Resolves: CVE-2021-45444 - do not perform PROMPT_SUBST evaluation on %F/%K arguments
This commit is contained in:
Kamil Dudka
Stepan Oksanichenko
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b2dac3124a
commit
3679e911ec
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966ea0498fb94140f3caf12af88e98b0e4d02078 zsh-5.8.tar.xz
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@ -0,0 +1,109 @@
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From 02e0f94fff27cad2ba4e65bdc4b21146b3bd9a97 Mon Sep 17 00:00:00 2001
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From: Oliver Kiddle <opk@zsh.org>
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Date: Wed, 15 Dec 2021 01:56:40 +0100
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Subject: [PATCH 1/2] security/41: Don't perform PROMPT_SUBST evaluation on
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%F/%K arguments
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Mitigates CVE-2021-45444
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Upstream-commit: c187154f47697cdbf822c2f9d714d570ed4a0fd1
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Signed-off-by: Kamil Dudka <kdudka@redhat.com>
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---
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Src/prompt.c | 10 ++++++++++
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1 file changed, 10 insertions(+)
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diff --git a/Src/prompt.c b/Src/prompt.c
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index b65bfb8..91e21c8 100644
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--- a/Src/prompt.c
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+++ b/Src/prompt.c
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@@ -244,6 +244,12 @@ parsecolorchar(zattr arg, int is_fg)
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bv->fm += 2; /* skip over F{ */
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if ((ep = strchr(bv->fm, '}'))) {
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char oc = *ep, *col, *coll;
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+ int ops = opts[PROMPTSUBST], opb = opts[PROMPTBANG];
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+ int opp = opts[PROMPTPERCENT];
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+
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+ opts[PROMPTPERCENT] = 1;
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+ opts[PROMPTSUBST] = opts[PROMPTBANG] = 0;
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+
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*ep = '\0';
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/* expand the contents of the argument so you can use
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* %v for example */
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@@ -252,6 +258,10 @@ parsecolorchar(zattr arg, int is_fg)
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arg = match_colour((const char **)&coll, is_fg, 0);
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free(col);
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bv->fm = ep;
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+
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+ opts[PROMPTSUBST] = ops;
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+ opts[PROMPTBANG] = opb;
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+ opts[PROMPTPERCENT] = opp;
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} else {
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arg = match_colour((const char **)&bv->fm, is_fg, 0);
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if (*bv->fm != '}')
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--
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2.34.1
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From 6102afb5dfd7c704f9cf99bedb9c3ec3c7dbe8e3 Mon Sep 17 00:00:00 2001
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From: dana <dana@dana.is>
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Date: Tue, 21 Dec 2021 13:13:33 -0600
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Subject: [PATCH 2/2] CVE-2021-45444: Update NEWS/README
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Upstream-commit: bdc4d70a7e033b754e68a8659a037ea0fc5f38de
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Signed-off-by: Kamil Dudka <kdudka@redhat.com>
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---
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NEWS | 20 ++++++++++++++++++++
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README | 6 ++++++
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2 files changed, 26 insertions(+)
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diff --git a/NEWS b/NEWS
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index 964e163..327b449 100644
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--- a/NEWS
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+++ b/NEWS
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@@ -4,6 +4,26 @@ CHANGES FROM PREVIOUS VERSIONS OF ZSH
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Note also the list of incompatibilities in the README file.
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+Changes since 5.8
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+-----------------
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+
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+CVE-2021-45444: Some prompt expansion sequences, such as %F, support
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+'arguments' which are themselves expanded in case they contain colour
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+values, etc. This additional expansion would trigger PROMPT_SUBST
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+evaluation, if enabled. This could be abused to execute code the user
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+didn't expect. e.g., given a certain prompt configuration, an attacker
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+could trick a user into executing arbitrary code by having them check
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+out a Git branch with a specially crafted name.
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+
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+This is fixed in the shell itself by no longer performing PROMPT_SUBST
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+evaluation on these prompt-expansion arguments.
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+
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+Users who are concerned about an exploit but unable to update their
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+binaries may apply the partial work-around described in the file
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+Etc/CVE-2021-45444-VCS_Info-workaround.patch included with the shell
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+source. [ Reported by RyotaK <security@ryotak.me>. Additional thanks to
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+Marc Cornellà <hello@mcornella.com>. ]
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+
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Changes since 5.7.1-test-3
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--------------------------
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diff --git a/README b/README
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index 7f1dd5f..c9e994a 100644
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--- a/README
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+++ b/README
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@@ -31,6 +31,12 @@ Zsh is a shell with lots of features. For a list of some of these, see the
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file FEATURES, and for the latest changes see NEWS. For more
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details, see the documentation.
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+Incompatibilities since 5.8
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+---------------------------
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+
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+PROMPT_SUBST expansion is no longer performed on arguments to prompt-
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+expansion sequences such as %F.
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+
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Incompatibilities since 5.7.1
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-----------------------------
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--
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2.34.1
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8
zsh.spec
8
zsh.spec
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@ -1,7 +1,7 @@
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Summary: Powerful interactive shell
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Name: zsh
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Version: 5.8
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Release: 8%{?dist}
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Release: 9%{?dist}
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License: MIT
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URL: http://zsh.sourceforge.net/
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Source0: https://downloads.sourceforge.net/%{name}/%{name}-%{version}.tar.xz
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@ -15,6 +15,9 @@ Source6: dotzshrc
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# complete file arguments after rpmbuild -r/-b/-t
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Patch1: 0001-zsh-5.8-comp-rpm.patch
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# do not perform PROMPT_SUBST evaluation on %F/%K arguments (CVE-2021-45444)
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Patch2: 0002-zsh-5.8-CVE-2021-45444.patch
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BuildRequires: autoconf
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BuildRequires: coreutils
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BuildRequires: gawk
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@ -158,6 +161,9 @@ fi
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%doc Doc/*.html
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%changelog
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* Tue Feb 22 2022 Kamil Dudka <kdudka@redhat.com> - 5.8-9
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- do not perform PROMPT_SUBST evaluation on %F/%K arguments (CVE-2021-45444)
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* Thu Nov 25 2021 Debarshi Ray <rishi@fedoraproject.org> - 5.8-8
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- Overwrite PROMPT only if it's set to the built-in default (#2026749)
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