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tcpdump.c
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/*
* Copyright (c) 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1997, 2000
* The Regents of the University of California. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that: (1) source code distributions
* retain the above copyright notice and this paragraph in its entirety, (2)
* distributions including binary code include the above copyright notice and
* this paragraph in its entirety in the documentation or other materials
* provided with the distribution, and (3) all advertising materials mentioning
* features or use of this software display the following acknowledgement:
* ``This product includes software developed by the University of California,
* Lawrence Berkeley Laboratory and its contributors.'' Neither the name of
* the University nor the names of its contributors may be used to endorse
* or promote products derived from this software without specific prior
* written permission.
* THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED
* WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
*
* Support for splitting captures into multiple files with a maximum
* file size:
*
* Copyright (c) 2001
* Seth Webster <[email protected]>
*/
/*
* tcpdump - dump traffic on a network
*
* First written in 1987 by Van Jacobson, Lawrence Berkeley Laboratory.
* Mercilessly hacked and occasionally improved since then via the
* combined efforts of Van, Steve McCanne and Craig Leres of LBL.
*/
#include <config.h>
#ifndef TCPDUMP_CONFIG_H_
#error "The included config.h header is not from the tcpdump build."
#endif
#include "netdissect-stdinc.h"
/*
* This must appear after including netdissect-stdinc.h, so that _U_ is
* defined.
*/
#ifndef lint
static const char copyright[] _U_ =
"@(#) Copyright (c) 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1997, 2000\n\
The Regents of the University of California. All rights reserved.\n";
#endif
#include <sys/stat.h>
#include <fcntl.h>
#ifdef HAVE_LIBCRYPTO
#include <openssl/crypto.h>
#endif
#ifdef HAVE_GETOPT_LONG
#include <getopt.h>
#else
#include "missing/getopt_long.h"
#endif
/* Capsicum-specific code requires macros from <net/bpf.h>, which will fail
* to compile if <pcap.h> has already been included; including the headers
* in the opposite order works fine. For the most part anyway, because in
* FreeBSD <pcap/pcap.h> declares bpf_dump() instead of <net/bpf.h>. Thus
* interface.h takes care of it later to avoid a compiler warning.
*/
#ifdef HAVE_CAPSICUM
#include <sys/capsicum.h>
#include <sys/ioccom.h>
#include <net/bpf.h>
#include <libgen.h>
#ifdef HAVE_CASPER
#include <libcasper.h>
#include <casper/cap_dns.h>
#include <sys/nv.h>
#endif /* HAVE_CASPER */
#endif /* HAVE_CAPSICUM */
#ifdef HAVE_PCAP_OPEN
/*
* We found pcap_open() in the capture library, so we'll be using
* the remote capture APIs; define PCAP_REMOTE before we include pcap.h,
* so we get those APIs declared, and the types and #defines that they
* use defined.
*
* WinPcap's headers require that PCAP_REMOTE be defined in order to get
* remote-capture APIs declared and types and #defines that they use
* defined.
*
* (Versions of libpcap with those APIs, and thus Npcap, which is based on
* those versions of libpcap, don't require it.)
*/
#define HAVE_REMOTE
#endif
#include <pcap.h>
#include <signal.h>
#include <stdio.h>
#include <stdarg.h>
#include <stdlib.h>
#include <string.h>
#include <limits.h>
#ifdef _WIN32
#include <windows.h>
#else
#include <sys/time.h>
#include <sys/wait.h>
#include <sys/resource.h>
#include <pwd.h>
#include <grp.h>
#endif /* _WIN32 */
/*
* Pathname separator.
* Use this in pathnames, but do *not* use it in URLs.
*/
#ifdef _WIN32
#define PATH_SEPARATOR '\\'
#else
#define PATH_SEPARATOR '/'
#endif
/* capabilities convenience library */
/* If a code depends on HAVE_LIBCAP_NG, it depends also on HAVE_CAP_NG_H.
* If HAVE_CAP_NG_H is not defined, undefine HAVE_LIBCAP_NG.
* Thus, the later tests are done only on HAVE_LIBCAP_NG.
