Fixes CVE-2021-4034, local privilege escalation with 'pkexec': https://www.openwall.com/lists/oss-security/2022/01/25/11 Patch from . From a2bf5c9c83b6ae46cbd5c779d3055bff81ded683 Mon Sep 17 00:00:00 2001 From: Jan Rybar Date: Tue, 25 Jan 2022 17:21:46 +0000 Subject: [PATCH] pkexec: local privilege escalation (CVE-2021-4034) --- src/programs/pkcheck.c | 5 +++++ src/programs/pkexec.c | 23 ++++++++++++++++++++--- 2 files changed, 25 insertions(+), 3 deletions(-) diff --git a/src/programs/pkcheck.c b/src/programs/pkcheck.c index f1bb4e1..768525c 100644 --- a/src/programs/pkcheck.c +++ b/src/programs/pkcheck.c @@ -363,6 +363,11 @@ main (int argc, char *argv[]) local_agent_handle = NULL; ret = 126; + if (argc < 1) + { + exit(126); + } + /* Disable remote file access from GIO. */ setenv ("GIO_USE_VFS", "local", 1); diff --git a/src/programs/pkexec.c b/src/programs/pkexec.c index 7698c5c..84e5ef6 100644 --- a/src/programs/pkexec.c +++ b/src/programs/pkexec.c @@ -488,6 +488,15 @@ main (int argc, char *argv[]) pid_t pid_of_caller; gpointer local_agent_handle; + + /* + * If 'pkexec' is called THIS wrong, someone's probably evil-doing. Don't be nice, just bail out. + */ + if (argc<1) + { + exit(127); + } + ret = 127; authority = NULL; subject = NULL; @@ -614,10 +623,10 @@ main (int argc, char *argv[]) path = g_strdup (pwstruct.pw_shell); if (!path) - { + { g_printerr ("No shell configured or error retrieving pw_shell\n"); goto out; - } + } /* If you change this, be sure to change the if (!command_line) case below too */ command_line = g_strdup (path); @@ -636,7 +645,15 @@ main (int argc, char *argv[]) goto out; } g_free (path); - argv[n] = path = s; + path = s; + + /* argc<2 and pkexec runs just shell, argv is guaranteed to be null-terminated. + * /-less shell shouldn't happen, but let's be defensive and don't write to null-termination + */ + if (argv[n] != NULL) + { + argv[n] = path; + } } if (access (path, F_OK) != 0) {