| Summary: | <app-admin/sudo-1.8.28: bypass of Runas user restrictions (CVE-2019-14287) | ||
|---|---|---|---|
| Product: | Gentoo Security | Reporter: | Thomas Deutschmann (RETIRED) <whissi> |
| Component: | Vulnerabilities | Assignee: | Gentoo Security <security> |
| Status: | RESOLVED FIXED | ||
| Severity: | major | CC: | base-system |
| Priority: | Normal | Flags: | stable-bot:
sanity-check+
|
| Version: | unspecified | ||
| Hardware: | All | ||
| OS: | Linux | ||
| URL: | https://www.sudo.ws/alerts/minus_1_uid.html | ||
| Whiteboard: | A1 [glsa+ cve] | ||
| Package list: |
app-admin/sudo-1.8.28_p1-r2
|
Runtime testing required: | --- |
|
Description
Thomas Deutschmann (RETIRED)
2019-10-10 22:03:42 UTC
When sudo is configured to allow a user to run commands as an arbitrary user via the ALL keyword in a Runas specification, it is possible to run commands as root by specifying the user ID -1 or 4294967295.
This can be used by a user with sufficient sudo privileges to run commands as root even if the Runas specification explicitly disallows root access as long as the ALL keyword is listed first in the Runas specification.
Log entries for commands run this way will list the target user as 4294967295 instead of root. In addition, PAM session modules will not be run for the command.
Sudo versions affected:
=======================
Sudo versions prior to 1.8.28 are affected.
Details:
========
Exploiting the bug requires that the user have sudo privileges that allow them to run commands with an arbitrary user ID. Typically, this means that the user's sudoers entry has the special value ALL in the Runas specifier.
Sudo supports running a command with a user-specified user name or user ID, if permitted by the sudoers policy. For example, the following sudoers entry allow the id command to be run as any user because it includes the ALL keyword in the Runas specifier.
myhost alice = (ALL) /usr/bin/id
Not only is user is able to run the id command as any valid user, she is also able to run it as an arbitrary user ID by using the #uid syntax, for example:
sudo -u#1234 id -u
would return 1234. However, the setresuid(2) and setreuid(2) system calls, which sudo uses to change the user ID before running the command, treat user ID -1 (or its unsigned equivalent 4294967295), specially and do not change the user ID for this value. As a result,
sudo -u#-1 id -u
or
sudo -u#4294967295 id -u
will actually return 0. This is because the sudo command itself is already running as user ID 0 so when sudo tries to change to user ID -1, no change occurs.
This results in sudo log entries that report the command as being run by user ID 4294967295 and not root (or user ID 0). Additionally, because the user ID specified via the -u option does not exist in the password database, no PAM session modules will be run.
If a sudoers entry is written to allow the user to run a command as any user except root, the bug can be used to avoid this restriction. For example, given the following sudoers entry:
myhost bob = (ALL, !root) /usr/bin/vi
User bob is allowed to run vi as any user but root. However, due to the bug, bob is actually able to run vi as root by running sudo -u#-1 vi, violating the security policy.
Only sudoers entries where the ALL keyword is present in the Runas specifier are affected. For example, the following sudoers entry is unaffected:
myhost alice = /usr/bin/id
In this example, alice is only allowed to run the id command as root. Any attempt to run the command as a different user will be denied.
Fix:
====
The bug is fixed in sudo 1.8.28.
The bug has been referenced in the following commit(s): https://gitweb.gentoo.org/repo/gentoo.git/commit/?id=bc0fe8604ba04929688ee6873ecdc6cec4ea22d1 commit bc0fe8604ba04929688ee6873ecdc6cec4ea22d1 Author: Thomas Deutschmann <whissi@gentoo.org> AuthorDate: 2019-10-14 15:52:33 +0000 Commit: Thomas Deutschmann <whissi@gentoo.org> CommitDate: 2019-10-14 15:52:33 +0000 app-admin/sudo: bump to v1.8.28 Bug: https://bugs.gentoo.org/697462 Package-Manager: Portage-2.3.76, Repoman-2.3.17 Signed-off-by: Thomas Deutschmann <whissi@gentoo.org> app-admin/sudo/Manifest | 1 + app-admin/sudo/sudo-1.8.28.ebuild | 251 ++++++++++++++++++++++++++++++++++++++ 2 files changed, 252 insertions(+) x86 stable The bug has been referenced in the following commit(s): https://gitweb.gentoo.org/repo/gentoo.git/commit/?id=491c3b2c497837cff2b3bc2d7da90154da353e41 commit 491c3b2c497837cff2b3bc2d7da90154da353e41 Author: Richard Freeman <rich0@gentoo.org> AuthorDate: 2019-10-14 23:35:47 +0000 Commit: Richard Freeman <rich0@gentoo.org> CommitDate: 2019-10-14 23:35:47 +0000 app-admin/sudo: amd64 stable Bug: https://bugs.gentoo.org/697462 Package-Manager: Portage-2.3.76, Repoman-2.3.16 Signed-off-by: Richard Freeman <rich0@gentoo.org> app-admin/sudo/sudo-1.8.28.ebuild | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) s390 stable sparc stable ppc stable ppc64 stable arm64 stable hppa stable arm stable sh stable m68k stable alpha stable ia64 stable. Maintainer(s), please cleanup. Security, please add it to the existing request, or file a new one. The bug has been referenced in the following commit(s): https://gitweb.gentoo.org/repo/gentoo.git/commit/?id=36ea8390dc830ff9e21c13519be217e74a5a6737 commit 36ea8390dc830ff9e21c13519be217e74a5a6737 Author: Lars Wendler <polynomial-c@gentoo.org> AuthorDate: 2019-11-22 10:30:19 +0000 Commit: Lars Wendler <polynomial-c@gentoo.org> CommitDate: 2019-11-22 10:33:33 +0000 app-admin/sudo: Security cleanup Bug: https://bugs.gentoo.org/697462 Package-Manager: Portage-2.3.79, Repoman-2.3.18 Signed-off-by: Lars Wendler <polynomial-c@gentoo.org> app-admin/sudo/Manifest | 1 - app-admin/sudo/sudo-1.8.27-r1.ebuild | 252 ----------------------------------- 2 files changed, 253 deletions(-) New GLSA request filed. Repository is clean! This issue was resolved and addressed in GLSA 202003-12 at https://security.gentoo.org/glsa/202003-12 by GLSA coordinator Thomas Deutschmann (whissi). |