*/
#ifdef HAVE_LIBCAP_NG
#ifdef HAVE_CAP_NG_H
#include <cap-ng.h>
#else
#undef HAVE_LIBCAP_NG
#endif /* HAVE_CAP_NG_H */
#endif /* HAVE_LIBCAP_NG */
#ifdef __FreeBSD__
#include <sys/sysctl.h>
#endif /* __FreeBSD__ */
#include "netdissect-stdinc.h"
#include "netdissect.h"
#include "interface.h"
#include "addrtoname.h"
#include "ascii_strcasecmp.h"
#include "print.h"
#include "diag-control.h"
#include "fptype.h"
#ifndef PATH_MAX
#define PATH_MAX 1024
#endif
#if defined(SIGINFO)
#define SIGNAL_REQ_INFO SIGINFO
#elif defined(SIGUSR1)
#define SIGNAL_REQ_INFO SIGUSR1
#endif
#if defined(SIGUSR2)
#define SIGNAL_FLUSH_PCAP SIGUSR2
#endif
static int Bflag; /* buffer size */
static int64_t Cflag; /* rotate dump files after this many bytes */
static int Cflag_count; /* Keep track of which file number we're writing */
static int Dflag; /* list available devices and exit */
#ifdef HAVE_PCAP_FINDALLDEVS_EX
static char *remote_interfaces_source; /* list available devices from this source and exit */
#endif
/*
* This is exported because, in some versions of libpcap, if libpcap
* is built with optimizer debugging code (which is *NOT* the default
* configuration!), the library *imports*(!) a variable named dflag,
* under the expectation that tcpdump is exporting it, to govern
* how much debugging information to print when optimizing
* the generated BPF code.
*
* This is a horrible hack; newer versions of libpcap don't import
* dflag but, instead, *if* built with optimizer debugging code,
* *export* a routine to set that flag.
*/
extern int dflag;
int dflag; /* print filter code */
static int Gflag; /* rotate dump files after this many seconds */
static int Gflag_count; /* number of files created with Gflag rotation */
static time_t Gflag_time; /* The last time_t the dump file was rotated. */
static int Lflag; /* list available data link types and exit */
static int Iflag; /* rfmon (monitor) mode */
#ifdef HAVE_PCAP_SET_TSTAMP_TYPE
static int Jflag; /* list available time stamp types */
static int jflag = -1; /* packet time stamp source */
#endif
static int lflag; /* line-buffered output */
static int pflag; /* don't go promiscuous */
static int Qflag = -1; /* restrict captured packet by send/receive direction */
static int Uflag; /* "unbuffered" output of dump files */
static int Wflag; /* recycle output files after this number of files */
static int WflagChars;
static char *zflag = NULL; /* compress each savefile using a specified command (like gzip or bzip2) */
static int timeout = 1000; /* default timeout = 1000 ms = 1 s */
#ifdef HAVE_PCAP_SET_IMMEDIATE_MODE
static int immediate_mode;
#endif
static int count_mode;
static u_int packets_to_skip;
static int infodelay;
static int infoprint;
char *program_name;
/* Forwards */
static int parse_int(const char *argname, const char *string, char **endp,
int minval, int maxval, int base);
static u_int parse_u_int(const char *argname, const char *string, char **endp,
u_int minval, u_int maxval, int base);
static int64_t parse_int64(const char *argname, const char *string,
char **endp, int64_t minval, int64_t maxval, int base);
static void (*setsignal (int sig, void (*func)(int)))(int);
static void cleanup(int);
#if defined(HAVE_FORK) || defined(HAVE_VFORK)
static void child_cleanup(int);
#endif
static void print_version(FILE *);
static void print_usage(FILE *);
static void print_packet(u_char *, const struct pcap_pkthdr *, const u_char *);
static void dump_packet_and_trunc(u_char *, const struct pcap_pkthdr *, const u_char *);
static void dump_packet(u_char *, const struct pcap_pkthdr *, const u_char *);
#ifdef SIGNAL_REQ_INFO
static void requestinfo(int);
#endif
#ifdef SIGNAL_FLUSH_PCAP
static void flushpcap(int);
#endif
#ifdef _WIN32
static HANDLE timer_handle = INVALID_HANDLE_VALUE;
static void CALLBACK verbose_stats_dump(PVOID param, BOOLEAN timer_fired);
#else /* _WIN32 */
static void verbose_stats_dump(int sig);
#endif /* _WIN32 */
static void info(int);
static u_int packets_captured;
static const struct tok status_flags[] = {
#ifdef PCAP_IF_UP
{ PCAP_IF_UP, "Up" },
#endif
#ifdef PCAP_IF_RUNNING
{ PCAP_IF_RUNNING, "Running" },
#endif
{ PCAP_IF_LOOPBACK, "Loopback" },
#ifdef PCAP_IF_WIRELESS
{ PCAP_IF_WIRELESS, "Wireless" },
#endif
{ 0, NULL }
};
static pcap_t *pd;
static pcap_dumper_t *pdd = NULL;
static int supports_monitor_mode;
extern int optind;
extern int opterr;
extern char *optarg;
struct dump_info {
char *WFileName;
char *CurrentFileName;
pcap_t *pd;
pcap_dumper_t *pdd;
netdissect_options *ndo;
#ifdef HAVE_CAPSICUM
int dirfd;
#endif
};
#if defined(HAVE_PCAP_SET_PARSER_DEBUG)
/*
* We have pcap_set_parser_debug() in libpcap; declare it (it's not declared
* by any libpcap header, because it's a special hack, only available if
* libpcap was configured to include it, and only intended for use by
* libpcap developers trying to debug the parser for filter expressions).
