/* $NetBSD: sf-pcap.c,v 1.11 2024/09/02 15:33:38 christos Exp $ */
/*
* Copyright (c) 1993, 1994, 1995, 1996, 1997
* 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.
*
* sf-pcap.c - libpcap-file-format-specific code from savefile.c
* Extraction/creation by Jeffrey Mogul, DECWRL
* Modified by Steve McCanne, LBL.
*
* Used to save the received packet headers, after filtering, to
* a file, and then read them later.
* The first record in the file contains saved values for the machine
* dependent values so we can print the dump file on any architecture.
*/
#include <sys/cdefs.h>
__RCSID("$NetBSD: sf-pcap.c,v 1.11 2024/09/02 15:33:38 christos Exp $");
#include <config.h>
#include <pcap-types.h>
#ifdef _WIN32
#include <io.h>
#include <fcntl.h>
#endif /* _WIN32 */
#include <errno.h>
#include <memory.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <limits.h> /* for INT_MAX */
#include "pcap-int.h"
#include "pcap-util.h"
#include "pcap-common.h"
#ifdef HAVE_OS_PROTO_H
#include "os-proto.h"
#endif
#include "sf-pcap.h"
/*
* Setting O_BINARY on DOS/Windows is a bit tricky
*/
#if defined(_WIN32)
#define SET_BINMODE(f) _setmode(_fileno(f), _O_BINARY)
#elif defined(MSDOS)
#if defined(__HIGHC__)
#define SET_BINMODE(f) setmode(f, O_BINARY)
#else
#define SET_BINMODE(f) setmode(fileno(f), O_BINARY)
#endif
#endif
/*
* Standard libpcap format.
*
* The same value is used in the rpcap protocol as an indication of
* the server byte order, to let the client know whether it needs to
* byte-swap some host-byte-order metadata.
*/
#define TCPDUMP_MAGIC 0xa1b2c3d4
/*
* Alexey Kuznetzov's modified libpcap format.
*/
#define KUZNETZOV_TCPDUMP_MAGIC 0xa1b2cd34
/*
* Reserved for Francisco Mesquita <
[email protected]>
* for another modified format.
*/
#define FMESQUITA_TCPDUMP_MAGIC 0xa1b234cd
/*
* Navtel Communications' format, with nanosecond timestamps,
* as per a request from Dumas Hwang <
[email protected]>.
*/
#define NAVTEL_TCPDUMP_MAGIC 0xa12b3c4d
/*
* Normal libpcap format, except for seconds/nanoseconds timestamps,
* as per a request by Ulf Lamping <
[email protected]>
*/
#define NSEC_TCPDUMP_MAGIC 0xa1b23c4d
/*
* This is a timeval as stored in a savefile.
* It has to use the same types everywhere, independent of the actual
* `struct timeval'; `struct timeval' has 32-bit tv_sec values on some
* platforms and 64-bit tv_sec values on other platforms, and writing
* out native `struct timeval' values would mean files could only be
* read on systems with the same tv_sec size as the system on which
* the file was written.
*
* THe fields are unsigned, as that's what the pcap draft specification
* says they are. (That gives pcap a 68-year Y2.038K reprieve, although
* in 2106 it runs out for good. pcapng doesn't have that problem,
* unless you pick a *really* high time stamp precision.)
*/
struct pcap_timeval {
bpf_u_int32 tv_sec; /* seconds */
bpf_u_int32 tv_usec; /* microseconds */
};
/*
* This is a `pcap_pkthdr' as actually stored in a savefile.
*
* Do not change the format of this structure, in any way (this includes
* changes that only affect the length of fields in this structure),
* and do not make the time stamp anything other than seconds and
* microseconds (e.g., seconds and nanoseconds). Instead:
*
* introduce a new structure for the new format;
*
* send mail to "
[email protected]", requesting
* a new magic number for your new capture file format, and, when
* you get the new magic number, put it in "savefile.c";
*
* use that magic number for save files with the changed record
* header;
*
* make the code in "savefile.c" capable of reading files with
* the old record header as well as files with the new record header
* (using the magic number to determine the header format).
*
* Then supply the changes by forking the branch at
*
*
https://github.com/the-tcpdump-group/libpcap/tree/master
*
* and issuing a pull request, so that future versions of libpcap and
* programs that use it (such as tcpdump) will be able to read your new
* capture file format.
*/
struct pcap_sf_pkthdr {
struct pcap_timeval ts; /* time stamp */
bpf_u_int32 caplen; /* length of portion present */
bpf_u_int32 len; /* length of this packet (off wire) */
};
/*
* How a `pcap_pkthdr' is actually stored in savefiles written
* by some patched versions of libpcap (e.g. the ones in Red
* Hat Linux 6.1 and 6.2).
*
* Do not change the format of this structure, in any way (this includes
* changes that only affect the length of fields in this structure).
* Instead, introduce a new structure, as per the above.
