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The previous work for unbounded memory usage and overflows on the buffer
API had several shortcomings:
1. The total size of the buffer was limited by arbitrarily small
precision on the storage type for buffer indexes (typedef'd as
`bufsize_t`). This is not a good design pattern in secure applications,
particualarly since it requires the addition of helper functions to cast
to/from the native `size` types and the custom type for the buffer, and
check for overflows.
2. The library was calling `abort` on overflow and memory allocation
failures. This is not a good practice for production libraries, since it
turns a potential RCE into a trivial, guaranteed DoS to the whole
application that is linked against the library. It defeats the whole
point of performing overflow or allocation checks when the checks will
crash the library and the enclosing program anyway.
3. The default size limits for buffers were essentially unbounded
(capped to the precision of the storage type) and could lead to DoS
attacks by simple memory exhaustion (particularly critical in 32-bit
platforms). This is not a good practice for a library that handles
arbitrary user input.
Hence, this patchset provides slight (but in my opinion critical)
improvements on this area, copying some of the patterns we've used in
the past for high throughput, security sensitive Markdown parsers:
1. The storage type for buffer sizes is now platform native (`ssize_t`).
Ideally, this would be a `size_t`, but several parts of the code expect
buffer indexes to be possibly negative. Either way, switching to a
`size` type is an strict improvement, particularly in 64-bit platforms.
All the helpers that assured that values cannot escape the `size` range
have been removed, since they are superfluous.
2. The overflow checks have been removed. Instead, the maximum size for
a buffer has been set to a safe value for production usage (32mb) that
can be proven not to overflow in practice. Users that need to parse
particularly large Markdown documents can increase this value. A static,
compile-time check has been added to ensure that the maximum buffer size
cannot overflow on any growth operations.
3. The library no longer aborts on buffer overflow. The CMark library
now follows the convention of other Markdown implementations (such as
Hoedown and Sundown) and silently handles buffer overflows and
allocation failures by dropping data from the buffer. The result is
that pathological Markdown documents that try to exploit the library
will instead generate truncated (but valid, and safe) outputs.
All tests after these small refactorings have been verified to pass.
---
NOTE: Regarding 32 bit overflows, generating test cases that crash the
library is trivial (any input document larger than 2gb will crash
CMark), but most Python implementations have issues with large strings
to begin with, so a test case cannot be added to the pathological tests
suite, since it's written in Python.
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- Implement cmark_isalpha.
- Check for ASCII character before implicit cast to char.
- Use internal ctype functions in commonmark.c.
Fixes test failures on Windows and undefined behavior.
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We don't want a blank line before a code block when it's
the first thing in a list item.
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We generally want this option to prohibit any breaking
in things like headers (not just wraps, but softbreaks).
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This is an alternate solution for pull request #132,
which introduced a new warning on the comparison:
latex.c:191:20: warning: comparison of integers of
different signs: 'size_t' (aka 'unsigned long') and 'bufsize_t'
(aka 'int') [-Wsign-compare]
if (realurllen == link_text->as.literal.len &&
~~~~~~~~~~ ^ ~~~~~~~~~~~~~~~~~~~~~~~~~
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inlines: Remove unused variable "link_text"
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Changed type from int to size_t to fix implicit type conversion warning
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I thought I had an outdated version of the binary because it printed 2015 for
the version string.
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in cmark.h and its man page. Closes #124.
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returned by cmark_render_html etc. Closes #124.
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Previously we did this manually, which introduces many
places where errors can creep in.
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This change allows us to pass the new test introduced in
75f231503d2b5854f1ff517402d2751811295bf7.
Previously when a list marker was followed only by spaces,
cmark expected the following content to be indented by
the same number of spaces. But in this case we should
treat the line just like a blank line and set list padding
accordingly.
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- Extend CMARK_OPT_NOBREAKS to all renderers and add `--nobreaks`.
- Do not autowrap, regardless of width parameter, if CMARK_OPT_NOBREAKS
is set.
- Fixed CMARK_OPT_HARDBREAKS for LaTeX and man renderers.