*/
#ifdef _WIN32
__declspec(dllimport)
#else /* _WIN32 */
extern
#endif /* _WIN32 */
void pcap_set_parser_debug(int);
#elif defined(HAVE_PCAP_DEBUG) || defined(HAVE_YYDEBUG)
/*
* We don't have pcap_set_parser_debug() in libpcap, but we do have
* pcap_debug or yydebug. Make a local version of pcap_set_parser_debug()
* to set the flag, and define HAVE_PCAP_SET_PARSER_DEBUG.
*/
static void
pcap_set_parser_debug(int value)
{
#ifdef HAVE_PCAP_DEBUG
extern int pcap_debug;
pcap_debug = value;
#else /* HAVE_PCAP_DEBUG */
extern int yydebug;
yydebug = value;
#endif /* HAVE_PCAP_DEBUG */
}
#define HAVE_PCAP_SET_PARSER_DEBUG
#endif // HAVE_PCAP_SET_PARSER_DEBUG, HAVE_PCAP_DEBUG, HAVE_YYDEBUG
#if defined(HAVE_PCAP_SET_OPTIMIZER_DEBUG)
/*
* We have pcap_set_optimizer_debug() in libpcap; declare it (it's not declared
* by any libpcap header, because it's a special hack, only available if
* libpcap was configured to include it, and only intended for use by
* libpcap developers trying to debug the optimizer for filter expressions).
*/
#ifdef _WIN32
__declspec(dllimport)
#else /* _WIN32 */
extern
#endif /* _WIN32 */
void pcap_set_optimizer_debug(int);
#endif // HAVE_PCAP_SET_OPTIMIZER_DEBUG
static void NORETURN
exit_tcpdump(const int status)
{
nd_cleanup();
exit(status);
}
/* VARARGS */
static void NORETURN PRINTFLIKE(1, 2)
error(FORMAT_STRING(const char *fmt), ...)
{
va_list ap;
(void)fprintf(stderr, "%s: ", program_name);
va_start(ap, fmt);
(void)vfprintf(stderr, fmt, ap);
va_end(ap);
if (*fmt) {
fmt += strlen(fmt);
if (fmt[-1] != '\n')
(void)fputc('\n', stderr);
}
exit_tcpdump(S_ERR_HOST_PROGRAM);
/* NOTREACHED */
}
/* VARARGS */
static void PRINTFLIKE(1, 2)
warning(FORMAT_STRING(const char *fmt), ...)
