path: root/pcap-util.c

/*
 * 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.
 *
 * pcap-util.c - common code for various files
 */

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

#include <pcap-types.h>

#include "pcap-int.h"
#include "extract.h"
#include "pcap-usb-linux-common.h"

#include "pcap-util.h"

#include "pflog.h"
#include "pcap/can_socketcan.h"
#include "pcap/sll.h"
#include "pcap/usb.h"
#include "pcap/nflog.h"

/*
 * Most versions of the DLT_PFLOG pseudo-header have UID and PID fields
 * that are saved in host byte order.
 *
 * When reading a DLT_PFLOG packet, we need to convert those fields from
 * the byte order of the host that wrote the file to this host's byte
 * order.
 */
static void
swap_pflog_header(const struct pcap_pkthdr *hdr, u_char *buf)
{
	u_int caplen = hdr->caplen;
	u_int length = hdr->len;
	u_int pfloghdr_length;
	struct pfloghdr *pflhdr = (struct pfloghdr *)buf;

	if (caplen < (u_int) (offsetof(struct pfloghdr, uid) + sizeof pflhdr->uid) ||
	    length < (u_int) (offsetof(struct pfloghdr, uid) + sizeof pflhdr->uid)) {
		/* Not enough data to have the uid field */
		return;
	}

	pfloghdr_length = pflhdr->length;

	if (pfloghdr_length < (u_int) (offsetof(struct pfloghdr, uid) + sizeof pflhdr->uid)) {
		/* Header doesn't include uid field */
		return;
	}
	pflhdr->uid = SWAPLONG(pflhdr->uid);

	if (caplen < (u_int) (offsetof(struct pfloghdr, pid) + sizeof pflhdr->pid) ||
	    length < (u_int) (offsetof(struct pfloghdr, pid) + sizeof pflhdr->pid)) {
		/* Not enough data to have the pid field */
		return;
	}
	if (pfloghdr_length < (u_int) (offsetof(struct pfloghdr, pid) + sizeof pflhdr->pid)) {
		/* Header doesn't include pid field */
		return;
	}
	pflhdr->pid = SWAPLONG(pflhdr->pid);

	if (caplen < (u_int) (offsetof(struct pfloghdr, rule_uid) + sizeof pflhdr->rule_uid) ||
	    length < (u_int) (offsetof(struct pfloghdr, rule_uid) + sizeof pflhdr->rule_uid)) {
		/* Not enough data to have the rule_uid field */
		return;
	}
	if (pfloghdr_length < (u_int) (offsetof(struct pfloghdr, rule_uid) + sizeof pflhdr->rule_uid)) {
		/* Header doesn't include rule_uid field */
		return;
	}
	pflhdr->rule_uid = SWAPLONG(pflhdr->rule_uid);

	if (caplen < (u_int) (offsetof(struct pfloghdr, rule_pid) + sizeof pflhdr->rule_pid) ||
	    length < (u_int) (offsetof(struct pfloghdr, rule_pid) + sizeof pflhdr->rule_pid)) {
		/* Not enough data to have the rule_pid field */
		return;
	}
	if (pfloghdr_length < (u_int) (offsetof(struct pfloghdr, rule_pid) + sizeof pflhdr->rule_pid)) {
		/* Header doesn't include rule_pid field */
		return;
	}
	pflhdr->rule_pid = SWAPLONG(pflhdr->rule_pid);
}

/*
 * DLT_LINUX_SLL packets with a protocol type of LINUX_SLL_P_CAN or
 * LINUX_SLL_P_CANFD have SocketCAN headers in front of the payload,
 * with the CAN ID being in host byte order.
 *
 * When reading a DLT_LINUX_SLL packet, we need to check for those
 * packets and convert the CAN ID from the byte order of the host that
 * wrote the file to this host's byte order.
 */
static void
swap_linux_sll_header(const struct pcap_pkthdr *hdr, u_char *buf)
{
	u_int caplen = hdr->caplen;
	u_int length = hdr->len;
	struct sll_header *shdr = (struct sll_header *)buf;
	uint16_t protocol;
	pcap_can_socketcan_hdr *chdr;

	if (caplen < (u_int) sizeof(struct sll_header) ||
	    length < (u_int) sizeof(struct sll_header)) {
		/* Not enough data to have the protocol field */
		return;
	}

	protocol = EXTRACT_BE_U_2(&shdr->sll_protocol);
	if (protocol != LINUX_SLL_P_CAN && protocol != LINUX_SLL_P_CANFD)
		return;