*/
struct pcap_sf_patched_pkthdr {
struct pcap_timeval ts; /* time stamp */
bpf_u_int32 caplen; /* length of portion present */
bpf_u_int32 len; /* length of this packet (off wire) */
int index;
unsigned short protocol;
unsigned char pkt_type;
};
static int pcap_next_packet(pcap_t *p, struct pcap_pkthdr *hdr, u_char **datap);
#ifdef _WIN32
/*
* This isn't exported on Windows, because it would only work if both
* libpcap and the code using it were using the same C runtime; otherwise they
* would be using different definitions of a FILE structure.
*
* Instead we define this as a macro in pcap/pcap.h that wraps the hopen
* version that we do export, passing it a raw OS HANDLE, as defined by the
* Win32 / Win64 ABI, obtained from the _fileno() and _get_osfhandle()
* functions of the appropriate CRT.
*/
static pcap_dumper_t *pcap_dump_fopen(pcap_t *p, FILE *f);
#endif /* _WIN32 */
/*
* Private data for reading pcap savefiles.
*/
typedef enum {
NOT_SWAPPED,
SWAPPED,
MAYBE_SWAPPED
} swapped_type_t;
typedef enum {
PASS_THROUGH,
SCALE_UP,
SCALE_DOWN
} tstamp_scale_type_t;
struct pcap_sf {
size_t hdrsize;
swapped_type_t lengths_swapped;
tstamp_scale_type_t scale_type;
};
/*
* Check whether this is a pcap savefile and, if it is, extract the
* relevant information from the header.
*/
pcap_t *
pcap_check_header(const uint8_t *magic, FILE *fp, u_int precision, char *errbuf,
int *err)
{
bpf_u_int32 magic_int;
struct pcap_file_header hdr;
size_t amt_read;
pcap_t *p;
int swapped = 0;
struct pcap_sf *ps;
/*
* Assume no read errors.
*/
*err = 0;
/*
* Check whether the first 4 bytes of the file are the magic
* number for a pcap savefile, or for a byte-swapped pcap
* savefile.
*/
memcpy(&magic_int, magic, sizeof(magic_int));
if (magic_int != TCPDUMP_MAGIC &&
magic_int != KUZNETZOV_TCPDUMP_MAGIC &&
magic_int != NSEC_TCPDUMP_MAGIC) {
magic_int = SWAPLONG(magic_int);
if (magic_int != TCPDUMP_MAGIC &&
magic_int != KUZNETZOV_TCPDUMP_MAGIC &&
magic_int != NSEC_TCPDUMP_MAGIC)
return (NULL); /* nope */
swapped = 1;
}
/*
* They are. Put the magic number in the header, and read
* the rest of the header.
*/
hdr.magic = magic_int;
amt_read = fread(((char *)&hdr) + sizeof hdr.magic, 1,
sizeof(hdr) - sizeof(hdr.magic), fp);
if (amt_read != sizeof(hdr) - sizeof(hdr.magic)) {
if (ferror(fp)) {
pcapint_fmt_errmsg_for_errno(errbuf, PCAP_ERRBUF_SIZE,
errno, "error reading dump file");
} else {
snprintf(errbuf, PCAP_ERRBUF_SIZE,
"truncated dump file; tried to read %zu file header bytes, only got %zu",
sizeof(hdr), amt_read);
}
*err = 1;
return (NULL);
}
/*
* If it's a byte-swapped capture file, byte-swap the header.
*/
if (swapped) {
hdr.version_major = SWAPSHORT(hdr.version_major);
hdr.version_minor = SWAPSHORT(hdr.version_minor);
hdr.thiszone = SWAPLONG(hdr.thiszone);
hdr.sigfigs = SWAPLONG(hdr.sigfigs);
hdr.snaplen = SWAPLONG(hdr.snaplen);
hdr.linktype = SWAPLONG(hdr.linktype);
}
if (hdr.version_major < PCAP_VERSION_MAJOR) {
snprintf(errbuf, PCAP_ERRBUF_SIZE,
"archaic pcap savefile format");
*err = 1;
return (NULL);
}
/*
* currently only versions 2.[0-4] are supported with
* the exception of 543.0 for DG/UX tcpdump.
*/
if (! ((hdr.version_major == PCAP_VERSION_MAJOR &&
hdr.version_minor <= PCAP_VERSION_MINOR) ||
(hdr.version_major == 543 &&
hdr.version_minor == 0))) {
snprintf(errbuf, PCAP_ERRBUF_SIZE,
"unsupported pcap savefile version %u.%u",
hdr.version_major, hdr.version_minor);
*err = 1;
return NULL;
}
/*
* Check the main reserved field.
*/
if (LT_RESERVED1(hdr.linktype) != 0) {
snprintf(errbuf, PCAP_ERRBUF_SIZE,
"savefile linktype reserved field not zero (0x%08x)",
LT_RESERVED1(hdr.linktype));
*err = 1;
return NULL;
}
/*
* OK, this is a good pcap file.
