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| author | Andreas Baumann <abaumann@yahoo.com> | 2009-02-22 11:50:11 +0100 |
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| committer | Andreas Baumann <abaumann@yahoo.com> | 2009-02-22 11:50:11 +0100 |
| commit | 32bdbff73349e10a1958f4fb89db8e33fb62f2dd (patch) | |
| tree | e3351ca1cded7861c55f02fea127a9c51c41b024 /docs/daemon | |
| parent | bdb2a7d1d2ba1ea54782475c134b1e3018f80db4 (diff) | |
| download | wolfbones-32bdbff73349e10a1958f4fb89db8e33fb62f2dd.tar.gz wolfbones-32bdbff73349e10a1958f4fb89db8e33fb62f2dd.tar.bz2 | |
updated all documentation and todo lists
Diffstat (limited to 'docs/daemon')
| -rw-r--r-- | docs/daemon/CS4-07.html | 147 | ||||
| -rw-r--r-- | docs/daemon/README | 3 | ||||
| -rw-r--r-- | docs/daemon/TODOS | 10 |
3 files changed, 153 insertions, 7 deletions
diff --git a/docs/daemon/CS4-07.html b/docs/daemon/CS4-07.html new file mode 100644 index 0000000..716c999 --- /dev/null +++ b/docs/daemon/CS4-07.html @@ -0,0 +1,147 @@ +<HTML> +<TITLE>Process Persona in Unix</TITLE> +<body alink="#ff0000" vlink="#551a8b" link="#0000ee" text="#000000" +bgcolor="#FFFFFF"> +<PRE> +============================================================================== +<A HREF="CS4-01.html">C-Scene Issue #04</A> +Process Persona in Unix +<A HREF="../people/zwarich.html">Cameron Zwarich</A> +============================================================================== + + +In Unix, each process has a "persona". This persona tells the process (and +other processes) who exactly is running the process and what persmissions +are given to the process. + +Each process has a real user ID and an effective user ID. The real user ID is +the same as the user ID of its parent (unless it has been changed). The +effective user ID of a program corresponds to the set user ID bit on the file +being executed. + +The real user ID is used to determine which user started the process, and +the effective user ID determines what permissions the process has, like which +files it can access in what ways, and what ports it can bind to, etc. + +Each process also has a real group ID and an effective group ID. These follow +the same general rules as their corresponding user counterparts, but the +permissions are only for file access where a specific group is given +special permissions that the world isn't given. + +--- NOTE --- +Executables owned by root with a set ID bit are very insecure. Make sure +that you do all of your root-needing stuff at the BEGINNING of the program's +execution, then assume the identity of another user (traditionally nobody). +--- END NOTE --- + +Getting the Persona of the Current Process +------------------------------------------ + +Suppose you need to find out which user executed your process, or what +permissions you have before you attempt to do something. Or what if you need +to get a particular user's password file information (read my article on this +too :). This is when you need to get the persona of a process. + +getuid() returns the real user ID (uid) of the current process. geteuid() +returns the effective user ID (euid) of the current process. + +getgid() returns the real group ID (gid) of the current process. getegid() +returns the effective group ID (egid) of the current process. + +Here is an example which prints the uid, euid, gid, and egid of itself. + +#include <stdio.h> +#include <unistd.h> + +int main (void) +{ + printf("uid: %d\neuid: %d\ngid: %d\negid: %d\n", getuid(), geteuid(), + getgid(), getegid()); + exit(0); +} + +That wasn't that hard at all. Play around with set ID bits on the executable +and see how the output changes for some fun. + +Setting the Persona of the Current Process +------------------------------------------ + +In the life of some programs, you may have to do something that requires a +super-user uid (0) to do. Your program might require access by normal users +also though. What do you do? Well, you make the file root-owned and set the +set user ID bit on the process. Here is a little function you might want to +add to your root .profile (Bash is the best shell :): + +function change-to-setuid () { chown 0:0 $1; chmod +s $1; } + +That would be called as: "change-to-setuid <my-exec>". + +If you are using a non-Bourne shell, then write something corresponding to +that, its not really all that hard. You should be using Bash anyways. + +I will explain six functions, setuid(), setreuid(), seteuid(), setgid(), +setregid() and setegid(). Only setuid() and setgid() conform to Posix.1. +setreuid(), seteuid(), setregid(), and setegid() all conform to the BSD 4.3 +standard. You cannot change to a user ID or a group ID other then your +current one unless you have super-user priveleges. + +setuid() sets both the real and effective user ID's to its only argument. +setreuid() takes two arguments, the new real and effective user ID's +respectively. The seteuid() sets the effective user ID to its only argument. +The group-related functions do the same actions but with group ID's. + +With the Posix.1 functions, you can (on most systems) regain priveleges that +you gave up with setuid()/setgid(). You can switch back to the effective +user/group ID you had before if you were run with a set ID bit and you +assumed another user to do some work. + +Here is an example that uses the Posix functions to set the user/group IDs to +its two arguments, respectively: + +#include <stdio.h> +#include <unistd.h> +#include <sys/types.h> + +int main (int argc, char **argv) +{ + if (argc < 3) + { + fputs("Insufficient arguments\n", stderr); + exit(1); + } + + printf("My old uid was %d, and my old gid was %d. ", getuid(), getgid()); + setuid(atoi(argv[1])); + setgid(atoi(argv[2])); + printf("My new uid is %d, and my new gid is %d\n", getuid(), getgid()); +} + +Functions +--------- + +#include <unistd.h> +#include <sys/types.h> + +uid_t getuid(void) +uid_t geteuid(void) + +gid_t getgid(void) +gid_t getegid(void) + +int setuid(uid_t uid) +int setreuid(uid_t ruid, uid_t euid) +int seteuid(uid_t euid) + +int setgid(gid_t gid) +int setregid(gid_t rgid, gid_t egid) +int setegeid(gid_t egid) + +</PRE> +<HR> +<I><FONT COLOR="#008080" SIZE=-1> +This page is Copyright © 1997 By +<A HREF="http://cscene.oftheinter.net">C Scene</A>. All Rights Reserved +</FONT></I> +<HR> +</BODY> +</HTML> diff --git a/docs/daemon/README b/docs/daemon/README index 3fe39f5..5cdf64d 100644 --- a/docs/daemon/README +++ b/docs/daemon/README @@ -1,6 +1,7 @@ How Unix daemons work see: - general introduction: http://www.enderunix.org/documents/eng/daemon.php -- for handling user/groups: http://www.gmonline.demon.co.uk/cscene/CS4/CS4-07.html +- for handling user/groups: + http://vmlinux.org/jocke/mirror/cscene.oftheinter.net/www.syclus.com/cscene/CS4/CS4-07.html Other projects: - libdaemon (in C): http://0pointer.de/lennart/projects/libdaemon/ diff --git a/docs/daemon/TODOS b/docs/daemon/TODOS index 5078f11..90de762 100644 --- a/docs/daemon/TODOS +++ b/docs/daemon/TODOS @@ -1,6 +1,4 @@ -- Sanitize public header files - - Check how much of signals.h should really leak up to the testd.c - - What exactly should be in libwolf_port.a? strdup, stdbool, snprintf - for sure. What about lockf? The answer is: it depends :-) - - log.h must be cleaned heavily - - all header files must be documented properly +- check against things done in other libraries + - POCO ServiceApplication + - libdaemon +- do a security survey |