{
va_list ap;
(void)fprintf(stderr, "%s: WARNING: ", program_name);
va_start(ap, fmt);
(void)vfprintf(stderr, fmt, ap);
va_end(ap);
if (*fmt) {
fmt += strlen(fmt);
if (fmt[-1] != '\n')
(void)fputc('\n', stderr);
}
}
#ifdef HAVE_PCAP_SET_TSTAMP_TYPE
static void NORETURN
show_tstamp_types_and_exit(pcap_t *pc, const char *device)
{
int n_tstamp_types;
int *tstamp_types = 0;
const char *tstamp_type_name;
int i;
n_tstamp_types = pcap_list_tstamp_types(pc, &tstamp_types);
if (n_tstamp_types < 0)
error("%s", pcap_geterr(pc));
if (n_tstamp_types == 0) {
fprintf(stderr, "Time stamp type cannot be set for %s\n",
device);
exit_tcpdump(S_SUCCESS);
}
fprintf(stdout, "Time stamp types for %s (use option -j to set):\n",
device);
for (i = 0; i < n_tstamp_types; i++) {
tstamp_type_name = pcap_tstamp_type_val_to_name(tstamp_types[i]);
if (tstamp_type_name != NULL) {
(void) fprintf(stdout, " %s (%s)\n", tstamp_type_name,
pcap_tstamp_type_val_to_description(tstamp_types[i]));
} else {
(void) fprintf(stdout, " %d\n", tstamp_types[i]);
}
}
pcap_free_tstamp_types(tstamp_types);
exit_tcpdump(S_SUCCESS);
}
#endif // HAVE_PCAP_SET_TSTAMP_TYPE
static void NORETURN
show_dlts_and_exit(pcap_t *pc, const char *device)
{
int n_dlts, i;
int *dlts = 0;
const char *dlt_name;
n_dlts = pcap_list_datalinks(pc, &dlts);
if (n_dlts < 0)
error("%s", pcap_geterr(pc));
else if (n_dlts == 0 || !dlts)
error("No data link types.");
/*
* If the interface is known to support monitor mode, indicate
* whether these are the data link types available when not in
* monitor mode, if -I wasn't specified, or when in monitor mode,
* when -I was specified (the link-layer types available in
* monitor mode might be different from the ones available when
* not in monitor mode).
*/
(void) fprintf(stdout, "Data link types for ");
if (supports_monitor_mode)
(void) fprintf(stdout, "%s %s",
device,
Iflag ? "when in monitor mode" : "when not in monitor mode");
else
(void) fprintf(stdout, "%s",
device);
(void) fprintf(stdout, " (use option -y to set):\n");
for (i = 0; i < n_dlts; i++) {
dlt_name = pcap_datalink_val_to_name(dlts[i]);
if (dlt_name != NULL) {
(void) fprintf(stdout, " %s (%s)", dlt_name,
pcap_datalink_val_to_description(dlts[i]));
/*
* OK, does tcpdump handle that type?
*/
if (!has_printer(dlts[i]))
(void) fprintf(stdout, " (printing not supported)");
fprintf(stdout, "\n");
} else {
(void) fprintf(stdout, " DLT %d (printing not supported)\n",
dlts[i]);
}
}
pcap_free_datalinks(dlts);
exit_tcpdump(S_SUCCESS);
}
static void NORETURN
show_devices_and_exit(void)
{
pcap_if_t *dev, *devlist;
char ebuf[PCAP_ERRBUF_SIZE];
int i;
if (pcap_findalldevs(&devlist, ebuf) < 0)
error("%s", ebuf);
for (i = 0, dev = devlist; dev != NULL; i++, dev = dev->next) {
printf("%d.%s", i+1, dev->name);
if (dev->description != NULL)
printf(" (%s)", dev->description);
if (dev->flags != 0) {
printf(" [");
printf("%s", bittok2str(status_flags, "none", dev->flags));
#ifdef PCAP_IF_WIRELESS
if (dev->flags & PCAP_IF_WIRELESS) {
switch (dev->flags & PCAP_IF_CONNECTION_STATUS) {
case PCAP_IF_CONNECTION_STATUS_UNKNOWN:
printf(", Association status unknown");
break;
case PCAP_IF_CONNECTION_STATUS_CONNECTED:
printf(", Associated");
break;
case PCAP_IF_CONNECTION_STATUS_DISCONNECTED:
printf(", Not associated");
break;
case PCAP_IF_CONNECTION_STATUS_NOT_APPLICABLE:
break;
}
} else {
switch (dev->flags & PCAP_IF_CONNECTION_STATUS) {
case PCAP_IF_CONNECTION_STATUS_UNKNOWN:
printf(", Connection status unknown");
break;
case PCAP_IF_CONNECTION_STATUS_CONNECTED:
printf(", Connected");
break;
case PCAP_IF_CONNECTION_STATUS_DISCONNECTED:
printf(", Disconnected");
break;
case PCAP_IF_CONNECTION_STATUS_NOT_APPLICABLE:
break;
}
}
#endif // PCAP_IF_WIRELESS
printf("]");
}
printf("\n");
}
pcap_freealldevs(devlist);
exit_tcpdump(S_SUCCESS);
}
#ifdef HAVE_PCAP_FINDALLDEVS_EX
static void NORETURN
show_remote_devices_and_exit(void)
{
pcap_if_t *dev, *devlist;
char ebuf[PCAP_ERRBUF_SIZE];
int i;
if (pcap_findalldevs_ex(remote_interfaces_source, NULL, &devlist,
ebuf) < 0) {
if (strcmp(ebuf, "not supported") == 0) {
/*
* macOS 14's pcap_findalldevs_ex(), which is a
* stub that always returns -1 with an error
* message of "not supported".