* Allocate a pcap_t for it.
*/
p = PCAP_OPEN_OFFLINE_COMMON(errbuf, struct pcap_sf);
if (p == NULL) {
/* Allocation failed. */
*err = 1;
return (NULL);
}
p->swapped = swapped;
p->version_major = hdr.version_major;
p->version_minor = hdr.version_minor;
p->linktype = linktype_to_dlt(LT_LINKTYPE(hdr.linktype));
p->linktype_ext = LT_LINKTYPE_EXT(hdr.linktype);
p->snapshot = pcapint_adjust_snapshot(p->linktype, hdr.snaplen);
p->next_packet_op = pcap_next_packet;
ps = p->priv;
p->opt.tstamp_precision = precision;
/*
* Will we need to scale the timestamps to match what the
* user wants?
*/
switch (precision) {
case PCAP_TSTAMP_PRECISION_MICRO:
if (magic_int == NSEC_TCPDUMP_MAGIC) {
/*
* The file has nanoseconds, the user
* wants microseconds; scale the
* precision down.
*/
ps->scale_type = SCALE_DOWN;
} else {
/*
* The file has microseconds, the
* user wants microseconds; nothing to do.
*/
ps->scale_type = PASS_THROUGH;
}
break;
case PCAP_TSTAMP_PRECISION_NANO:
if (magic_int == NSEC_TCPDUMP_MAGIC) {
/*
* The file has nanoseconds, the
* user wants nanoseconds; nothing to do.
*/
ps->scale_type = PASS_THROUGH;
} else {
/*
* The file has microseconds, the user
* wants nanoseconds; scale the
* precision up.
*/
ps->scale_type = SCALE_UP;
}
break;
default:
snprintf(errbuf, PCAP_ERRBUF_SIZE,
"unknown time stamp resolution %u", precision);
free(p);
*err = 1;
return (NULL);
}
/*
* We interchanged the caplen and len fields at version 2.3,
* in order to match the bpf header layout. But unfortunately
* some files were written with version 2.3 in their headers
* but without the interchanged fields.
*
* In addition, DG/UX tcpdump writes out files with a version
* number of 543.0, and with the caplen and len fields in the
* pre-2.3 order.
*/
switch (hdr.version_major) {
case 2:
if (hdr.version_minor < 3)
ps->lengths_swapped = SWAPPED;
else if (hdr.version_minor == 3)
ps->lengths_swapped = MAYBE_SWAPPED;
else
ps->lengths_swapped = NOT_SWAPPED;
break;
case 543:
ps->lengths_swapped = SWAPPED;
break;
default:
ps->lengths_swapped = NOT_SWAPPED;
break;
}
if (magic_int == KUZNETZOV_TCPDUMP_MAGIC) {
/*
* XXX - the patch that's in some versions of libpcap
* changes the packet header but not the magic number,
* and some other versions with this magic number have
* some extra debugging information in the packet header;
* we'd have to use some hacks^H^H^H^H^Hheuristics to
* detect those variants.
*
* Ethereal does that, but it does so by trying to read
* the first two packets of the file with each of the
* record header formats. That currently means it seeks
* backwards and retries the reads, which doesn't work
* on pipes. We want to be able to read from a pipe, so
* that strategy won't work; we'd have to buffer some
* data ourselves and read from that buffer in order to
* make that work.
*/
ps->hdrsize = sizeof(struct pcap_sf_patched_pkthdr);
if (p->linktype == DLT_EN10MB) {
/*
* This capture might have been done in raw mode
* or cooked mode.
*
* If it was done in cooked mode, p->snapshot was
* passed to recvfrom() as the buffer size, meaning
* that the most packet data that would be copied
* would be p->snapshot. However, a faked Ethernet
* header would then have been added to it, so the
* most data that would be in a packet in the file
* would be p->snapshot + 14.
*
* We can't easily tell whether the capture was done
* in raw mode or cooked mode, so we'll assume it was
* cooked mode, and add 14 to the snapshot length.
* That means that, for a raw capture, the snapshot
* length will be misleading if you use it to figure
* out why a capture doesn't have all the packet data,
* but there's not much we can do to avoid that.
*
* But don't grow the snapshot length past the
* maximum value of an int.
*/
if (p->snapshot <= INT_MAX - 14)
p->snapshot += 14;
else
p->snapshot = INT_MAX;
}
} else
ps->hdrsize = sizeof(struct pcap_sf_pkthdr);
/*
* Allocate a buffer for the packet data.
* Choose the minimum of the file's snapshot length and 2K bytes;
* that should be enough for most network packets - we'll grow it
* if necessary. That way, we don't allocate a huge chunk of
* memory just because there's a huge snapshot length, as the
* snapshot length might be larger than the size of the largest
* packet.
