diff options
| author | Ulrich Drepper <drepper@redhat.com> | 1999-09-20 04:59:24 +0000 |
|---|---|---|
| committer | Ulrich Drepper <drepper@redhat.com> | 1999-09-20 04:59:24 +0000 |
| commit | 3a4cbb41861badaf557b1896542c00d4f40d9f45 (patch) | |
| tree | 156bc6fb89961a5905239aa7dbc1affa3fd06b5d /manual/filesys.texi | |
| parent | 1d8004b2760e61d7e9fd67caa42bd6d0004a9f9d (diff) | |
Update.
* manual/filesys.texi (Testing File Access): Correct description of
SUID.
1999-08025 H.J. Lu <hjl@gnu.org>
* csu/defs.awk (.end): Only match with leading white spaces.
(.align): Likewise.
1999-09-19 Ulrich Drepper <drepper@cygnus.com>
Diffstat (limited to 'manual/filesys.texi')
| -rw-r--r-- | manual/filesys.texi | 27 |
1 files changed, 14 insertions, 13 deletions
diff --git a/manual/filesys.texi b/manual/filesys.texi index 728b904d66..5a3f0c51be 100644 --- a/manual/filesys.texi +++ b/manual/filesys.texi @@ -2267,19 +2267,20 @@ The file resides on a read-only file system. @cindex access, testing for @cindex setuid programs and file access -When a program runs as a privileged user, this permits it to access -files off-limits to ordinary users---for example, to modify -@file{/etc/passwd}. Programs designed to be run by ordinary users but -access such files use the setuid bit feature so that they always run -with @code{root} as the effective user ID. - -Since the program runs as @code{root}, it has permission to access -whatever file the user specifies---but usually the desired behavior is -to permit only those files which the user could ordinarily access. - -The program therefore must explicitly check whether @emph{the user} -would have the necessary access to a file, before it reads or writes the -file. +In some situations it is desirable to allow programs to access files or +devices even if this is not possible with the permissions granted to the +user. One possible solution is to set the setuid-bit of the program +file. If such a program is started the @emph{effective} user ID of the +process is changed to that of the owner of the program file. So to +allow write access to files like @file{/etc/passwd}, which normally can +be written only by the super-user, the modifying program will have to be +owned by @code{root} and the setuid-bit must be set. + +But beside the files the program is intended to change the user should +not be allowed to access any file to which s/he would not have access +anyway. The program therefore must explicitly check whether @emph{the +user} would have the necessary access to a file, before it reads or +writes the file. To do this, use the function @code{access}, which checks for access permission based on the process's @emph{real} user ID rather than the |