	/*
	 * SocketCAN packet; fix up the packet's header.
	 */
	chdr = (pcap_can_socketcan_hdr *)(buf + sizeof(struct sll_header));
	if (caplen < (u_int) sizeof(struct sll_header) + sizeof(chdr->can_id) ||
	    length < (u_int) sizeof(struct sll_header) + sizeof(chdr->can_id)) {
		/* Not enough data to have the CAN ID */
		return;
	}
	chdr->can_id = SWAPLONG(chdr->can_id);
}

/*
 * The same applies for DLT_LINUX_SLL2.
 */
static void
swap_linux_sll2_header(const struct pcap_pkthdr *hdr, u_char *buf)
{
	u_int caplen = hdr->caplen;
	u_int length = hdr->len;
	struct sll2_header *shdr = (struct sll2_header *)buf;
	uint16_t protocol;
	pcap_can_socketcan_hdr *chdr;

	if (caplen < (u_int) sizeof(struct sll2_header) ||
	    length < (u_int) sizeof(struct sll2_header)) {
		/* Not enough data to have the protocol field */
		return;
	}

	protocol = EXTRACT_BE_U_2(&shdr->sll2_protocol);
	if (protocol != LINUX_SLL_P_CAN && protocol != LINUX_SLL_P_CANFD)
		return;

	/*
	 * SocketCAN packet; fix up the packet's header.
	 */
	chdr = (pcap_can_socketcan_hdr *)(buf + sizeof(struct sll2_header));
	if (caplen < (u_int) sizeof(struct sll2_header) + sizeof(chdr->can_id) ||
	    length < (u_int) sizeof(struct sll2_header) + sizeof(chdr->can_id)) {
		/* Not enough data to have the CAN ID */
		return;
	}
	chdr->can_id = SWAPLONG(chdr->can_id);
}

/*
 * The DLT_USB_LINUX and DLT_USB_LINUX_MMAPPED headers are in host
 * byte order when capturing (it's supplied directly from a
 * memory-mapped buffer shared by the kernel).
 *
 * When reading a DLT_USB_LINUX or DLT_USB_LINUX_MMAPPED packet, we
 * need to convert it from the byte order of the host that wrote the
 * file to this host's byte order.
 */
static void
swap_linux_usb_header(const struct pcap_pkthdr *hdr, u_char *buf,
    int header_len_64_bytes)
{
	pcap_usb_header_mmapped *uhdr = (pcap_usb_header_mmapped *)buf;
	bpf_u_int32 offset = 0;

	/*
	 * "offset" is the offset *past* the field we're swapping;
	 * we skip the field *before* checking to make sure
	 * the captured data length includes the entire field.
	 */

	/*
	 * The URB id is a totally opaque value; do we really need to
	 * convert it to the reading host's byte order???
	 */
	offset += 8;			/* skip past id */
	if (hdr->caplen < offset)
		return;
	uhdr->id = SWAPLL(uhdr->id);

	offset += 4;			/* skip past various 1-byte fields */

	offset += 2;			/* skip past bus_id */
	if (hdr->caplen < offset)
		return;
	uhdr->bus_id = SWAPSHORT(uhdr->bus_id);

	offset += 2;			/* skip past various 1-byte fields */

	offset += 8;			/* skip past ts_sec */
	if (hdr->caplen < offset)
		return;
	uhdr->ts_sec = SWAPLL(uhdr->ts_sec);

	offset += 4;			/* skip past ts_usec */
	if (hdr->caplen < offset)
		return;
	uhdr->ts_usec = SWAPLONG(uhdr->ts_usec);