*/
p->bufsize = p->snapshot;
if (p->bufsize > 2048)
p->bufsize = 2048;
p->buffer = malloc(p->bufsize);
if (p->buffer == NULL) {
snprintf(errbuf, PCAP_ERRBUF_SIZE, "out of memory");
free(p);
*err = 1;
return (NULL);
}
p->cleanup_op = pcapint_sf_cleanup;
return (p);
}
/*
* Grow the packet buffer to the specified size.
*/
static int
grow_buffer(pcap_t *p, u_int bufsize)
{
void *bigger_buffer;
bigger_buffer = realloc(p->buffer, bufsize);
if (bigger_buffer == NULL) {
snprintf(p->errbuf, PCAP_ERRBUF_SIZE, "out of memory");
return (0);
}
p->buffer = bigger_buffer;
p->bufsize = bufsize;
return (1);
}
/*
* Read and return the next packet from the savefile. Return the header
* in hdr and a pointer to the contents in data. Return 1 on success, 0
* if there were no more packets, and -1 on an error.
*/
static int
pcap_next_packet(pcap_t *p, struct pcap_pkthdr *hdr, u_char **data)
{
struct pcap_sf *ps = p->priv;
struct pcap_sf_patched_pkthdr sf_hdr;
FILE *fp = p->rfile;
size_t amt_read;
bpf_u_int32 t;
/*
* Read the packet header; the structure we use as a buffer
* is the longer structure for files generated by the patched
* libpcap, but if the file has the magic number for an
* unpatched libpcap we only read as many bytes as the regular
* header has.
*/
amt_read = fread(&sf_hdr, 1, ps->hdrsize, fp);
if (amt_read != ps->hdrsize) {
if (ferror(fp)) {
pcapint_fmt_errmsg_for_errno(p->errbuf, PCAP_ERRBUF_SIZE,
errno, "error reading dump file");
return (-1);
} else {
if (amt_read != 0) {
snprintf(p->errbuf, PCAP_ERRBUF_SIZE,
"truncated dump file; tried to read %zu header bytes, only got %zu",
ps->hdrsize, amt_read);
return (-1);
}
/* EOF */
return (0);
}
}
if (p->swapped) {
/* these were written in opposite byte order */
hdr->caplen = SWAPLONG(sf_hdr.caplen);
hdr->len = SWAPLONG(sf_hdr.len);
hdr->ts.tv_sec = SWAPLONG(sf_hdr.ts.tv_sec);
hdr->ts.tv_usec = SWAPLONG(sf_hdr.ts.tv_usec);
} else {
hdr->caplen = sf_hdr.caplen;
hdr->len = sf_hdr.len;
hdr->ts.tv_sec = sf_hdr.ts.tv_sec;
hdr->ts.tv_usec = sf_hdr.ts.tv_usec;
}
switch (ps->scale_type) {
case PASS_THROUGH:
/*
* Just pass the time stamp through.
*/
break;
case SCALE_UP:
/*
* File has microseconds, user wants nanoseconds; convert
* it.
*/
hdr->ts.tv_usec = hdr->ts.tv_usec * 1000;
break;
case SCALE_DOWN:
/*
* File has nanoseconds, user wants microseconds; convert
* it.
*/
hdr->ts.tv_usec = hdr->ts.tv_usec / 1000;
break;
}
/* Swap the caplen and len fields, if necessary. */
switch (ps->lengths_swapped) {
case NOT_SWAPPED:
break;
case MAYBE_SWAPPED:
if (hdr->caplen <= hdr->len) {
/*
* The captured length is <= the actual length,
* so presumably they weren't swapped.
*/
break;
}
/* FALLTHROUGH */
case SWAPPED:
t = hdr->caplen;
hdr->caplen = hdr->len;
hdr->len = t;
break;
}
/*
* Is the packet bigger than we consider sane?
*/
if (hdr->caplen > max_snaplen_for_dlt(p->linktype)) {
/*
* Yes. This may be a damaged or fuzzed file.
*
* Is it bigger than the snapshot length?
* (We don't treat that as an error if it's not
* bigger than the maximum we consider sane; see
* below.)
*/
if (hdr->caplen > (bpf_u_int32)p->snapshot) {
snprintf(p->errbuf, PCAP_ERRBUF_SIZE,
"invalid packet capture length %u, bigger than "
"snaplen of %d", hdr->caplen, p->snapshot);
} else {
snprintf(p->errbuf, PCAP_ERRBUF_SIZE,
"invalid packet capture length %u, bigger than "
"maximum of %u", hdr->caplen,
max_snaplen_for_dlt(p->linktype));
}
return (-1);
}
if (hdr->caplen > (bpf_u_int32)p->snapshot) {
/*
* The packet is bigger than the snapshot length
* for this file.
*
* This can happen due to Solaris 2.3 systems tripping
* over the BUFMOD problem and not setting the snapshot
* length correctly in the savefile header.