*
* In this case, as we passed it an rpcap://
* URL, treat that as meaning "remote capture
* not supported".
*/
error("Remote capture not supported");
}
error("%s", ebuf);
}
for (i = 0, dev = devlist; dev != NULL; i++, dev = dev->next) {
printf("%d.%s", i+1, dev->name);
if (dev->description != NULL)
printf(" (%s)", dev->description);
if (dev->flags != 0)
printf(" [%s]", bittok2str(status_flags, "none", dev->flags));
printf("\n");
}
pcap_freealldevs(devlist);
exit_tcpdump(S_SUCCESS);
}
#endif /* HAVE_PCAP_FINDALLDEVS_EX */
/*
* Short options.
*
* Note that there we use all letters for short options except for g, k,
* o, and P, and those are used by other versions of tcpdump, and we should
* only use them for the same purposes that the other versions of tcpdump
* use them:
*
* macOS tcpdump uses -g to force non--v output for IP to be on one
* line, making it more "g"repable;
*
* macOS tcpdump uses -k to specify that packet comments in pcapng files
* should be printed;
*
* OpenBSD tcpdump uses -o to indicate that OS fingerprinting should be done
* for hosts sending TCP SYN packets;
*
* macOS tcpdump uses -P to indicate that -w should write pcapng rather
* than pcap files.
*
* macOS tcpdump also uses -Q to specify expressions that match packet
* metadata, including but not limited to the packet direction.
* The expression syntax is different from a simple "in|out|inout",
* and those expressions aren't accepted by macOS tcpdump, but the
* equivalents would be "in" = "dir=in", "out" = "dir=out", and
* "inout" = "dir=in or dir=out", and the parser could conceivably
* special-case "in", "out", and "inout" as expressions for backwards
* compatibility, so all is not (yet) lost.
*/
/*
* Set up flags that might or might not be supported depending on the
* version of libpcap we're using.
*/
#ifdef HAVE_PCAP_SET_TSTAMP_TYPE
#define j_FLAG "j:"
#define j_FLAG_USAGE " [ -j tstamptype ]"
#define J_FLAG "J"
#else /* HAVE_PCAP_SET_TSTAMP_TYPE */
#define j_FLAG
#define j_FLAG_USAGE
#define J_FLAG
#endif /* HAVE_PCAP_SET_TSTAMP_TYPE */
#ifdef USE_LIBSMI
#define m_FLAG_USAGE "[ -m module ] ..."
#endif
#define SHORTOPTS "aAbB:c:C:dDeE:fF:G:hHi:I" j_FLAG J_FLAG "KlLm:M:nNOpqQ:r:s:StT:uUvV:w:W:xXy:Yz:Z:#"
/*
* Long options.
*
* We do not currently have long options corresponding to all short
* options; we should probably pick appropriate option names for them.
*
* However, the short options where the number of times the option is
* specified matters, such as -v and -d and -t, should probably not
* just map to a long option, as saying
*
* tcpdump --verbose --verbose
*
* doesn't make sense; it should be --verbosity={N} or something such
* as that.
*
* For long options with no corresponding short options, we define values
* outside the range of ASCII graphic characters, make that the last
* component of the entry for the long option, and have a case for that
* option in the switch statement.
