fragment_quote adds quotation to fragments if needed. It allocates a
buffer and grows it as needed.
Unfortunately the dst pointer is not updated after a realloc, which
means that dst still points into the old memory area. Further writing
characters into that area leads to out of boundy writes.
Proof of concept:
$ cat > poc.pc << EOF
Name: poc
Description: poc
Version: 1
CFlags: -Ia
CFlags: -I%%%%%%%%%%%%%%%%%%%%b
CFlags: -I%%%%%%%%%%%%%%%%%%%%c
CFlags: -Id
EOF
$ pkgconf --cflags poc.pc
Most reliable attempt is to compile pkgconf with address sanitizer,
but this file should lead to an abort on a glibc system due to modified
chunk pointers (tested with Linux on amd64).
But since this is undefined behaviour, it depends on system details.
Parsing a fragment which consists only of a single dash leads to
an out of boundary read. It duplicates the following entry which
is not expected behaviour if another fragment follows.
Proof of concept:
$ cat > poc.pc << "EOF"
Name: poc
Description: poc
Version: 1
Cflags: - -I/somewhere
EOF
$ PKG_CONFIG_PATH=. pkgconf --cflags poc
-I/somewhere -I/somewhere
If - is the last entry, it leads to an out of boundary read, which is
easy to see if pkgconf is compiled with address sanitizer.
According to
https://docs.microsoft.com/fr-fr/windows/win32/fileio/naming-a-file
backslashes (with slashes) are a path separator, hence must no be
considered as an escape code.
The first fix, in argvsplit.c, disables this. But because of fragment_quote(),
the backslashes are doubled. Hence the second fix in fragment.c
With this pc file :
prefix=C:/Documents/msys2/opt/efl_64
libdir=${prefix}/lib
includedir=${prefix}/include
Name: eina
Description: efl: eina
Version: 1.24.99
Requires.private: iconv
Libs: -L${libdir} -leina -pthread -levil
Libs.private: -lpsapi -lole32 -lws2_32 -lsecur32 -luuid -lregex -lm
Cflags:-I${includedir}/eina-1 -I${includedir}/efl-1
-I${includedir}/eina-1/eina -pthread
pkgconf.exe --cflags eina
returns :
-IC:\Documents\msys2\opt\efl_64/include/eina-1
-IC:\Documents\msys2\opt\efl_64/include/efl-1
-IC:\Documents\msys2\opt\efl_64/include/eina-1/eina -pthread
-DWINICONV_CONST= -IC:\Documents\msys2\opt\ewpi_64/include
we now use POSIX-style quoting for all fragments. it is our belief that this is the
most optimal behaviour for portability, because all POSIX-compliant tools require
single-quotes to be considered as literal (closes#153).
because of this, we are able to remove some hacks on the lexer side which were there
to simulate pkg-config quoting, but were basically utterly wrong (closes#139).
Due to the way that tokens are merged together for arguments which require explicit whitespace, an
empty token could result in a fragment like:
{.type = 'I', .data = '/usr/include '}
Such a fragment would be treated differently than:
{.type = 'I', .data = '/usr/include'}
This difference causes the compiler to include a system include path as part of the additional includes, thus
breaking things like include path shadowing, resulting in random build failures. As such, we skip empty tokens
from the tokenizer as they do not have any relevance anyway.
Tobias Stoeckmann
Ariadne Conill