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Diffstat (limited to 'Documentation/SAK.txt')
| -rw-r--r-- | Documentation/SAK.txt | 65 |
1 files changed, 34 insertions, 31 deletions
diff --git a/Documentation/SAK.txt b/Documentation/SAK.txt index 74be14679ed8..260e1d3687bd 100644 --- a/Documentation/SAK.txt +++ b/Documentation/SAK.txt @@ -1,5 +1,9 @@ -Linux 2.4.2 Secure Attention Key (SAK) handling -18 March 2001, Andrew Morton +========================================= +Linux Secure Attention Key (SAK) handling +========================================= + +:Date: 18 March 2001 +:Author: Andrew Morton An operating system's Secure Attention Key is a security tool which is provided as protection against trojan password capturing programs. It @@ -13,7 +17,7 @@ this sequence. It is only available if the kernel was compiled with sysrq support. The proper way of generating a SAK is to define the key sequence using -`loadkeys'. This will work whether or not sysrq support is compiled +``loadkeys``. This will work whether or not sysrq support is compiled into the kernel. SAK works correctly when the keyboard is in raw mode. This means that @@ -25,64 +29,63 @@ What key sequence should you use? Well, CTRL-ALT-DEL is used to reboot the machine. CTRL-ALT-BACKSPACE is magical to the X server. We'll choose CTRL-ALT-PAUSE. -In your rc.sysinit (or rc.local) file, add the command +In your rc.sysinit (or rc.local) file, add the command:: echo "control alt keycode 101 = SAK" | /bin/loadkeys And that's it! Only the superuser may reprogram the SAK key. -NOTES -===== +.. note:: -1: Linux SAK is said to be not a "true SAK" as is required by - systems which implement C2 level security. This author does not - know why. + 1. Linux SAK is said to be not a "true SAK" as is required by + systems which implement C2 level security. This author does not + know why. -2: On the PC keyboard, SAK kills all applications which have - /dev/console opened. + 2. On the PC keyboard, SAK kills all applications which have + /dev/console opened. - Unfortunately this includes a number of things which you don't - actually want killed. This is because these applications are - incorrectly holding /dev/console open. Be sure to complain to your - Linux distributor about this! + Unfortunately this includes a number of things which you don't + actually want killed. This is because these applications are + incorrectly holding /dev/console open. Be sure to complain to your + Linux distributor about this! - You can identify processes which will be killed by SAK with the - command + You can identify processes which will be killed by SAK with the + command:: # ls -l /proc/[0-9]*/fd/* | grep console l-wx------ 1 root root 64 Mar 18 00:46 /proc/579/fd/0 -> /dev/console - Then: + Then:: # ps aux|grep 579 root 579 0.0 0.1 1088 436 ? S 00:43 0:00 gpm -t ps/2 - So `gpm' will be killed by SAK. This is a bug in gpm. It should - be closing standard input. You can work around this by finding the - initscript which launches gpm and changing it thusly: + So ``gpm`` will be killed by SAK. This is a bug in gpm. It should + be closing standard input. You can work around this by finding the + initscript which launches gpm and changing it thusly: - Old: + Old:: daemon gpm - New: + New:: daemon gpm < /dev/null - Vixie cron also seems to have this problem, and needs the same treatment. + Vixie cron also seems to have this problem, and needs the same treatment. - Also, one prominent Linux distribution has the following three - lines in its rc.sysinit and rc scripts: + Also, one prominent Linux distribution has the following three + lines in its rc.sysinit and rc scripts:: exec 3<&0 exec 4>&1 exec 5>&2 - These commands cause *all* daemons which are launched by the - initscripts to have file descriptors 3, 4 and 5 attached to - /dev/console. So SAK kills them all. A workaround is to simply - delete these lines, but this may cause system management - applications to malfunction - test everything well. + These commands cause **all** daemons which are launched by the + initscripts to have file descriptors 3, 4 and 5 attached to + /dev/console. So SAK kills them all. A workaround is to simply + delete these lines, but this may cause system management + applications to malfunction - test everything well. |