*
* libpcap 0.4 and later on Solaris 2.3 should set the
* snapshot length correctly in the pcap file header,
* even though they don't set a snapshot length in bufmod
* (the buggy bufmod chops off the *beginning* of the
* packet if a snapshot length is specified); they should
* also reduce the captured length, as supplied to the
* per-packet callback, to the snapshot length if it's
* greater than the snapshot length, so the code using
* libpcap should see the packet cut off at the snapshot
* length, even though the full packet is copied up to
* userland.
*
* However, perhaps some versions of libpcap failed to
* set the snapshot length correctly in the file header
* or the per-packet header, or perhaps this is a
* corrupted savefile or a savefile built/modified by a
* fuzz tester, so we check anyway. We grow the buffer
* to be big enough for the snapshot length, read up
* to the snapshot length, discard the rest of the
* packet, and report the snapshot length as the captured
* length; we don't want to hand our caller a packet
* bigger than the snapshot length, because they might
* be assuming they'll never be handed such a packet,
* and might copy the packet into a snapshot-length-
* sized buffer, assuming it'll fit.
*/
size_t bytes_to_discard;
size_t bytes_to_read, bytes_read;
char discard_buf[4096];
if (hdr->caplen > p->bufsize) {
/*
* Grow the buffer to the snapshot length.
*/
if (!grow_buffer(p, p->snapshot))
return (-1);
}
/*
* Read the first p->snapshot bytes into the buffer.
*/
amt_read = fread(p->buffer, 1, p->snapshot, fp);
if (amt_read != (bpf_u_int32)p->snapshot) {
if (ferror(fp)) {
pcapint_fmt_errmsg_for_errno(p->errbuf,
PCAP_ERRBUF_SIZE, errno,
"error reading dump file");
} else {
/*
* Yes, this uses hdr->caplen; technically,
* it's true, because we would try to read
* and discard the rest of those bytes, and
* that would fail because we got EOF before
* the read finished.
*/
snprintf(p->errbuf, PCAP_ERRBUF_SIZE,
"truncated dump file; tried to read %d captured bytes, only got %zu",
p->snapshot, amt_read);
}
return (-1);
}
/*
* Now read and discard what's left.
*/
bytes_to_discard = hdr->caplen - p->snapshot;
bytes_read = amt_read;
while (bytes_to_discard != 0) {
bytes_to_read = bytes_to_discard;
if (bytes_to_read > sizeof (discard_buf))
bytes_to_read = sizeof (discard_buf);
amt_read = fread(discard_buf, 1, bytes_to_read, fp);
bytes_read += amt_read;
if (amt_read != bytes_to_read) {
if (ferror(fp)) {
pcapint_fmt_errmsg_for_errno(p->errbuf,
PCAP_ERRBUF_SIZE, errno,
"error reading dump file");
} else {
snprintf(p->errbuf, PCAP_ERRBUF_SIZE,
"truncated dump file; tried to read %u captured bytes, only got %zu",
hdr->caplen, bytes_read);
}
return (-1);
}
bytes_to_discard -= amt_read;
}
/*
* Adjust caplen accordingly, so we don't get confused later
* as to how many bytes we have to play with.
*/
hdr->caplen = p->snapshot;
} else {
/*
* The packet is within the snapshot length for this file.
*/
if (hdr->caplen > p->bufsize) {
/*
* Grow the buffer to the next power of 2, or
* the snaplen, whichever is lower.
*/
u_int new_bufsize;
new_bufsize = hdr->caplen;
/*
*
https://graphics.stanford.edu/~seander/bithacks.html#RoundUpPowerOf2
*/
new_bufsize--;
new_bufsize |= new_bufsize >> 1;
new_bufsize |= new_bufsize >> 2;
new_bufsize |= new_bufsize >> 4;
new_bufsize |= new_bufsize >> 8;
new_bufsize |= new_bufsize >> 16;
new_bufsize++;
if (new_bufsize > (u_int)p->snapshot)
new_bufsize = p->snapshot;
if (!grow_buffer(p, new_bufsize))
return (-1);
}
/* read the packet itself */
amt_read = fread(p->buffer, 1, hdr->caplen, fp);
if (amt_read != hdr->caplen) {
if (ferror(fp)) {
pcapint_fmt_errmsg_for_errno(p->errbuf,
PCAP_ERRBUF_SIZE, errno,
"error reading dump file");
} else {
snprintf(p->errbuf, PCAP_ERRBUF_SIZE,
"truncated dump file; tried to read %u captured bytes, only got %zu",
hdr->caplen, amt_read);
}
return (-1);
}
}
*data = p->buffer;
pcapint_post_process(p->linktype, p->swapped, hdr, *data);
return (1);
}
static int
sf_write_header(pcap_t *p, FILE *fp, int linktype, int snaplen)
{
struct pcap_file_header hdr;
hdr.magic = p->opt.tstamp_precision == PCAP_TSTAMP_PRECISION_NANO ? NSEC_TCPDUMP_MAGIC : TCPDUMP_MAGIC;
hdr.version_major = PCAP_VERSION_MAJOR;
hdr.version_minor = PCAP_VERSION_MINOR;
/*
*
https://www.tcpdump.org/manpages/pcap-savefile.5.txt states:
* thiszone (Reserved1): 4-byte not used - SHOULD be filled with 0
* sigfigs (Reserved2): 4-byte not used - SHOULD be filled with 0
*/
hdr.thiszone = 0;
hdr.sigfigs = 0;
hdr.snaplen = snaplen;
hdr.linktype = linktype;
if (fwrite((char *)&hdr, sizeof(hdr), 1, fp) != 1)
return (-1);
return (0);
}
/*
* Output a packet to the initialized dump file.
