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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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| 1146 |
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| 1147 |
Fix 2008/02/05 |
Fix 2008/02/05 |
| 1148 |
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| 1149 |
@ Use find_task_by_vpid() instead of find_task_pid(). |
@ Use find_task_by_vpid() instead of find_task_by_pid(). |
| 1150 |
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| 1151 |
Kernel 2.6.24 introduced PID namespace. |
Kernel 2.6.24 introduced PID namespace. |
| 1152 |
To search PID given from userland, the kernel needs to use |
To search PID given from userland, the kernel needs to use |
| 1153 |
find_task_by_vpid() instead of find_task_pid(). |
find_task_by_vpid() instead of find_task_by_pid(). |
| 1154 |
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| 1155 |
Fix 2008/02/14 |
Fix 2008/02/14 |
| 1156 |
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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 |
| 1222 |
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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 |
| 1226 |
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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. |
| 1236 |
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| 1237 |
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This handler is triggered when a process requested to execute a program |
| 1238 |
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but the request was rejected by the policy. |
| 1239 |
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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. |
| 1241 |
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| 1242 |
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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 |
| 1244 |
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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. |
| 1246 |
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| 1247 |
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By default, this handler does nothing (i.e. merely reject execve() |
| 1248 |
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request). You can specify any program to start what you want to do. |
| 1249 |
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| 1250 |
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You can redirect attackers to somewhere else (e.g. honey pot). |
| 1251 |
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This makes it possible to act your Linux box as an on-demand honey pot |
| 1252 |
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while keeping regular services for your usage. |
| 1253 |
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| 1254 |
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You can collect information of the attacker (e.g. IP address) and |
| 1255 |
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update firewall configuration. |
| 1256 |
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| 1257 |
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You can silently terminate a process who requested execve() |
| 1258 |
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that is not permitted by policy. |
| 1259 |
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| 1260 |
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Fix 2008/03/03 |
| 1261 |
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| 1262 |
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@ Add "force_alt_exec" keyword. |
| 1263 |
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| 1264 |
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To be able to fully utilize "alt_exec" feature, |
| 1265 |
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I added "force_alt_exec" keyword so that |
| 1266 |
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all execute requests are replaced by the execute request of a program |
| 1267 |
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specified by alt_exec feature. |
| 1268 |
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| 1269 |
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If this keyword is specified for a domain, the domain no longer |
| 1270 |
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executes any programs regardless of the mode of file access control |
| 1271 |
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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 |
| 1273 |
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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. |
| 1275 |
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| 1276 |
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If you can tolerate that there is no chance to return an error code |
| 1277 |
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to the caller to tell the execute request was rejected, |
| 1278 |
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this is more flexible approach than in-kernel execve() parameter |
| 1279 |
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checking because we can do argv[] and envp[] checking easily. |
| 1280 |
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| 1281 |
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Fix 2008/03/04 |
| 1282 |
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| 1283 |
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@ Use string for access control mode. |
| 1284 |
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| 1285 |
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An integer expression for access control mode sometimes confuses |
| 1286 |
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administrators because profile number is also an integer expression. |
| 1287 |
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To avoid confusion between profile number and access control mode, |
| 1288 |
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I introduced a string expression for access control mode. |
| 1289 |
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| 1290 |
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Modes which take an integer between 0 and 3. |
| 1291 |
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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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| 1297 |
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Modes which take 0 or 1. |
| 1298 |
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0 -> disabled |
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1 -> enabled |
| 1301 |
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| 1302 |
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Fix 2008/03/10 |
| 1303 |
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| 1304 |
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@ Rename "force_alt_exec" keyword to "execute_handler". |
| 1305 |
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| 1306 |
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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 |
| 1308 |
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to domain policy. |
| 1309 |
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| 1310 |
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The "execute_handler" keyword takes one pathname which is |
| 1311 |
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invoked whenever execve() request is issued. Thus, any "allow_execute" |
| 1312 |
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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() |
| 1314 |
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requests in userspace, although there is no way to tell the caller |
| 1315 |
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that the execve() request was rejected. |
| 1316 |
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| 1317 |
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@ Rename "alt_exec" keyword to "denied_execute_handler". |
| 1318 |
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| 1319 |
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The "denied_execute_handler" keyword takes one pathname which is |
| 1320 |
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invoked only when execve() request was rejected. In other words, |
| 1321 |
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this program is invoked only when the following conditions are met. |
| 1322 |
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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. |
| 1326 |
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| 1327 |
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This keyword is designed for handling unexpected/undesirable execve() |
| 1328 |
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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 |
| 1331 |
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| 1332 |
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@ Fix wrong/redundant locks in pre-vfs functions. |
| 1333 |
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| 1334 |
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lock_kernel()/unlock_kernel() in pre_vfs_rename() were redundant for |
| 1335 |
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2.6 kernels. |
| 1336 |
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| 1337 |
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Locking order in pre_vfs_link() and pre_vfs_unlink() for 2.4 kernels |
| 1338 |
