diff options
Diffstat (limited to 'lib/libc')
| -rw-r--r-- | lib/libc/sys/getlogin.2 | 47 |
1 files changed, 46 insertions, 1 deletions
diff --git a/lib/libc/sys/getlogin.2 b/lib/libc/sys/getlogin.2 index 5b351ca..b0c6f1b 100644 --- a/lib/libc/sys/getlogin.2 +++ b/lib/libc/sys/getlogin.2 @@ -66,6 +66,50 @@ This call is restricted to the super-user, and is normally used only when a new session is being created on behalf of the named user (for example, at login time, or when a remote shell is invoked). +.Pp +.Em NOTE: +There is only one `login name' per `session . +.Pp +It is +.Em CRITICALLY +important to ensure that +.Fn setlogin +is only ever called after the process has taken adequate steps to ensure +that it is detached from it's parent's session. +Making a +.Fn setsid +system call is the +.Em ONLY +way to do this. The +.Fn daemon +library call calls +.Fn setsid +which is an ideal way of detaching from a controlling terminal and +forking into the background. +.Pp +In particular, doing a +.Fn "ioctl" "ttyfd" "TIOCNOTTY" "..." +or +.Fn "setpgrp" "..." +is +.Em NOT +sufficient. +.Pp +Once a parent process does a +.Fn setsid +call, it is acceptable for some child of that process to then do a +.Fn setlogin +even though it is not the session leader, but beware that ALL processes +in the session will change their login name at the same time, even the +parent. +.Pp +This is not the same as the traditional UNIX behavior of inheriting privilege. +.Pp +Since the +.Fn setlogin +system call is restricted to the super-user, it is assumed that (like +all other privileged programs) the programmer has taken adequate +precautions to prevent security violations. .Sh RETURN VALUES If a call to .Fn getlogin @@ -101,7 +145,8 @@ characters, currently 12. The caller tried to set the login name and was not the super-user. .El .Sh SEE ALSO -.Xr setsid 2 +.Xr setsid 2 , +.Xr daemon 3 .Sh BUGS Login names are limited in length by .Fn setlogin . |