*/
void
pcap_dump(u_char *user, const struct pcap_pkthdr *h, const u_char *sp)
{
register FILE *f;
struct pcap_sf_pkthdr sf_hdr;
f = (FILE *)user;
/*
* If the output file handle is in an error state, don't write
* anything.
*
* While in principle a file handle can return from an error state
* to a normal state (for example if a disk that is full has space
* freed), we have possibly left a broken file already, and won't
* be able to clean it up. The safest option is to do nothing.
*
* Note that if we could guarantee that fwrite() was atomic we
* might be able to insure that we don't produce a corrupted file,
* but the standard defines fwrite() as a series of fputc() calls,
* so we really have no insurance that things are not fubared.
*
*
http://pubs.opengroup.org/onlinepubs/009695399/functions/fwrite.html
*/
if (ferror(f))
return;
/*
* Better not try writing pcap files after
* 2106-02-07 06:28:15 UTC; switch to pcapng.
* (And better not try writing pcap files with time stamps
* that predate 1970-01-01 00:00:00 UTC; that's not supported.
* You could try using pcapng with the if_tsoffset field in
* the IDB for the interface(s) with packets with those time
* stamps, but you may also have to get a link-layer type for
* IBM Bisync or whatever link layer even older forms
* of computer communication used.)
*/
sf_hdr.ts.tv_sec = (bpf_u_int32)h->ts.tv_sec;
sf_hdr.ts.tv_usec = (bpf_u_int32)h->ts.tv_usec;
sf_hdr.caplen = h->caplen;
sf_hdr.len = h->len;
/*
* We only write the packet if we can write the header properly.
*
* This doesn't prevent us from having corrupted output, and if we
* for some reason don't get a complete write we don't have any
* way to set ferror() to prevent future writes from being
* attempted, but it is better than nothing.
*/
if (fwrite(&sf_hdr, sizeof(sf_hdr), 1, f) == 1) {
(void)fwrite(sp, h->caplen, 1, f);
}
}
static pcap_dumper_t *
pcap_setup_dump(pcap_t *p, int linktype, FILE *f, const char *fname)
{
#if defined(_WIN32) || defined(MSDOS)
/*
* If we're writing to the standard output, put it in binary
* mode, as savefiles are binary files.
*
* Otherwise, we turn off buffering.
* XXX - why? And why not on the standard output?
*/
if (f == stdout)
SET_BINMODE(f);
else
setvbuf(f, NULL, _IONBF, 0);
#endif
if (sf_write_header(p, f, linktype, p->snapshot) == -1) {
pcapint_fmt_errmsg_for_errno(p->errbuf, PCAP_ERRBUF_SIZE,
errno, "Can't write to %s", fname);
if (f != stdout)
(void)fclose(f);
return (NULL);
}
return ((pcap_dumper_t *)f);
}
/*
* Initialize so that sf_write() will output to the file named 'fname'.
*/
pcap_dumper_t *
pcap_dump_open(pcap_t *p, const char *fname)
{
FILE *f;
int linktype;
/*
* If this pcap_t hasn't been activated, it doesn't have a
* link-layer type, so we can't use it.
*/
if (!p->activated) {
snprintf(p->errbuf, PCAP_ERRBUF_SIZE,
"%s: not-yet-activated pcap_t passed to pcap_dump_open",
fname);
return (NULL);
}
linktype = dlt_to_linktype(p->linktype);
if (linktype == -1) {
snprintf(p->errbuf, PCAP_ERRBUF_SIZE,
"%s: link-layer type %d isn't supported in savefiles",
fname, p->linktype);
return (NULL);
}
linktype |= p->linktype_ext;
if (fname == NULL) {
snprintf(p->errbuf, PCAP_ERRBUF_SIZE,
"A null pointer was supplied as the file name");
return NULL;
}
if (fname[0] == '-' && fname[1] == '\0') {
f = stdout;
fname = "standard output";
} else {
/*
* "b" is supported as of C90, so *all* UN*Xes should
* support it, even though it does nothing. It's
* required on Windows, as the file is a binary file
* and must be written in binary mode.
