From 3d570b5a39f868209e4b38c43b0ba6bfefe8a9bf Mon Sep 17 00:00:00 2001 From: Guy Harris Date: Fri, 22 Jan 2016 16:40:44 -0800 Subject: Fix handling of the magic number. Just treat it as an array of bytes. When checking for whether it's a pcap file, also determine whether it's big-endian or little-endian. Note that reading it in *host* byte order will tell you whether it's in your byte order or byte-swapped; you have to know your byte order to know whether that means little-endian or big-endian. Have a #define for the magic number size, as all magic number values must be that size, and use that as the size of the magic-number arrays. Handle nanosecond timestamp resolution while we're at it. Change-Id: I4d83579d919ae9f15888afca14317631d413ca51 Reviewed-on: https://code.wireshark.org/review/13490 Reviewed-by: Guy Harris --- epan/dissectors/file-pcap.c | 67 +++++++++++++++++++++++++++++---------------- 1 file changed, 44 insertions(+), 23 deletions(-) (limited to 'epan/dissectors/file-pcap.c') diff --git a/epan/dissectors/file-pcap.c b/epan/dissectors/file-pcap.c index 3b0894b9e7..91dd9ae7af 100644 --- a/epan/dissectors/file-pcap.c +++ b/epan/dissectors/file-pcap.c @@ -64,25 +64,32 @@ static gint ett_pcap_timestamp = -1; static gboolean pref_dissect_next_layer = FALSE; -static const value_string magic_number_vals[] = { - { 0xA1B2C3D4, "Little-endian" }, - { 0xD4C3B2A1, "Big-endian" }, - { 0, NULL } -}; - void proto_register_file_pcap(void); void proto_reg_handoff_file_pcap(void); +#define MAGIC_NUMBER_SIZE 4 + static int dissect_pcap(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void *data _U_) { - static const guint8 pcap_magic[] = { 0xA1, 0xB2, 0xC3, 0xD4 }; - static const guint8 pcap_swapped_magic[] = { 0xD4, 0xC3, 0xB2, 0xA1 }; + static const guint8 pcap_big_endian_magic[MAGIC_NUMBER_SIZE] = { + 0xa1, 0xb2, 0xc3, 0xd4 + }; + static const guint8 pcap_little_endian_magic[MAGIC_NUMBER_SIZE] = { + 0xd4, 0xc3, 0xb2, 0xa1 + }; + static const guint8 pcap_nsec_big_endian_magic[MAGIC_NUMBER_SIZE] = { + 0xa1, 0xb2, 0x3c, 0xd4 + }; + static const guint8 pcap_nsec_little_endian_magic[MAGIC_NUMBER_SIZE] = { + 0xd4, 0x3c, 0xb2, 0xa1 + }; volatile gint offset = 0; proto_tree *main_tree; proto_item *main_item; proto_tree *header_tree; proto_item *header_item; + proto_item *magic_number_item; proto_tree *packet_tree; proto_item *packet_item; proto_tree *timestamp_tree; @@ -90,15 +97,37 @@ dissect_pcap(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void *data _U_ proto_tree *packet_data_tree; proto_item *packet_data_item; volatile guint32 encoding; + guint timestamp_scale_factor; + const char *magic; guint32 origin_length; guint32 length; guint32 link_type; volatile guint32 frame_number = 1; nstime_t timestamp; - if (tvb_memeql(tvb, 0, pcap_magic, sizeof(pcap_magic)) && - tvb_memeql(tvb, 0, pcap_swapped_magic, sizeof(pcap_swapped_magic))) + if (tvb_memeql(tvb, 0, pcap_big_endian_magic, MAGIC_NUMBER_SIZE) == 0) { + encoding = ENC_BIG_ENDIAN; + timestamp_scale_factor = 1000; + magic = "Big-endian"; + } else if (tvb_memeql(tvb, 0, pcap_little_endian_magic, MAGIC_NUMBER_SIZE) == 0) { + encoding = ENC_LITTLE_ENDIAN; + timestamp_scale_factor = 1000; + magic = "Little-endian"; + } else if (tvb_memeql(tvb, 0, pcap_nsec_big_endian_magic, MAGIC_NUMBER_SIZE) == 0) { + encoding = ENC_BIG_ENDIAN; + timestamp_scale_factor = 1; + magic = "Big-endian, nanosecond resolution"; + } else if (tvb_memeql(tvb, 0, pcap_nsec_little_endian_magic, MAGIC_NUMBER_SIZE) == 0) { + encoding = ENC_LITTLE_ENDIAN; + timestamp_scale_factor = 1; + magic = "Little-endian, nanosecond resolution"; + } else { + /* + * Not one of the magic numbers we recognize. + * XXX - add them? + */ return 0; + } main_item = proto_tree_add_item(tree, proto_pcap, tvb, offset, -1, ENC_NA); main_tree = proto_item_add_subtree(main_item, ett_pcap); @@ -106,16 +135,8 @@ dissect_pcap(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void *data _U_ header_item = proto_tree_add_item(main_tree, hf_pcap_header , tvb, offset, 24, ENC_NA); header_tree = proto_item_add_subtree(header_item, ett_pcap_header); - proto_tree_add_item(header_tree, hf_pcap_header_magic_number, tvb, offset, 4, ENC_HOST_ENDIAN); - encoding = tvb_get_guint32(tvb, offset, ENC_HOST_ENDIAN); - if (encoding == 0xA1B2C3D4) { - encoding = ENC_LITTLE_ENDIAN; - } else if (encoding == 0xD4C3B2A1) { - encoding = ENC_BIG_ENDIAN; - } else { - expert_add_info(pinfo, main_item, &ei_unknown_encoding); - return offset; - } + magic_number_item = proto_tree_add_item(header_tree, hf_pcap_header_magic_number, tvb, offset, 4, ENC_NA); + proto_item_append_text(magic_number_item, " (%s)", magic); offset += 4; proto_tree_add_item(header_tree, hf_pcap_header_version_major, tvb, offset, 2, encoding); @@ -143,7 +164,7 @@ dissect_pcap(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void *data _U_ proto_item_append_text(packet_item, " %u", frame_number); timestamp.secs = tvb_get_guint32(tvb, offset, encoding); - timestamp.nsecs = tvb_get_guint32(tvb, offset + 4, encoding) * 1000; + timestamp.nsecs = tvb_get_guint32(tvb, offset + 4, encoding) * timestamp_scale_factor; timestamp_item = proto_tree_add_time(packet_tree, hf_pcap_packet_timestamp, tvb, offset, 8, ×tamp); timestamp_tree = proto_item_add_subtree(timestamp_item, ett_pcap_timestamp); @@ -203,8 +224,8 @@ proto_register_file_pcap(void) NULL, HFILL } }, { &hf_pcap_header_magic_number, - { "Magic Bytes", "pcap.header.magic_bytes", - FT_UINT32, BASE_HEX, VALS(magic_number_vals), 0x00, + { "Magic Number", "pcap.header.magic_number", + FT_BYTES, BASE_NONE, NULL, 0x00, NULL, HFILL } }, { &hf_pcap_header_version_major, -- cgit v1.2.1