Reviewed-by: Michael Tremer michael.tremer@ipfire.org
On 11 Apr 2022, at 14:40, Adolf Belka adolf.belka@ipfire.org wrote:
- Malicious filenames can make xzgrep to write to arbitrary files or (with a GNU sed extension) lead to arbitrary code execution.
- xzgrep from XZ Utils versions up to and including 5.2.5 are affected. 5.3.1alpha and 5.3.2alpha are affected as well.
- This bug was inherited from gzip's zgrep. gzip 1.12 includes a fix for zgrep.
- CU167 has gzip-1.12 with the fix already merged.
Signed-off-by: Adolf Belka adolf.belka@ipfire.org
lfs/xz | 1 + src/patches/xzgrep-ZDI-CAN-16587.patch | 94 ++++++++++++++++++++++++++ 2 files changed, 95 insertions(+) create mode 100644 src/patches/xzgrep-ZDI-CAN-16587.patch
diff --git a/lfs/xz b/lfs/xz index 586fbc90f..9345df954 100644 --- a/lfs/xz +++ b/lfs/xz @@ -75,6 +75,7 @@ $(subst %,%_BLAKE2,$(objects)) : $(TARGET) : $(patsubst %,$(DIR_DL)/%,$(objects)) @$(PREBUILD) @rm -rf $(DIR_APP) && cd $(DIR_SRC) && tar axf $(DIR_DL)/$(DL_FILE)
- cd $(DIR_APP) && patch -p1 -i $(DIR_SRC)/src/patches/xzgrep-ZDI-CAN-16587.patch cd $(DIR_APP) && ./configure --prefix=$(PREFIX) cd $(DIR_APP) && make $(MAKETUNING) cd $(DIR_APP) && make install
diff --git a/src/patches/xzgrep-ZDI-CAN-16587.patch b/src/patches/xzgrep-ZDI-CAN-16587.patch new file mode 100644 index 000000000..406ded590 --- /dev/null +++ b/src/patches/xzgrep-ZDI-CAN-16587.patch @@ -0,0 +1,94 @@ +From 69d1b3fc29677af8ade8dc15dba83f0589cb63d6 Mon Sep 17 00:00:00 2001 +From: Lasse Collin lasse.collin@tukaani.org +Date: Tue, 29 Mar 2022 19:19:12 +0300 +Subject: [PATCH] xzgrep: Fix escaping of malicious filenames (ZDI-CAN-16587).
+Malicious filenames can make xzgrep to write to arbitrary files +or (with a GNU sed extension) lead to arbitrary code execution.
+xzgrep from XZ Utils versions up to and including 5.2.5 are +affected. 5.3.1alpha and 5.3.2alpha are affected as well. +This patch works for all of them.
+This bug was inherited from gzip's zgrep. gzip 1.12 includes +a fix for zgrep.
+The issue with the old sed script is that with multiple newlines, +the N-command will read the second line of input, then the +s-commands will be skipped because it's not the end of the +file yet, then a new sed cycle starts and the pattern space +is printed and emptied. So only the last line or two get escaped.
+One way to fix this would be to read all lines into the pattern +space first. However, the included fix is even simpler: All lines +except the last line get a backslash appended at the end. To ensure +that shell command substitution doesn't eat a possible trailing +newline, a colon is appended to the filename before escaping. +The colon is later used to separate the filename from the grep +output so it is fine to add it here instead of a few lines later.
+The old code also wasn't POSIX compliant as it used \n in the +replacement section of the s-command. Using <newline> is the +POSIX compatible method.
+LC_ALL=C was added to the two critical sed commands. POSIX sed +manual recommends it when using sed to manipulate pathnames +because in other locales invalid multibyte sequences might +cause issues with some sed implementations. In case of GNU sed, +these particular sed scripts wouldn't have such problems but some +other scripts could have, see:
- info '(sed)Locale Considerations'
+This vulnerability was discovered by: +cleemy desu wayo working with Trend Micro Zero Day Initiative
+Thanks to Jim Meyering and Paul Eggert discussing the different +ways to fix this and for coordinating the patch release schedule +with gzip. +---
- src/scripts/xzgrep.in | 20 ++++++++++++--------
- 1 file changed, 12 insertions(+), 8 deletions(-)
+diff --git a/src/scripts/xzgrep.in b/src/scripts/xzgrep.in +index b180936..e5186ba 100644 +--- a/src/scripts/xzgrep.in ++++ b/src/scripts/xzgrep.in +@@ -180,22 +180,26 @@ for i; do
{ test $# -eq 1 || test $no_filename -eq 1; }; theneval "$grep"else++ # Append a colon so that the last character will never be a newline ++ # which would otherwise get lost in shell command substitution. ++ i="$i:" ++ ++ # Escape & \ | and newlines only if such characters are present ++ # (speed optimization).
case $i in(*'- '* | *'&'* | *''* | *'|'*)
+- i=$(printf '%s\n' "$i" | +- sed ' +- $!N +- $s/[&|]/\&/g +- $s/\n/\n/g +- ');; ++ i=$(printf '%s\n' "$i" | LC_ALL=C sed 's/[&|]/\&/g; $!s/$/\/');;
esac+- sed_script="s|^|$i:|" ++ ++ # $i already ends with a colon so don't add it here. ++ sed_script="s|^|$i|"
# Fail if grep or sed fails.r=$(exec 4>&1+- (eval "$grep" 4>&-; echo $? >&4) 3>&- | sed "$sed_script" >&3 4>&- ++ (eval "$grep" 4>&-; echo $? >&4) 3>&- | ++ LC_ALL=C sed "$sed_script" >&3 4>&-
) || r=2exit $rfi >&3 5>&-+-- +2.35.1
-- 2.35.1