	offset += 4;			/* skip past status */
	if (hdr->caplen < offset)
		return;
	uhdr->status = SWAPLONG(uhdr->status);

	offset += 4;			/* skip past urb_len */
	if (hdr->caplen < offset)
		return;
	uhdr->urb_len = SWAPLONG(uhdr->urb_len);

	offset += 4;			/* skip past data_len */
	if (hdr->caplen < offset)
		return;
	uhdr->data_len = SWAPLONG(uhdr->data_len);

	if (uhdr->transfer_type == URB_ISOCHRONOUS) {
		offset += 4;			/* skip past s.iso.error_count */
		if (hdr->caplen < offset)
			return;
		uhdr->s.iso.error_count = SWAPLONG(uhdr->s.iso.error_count);

		offset += 4;			/* skip past s.iso.numdesc */
		if (hdr->caplen < offset)
			return;
		uhdr->s.iso.numdesc = SWAPLONG(uhdr->s.iso.numdesc);
	} else
		offset += 8;			/* skip USB setup header */

	/*
	 * With the old header, there are no isochronous descriptors
	 * after the header.
	 *
	 * With the new header, the actual number of descriptors in
	 * the header is not s.iso.numdesc, it's ndesc - only the
	 * first N descriptors, for some value of N, are put into
	 * the header, and ndesc is set to the actual number copied.
	 * In addition, if s.iso.numdesc is negative, no descriptors
	 * are captured, and ndesc is set to 0.
	 */
	if (header_len_64_bytes) {
		/*
		 * This is either the "version 1" header, with
		 * 16 bytes of additional fields at the end, or
		 * a "version 0" header from a memory-mapped
		 * capture, with 16 bytes of zeroed-out padding
		 * at the end.  Byte swap them as if this were
		 * a "version 1" header.
		 */
		offset += 4;			/* skip past interval */
		if (hdr->caplen < offset)
			return;
		uhdr->interval = SWAPLONG(uhdr->interval);

		offset += 4;			/* skip past start_frame */
		if (hdr->caplen < offset)
			return;
		uhdr->start_frame = SWAPLONG(uhdr->start_frame);

		offset += 4;			/* skip past xfer_flags */
		if (hdr->caplen < offset)
			return;
		uhdr->xfer_flags = SWAPLONG(uhdr->xfer_flags);

		offset += 4;			/* skip past ndesc */
		if (hdr->caplen < offset)
			return;
		uhdr->ndesc = SWAPLONG(uhdr->ndesc);

		if (uhdr->transfer_type == URB_ISOCHRONOUS) {
			/* swap the values in struct linux_usb_isodesc */
			usb_isodesc *pisodesc;
			uint32_t i;

			pisodesc = (usb_isodesc *)(void *)(buf+offset);
			for (i = 0; i < uhdr->ndesc; i++) {
				offset += 4;		/* skip past status */
				if (hdr->caplen < offset)
					return;
				pisodesc->status = SWAPLONG(pisodesc->status);

				offset += 4;		/* skip past offset */
				if (hdr->caplen < offset)
					return;
				pisodesc->offset = SWAPLONG(pisodesc->offset);

				offset += 4;		/* skip past len */
				if (hdr->caplen < offset)
					return;
				pisodesc->len = SWAPLONG(pisodesc->len);

				offset += 4;		/* skip past padding */

				pisodesc++;
			}
		}
	}
}

/*
 * The DLT_NFLOG "packets" have a mixture of big-endian and host-byte-order
 * data.  They begin with a fixed-length header with big-endian fields,
 * followed by a set of TLVs, where the type and length are in host
 * byte order but the values are either big-endian or are a raw byte
 * sequence that's the same regardless of the host's byte order.
 *
 * When reading a DLT_NFLOG packet, we need to convert the type and
 * length values from the byte order of the host that wrote the file
 * to the byte order of this host.
 */
static void
swap_nflog_header(const struct pcap_pkthdr *hdr, u_char *buf)
{
	u_char *p = buf;
	nflog_hdr_t *nfhdr = (nflog_hdr_t *)buf;
	nflog_tlv_t *tlv;
	u_int caplen = hdr->caplen;
	u_int length = hdr->len;
	uint16_t size;