*/
#define OPTION_VERSION 128
#define OPTION_TSTAMP_PRECISION 129
#define OPTION_IMMEDIATE_MODE 130
#define OPTION_PRINT 131
#define OPTION_LIST_REMOTE_INTERFACES 132
#define OPTION_TSTAMP_MICRO 133
#define OPTION_TSTAMP_NANO 134
#define OPTION_FP_TYPE 135
#define OPTION_COUNT 136
#define OPTION_PRINT_SAMPLING 137
#define OPTION_LENGTHS 138
#define OPTION_TIME_T_SIZE 139
#define OPTION_SKIP 140
static const struct option longopts[] = {
{ "buffer-size", required_argument, NULL, 'B' },
{ "list-interfaces", no_argument, NULL, 'D' },
#ifdef HAVE_PCAP_FINDALLDEVS_EX
{ "list-remote-interfaces", required_argument, NULL, OPTION_LIST_REMOTE_INTERFACES },
#endif
{ "help", no_argument, NULL, 'h' },
{ "interface", required_argument, NULL, 'i' },
{ "monitor-mode", no_argument, NULL, 'I' },
#ifdef HAVE_PCAP_SET_TSTAMP_TYPE
{ "time-stamp-type", required_argument, NULL, 'j' },
{ "list-time-stamp-types", no_argument, NULL, 'J' },
#endif
#ifdef HAVE_PCAP_SET_TSTAMP_PRECISION
{ "micro", no_argument, NULL, OPTION_TSTAMP_MICRO},
{ "nano", no_argument, NULL, OPTION_TSTAMP_NANO},
{ "time-stamp-precision", required_argument, NULL, OPTION_TSTAMP_PRECISION},
#endif
{ "dont-verify-checksums", no_argument, NULL, 'K' },
{ "list-data-link-types", no_argument, NULL, 'L' },
{ "no-optimize", no_argument, NULL, 'O' },
{ "no-promiscuous-mode", no_argument, NULL, 'p' },
{ "direction", required_argument, NULL, 'Q' },
{ "snapshot-length", required_argument, NULL, 's' },
{ "absolute-tcp-sequence-numbers", no_argument, NULL, 'S' },
{ "packet-buffered", no_argument, NULL, 'U' },
{ "linktype", required_argument, NULL, 'y' },
#ifdef HAVE_PCAP_SET_IMMEDIATE_MODE
{ "immediate-mode", no_argument, NULL, OPTION_IMMEDIATE_MODE },
#endif
#ifdef HAVE_PCAP_SET_PARSER_DEBUG
{ "debug-filter-parser", no_argument, NULL, 'Y' },
#endif
{ "relinquish-privileges", required_argument, NULL, 'Z' },
{ "count", no_argument, NULL, OPTION_COUNT },
{ "fp-type", no_argument, NULL, OPTION_FP_TYPE },
{ "number", no_argument, NULL, '#' },
{ "print", no_argument, NULL, OPTION_PRINT },
{ "print-sampling", required_argument, NULL, OPTION_PRINT_SAMPLING },
{ "lengths", no_argument, NULL, OPTION_LENGTHS },
{ "time-t-size", no_argument, NULL, OPTION_TIME_T_SIZE },
{ "skip", required_argument, NULL, OPTION_SKIP },
{ "version", no_argument, NULL, OPTION_VERSION },
{ NULL, 0, NULL, 0 }
};
#ifdef HAVE_PCAP_FINDALLDEVS_EX
#define LIST_REMOTE_INTERFACES_USAGE " [ --list-remote-interfaces remote-source ]"
#else
#define LIST_REMOTE_INTERFACES_USAGE
#endif
#ifdef HAVE_PCAP_SET_IMMEDIATE_MODE
#define IMMEDIATE_MODE_USAGE " [ --immediate-mode ]"
#else
#define IMMEDIATE_MODE_USAGE ""
#endif
#ifndef _WIN32
/* Drop root privileges and chroot if necessary */
static void
droproot(const char *username, const char *chroot_dir)
{
struct passwd *pw = NULL;
if (chroot_dir && !username)
error("Chroot without dropping root is insecure");
pw = getpwnam(username);
if (pw) {
if (chroot_dir) {
if (chroot(chroot_dir) != 0 || chdir ("/") != 0)
error("Couldn't chroot/chdir to '%.64s': %s",
chroot_dir, pcap_strerror(errno));
}
#ifdef HAVE_LIBCAP_NG
{
int ret = capng_change_id(pw->pw_uid, pw->pw_gid, CAPNG_NO_FLAG);
if (ret < 0)
error("capng_change_id(): return %d\n", ret);
else
fprintf(stderr, "dropped privs to %s\n", username);
}
#else
if (initgroups(pw->pw_name, pw->pw_gid) != 0 ||
setgid(pw->pw_gid) != 0 || setuid(pw->pw_uid) != 0)
error("Couldn't change to '%.32s' uid=%lu gid=%lu: %s",
username,
(unsigned long)pw->pw_uid,
(unsigned long)pw->pw_gid,
pcap_strerror(errno));
else {
fprintf(stderr, "dropped privs to %s\n", username);
}
#endif /* HAVE_LIBCAP_NG */
} else
error("Couldn't find user '%.32s'", username);
#ifdef HAVE_LIBCAP_NG
/* We don't need CAP_SETUID, CAP_SETGID and CAP_SYS_CHROOT anymore. */
