- Please note that s\bsu\bud\bdo\bo will normally only log the command
- it explicitly runs. If a user runs a command such as sudo
- su or sudo sh, subsequent commands run from that shell
- will _\bn_\bo_\bt be logged, nor will s\bsu\bud\bdo\bo's access control affect
- them. The same is true for commands that offer shell
- escapes (including most editors). Because of this, care
- must be taken when giving users access to commands via
- s\bsu\bud\bdo\bo to verify that the command does not inadvertently
- give the user an effective root shell. For more informa
- tion, please see the PREVENTING SHELL ESCAPES section in
- _\bs_\bu_\bd_\bo_\be_\br_\bs(4).
+ invoking process permitted by the _\be_\bn_\bv_\b__\bc_\bh_\be_\bc_\bk and _\be_\bn_\bv_\b__\bk_\be_\be_\bp _\bs_\bu_\bd_\bo_\be_\br_\bs
+ options. There is effectively a whitelist for environment variables.
+
+ If, however, the _\be_\bn_\bv_\b__\br_\be_\bs_\be_\bt option is disabled in _\bs_\bu_\bd_\bo_\be_\br_\bs, any variables
+ not explicitly denied by the _\be_\bn_\bv_\b__\bc_\bh_\be_\bc_\bk and _\be_\bn_\bv_\b__\bd_\be_\bl_\be_\bt_\be options are
+ inherited from the invoking process. In this case, _\be_\bn_\bv_\b__\bc_\bh_\be_\bc_\bk and
+ _\be_\bn_\bv_\b__\bd_\be_\bl_\be_\bt_\be behave like a blacklist. Since it is not possible to
+ blacklist all potentially dangerous environment variables, use of the
+ default _\be_\bn_\bv_\b__\br_\be_\bs_\be_\bt behavior is encouraged.
+
+ In all cases, environment variables with a value beginning with () are
+ removed as they could be interpreted as b\bba\bas\bsh\bh functions. The list of
+ environment variables that s\bsu\bud\bdo\bo allows or denies is contained in the
+ output of sudo -V when run as root.
+
+ Note that the dynamic linker on most operating systems will remove
+ variables that can control dynamic linking from the environment of
+ setuid executables, including s\bsu\bud\bdo\bo. Depending on the operating system
+ this may include _RLD*, DYLD_*, LD_*, LDR_*, LIBPATH, SHLIB_PATH, and
+ others. These type of variables are removed from the environment
+ before s\bsu\bud\bdo\bo even begins execution and, as such, it is not possible for
+ s\bsu\bud\bdo\bo to preserve them.
+
+ To prevent command spoofing, s\bsu\bud\bdo\bo checks "." and "" (both denoting
+ current directory) last when searching for a command in the user's PATH
+ (if one or both are in the PATH). Note, however, that the actual PATH
+ environment variable is _\bn_\bo_\bt modified and is passed unchanged to the
+ program that s\bsu\bud\bdo\bo executes.
+
+ s\bsu\bud\bdo\bo will check the ownership of its time stamp directory
+ (_\b/_\bv_\ba_\br_\b/_\ba_\bd_\bm_\b/_\bs_\bu_\bd_\bo by default) and ignore the directory's contents if it is
+ not owned by root or if it is writable by a user other than root. On
+ systems that allow non-root users to give away files via _\bc_\bh_\bo_\bw_\bn(2), if
+ the time stamp directory is located in a directory writable by anyone
+ (e.g., _\b/_\bt_\bm_\bp), it is possible for a user to create the time stamp
+ directory before s\bsu\bud\bdo\bo is run. However, because s\bsu\bud\bdo\bo checks the
+ ownership and mode of the directory and its contents, the only damage
+ that can be done is to "hide" files by putting them in the time stamp
+ dir. This is unlikely to happen since once the time stamp dir is owned
+ by root and inaccessible by any other user, the user placing files
+ there would be unable to get them back out. To get around this issue
+ you can use a directory that is not world-writable for the time stamps
+ (_\b/_\bv_\ba_\br_\b/_\ba_\bd_\bm_\b/_\bs_\bu_\bd_\bo for instance) or create _\b/_\bv_\ba_\br_\b/_\ba_\bd_\bm_\b/_\bs_\bu_\bd_\bo with the
+ appropriate owner (root) and permissions (0700) in the system startup
+ files.