From cdbc3fa8edc5b42391a5f2bfe1a8f6099929acf7 Mon Sep 17 00:00:00 2001 From: Alan Coopersmith Date: Fri, 6 Jan 2023 12:50:48 -0800 Subject: [PATCH libXpm 5/6] Fix CVE-2022-4883: compression commands depend on $PATH By default, on all platforms except MinGW, libXpm will detect if a filename ends in .Z or .gz, and will when reading such a file fork off an uncompress or gunzip command to read from via a pipe, and when writing such a file will fork off a compress or gzip command to write to via a pipe. In libXpm 3.5.14 or older these are run via execlp(), relying on $PATH to find the commands. If libXpm is called from a program running with raised privileges, such as via setuid, then a malicious user could set $PATH to include programs of their choosing to be run with those privileges. Signed-off-by: Alan Coopersmith --- README.md | 12 ++++++++++++ configure.ac | 14 ++++++++++++++ src/RdFToI.c | 17 ++++++++++++++--- src/WrFFrI.c | 4 ++-- 4 files changed, 42 insertions(+), 5 deletions(-) diff --git a/README.md b/README.md index f3f4c93..0b1c886 100644 --- a/README.md +++ b/README.md @@ -31,3 +31,15 @@ if it can't find the file it was asked to open. It relies on the --enable-open-zfile feature to open the file, and is enabled by default when --enable-open-zfile is enabled, and can be disabled by passing the --disable-stat-zfile flag to the configure script. + +All of these commands will be executed with whatever userid & privileges the +function is called with, relying on the caller to ensure the correct euid, +egid, etc. are set before calling. + +To reduce risk, the paths to these commands are now set at configure time to +the first version found in the PATH used to run configure, and do not depend +on the PATH environment variable set at runtime. + +To specify paths to be used for these commands instead of searching $PATH, pass +the XPM_PATH_COMPRESS, XPM_PATH_UNCOMPRESS, XPM_PATH_GZIP, and XPM_PATH_GUNZIP +variables to the configure command. diff --git a/configure.ac b/configure.ac index 85e2c73..4fc370d 100644 --- a/configure.ac +++ b/configure.ac @@ -49,6 +49,14 @@ if test "x$USE_GETTEXT" = "xyes" ; then fi AM_CONDITIONAL(USE_GETTEXT, test "x$USE_GETTEXT" = "xyes") +dnl Helper macro to find absolute path to program and add a #define for it +AC_DEFUN([XPM_PATH_PROG],[ +AC_PATH_PROG([$1], [$2], []) +AS_IF([test "x$$1" = "x"], + [AC_MSG_ERROR([$2 not found, set $1 or use --disable-stat-zfile])]) +AC_DEFINE_UNQUOTED([$1], ["$$1"], [Path to $2]) +]) dnl End of AC_DEFUN([XPM_PATH_PROG]... + # Optional feature: When a filename ending in .Z or .gz is requested, # open a pipe to a newly forked compress/uncompress/gzip/gunzip command to # handle it. @@ -64,6 +72,12 @@ AC_ARG_ENABLE(open-zfile, AC_MSG_RESULT([$OPEN_ZFILE]) if test x$OPEN_ZFILE = xno ; then AC_DEFINE(NO_ZPIPE, 1, [Define to 1 to disable decompression via pipes]) +else + XPM_PATH_PROG([XPM_PATH_COMPRESS], [compress]) + XPM_PATH_PROG([XPM_PATH_UNCOMPRESS], [uncompress]) + XPM_PATH_PROG([XPM_PATH_GZIP], [gzip]) + XPM_PATH_PROG([XPM_PATH_GUNZIP], [gunzip]) + AC_CHECK_FUNCS([closefrom close_range], [break]) fi # Optional feature: When ___.xpm is requested, also look for ___.xpm.Z & .gz diff --git a/src/RdFToI.c b/src/RdFToI.c index bd09611..a91d337 100644 --- a/src/RdFToI.c +++ b/src/RdFToI.c @@ -43,6 +43,7 @@ #include #include #include +#include #else #ifdef FOR_MSW #include @@ -161,7 +162,17 @@ xpmPipeThrough( goto err; if ( 0 == pid ) { - execlp(cmd, cmd, arg1, (char *)NULL); +#ifdef HAVE_CLOSEFROM + closefrom(3); +#elif defined(HAVE_CLOSE_RANGE) +# ifdef CLOSE_RANGE_UNSHARE +# define close_range_flags CLOSE_RANGE_UNSHARE +# else +# define close_range_flags 0 +#endif + close_range(3, ~0U, close_range_flags); +#endif + execl(cmd, cmd, arg1, (char *)NULL); perror(cmd); goto err; } @@ -235,12 +246,12 @@ OpenReadFile( if ( ext && !strcmp(ext, ".Z") ) { mdata->type = XPMPIPE; - mdata->stream.file = xpmPipeThrough(fd, "uncompress", "-c", "r"); + mdata->stream.file = xpmPipeThrough(fd, XPM_PATH_UNCOMPRESS, "-c", "r"); } else if ( ext && !strcmp(ext, ".gz") ) { mdata->type = XPMPIPE; - mdata->stream.file = xpmPipeThrough(fd, "gunzip", "-qc", "r"); + mdata->stream.file = xpmPipeThrough(fd, XPM_PATH_GUNZIP, "-qc", "r"); } else #endif /* z-files */ diff --git a/src/WrFFrI.c b/src/WrFFrI.c index 328c987..d59098f 100644 --- a/src/WrFFrI.c +++ b/src/WrFFrI.c @@ -342,10 +342,10 @@ OpenWriteFile( #ifndef NO_ZPIPE len = strlen(filename); if (len > 2 && !strcmp(".Z", filename + (len - 2))) { - mdata->stream.file = xpmPipeThrough(fd, "compress", NULL, "w"); + mdata->stream.file = xpmPipeThrough(fd, XPM_PATH_COMPRESS, NULL, "w"); mdata->type = XPMPIPE; } else if (len > 3 && !strcmp(".gz", filename + (len - 3))) { - mdata->stream.file = xpmPipeThrough(fd, "gzip", "-q", "w"); + mdata->stream.file = xpmPipeThrough(fd, XPM_PATH_GZIP, "-q", "w"); mdata->type = XPMPIPE; } else #endif -- 2.39.0