forked from osmocom/wireshark
jpeg: refactor the parsing of Exif data
After the recent updates, the `process_app1_segment` function has grown very large. Split it into three functions and make some extra improvements: * Indent continuation lines consistently. * Give variables more descriptive names (e.g. no more `val_16`, `val_32`). * Remove the need to do arithmetic with the `tiff_start` (and the variable itself) by using a subset TVB for the TIFF data. * Remove unnecessary return values. * Make miscellaneous style improvements. There should be no difference in behavior, except that the error message associated with `ei_next_ifd_offset` now shows the correct number (previously the number was `offset + tiff_start`, when it should have been `offset - tiff_start`; with the removal of `tiff_start` this bug got fixed by itself).
This commit is contained in:
Роман Донченко
Wireshark GitLab Utility
parent
aac98e48d8
commit
be38ad12ab
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@ -602,11 +602,193 @@ process_app0_segment(proto_tree *tree, tvbuff_t *tvb, packet_info *pinfo, guint3
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return offset;
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}
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static void
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process_tiff_ifd_chain(proto_tree *tree, tvbuff_t *tvb, packet_info *pinfo,
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guint encoding, guint32 start_ifd_offset)
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{
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guint32 next_ifd_offset = start_ifd_offset;
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for (unsigned ifd_index = 0;; ++ifd_index) {
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int offset = next_ifd_offset;
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/*
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* Process the IFD
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*/
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guint32 num_fields = tvb_get_guint16(tvb, offset, encoding);
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proto_tree *subtree_ifd = proto_tree_add_subtree_format(tree, tvb, offset, num_fields * 12 + 6,
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ett_ifd, NULL, "Image File Directory #%u", ifd_index);
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proto_tree_add_item(subtree_ifd, hf_ifd_num_fields, tvb, offset, 2, encoding);
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offset += 2;
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while (num_fields-- > 0) {
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guint32 field_type, value_count, value_size;
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gint value_hf;
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proto_tree_add_item(subtree_ifd, hf_ifd_tag, tvb, offset, 2, encoding);
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offset += 2;
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proto_tree_add_item_ret_uint(subtree_ifd, hf_ifd_type, tvb, offset, 2, encoding, &field_type);
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offset += 2;
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proto_tree_add_item_ret_uint(subtree_ifd, hf_ifd_count, tvb, offset, 4, encoding, &value_count);
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offset += 4;
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switch (field_type) {
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case EXIF_TYPE_BYTE:
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value_size = 1; value_hf = hf_ifd_value_byte; break;
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case EXIF_TYPE_ASCII:
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value_size = 1; value_hf = hf_ifd_value_ascii; break;
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case EXIF_TYPE_SHORT:
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value_size = 2; value_hf = hf_ifd_value_short; break;
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case EXIF_TYPE_LONG:
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value_size = 4; value_hf = hf_ifd_value_long; break;
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case EXIF_TYPE_RATIONAL:
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value_size = 8; value_hf = hf_ifd_value_rational; break;
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case EXIF_TYPE_UNDEFINED:
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value_size = 1; value_hf = hf_ifd_value_undefined; break;
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case EXIF_TYPE_SLONG:
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value_size = 4; value_hf = hf_ifd_value_slong; break;
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case EXIF_TYPE_SRATIONAL:
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value_size = 8; value_hf = hf_ifd_value_srational; break;
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default:
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value_size = 0; value_hf = -1; break;
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}
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int value_offset = -1;
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proto_tree *value_parent = NULL;
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if (value_size == 0 || 4 / value_size < value_count) {
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/* The value(s) are located outside the IFD, and the offset field points to them. */
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guint32 value_offset_uint;
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proto_item *offset_item = proto_tree_add_item_ret_uint(
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subtree_ifd, hf_ifd_offset, tvb, offset, 4, encoding, &value_offset_uint);
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if (value_offset_uint < tvb_reported_length(tvb)) {
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value_offset = (int)value_offset_uint;
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} else {
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expert_add_info_format(pinfo, offset_item, &ei_ifd_value_offset,
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"bogus, should be < %u", tvb_reported_length(tvb));
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}
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value_parent = tree;
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} else {
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/* The value(s) are small enough to fit directly in the offset field. */
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value_offset = offset;
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value_parent = subtree_ifd;
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}
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if (value_offset >= 0) {
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if (value_hf == hf_ifd_value_ascii || value_hf == hf_ifd_value_undefined)
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proto_tree_add_item(value_parent, value_hf, tvb, value_offset, value_count, ENC_NA);
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else if (value_size != 0)
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for (guint32 i = 0; i < value_count; ++i) {
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proto_item *value_item = proto_tree_add_item(value_parent, value_hf, tvb,
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value_offset, value_size, encoding);
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if (value_hf == hf_ifd_value_rational) {
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proto_tree *subtree_value = proto_item_add_subtree(value_item, ett_rational);
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guint32 num, denom;