*/
f = pcapint_charset_fopen(fname, "wb");
if (f == NULL) {
pcapint_fmt_errmsg_for_errno(p->errbuf, PCAP_ERRBUF_SIZE,
errno, "%s", fname);
return (NULL);
}
}
return (pcap_setup_dump(p, linktype, f, fname));
}
#ifdef _WIN32
/*
* Initialize so that sf_write() will output to a stream wrapping the given raw
* OS file HANDLE.
*/
pcap_dumper_t *
pcap_dump_hopen(pcap_t *p, intptr_t osfd)
{
int fd;
FILE *file;
fd = _open_osfhandle(osfd, _O_APPEND);
if (fd < 0) {
pcapint_fmt_errmsg_for_errno(p->errbuf, PCAP_ERRBUF_SIZE,
errno, "_open_osfhandle");
return NULL;
}
file = _fdopen(fd, "wb");
if (file == NULL) {
pcapint_fmt_errmsg_for_errno(p->errbuf, PCAP_ERRBUF_SIZE,
errno, "_fdopen");
_close(fd);
return NULL;
}
return pcap_dump_fopen(p, file);
}
#endif /* _WIN32 */
/*
* Initialize so that sf_write() will output to the given stream.
*/
#ifdef _WIN32
static
#endif /* _WIN32 */
pcap_dumper_t *
pcap_dump_fopen(pcap_t *p, FILE *f)
{
int linktype;
linktype = dlt_to_linktype(p->linktype);
if (linktype == -1) {
snprintf(p->errbuf, PCAP_ERRBUF_SIZE,
"stream: link-layer type %d isn't supported in savefiles",
p->linktype);
return (NULL);
}
linktype |= p->linktype_ext;
return (pcap_setup_dump(p, linktype, f, "stream"));
}
pcap_dumper_t *
pcap_dump_open_append(pcap_t *p, const char *fname)
{
FILE *f;
int linktype;
size_t amt_read;
struct pcap_file_header ph;
linktype = dlt_to_linktype(p->linktype);
if (linktype == -1) {
snprintf(p->errbuf, PCAP_ERRBUF_SIZE,
"%s: link-layer type %d isn't supported in savefiles",
fname, linktype);
return (NULL);
}
if (fname == NULL) {
snprintf(p->errbuf, PCAP_ERRBUF_SIZE,
"A null pointer was supplied as the file name");
return NULL;
}
if (fname[0] == '-' && fname[1] == '\0')
return (pcap_setup_dump(p, linktype, stdout, "standard output"));
/*
* "a" will cause the file *not* to be truncated if it exists
* but will cause it to be created if it doesn't. It will
* also cause all writes to be done at the end of the file,
* but will allow reads to be done anywhere in the file. This
* is what we need, because we need to read from the beginning
* of the file to see if it already has a header and packets
* or if it doesn't.
*
* "b" is supported as of C90, so *all* UN*Xes should support it,
* even though it does nothing. It's required on Windows, as the
* file is a binary file and must be read in binary mode.
*/
f = pcapint_charset_fopen(fname, "ab+");
if (f == NULL) {
pcapint_fmt_errmsg_for_errno(p->errbuf, PCAP_ERRBUF_SIZE,
errno, "%s", fname);
return (NULL);
}
/*
* Try to read a pcap header.
*
* We do not assume that the file will be positioned at the
* beginning immediately after we've opened it - we seek to
* the beginning. ISO C says it's implementation-defined
* whether the file position indicator is at the beginning
* or the end of the file after an append-mode open, and
* it wasn't obvious from the Single UNIX Specification
* or the Microsoft documentation how that works on SUS-
* compliant systems or on Windows.
*/
if (fseek(f, 0, SEEK_SET) == -1) {
pcapint_fmt_errmsg_for_errno(p->errbuf, PCAP_ERRBUF_SIZE,
errno, "Can't seek to the beginning of %s", fname);
(void)fclose(f);
return (NULL);
}
amt_read = fread(&ph, 1, sizeof (ph), f);
if (amt_read != sizeof (ph)) {
if (ferror(f)) {
pcapint_fmt_errmsg_for_errno(p->errbuf, PCAP_ERRBUF_SIZE,
errno, "%s", fname);
(void)fclose(f);
return (NULL);
} else if (feof(f) && amt_read > 0) {
snprintf(p->errbuf, PCAP_ERRBUF_SIZE,
"%s: truncated pcap file header", fname);
(void)fclose(f);
return (NULL);
}
}
#if defined(_WIN32) || defined(MSDOS)
/*
* We turn off buffering.
* XXX - why? And why not on the standard output?
*/
setvbuf(f, NULL, _IONBF, 0);
#endif
/*
* If a header is already present and:
*
* it's not for a pcap file of the appropriate resolution
* and the right byte order for this machine;
*
* the link-layer header types don't match;
*
* the snapshot lengths don't match;
*
* return an error.
*/
if (amt_read > 0) {
/*
* A header is already present.
* Do the checks.