- Ensure that no auto-wrapping occurs if CMARK_OPT_NOBREAKS is enabled,
or if output is CommonMark and CMARK_OPT_HARDBREAKS is enabled.
- Updated man pages.
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Add library option to render softbreaks as spaces
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Set stdin to binary mode on Windows
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Fixes EOLs when reading from stdin.
Fully fixes issue #113.
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Adds an internal field to the parser struct to keep track
of last_buffer_ended_with_cr.
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Reset partially_consumed_tab on every new line
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Now that cmark supports different line endings, files must be openend
in binary mode on Windows.
Fixes issue #113.
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Fixes issue #114.
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Under MSVC, we used to compile in C++ mode to get some C99 features
like mixing declarations and code. With newer MSVC versions, it's
possible to build in plain C mode.
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They're not supported by MSVC.
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Newer MSVC versions support enough of C99 to be able to compile cmark
in plain C mode. Only the "inline" keyword is still unsupported.
We have to use "__inline" instead.
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We need to cast value passed to isspace(3) to unsigned char to explicitly
prevent possibly undefined behavior.
/tmp/pkgsrc-tmp/wip/cmark/work/cmark-0.24.1/src/commonmark.c: In function 'S_render_node':
/tmp/pkgsrc-tmp/wip/cmark/work/cmark-0.24.1/src/commonmark.c:273:9: warning: array subscript has type 'char' [-Wchar-subscripts]
(code_len > 2 && !isspace(code[0]) &&
^
/tmp/pkgsrc-tmp/wip/cmark/work/cmark-0.24.1/src/commonmark.c:274:10: warning: array subscript has type 'char' [-Wchar-subscripts]
!(isspace(code[code_len - 1]) && isspace(code[code_len - 2]))) &&
^
/tmp/pkgsrc-tmp/wip/cmark/work/cmark-0.24.1/src/commonmark.c:274:10: warning: array subscript has type 'char' [-Wchar-subscripts]
CTYPE(3) Library Functions Manual CTYPE(3)
NAME
isalpha, isupper, islower, isdigit, isxdigit, isalnum, isspace, ispunct,
isprint, isgraph, iscntrl, isblank, toupper, tolower, - character
classification and mapping functions
LIBRARY
Standard C Library (libc, -lc)
CAVEATS
The first argument of these functions is of type int, but only a very
restricted subset of values are actually valid. The argument must either
be the value of the macro EOF (which has a negative value), or must be a
non-negative value within the range representable as unsigned char.
Passing invalid values leads to undefined behavior.
NetBSD 7.99 February 25, 2015 NetBSD 7.99
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This reverts commit 4d2d486333c358eb3adf3d0649163e319a3b8b69.
This commit caused a valgrind invalid read.
==29731== Invalid read of size 4
==29731== at 0x40500E: S_process_line (blocks.c:1050)
==29731== by 0x403CF7: S_parser_feed (blocks.c:526)
==29731== by 0x403BC9: cmark_parser_feed (blocks.c:494)
==29731== by 0x433A95: main (main.c:168)
==29731== Address 0x51d5b60 is 64 bytes inside a block of size 128 free'd
==29731== at 0x4C27D4E: free (vg_replace_malloc.c:427)
==29731== by 0x4015F0: S_free_nodes (node.c:134)
==29731== by 0x401634: cmark_node_free (node.c:142)
==29731== by 0x4033B1: finalize (blocks.c:259)
==29731== by 0x40365E: add_child (blocks.c:337)
==29731== by 0x4046D8: try_new_container_starts (blocks.c:836)
==29731== by 0x404F12: S_process_line (blocks.c:1015)
==29731== by 0x403CF7: S_parser_feed (blocks.c:526)
==29731== by 0x403BC9: cmark_parser_feed (blocks.c:494)
==29731== by 0x433A95: main (main.c:168)
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It's a programming error if the type is out of range.
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https://github.com/MathieuDuponchelle/cmark into MathieuDuponchelle-refactor-S_processLine
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It's the core of the program and I had too much trouble making
sense of it, two loops with many cases and other code
interspersed hurt my head.
All the tests still passed before rebasing, now I've got the
exact same set of issues as master.
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