OpenSystemsDevelopment / qpdf

Commit 7b9f23a99a1ea3e97eaecf80ef29e2805e351b8f

Authored by Jay Berkenbilt
1 parent fa76d817

Ignore zlib data check errors (fixes #191)

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Showing 3 changed files with 17 additions and 3 deletions
ChangeLog
  View file @7b9f23a
  1 +2018-03-03 Jay Berkenbilt <ejb@ql.org>
  2 +
  3 + * Ignore zlib data check errors while uncompressing streams. This
  4 + is consistent with behaviors of other readers and enables handling
  5 + of some incorrectly written zlib strems. Fixes #191.
  6 +
1 7 2018-02-25 Jay Berkenbilt <ejb@ql.org>
2 8  
3 9 * 8.0.0: release
... ...
libqpdf/Pl_Flate.cc
  View file @7b9f23a
1 1 #include <qpdf/Pl_Flate.hh>
2 2 #include <zlib.h>
  3 +#include <string.h>
3 4  
4 5 #include <qpdf/QUtil.hh>
5 6  
... ... @@ -71,7 +72,8 @@ Pl_Flate::write(unsigned char* data, size_t len)
71 72 while (bytes_left > 0)
72 73 {
73 74 size_t bytes = (bytes_left >= max_bytes ? max_bytes : bytes_left);
74   - handleData(buf, bytes, Z_NO_FLUSH);
  75 + handleData(buf, bytes,
  76 + (action == a_inflate ? Z_SYNC_FLUSH : Z_NO_FLUSH));
75 77 bytes_left -= bytes;
76 78 buf += bytes;
77 79 }
... ... @@ -125,6 +127,14 @@ Pl_Flate::handleData(unsigned char* data, int len, int flush)
125 127 {
126 128 err = inflate(&zstream, flush);
127 129 }
  130 + if ((action == a_inflate) && (err != Z_OK) && zstream.msg &&
  131 + (strcmp(zstream.msg, "incorrect data check") == 0))
  132 + {
  133 + // Other PDF readers ignore this specific error. Combining
  134 + // this with Z_SYNC_FLUSH enables qpdf to handle some
  135 + // broken zlib streams without losing data.
  136 + err = Z_STREAM_END;
  137 + }
128 138 switch (err)
129 139 {
130 140 case Z_BUF_ERROR:
... ...
qpdf/qtest/qpdf/issue-106.out
  View file @7b9f23a
1 1 WARNING: issue-106.pdf: file is damaged
2 2 WARNING: issue-106.pdf (offset 809): xref not found
3 3 WARNING: issue-106.pdf: Attempting to reconstruct cross-reference table
4   -WARNING: issue-106.pdf (offset 965): error decoding stream data for object 8 0: stream inflate: inflate: data: incorrect data check
5   -WARNING: issue-106.pdf (offset 965): stream will be re-processed without filtering to avoid data loss
6 4 qpdf: operation succeeded with warnings; resulting file may have some problems
... ...