diff options
Diffstat (limited to 'Documentation/seclvl.txt')
| -rw-r--r-- | Documentation/seclvl.txt | 97 |
1 files changed, 0 insertions, 97 deletions
diff --git a/Documentation/seclvl.txt b/Documentation/seclvl.txt deleted file mode 100644 index 97274d122d0e28..00000000000000 --- a/Documentation/seclvl.txt +++ /dev/null @@ -1,97 +0,0 @@ -BSD Secure Levels Linux Security Module -Michael A. Halcrow <mike@halcrow.us> - - -Introduction - -Under the BSD Secure Levels security model, sets of policies are -associated with levels. Levels range from -1 to 2, with -1 being the -weakest and 2 being the strongest. These security policies are -enforced at the kernel level, so not even the superuser is able to -disable or circumvent them. This hardens the machine against attackers -who gain root access to the system. - - -Levels and Policies - -Level -1 (Permanently Insecure): - - Cannot increase the secure level - -Level 0 (Insecure): - - Cannot ptrace the init process - -Level 1 (Default): - - /dev/mem and /dev/kmem are read-only - - IMMUTABLE and APPEND extended attributes, if set, may not be unset - - Cannot load or unload kernel modules - - Cannot write directly to a mounted block device - - Cannot perform raw I/O operations - - Cannot perform network administrative tasks - - Cannot setuid any file - -Level 2 (Secure): - - Cannot decrement the system time - - Cannot write to any block device, whether mounted or not - - Cannot unmount any mounted filesystems - - -Compilation - -To compile the BSD Secure Levels LSM, seclvl.ko, enable the -SECURITY_SECLVL configuration option. This is found under Security -options -> BSD Secure Levels in the kernel configuration menu. - - -Basic Usage - -Once the machine is in a running state, with all the necessary modules -loaded and all the filesystems mounted, you can load the seclvl.ko -module: - -# insmod seclvl.ko - -The module defaults to secure level 1, except when compiled directly -into the kernel, in which case it defaults to secure level 0. To raise -the secure level to 2, the administrator writes ``2'' to the -seclvl/seclvl file under the sysfs mount point (assumed to be /sys in -these examples): - -# echo -n "2" > /sys/seclvl/seclvl - -Alternatively, you can initialize the module at secure level 2 with -the initlvl module parameter: - -# insmod seclvl.ko initlvl=2 - -At this point, it is impossible to remove the module or reduce the -secure level. If the administrator wishes to have the option of doing -so, he must provide a module parameter, sha1_passwd, that specifies -the SHA1 hash of the password that can be used to reduce the secure -level to 0. - -To generate this SHA1 hash, the administrator can use OpenSSL: - -# echo -n "boogabooga" | openssl sha1 -abeda4e0f33defa51741217592bf595efb8d289c - -In order to use password-instigated secure level reduction, the SHA1 -crypto module must be loaded or compiled into the kernel: - -# insmod sha1.ko - -The administrator can then insmod the seclvl module, including the -SHA1 hash of the password: - -# insmod seclvl.ko - sha1_passwd=abeda4e0f33defa51741217592bf595efb8d289c - -To reduce the secure level, write the password to seclvl/passwd under -your sysfs mount point: - -# echo -n "boogabooga" > /sys/seclvl/passwd - -The September 2004 edition of Sys Admin Magazine has an article about -the BSD Secure Levels LSM. I encourage you to refer to that article -for a more in-depth treatment of this security module: - -http://www.samag.com/documents/s=9304/sam0409a/0409a.htm |