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Notes for TOMOYO Linux project |
Notes for TOMOYO Linux project |
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This is a handy Mandatory Access Control patch for Linux kernels. |
This is a handy Mandatory Access Control patch for Linux kernels. |
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This patch is released under the GPL. |
This patch is released under the GPLv2. |
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Project URL: http://tomoyo.sourceforge.jp/ |
Project URL: http://tomoyo.sourceforge.jp/ |
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| 1203 |
I made "(current->uid == 0 && current->euid == 0)" requirement optional. |
I made "(current->uid == 0 && current->euid == 0)" requirement optional. |
| 1204 |
If this requirement is disabled, only "conventional DAC permission |
If this requirement is disabled, only "conventional DAC permission |
| 1205 |
checks" and "/proc/ccs/manager checks" are used. |
checks" and "/proc/ccs/manager checks" are used. |
| 1206 |
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| 1207 |
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Fix 2008/02/29 |
| 1208 |
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| 1209 |
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@ Add sleep_on_violation feature. |
| 1210 |
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| 1211 |
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Some exploit codes (e.g. trans2open for Samba) continue running |
| 1212 |
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until it achieves the purpose of the exploit code (e.g. invoke /bin/sh). |
| 1213 |
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| 1214 |
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If such code is injected due to buffer overflow but the kernel |
| 1215 |
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rejects the request, it triggers infinite "Permission denied" loop. |
| 1216 |
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As a result, the CPU usage becomes 100% and gives bad effects to |
| 1217 |
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the rest of processes. |
| 1218 |
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This is a side effect of rejecting the request from the exploit code |
| 1219 |
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which wouldn't happen if the request from the exploit code was granted. |
| 1220 |
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| 1221 |
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To avoid such CPU consumption, I added a penalty that forcibly |
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sleeps for specified period when a request is rejected. |
| 1223 |
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| 1224 |
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This penalty doesn't work if the exploit code does nothing but |
| 1225 |
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continue running, but I think most exploit code's purpose is |
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to start some program rather than to slow down the target system. |
| 1227 |
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| 1228 |
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@ Add alt_exec feature. |
| 1229 |
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| 1230 |
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Since TOMOYO Linux's approach is "know all essential requests in advance |
| 1231 |
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and create policy that permits only them", you can regard anomalous |
| 1232 |
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requests as attacks (if you want to do so). |
| 1233 |
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| 1234 |
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Common MAC implementations merely reject requests that violate policy. |
| 1235 |
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But I added a special handler for execve() to TOMOYO Linux. |
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| 1237 |
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This handler is triggered when a process requested to execute a program |
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but the request was rejected by the policy. |
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This handler executes a program specified by the administrator |
| 1240 |
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instead of a program requested by the process. |
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Most attackers attempt to execute /bin/sh to start something malicious. |
| 1243 |
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Attackers execute an exploit code using buffer overflow vulnerability |
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to steal control of a process. But this handler can get back control |
| 1245 |
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if an exploit code requests execve() that is not permitted by policy. |
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By default, this handler does nothing (i.e. merely reject execve() |
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request). You can specify any program to start what you want to do. |
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You can redirect attackers to somewhere else (e.g. honey pot). |
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This makes it possible to act your Linux box as an on-demand honey pot |
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while keeping regular services for your usage. |
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You can collect information of the attacker (e.g. IP address) and |
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update firewall configuration. |
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You can silently terminate a process who requested execve() |
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that is not permitted by policy. |
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Fix 2008/03/03 |
| 1261 |
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@ Add "force_alt_exec" keyword. |
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To be able to fully utilize "alt_exec" feature, |
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I added "force_alt_exec" keyword so that |
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all execute requests are replaced by the execute request of a program |
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specified by alt_exec feature. |
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| 1269 |
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If this keyword is specified for a domain, the domain no longer |
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executes any programs regardless of the mode of file access control |
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(i.e. the domain won't execute even if MAC_FOR_FILE=0 ). |
| 1272 |
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Instead, the domain executes the program specified by alt_exec feature |
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and the program specified by alt_exec feature validates the execute |
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request and executes it if it is appropriate to execute. |
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If you can tolerate that there is no chance to return an error code |
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to the caller to tell the execute request was rejected, |
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this is more flexible approach than in-kernel execve() parameter |
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checking because we can do argv[] and envp[] checking easily. |
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Fix 2008/03/04 |
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@ Use string for access control mode. |
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An integer expression for access control mode sometimes confuses |
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administrators because profile number is also an integer expression. |
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To avoid confusion between profile number and access control mode, |
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I introduced a string expression for access control mode. |
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Modes which take an integer between 0 and 3. |
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0 -> disabled |
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1 -> learning |
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2 -> permissive |
