errno) {
ERROR("Invalid gid");
}
} else {
errno = 0;
group_entry = getgrnam(optarg);
if (group_entry == NULL) {
if (errno) {
PERROR("getgrnam()");
} else {
ERROR("Group name not found\n");
}
}
gid = group_entry->gr_gid;
}
break;
case 'x':
xdump = 1;
break;
default:
printf("Error!\n");
usage();
}
}
if (!iff) ERROR ("No interface specified\n");
buf = malloc(snaplen);
if (!buf) PERROR("malloc");
/* Prepare socket according to options */
s = socket(PF_PACKET, SOCK_RAW, htons(ptype));
if (s == -1) PERROR("socket");
if (iff) {
struct ifreq ifr;
strncpy(ifr.ifr_name, iff, IF_NAMESIZE);
if (ioctl(s, SIOCGIFINDEX, &ifr) == -1) PERROR("ioctl");
ifidx = ifr.ifr_ifindex;
}
if (promisc) {
struct packet_mreq mreq;
mreq.mr_ifindex = ifidx;
mreq.mr_type = PACKET_MR_PROMISC;
mreq.mr_alen = 0;
if (setsockopt(s, SOL_PACKET, PACKET_ADD_MEMBERSHIP, &mreq, sizeof(mreq)) == -1)
PERROR("setsockopt");
}
if (ifidx || (ptype != ETH_P_ALL)) {
sll.sll_family = AF_PACKET;
sll.sll_protocol = htons(ptype);
sll.sll_ifindex = ifidx;
if (bind(s, (struct sockaddr *)&sll, sizeof(sll)) == -1) PERROR("bind");
}
l = sizeof(sll);
if (getsockname(s, (struct sockaddr *)&sll, &l) == -1)
PERROR("getsockname");
linktype = arphdr_to_linktype(sll.sll_hatype);
if (daemonize) {
openlog("net2pcap", LOG_PID|LOG_NDELAY, LOG_DAEMON);
if (daemon(0, 0) != 0)
PERROR("daemon()");
daemonize++;
}
if (newroot) {
if (chroot(newroot) != 0)
PERROR("chroot");
if (chdir("/") != 0)
PERROR("chdir(/)");
}
if (uid && !gid) {
/*
* uid set but gid not, good behavior is to
* set gid to primary group of uid
*/
errno = 0;
user_entry = getpwuid(uid);
if (!user_entry) {
if (errno)
PERROR("getpwuid()");
else
ERROR("uid %d does not exist,"
" cannot find primary group\n",
uid);
}
gid = user_entry->pw_gid;
}
if (gid && (setgid(gid) == -1))
PERROR("setgid()");
if (uid && (setuid(uid) == -1))
PERROR("setuid()");
#if HAVE_SECCOMP_H
ctx = seccomp_init(SCMP_ACT_KILL);
if (ctx == NULL)
ERROR("Cannot go into SECCOMPv2");
seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(open), 1,
SCMP_A1(SCMP_CMP_EQ, O_CREAT|O_WRONLY|O_APPEND|O_LARGEFILE));
seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(socketcall), 0);
seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(close), 0);
seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(write), 0);
seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(gettimeofday), 0);
seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(read), 0);
seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(exit), 0);
seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(_llseek), 0);
seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(_newselect), 0);
seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(exit_group), 0);
seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(rt_sigreturn), 0);
seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(sigreturn), 0);
if (daemonize) {
seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(time), 0);
seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(fstat64), 0);
seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(mmap2), 0);
seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(munmap), 0);
}
if (seccomp_load(ctx) < 0)
ERROR("Cannot load SECCOMP filters");
LOG(LOG_INFO,"Started [sandboxed].\n");
seccomp_release(ctx);
#else
LOG(LOG_INFO,"Started.\n");
#endif /* HAVE_SECCOMP_H */
while (!term_received) { /* Main loop */
off_t filepos;
/* Prepare capture file */
f = open(fcap, O_CREAT|O_WRONLY|O_APPEND, CRATIONMASK);
if (f == -1) PERROR("open(append)");
filepos = lseek(f, 0, SEEK_END);
if (filepos == -1) PERROR("lseek");
if (!filepos) { /* Empty file --> add header */
LOG(LOG_NOTICE, "Creating capture file %s\n", fcap);
if (gettimeofday(&native_tv, &tz) == -1) PERROR("gettimeofday");
hdr.magic = PCAP_MAGIC;
hdr.version_major = PCAP_VERSION_MAJOR;
hdr.version_minor = PCAP_VERSION_MINOR;
hdr.thiszone = tz.tz_dsttime; /* XXX */
hdr.sigfigs = 0;
hdr.snaplen = snaplen;
hdr.linktype = linktype;
xwrite(f, &hdr, sizeof(hdr));
} else
LOG(LOG_NOTICE, "Appending to capture file %s\n", fcap);
hup_received = 0;
pktnb = 0;
while (!hup_received && !term_received) { /* Receive loop */
FD_ZERO(&readset);
FD_SET(s, &readset);
FD_SET(sigfd, &readset);
if (select(MAX(s, sigfd) + 1, &readset, NULL, NULL, NULL) == -1)
PERROR("select()");
if (FD_ISSET(s, &readset))
{
ssize_t rcvdlen = recv(s, buf, snaplen, 0);
if (rcvdlen == -1)
PERROR("recv");
if (xdump && !daemonize)
hexdump(buf, rcvdlen);
gettimeofday(&native_tv, NULL);
phdr.ts.tv_sec = NATIVE2COMPAT(native_tv.tv_sec);
phdr.ts.tv_usec = NATIVE2COMPAT(native_tv.tv_usec);
phdr.len = rcvdlen;
phdr.caplen = rcvdlen;
xwrite(f, &phdr, sizeof(phdr));
xwrite(f, buf, rcvdlen);
pktnb++;
}
if (FD_ISSET(sigfd, &readset))
{
if (read(sigfd, &sigfdinfo, sizeof(sigfdinfo)) != sizeof(sigfdinfo))
PERROR("read(signalfd_siginfo)");
switch (sigfdinfo.ssi_signo)
{
case SIGINT:
case SIGTERM:
term_received = 1;
break;
case SIGHUP:
hup_received = 1;
break;
default:
ERROR("signal %d received", sigfdinfo.ssi_signo);
}
}
}
LOG(LOG_INFO,"Received %lld packets\n", pktnb);
if (close(f) == -1) PERROR("close");
}
if (daemonize) closelog();
LOG(LOG_INFO,"Stopped.\n");
exit(EXIT_SUCCESS);
}