*/
switch (ph.magic) {
case TCPDUMP_MAGIC:
if (p->opt.tstamp_precision != PCAP_TSTAMP_PRECISION_MICRO) {
snprintf(p->errbuf, PCAP_ERRBUF_SIZE,
"%s: different time stamp precision, cannot append to file", fname);
(void)fclose(f);
return (NULL);
}
break;
case NSEC_TCPDUMP_MAGIC:
if (p->opt.tstamp_precision != PCAP_TSTAMP_PRECISION_NANO) {
snprintf(p->errbuf, PCAP_ERRBUF_SIZE,
"%s: different time stamp precision, cannot append to file", fname);
(void)fclose(f);
return (NULL);
}
break;
case SWAPLONG(TCPDUMP_MAGIC):
case SWAPLONG(NSEC_TCPDUMP_MAGIC):
snprintf(p->errbuf, PCAP_ERRBUF_SIZE,
"%s: different byte order, cannot append to file", fname);
(void)fclose(f);
return (NULL);
case KUZNETZOV_TCPDUMP_MAGIC:
case SWAPLONG(KUZNETZOV_TCPDUMP_MAGIC):
case NAVTEL_TCPDUMP_MAGIC:
case SWAPLONG(NAVTEL_TCPDUMP_MAGIC):
snprintf(p->errbuf, PCAP_ERRBUF_SIZE,
"%s: not a pcap file to which we can append", fname);
(void)fclose(f);
return (NULL);
default:
snprintf(p->errbuf, PCAP_ERRBUF_SIZE,
"%s: not a pcap file", fname);
(void)fclose(f);
return (NULL);
}
/*
* Good version?
*/
if (ph.version_major != PCAP_VERSION_MAJOR ||
ph.version_minor != PCAP_VERSION_MINOR) {
snprintf(p->errbuf, PCAP_ERRBUF_SIZE,
"%s: version is %u.%u, cannot append to file", fname,
ph.version_major, ph.version_minor);
(void)fclose(f);
return (NULL);
}
if ((bpf_u_int32)linktype != ph.linktype) {
snprintf(p->errbuf, PCAP_ERRBUF_SIZE,
"%s: different linktype, cannot append to file", fname);
(void)fclose(f);
return (NULL);
}
if ((bpf_u_int32)p->snapshot != ph.snaplen) {
snprintf(p->errbuf, PCAP_ERRBUF_SIZE,
"%s: different snaplen, cannot append to file", fname);
(void)fclose(f);
return (NULL);
}
} else {
/*
* A header isn't present; attempt to write it.
*/
if (sf_write_header(p, f, linktype, p->snapshot) == -1) {
pcapint_fmt_errmsg_for_errno(p->errbuf, PCAP_ERRBUF_SIZE,
errno, "Can't write to %s", fname);
(void)fclose(f);
return (NULL);
}
}
/*
* Start writing at the end of the file.
*
* XXX - this shouldn't be necessary, given that we're opening
* the file in append mode, and ISO C specifies that all writes
* are done at the end of the file in that mode.
*/
if (fseek(f, 0, SEEK_END) == -1) {
pcapint_fmt_errmsg_for_errno(p->errbuf, PCAP_ERRBUF_SIZE,
errno, "Can't seek to the end of %s", fname);
(void)fclose(f);
return (NULL);
}
return ((pcap_dumper_t *)f);
}
FILE *
pcap_dump_file(pcap_dumper_t *p)
{
return ((FILE *)p);
}
long
pcap_dump_ftell(pcap_dumper_t *p)
{
return (ftell((FILE *)p));
}
#if defined(HAVE_FSEEKO)
/*
* We have fseeko(), so we have ftello().
* If we have large file support (files larger than 2^31-1 bytes),
* ftello() will give us a current file position with more than 32
* bits.
*/
int64_t
pcap_dump_ftell64(pcap_dumper_t *p)
{
return (ftello((FILE *)p));
}
#elif defined(_MSC_VER)
/*
* We have Visual Studio; we support only 2005 and later, so we have
* _ftelli64().
*/
int64_t
pcap_dump_ftell64(pcap_dumper_t *p)
{
return (_ftelli64((FILE *)p));
}
#else
/*
* We don't have ftello() or _ftelli64(), so fall back on ftell().
* Either long is 64 bits, in which case ftell() should suffice,
* or this is probably an older 32-bit UN*X without large file
* support, which means you'll probably get errors trying to
* write files > 2^31-1, so it won't matter anyway.
*
* XXX - what about MinGW?
*/
int64_t
pcap_dump_ftell64(pcap_dumper_t *p)
{
return (ftell((FILE *)p));
}
#endif
int
pcap_dump_flush(pcap_dumper_t *p)
{
if (fflush((FILE *)p) == EOF)
return (-1);
else
return (0);
}
void
pcap_dump_close(pcap_dumper_t *p)
{
#ifdef notyet
if (ferror((FILE *)p))
return-an-error;
/* XXX should check return from fclose() too */
#endif
(void)fclose((FILE *)p);
}