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proto_tree_add_item_ret_uint(
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subtree_value, hf_ifd_value_rational_numerator, tvb,
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value_offset, 4, encoding, &num);
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proto_tree_add_item_ret_uint(
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subtree_value, hf_ifd_value_rational_denominator, tvb,
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value_offset + 4, 4, encoding, &denom);
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proto_item_set_text(value_item, "Value: %"PRIu32"/%"PRIu32, num, denom);
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}
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else if (value_hf == hf_ifd_value_srational) {
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proto_tree *subtree_value = proto_item_add_subtree(value_item, ett_srational);
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gint32 num, denom;
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proto_tree_add_item_ret_int(
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subtree_value, hf_ifd_value_srational_numerator, tvb,
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value_offset, 4, encoding, &num);
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proto_tree_add_item_ret_int(
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subtree_value, hf_ifd_value_srational_denominator, tvb,
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value_offset + 4, 4, encoding, &denom);
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proto_item_set_text(value_item, "Value: %"PRIi32"/%"PRIi32, num, denom);
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}
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value_offset += value_size;
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}
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}
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offset += 4;
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}
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/*
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* Offset to the next IFD
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*/
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proto_item *next_ifd_offset_item = proto_tree_add_item_ret_uint(
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subtree_ifd, hf_next_ifd_offset, tvb, offset, 4, encoding, &next_ifd_offset);
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offset += 4;
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if (next_ifd_offset == 0)
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break;
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if (next_ifd_offset < (guint32)offset) {
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expert_add_info_format(pinfo, next_ifd_offset_item, &ei_next_ifd_offset,
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" (bogus, should be >= %u)", offset);
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return;
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}
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}
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}
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static void
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process_tiff(proto_tree *tree, tvbuff_t *tvb, packet_info *pinfo)
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{
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/*
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* Endianness
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*/
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guint encoding;
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int offset = 0;
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guint16 byte_order = tvb_get_ntohs(tvb, offset);
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if (byte_order == 0x4949) {
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encoding = ENC_LITTLE_ENDIAN;
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proto_tree_add_uint_format_value(tree, hf_endianness, tvb, offset, 2, byte_order, "little endian");
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} else if (byte_order == 0x4D4D) {
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encoding = ENC_BIG_ENDIAN;
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proto_tree_add_uint_format_value(tree, hf_endianness, tvb, offset, 2, byte_order, "big endian");
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} else {
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/* Error: invalid endianness encoding */
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proto_tree_add_uint_format_value(tree, hf_endianness, tvb, offset, 2, byte_order,
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"Incorrect encoding 0x%04x- skipping the remainder of this application marker", byte_order);
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return;
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}
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offset += 2;
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/*
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* Fixed value 42 = 0x002a
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*/
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offset += 2;
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/*
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* Offset to IFD
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*/
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guint32 start_ifd_offset;
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proto_item* start_ifd_offset_item = proto_tree_add_item_ret_uint(
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tree, hf_start_ifd_offset, tvb, offset, 4, encoding, &start_ifd_offset);
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offset += 4;
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/*
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* Check for a bogus offset value.
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* XXX - bogus value message should also deal with a
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* value that's too large and causes an overflow.
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* Or should it just check against the segment length,
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* which is 16 bits?
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*/
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if (start_ifd_offset < (guint32)offset) {
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expert_add_info_format(pinfo, start_ifd_offset_item, &ei_start_ifd_offset,
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" (bogus, should be >= %u)", offset);
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return;
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}
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/*
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* Skip the following portion
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*/
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if (start_ifd_offset > (guint32)offset) {
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proto_tree_add_bytes_format_value(tree, hf_skipped_tiff_data, tvb, offset, start_ifd_offset - offset, NULL,
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"%u bytes", start_ifd_offset - offset);
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}
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process_tiff_ifd_chain(tree, tvb, pinfo, encoding, start_ifd_offset);
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}
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/* Process an APP1 block.
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*
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* XXX - This code only works on US-ASCII systems!!!