DIAG_OFF_ASSIGN_ENUM
capng_updatev(
CAPNG_DROP,
CAPNG_EFFECTIVE | CAPNG_PERMITTED,
CAP_SETUID,
CAP_SETGID,
CAP_SYS_CHROOT,
-1);
DIAG_ON_ASSIGN_ENUM
capng_apply(CAPNG_SELECT_BOTH);
#endif /* HAVE_LIBCAP_NG */
}
#endif /* _WIN32 */
static int
getWflagChars(int x)
{
int c = 0;
x -= 1;
while (x > 0) {
c += 1;
x /= 10;
}
return c;
}
static void
MakeFilename(char *buffer, char *orig_name, int cnt, int max_chars)
{
char *filename = malloc(PATH_MAX + 1);
if (filename == NULL)
error("%s: malloc", __func__);
if (strlen(orig_name) == 0)
error("an empty string is not a valid file name");
/* Process with strftime if Gflag is set. */
if (Gflag != 0) {
struct tm *local_tm;
/* Convert Gflag_time to a usable format */
if ((local_tm = localtime(&Gflag_time)) == NULL) {
error("%s: localtime", __func__);
}
/* There's no good way to detect an error in strftime since a return
* value of 0 isn't necessarily failure; if orig_name is an empty
* string, the formatted string will be empty.
*
* However, the C90 standard says that, if there *is* a
* buffer overflow, the content of the buffer is undefined,
* so we must check for a buffer overflow.
*
* So we check above for an empty orig_name, and only call
* strftime() if it's non-empty, in which case the return
* value will only be 0 if the formatted date doesn't fit
* in the buffer.
*
* (We check above because, even if we don't use -G, we
* want a better error message than "tcpdump: : No such
* file or directory" for this case.)
*/
if (strftime(filename, PATH_MAX, orig_name, local_tm) == 0) {
error("%s: strftime", __func__);
}
} else {
strncpy(filename, orig_name, PATH_MAX);
}
if (cnt == 0 && max_chars == 0)
strncpy(buffer, filename, PATH_MAX + 1);
else
if (snprintf(buffer, PATH_MAX + 1, "%s%0*d", filename, max_chars, cnt) > PATH_MAX)
/* Report an error if the filename is too large */
error("too many output files or filename is too long (> %d)", PATH_MAX);
free(filename);
}
static char *
get_next_file(FILE *VFile, char *ptr)
{
char *ret;
size_t len;
ret = fgets(ptr, PATH_MAX, VFile);
if (!ret)
return NULL;
len = strlen (ptr);
if (len > 0 && ptr[len - 1] == '\n')
ptr[len - 1] = '\0';
return ret;
}
#ifdef HAVE_CASPER
static cap_channel_t *
capdns_setup(void)
{
cap_channel_t *capcas, *capdnsloc;
const char *types[1];
int families[2];
capcas = cap_init();
if (capcas == NULL)
error("unable to create casper process");
capdnsloc = cap_service_open(capcas, "system.dns");
/* Casper capability no longer needed. */
cap_close(capcas);
if (capdnsloc == NULL)
error("unable to open system.dns service");
/* Limit system.dns to reverse DNS lookups. */
types[0] = "ADDR";
if (cap_dns_type_limit(capdnsloc, types, 1) < 0)
error("unable to limit access to system.dns service");
families[0] = AF_INET;
/* Casper is a feature of FreeBSD, which defines AF_INET6. */
families[1] = AF_INET6;
if (cap_dns_family_limit(capdnsloc, families, 2) < 0)
error("unable to limit access to system.dns service");
return (capdnsloc);
}
#endif /* HAVE_CASPER */
#ifdef HAVE_PCAP_SET_TSTAMP_PRECISION
static int
tstamp_precision_from_string(const char *precision)
{
if (strncmp(precision, "nano", strlen("nano")) == 0)
return PCAP_TSTAMP_PRECISION_NANO;
if (strncmp(precision, "micro", strlen("micro")) == 0)
return PCAP_TSTAMP_PRECISION_MICRO;
return -EINVAL;
}
static const char *
tstamp_precision_to_string(int precision)
{
switch (precision) {
case PCAP_TSTAMP_PRECISION_MICRO:
return "micro";
case PCAP_TSTAMP_PRECISION_NANO:
return "nano";
default:
return "unknown";
}
}
#endif // HAVE_PCAP_SET_TSTAMP_PRECISION
#ifdef HAVE_CAPSICUM
/*
* Ensure that, on a dump file's descriptor, we have all the rights
* necessary to make the standard I/O library work with an fdopen()ed
* FILE * from that descriptor.