	if (caplen < (u_int) sizeof(nflog_hdr_t) ||
	    length < (u_int) sizeof(nflog_hdr_t)) {
		/* Not enough data to have any TLVs. */
		return;
	}

	if (nfhdr->nflog_version != 0) {
		/* Unknown NFLOG version */
		return;
	}

	length -= sizeof(nflog_hdr_t);
	caplen -= sizeof(nflog_hdr_t);
	p += sizeof(nflog_hdr_t);

	while (caplen >= sizeof(nflog_tlv_t)) {
		tlv = (nflog_tlv_t *) p;

		/* Swap the type and length. */
		tlv->tlv_type = SWAPSHORT(tlv->tlv_type);
		tlv->tlv_length = SWAPSHORT(tlv->tlv_length);

		/* Get the length of the TLV. */
		size = tlv->tlv_length;
		if (size % 4 != 0)
			size += 4 - size % 4;

		/* Is the TLV's length less than the minimum? */
		if (size < sizeof(nflog_tlv_t)) {
			/* Yes. Give up now. */
			return;
		}

		/* Do we have enough data for the full TLV? */
		if (caplen < size || length < size) {
			/* No. */
			return;
		}

		/* Skip over the TLV. */
		length -= size;
		caplen -= size;
		p += size;
	}
}

static void
swap_pseudo_headers(int linktype, struct pcap_pkthdr *hdr, u_char *data)
{
	/*
	 * Convert pseudo-headers from the byte order of
	 * the host on which the file was saved to our
	 * byte order, as necessary.
	 */
	switch (linktype) {

	case DLT_PFLOG:
		swap_pflog_header(hdr, data);
		break;

	case DLT_LINUX_SLL:
		swap_linux_sll_header(hdr, data);
		break;

	case DLT_LINUX_SLL2:
		swap_linux_sll2_header(hdr, data);
		break;

	case DLT_USB_LINUX:
		swap_linux_usb_header(hdr, data, 0);
		break;

	case DLT_USB_LINUX_MMAPPED:
		swap_linux_usb_header(hdr, data, 1);
		break;

	case DLT_NFLOG:
		swap_nflog_header(hdr, data);
		break;
	}
}

void
pcap_post_process(int linktype, int swapped, struct pcap_pkthdr *hdr,
    u_char *data)
{
	if (swapped)
		swap_pseudo_headers(linktype, hdr, data);

	fixup_pcap_pkthdr(linktype, hdr, data);
}

void
fixup_pcap_pkthdr(int linktype, struct pcap_pkthdr *hdr, const u_char *data)
{
	const pcap_usb_header_mmapped *usb_hdr;

	usb_hdr = (const pcap_usb_header_mmapped *) data;
	if (linktype == DLT_USB_LINUX_MMAPPED &&
	    hdr->caplen >= sizeof (pcap_usb_header_mmapped)) {
		/*
		 * In older versions of libpcap, in memory-mapped captures,
		 * the "on-the-bus length" for completion events for
		 * incoming isochronous transfers was miscalculated; it
		 * needed to be calculated based on the* offsets and lengths
		 * in the descriptors, not on the raw URB length, but it
		 * wasn't.
		 *
		 * If this packet contains transferred data (yes, data_flag
		 * is 0 if we *do* have data), and the total on-the-network
		 * length is equal to the value calculated from the raw URB
		 * length, then it might be one of those transfers.
		 *
		 * We only do this if we have the full USB pseudo-header.
		 */
		if (!usb_hdr->data_flag &&
		    hdr->len == sizeof(pcap_usb_header_mmapped) +
		      (usb_hdr->ndesc * sizeof (usb_isodesc)) + usb_hdr->urb_len) {
			/*
			 * It might need fixing; fix it if it's a completion
			 * event for an incoming isochronous transfer.
			 */
			fix_linux_usb_mmapped_length(hdr, data);
		}
	}
}