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3 -> enforcing |
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Modes which take 0 or 1. |
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0 -> disabled |
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1 -> enabled |
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Fix 2008/03/10 |
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@ Rename "force_alt_exec" keyword to "execute_handler". |
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To be able to use different programs for validating execve() parameters, |
| 1307 |
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I moved the location to specify the program's pathname from profile |
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to domain policy. |
| 1309 |
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The "execute_handler" keyword takes one pathname which is |
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invoked whenever execve() request is issued. Thus, any "allow_execute" |
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keywords in a domain with "execute_handler" are ignored. |
| 1313 |
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This keyword is designed for validating expected/desirable execve() |
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requests in userspace, although there is no way to tell the caller |
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that the execve() request was rejected. |
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@ Rename "alt_exec" keyword to "denied_execute_handler". |
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The "denied_execute_handler" keyword takes one pathname which is |
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invoked only when execve() request was rejected. In other words, |
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this program is invoked only when the following conditions are met. |
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(1) None of "allow_execute" keywords in the domain matched. |
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(2) The execve() request was rejected in enforcing mode. |
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(3) "execute_handler" keyword is not used by the domain. |
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This keyword is designed for handling unexpected/undesirable execve() |
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requests, to redirect the process issuing such requests to somewhere. |
| 1329 |
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| 1330 |
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Fix 2008/03/18 |
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@ Fix wrong/redundant locks in pre-vfs functions. |
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lock_kernel()/unlock_kernel() in pre_vfs_rename() were redundant for |
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2.6 kernels. |
| 1336 |
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Locking order in pre_vfs_link() and pre_vfs_unlink() for 2.4 kernels |
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after 2.4.33 were different from before 2.4.32 . |
| 1339 |
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Fix 2008/03/28 |
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@ Disable execute handler loop. |
| 1343 |
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To be able to use "execute_handler" in a "keep_domain" domain, |
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ignore "execute_handler" and "denied_execute_handler" keywords |
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if the current process is executing programs specified by |
| 1347 |
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"execute_handler" or "denied_execute_handler" keyword. |
| 1348 |
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| 1349 |
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This exception is needed to avoid infinite execute handler loop. |
| 1350 |
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If a domain has both "keep_domain" and "execute_handler", |
| 1351 |
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any execute request by that domain is handled by an execute handler, |
| 1352 |
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and the execute handler attempts to process original execute request. |
| 1353 |
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But the original execute request is handled by the same execute handler |
| 1354 |
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unless the execute handler ignores "execute_handler". |
| 1355 |
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| 1356 |
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@ Update coding style. |
| 1357 |
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| 1358 |
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I rewrote the code to pass scripts/checkpatch.pl as much as possible. |
| 1359 |
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Function names were changed to use only lower letters. |
| 1360 |
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| 1361 |
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Version 1.6.0 2008/04/01 Feature enhancement release. |
| 1362 |
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| 1363 |
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Fix 2008/04/14 |
| 1364 |
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@ Fix "Compilation failures" and "Initialization ordering bugs" |
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with kernels before 2.4.30/2.6.11 . |
| 1367 |
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2.6 kernels before 2.6.9 didn't have include/linux/hardirq.h , |
| 1369 |
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resulting compilation error at #include <linux/hardirq.h> . |
| 1370 |
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I added #elif condition. |
| 1371 |
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| 1372 |
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CentOS 4.6's 2.6.9 kernel calls do_execve() before initialization of |
| 1373 |
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ccs_alloc(), resulting NULL pointer dereference. |
| 1374 |
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I changed __initcall to core_initcall. |
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CentOS 4.6's 2.6.9 kernel backported kzalloc() from 2.6.14 , |
| 1377 |
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resulting compilation error at kzalloc(). |
| 1378 |
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I modified prototype of kzalloc(). |
| 1379 |
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Fix 2008/04/20 |
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@ Fix "Compilation failures" with kernels before 2.4.30/2.6.11 . |
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Turbolinux 10 Server's 2.6.8 kernel backported kzalloc() as an inlined |
| 1385 |
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function, resulting compilation error at kzalloc(). |
| 1386 |
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I converted kzalloc() from an inlined function into a macro. |
| 1387 |
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Fix 2008/04/21 |
| 1389 |
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@ Add workaround for gcc 3.2.2's inline bug. |
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RedHat Linux 9's gcc 3.2.2 generated a bad code |
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if ((var_of_u8 & 0x000000BF) & 0x80000000) { } |
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where the expected code is |
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if ((var_of_u8 & 0xBF) & 0x80) { } |
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when embedding ccs_acl_type2() into print_entry(), |
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resulting runtime BUG(). |
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I added the expected code explicitly as a workaround. |
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Fix 2008/04/25 |
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@ Return -ENOMEM when find_next_domain() failed to create a new domain. |
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1.5.x returns -ENOMEM when FindNextDomain() failed to create a new |
| 1405 |
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domain, but I forgot to return -ENOMEM when find_next_domain() |
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failed to create a new domain. |
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Version 1.6.1 2008/??/?? Environment dependent bug fix release. |
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