*
* A long time ago in a galaxy far, far away, AT&T decided that, instead
* of providing separate APIs for getting and setting the FD_ flags on a
* descriptor, getting and setting the O_ flags on a descriptor, and
* locking files, they'd throw them all into a kitchen-sink fcntl() call
* along the lines of ioctl(), the fact that ioctl() operations are
* largely specific to particular character devices but fcntl() operations
* are either generic to all descriptors or generic to all descriptors for
* regular files notwithstanding.
*
* The Capsicum people decided that fine-grained control of descriptor
* operations was required, so that you need to grant permission for
* reading, writing, seeking, and fcntl-ing. The latter, courtesy of
* AT&T's decision, means that "fcntl-ing" isn't a thing, but a motley
* collection of things, so there are *individual* fcntls for which
* permission needs to be granted.
*
* The FreeBSD standard I/O people implemented some optimizations that
* requires that the standard I/O routines be able to determine whether
* the descriptor for the FILE * is open append-only or not; as that
* descriptor could have come from an open() rather than an fopen(),
* that requires that it be able to do an F_GETFL fcntl() to read
* the O_ flags.
*
* tcpdump uses ftell() to determine how much data has been written
* to a file in order to, when used with -C, determine when it's time
* to rotate capture files. ftell() therefore needs to do an lseek()
* to find out the file offset and must, thanks to the aforementioned
* optimization, also know whether the descriptor is open append-only
* or not.
*
* The net result of all the above is that we need to grant CAP_SEEK,
* CAP_WRITE, and CAP_FCNTL with the CAP_FCNTL_GETFL subcapability.
*
* Perhaps this is the universe's way of saying that either
*
* 1) there needs to be an fopenat() call and a pcap_dump_openat() call
* using it, so that Capsicum-capable tcpdump wouldn't need to do
* an fdopen()
*
* or
*
* 2) there needs to be a cap_fdopen() call in the FreeBSD standard
* I/O library that knows what rights are needed by the standard
* I/O library, based on the open mode, and assigns them, perhaps
* with an additional argument indicating, for example, whether
* seeking should be allowed, so that tcpdump doesn't need to know
* what the standard I/O library happens to require this week.
*/
static void
set_dumper_capsicum_rights(pcap_dumper_t *p)
{
int fd = fileno(pcap_dump_file(p));
cap_rights_t rights;
cap_rights_init(&rights, CAP_SEEK, CAP_WRITE, CAP_FCNTL);
if (cap_rights_limit(fd, &rights) < 0 && errno != ENOSYS) {
error("unable to limit dump descriptor");
}
if (cap_fcntls_limit(fd, CAP_FCNTL_GETFL) < 0 && errno != ENOSYS) {
error("unable to limit dump descriptor fcntls");
}
}
#endif // HAVE_CAPSICUM
/*
* Copy arg vector into a new buffer, concatenating arguments with spaces.
*/
static char *
copy_argv(char **argv)
{
char **p;
size_t len = 0;
char *buf;
char *src, *dst;
p = argv;
if (*p == NULL)
return 0;
while (*p)
len += strlen(*p++) + 1;
buf = (char *)malloc(len);
if (buf == NULL)