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*/
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static int
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static void
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process_app1_segment(proto_tree *tree, tvbuff_t *tvb, packet_info *pinfo, guint32 len,
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guint16 marker, const char *marker_name, gboolean show_first_identifier_not_jfif)
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{
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@ -615,7 +797,6 @@ process_app1_segment(proto_tree *tree, tvbuff_t *tvb, packet_info *pinfo, guint3
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char *str;
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gint str_size;
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int offset = 0;
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int tiff_start;
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ti = proto_tree_add_item(tree, hf_marker_segment,
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tvb, 0, -1, ENC_NA);
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@ -637,182 +818,14 @@ process_app1_segment(proto_tree *tree, tvbuff_t *tvb, packet_info *pinfo, guint3
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}
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if (strcmp(str, "Exif") == 0) {
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/*
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* Endianness
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*/
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int encoding;
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guint16 val_16;
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guint32 val_32;
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proto_item* tiff_item;
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offset++; /* Skip a byte supposed to be 0x00 */
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tiff_start = offset;
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val_16 = tvb_get_ntohs(tvb, offset);
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if (val_16 == 0x4949) {
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encoding = ENC_LITTLE_ENDIAN;
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proto_tree_add_uint_format_value(subtree, hf_endianness, tvb, offset, 2, val_16, "little endian");
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} else if (val_16 == 0x4D4D) {
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encoding = ENC_BIG_ENDIAN;
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proto_tree_add_uint_format_value(subtree, hf_endianness, tvb, offset, 2, val_16, "big endian");
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} else {
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/* Error: invalid endianness encoding */
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proto_tree_add_uint_format_value(subtree, hf_endianness, tvb, offset, 2, val_16,
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"Incorrect encoding 0x%04x- skipping the remainder of this application marker", val_16);
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return offset;
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}
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offset += 2;
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/*
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* Fixed value 42 = 0x002a
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*/
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offset += 2;
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/*
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* Offset to IFD
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*/
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tiff_item = proto_tree_add_item_ret_uint(subtree, hf_start_ifd_offset, tvb, offset, 4, encoding, &val_32);
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offset += 4;
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/*
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* Check for a bogus val_32 value.
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* XXX - bogus value message should also deal with a
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* value that's too large and causes an overflow.
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* Or should it just check against the segment length,
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* which is 16 bits?
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*/
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if (val_32 + tiff_start < (guint32)offset) {
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expert_add_info_format(pinfo, tiff_item, &ei_start_ifd_offset, " (bogus, should be >= %u)",
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offset- tiff_start);
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return offset;
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}
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/*
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* Skip the following portion
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*/
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if (val_32 + tiff_start > (guint32)offset) {
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proto_tree_add_bytes_format_value(subtree, hf_skipped_tiff_data, tvb, offset, val_32 + tiff_start - offset, NULL, "%u bytes",
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val_32 + tiff_start - offset);
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}
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for (unsigned ifd_index = 0;; ++ifd_index) {
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guint32 num_fields;
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proto_tree *subtree_ifd;
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offset = val_32 + tiff_start;
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/*
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* Process the IFD
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*/
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num_fields = tvb_get_guint16(tvb, offset, encoding);
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subtree_ifd = proto_tree_add_subtree_format(subtree, tvb, offset, num_fields * 12 + 6,
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ett_ifd, NULL, "Image File Directory #%u", ifd_index);
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proto_tree_add_item(subtree_ifd, hf_ifd_num_fields, tvb, offset, 2, encoding);
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offset += 2;
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while (num_fields-- > 0) {
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guint32 field_type, value_count, value_size;
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gint value_hf;
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proto_tree_add_item(subtree_ifd, hf_ifd_tag, tvb, offset, 2, encoding);
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offset += 2;
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proto_tree_add_item_ret_uint(subtree_ifd, hf_ifd_type, tvb, offset, 2, encoding, &field_type);
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offset += 2;
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proto_tree_add_item_ret_uint(subtree_ifd, hf_ifd_count, tvb, offset, 4, encoding, &value_count);
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offset += 4;
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switch (field_type) {
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case EXIF_TYPE_BYTE:
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value_size = 1; value_hf = hf_ifd_value_byte; break;
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case EXIF_TYPE_ASCII:
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value_size = 1; value_hf = hf_ifd_value_ascii; break;
