CVE-2021-3156 (Sudo Baron Samedit)

This repository is CVE-2021-3156 exploit targeting Linux x64. For writeup, please visit https://datafarm-cybersecurity.medium.com/exploit-writeup-for-cve-2021-3156-sudo-baron-samedit-7a9a4282cb31
Credit to Braon Samedit of Qualys for the original advisory.

Files

Exploit on glibc with tcache

• exploit_nss.py auto detect all requirements and number of entries in /etc/nsswitch.conf
• exploit_nss_manual.py simplified version of exploit_nss.py for better exploit understanding
• exploit_timestamp_race.c overwrite def_timestamp and race condition to modify /etc/passwd

Exploit on glibc without tcache

• exploit_defaults_mailer.py the exploit overwrite struct defaults to modify mailer binary path. It requires sudo compiled without disable-root-mailer such as CentOS 6 and 7.
• exploit_userspec.py the exploit overwrite struct userspec to bypass authentication and add a new user in /etc/passwd. Support only sudo version 1.8.9-1.8.23.
• exploit_cent7_userspec.py simplified version of exploit_userspec.py for understanding but target only CentOS 7 with default configuration
• exploit_nss_d9.py overwrite struct service_user on Debian 9 but support only default /etc/nsswith.conf
• exploit_nss_u16.py overwrite struct service_user on Ubuntu 16.04 but support only default /etc/nsswith.conf
• exploit_nss_u14.py overwrite struct service_user on Ubuntu 14.04 but support only default /etc/nsswith.conf

Others

• asm/ tinyelf library and executable for embedded in python exploit
• gdb/ scripts that used for debugging sudo heap

Choosing exploit

For Linux distributions that glibc has tcache support and enabled (CentOS 8, Ubuntu >= 17.10, Debian 10):

• try exploit_nss.py first
• If an error is not glibc tcache related, you can try exploit_timestamp_race.c next

For Linux distribution that glibc has no tcache support:

• if a target is Debian 9, Ubuntu 16.04, or Ubuntu 14.04, try exploit_nss_xxx.py for specific version first
• next, try exploit_defaults_mailer.py. If you know a target sudo is compiled with --disable-root-mailer, you can skip this exploit. The exploit attempt to check root mailer flag from sudo binary. But sudo permission on some Linux distribution is 4711 (srwx--x--x) which is impossible to check on target system. (Known work OS is CentOS 6 and 7)
• last, try exploit_userspec.py