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case EXIF_TYPE_SHORT:
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value_size = 2; value_hf = hf_ifd_value_short; break;
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case EXIF_TYPE_LONG:
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value_size = 4; value_hf = hf_ifd_value_long; break;
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case EXIF_TYPE_RATIONAL:
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value_size = 8; value_hf = hf_ifd_value_rational; break;
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case EXIF_TYPE_UNDEFINED:
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value_size = 1; value_hf = hf_ifd_value_undefined; break;
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case EXIF_TYPE_SLONG:
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value_size = 4; value_hf = hf_ifd_value_slong; break;
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case EXIF_TYPE_SRATIONAL:
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value_size = 8; value_hf = hf_ifd_value_srational; break;
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default:
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value_size = 0; value_hf = -1; break;
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}
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int value_offset = -1;
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proto_tree *value_parent = NULL;
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if (value_size == 0 || 4 / value_size < value_count) {
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/* The value(s) are located outside the IFD, and the offset field points to them. */
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guint32 value_offset_rel_limit = len + 2 - (guint32)tiff_start;
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guint32 value_offset_rel;
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proto_item *offset_item = proto_tree_add_item_ret_uint(
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subtree_ifd, hf_ifd_offset, tvb, offset, 4, encoding, &value_offset_rel);
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if (value_offset_rel < value_offset_rel_limit) {
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value_offset = tiff_start + (int)value_offset_rel;
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} else {
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expert_add_info_format(pinfo, offset_item, &ei_ifd_value_offset,
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"bogus, should be < %"PRIu32, value_offset_rel_limit);
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}
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value_parent = subtree;
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} else {
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/* The value(s) are small enough to fit directly in the offset field. */
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value_offset = offset;
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value_parent = subtree_ifd;
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}
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if (value_offset >= 0) {
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if (value_hf == hf_ifd_value_ascii || value_hf == hf_ifd_value_undefined)
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proto_tree_add_item(value_parent, value_hf, tvb, value_offset, value_count, ENC_NA);
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else if (value_size != 0)
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for (guint32 i = 0; i < value_count; ++i) {
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proto_item *value_item = proto_tree_add_item(value_parent, value_hf, tvb,
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value_offset, value_size, encoding);
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if (value_hf == hf_ifd_value_rational) {
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proto_tree *subtree_value = proto_item_add_subtree(value_item, ett_rational);
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guint32 num, denom;
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proto_tree_add_item_ret_uint(
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subtree_value, hf_ifd_value_rational_numerator, tvb,
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value_offset, 4, encoding, &num);
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proto_tree_add_item_ret_uint(
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subtree_value, hf_ifd_value_rational_denominator, tvb,
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value_offset + 4, 4, encoding, &denom);
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proto_item_set_text(value_item, "Value: %"PRIu32"/%"PRIu32, num, denom);
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}
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else if (value_hf == hf_ifd_value_srational) {
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proto_tree *subtree_value = proto_item_add_subtree(value_item, ett_srational);
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gint32 num, denom;
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proto_tree_add_item_ret_int(
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subtree_value, hf_ifd_value_srational_numerator, tvb,
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value_offset, 4, encoding, &num);
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proto_tree_add_item_ret_int(
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subtree_value, hf_ifd_value_srational_denominator, tvb,
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value_offset + 4, 4, encoding, &denom);
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proto_item_set_text(value_item, "Value: %"PRIi32"/%"PRIi32, num, denom);
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}
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value_offset += value_size;
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}
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}
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offset += 4;
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}
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/*
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* Offset to the next IFD
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*/
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tiff_item = proto_tree_add_item_ret_uint(subtree_ifd, hf_next_ifd_offset, tvb, offset, 4, encoding, &val_32);
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offset += 4;
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if (val_32 != 0 &&
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val_32 + tiff_start < (guint32)offset) {
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expert_add_info_format(pinfo, tiff_item, &ei_next_ifd_offset, " (bogus, should be >= %u)", offset + tiff_start);
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return offset;
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}
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if (val_32 == 0)
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break;
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}
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tvbuff_t *tvb_tiff = tvb_new_subset_remaining(tvb, offset);
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process_tiff(subtree, tvb_tiff, pinfo);
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} else {
|
||||
proto_tree_add_bytes_format_value(subtree, hf_remain_seg_data, tvb, offset, -1, NULL, "%u bytes", len - 2 - str_size);
|
||||
proto_item_append_text(ti, " (Unknown identifier)");
|
||||
}
|
||||
return offset;
|
||||
}
|
||||
|
||||
/* Process an APP2 block.
|
||||
|
|
|
|||
Loading…
Reference in New Issue