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after 2.4.33 were different from before 2.4.32 . |
| 1339 |
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| 1340 |
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Fix 2008/03/28 |
| 1341 |
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| 1342 |
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@ Disable execute handler loop. |
| 1343 |
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| 1344 |
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To be able to use "execute_handler" in a "keep_domain" domain, |
| 1345 |
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ignore "execute_handler" and "denied_execute_handler" keywords |
| 1346 |
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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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| 1365 |
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@ Fix "Compilation failures" and "Initialization ordering bugs" |
| 1366 |
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with kernels before 2.4.30/2.6.11 . |
| 1367 |
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| 1368 |
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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. |
| 1375 |
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| 1376 |
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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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| 1380 |
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Fix 2008/04/20 |
| 1381 |
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| 1382 |
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@ Fix "Compilation failures" with kernels before 2.4.30/2.6.11 . |
| 1383 |
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| 1384 |
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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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| 1388 |
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Fix 2008/04/21 |
| 1389 |
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| 1390 |
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@ Add workaround for gcc 3.2.2's inline bug. |
| 1391 |
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| 1392 |
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RedHat Linux 9's gcc 3.2.2 generated a bad code |
| 1393 |
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if ((var_of_u8 & 0x000000BF) & 0x80000000) { } |
| 1394 |
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where the expected code is |
| 1395 |
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if ((var_of_u8 & 0xBF) & 0x80) { } |
| 1396 |
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when embedding ccs_acl_type2() into print_entry(), |
| 1397 |
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resulting runtime BUG(). |
| 1398 |
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I added the expected code explicitly as a workaround. |
| 1399 |
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| 1400 |
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Fix 2008/05/06 |
| 1401 |
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| 1402 |
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@ Add memory quota. |
| 1403 |
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| 1404 |
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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() failed to |
| 1406 |
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create a new domain. |
| 1407 |
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| 1408 |
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A domain is automatically created by find_next_domain() only if |
| 1409 |
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the domain for the requested program doesn't exist. |
| 1410 |
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This behavior is for the administrator's convenience. |
| 1411 |
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The administrator needn't to know how many domains are needed for running |
| 1412 |
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the whole programs in the system beforehand when developing the policy. |
| 1413 |
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But the administrator does not want the kernel to reject execution of the |
| 1414 |
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requested program when developing the policy. |
| 1415 |
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| 1416 |
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So, I think it is better to grant execution of programs even if |
| 1417 |
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find_next_domain() failed to create a new domain than reject execution. |
| 1418 |
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Thus, I decided not to return -ENOMEM when find_next_domain() failed to |
| 1419 |
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create a new domain. This exception breaks the domain transition rules, |
| 1420 |
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so I print "transition_failed" warning in /proc/ccs/domain_policy |
| 1421 |
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when this exception happened. |
| 1422 |
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| 1423 |
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Also, to prevent the system from being halted by unexpectedly allocating |
| 1424 |
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all kernel memory for the policy, I added memory quota. |
| 1425 |
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This quota is configurable via /proc/ccs/meminfo like |
| 1426 |
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| 1427 |
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echo Shared: 1048576 > /proc/ccs/meminfo |
| 1428 |
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echo Private: 1048576 > /proc/ccs/meminfo |
| 1429 |
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| 1430 |
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Version 1.6.1 2008/05/10 Bug fix release. |
| 1431 |
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| 1432 |
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Fix 2008/06/04 |
| 1433 |
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| 1434 |
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@ Check open mode of /proc/ccs/ interface. |
| 1435 |
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| 1436 |
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It turned out that I can avoid allocating memory for reading if |
| 1437 |
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FMODE_READ is not set and memory for writing if FMODE_WRITE is not set. |
| 1438 |
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| 1439 |
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@ Wait for completion of /sbin/ccs-init . |
| 1440 |
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| 1441 |
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Since 2.4 kernel's call_usermodehelper() can't wait for termination of |
| 1442 |
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the executed program, I was using the close() request of |
| 1443 |
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/proc/ccs/meminfo to indicate that loading policy has finished. |
| 1444 |
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But since /proc/ccs/meminfo could be accessed for setting memory quota |
| 1445 |
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by /etc/ccs/ccs-post-init , I stopped using the close() request. |
| 1446 |
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The policy loader no longer need to access /proc/ccs/meminfo to notify |
| 1447 |
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the kernel that loading policy has finished. |
| 1448 |
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| 1449 |
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Fix 2008/06/05 |
| 1450 |
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| 1451 |
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@ Fix realpath for pipes and sockets. |
| 1452 |
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| 1453 |
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Kernel 2.6.22 and later use different method for calculating d_path(). |
| 1454 |
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Since fs/realpath.c didn't notice the change, the realpath of pipes |
| 1455 |
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appeared as "pipe:" rather than "pipe:[\$]" when they are opened via |
| 1456 |
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/proc/PID/fd/ directory. |
| 1457 |
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| 1458 |
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@ Add process's information into /proc/ccs/query . |
| 1459 |
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| 1460 |
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While /proc/ccs/grant_log and /proc/ccs/reject_log contain process's |
| 1461 |
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information, /proc/ccs/query doesn't contain it. |
| 1462 |
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To be able to utilize ccs-queryd and ccs-notifyd more, I added it into |
| 1463 |
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/proc/ccs/query . |
| 1464 |
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| 1465 |
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Fix 2008/06/10 |
| 1466 |
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| 1467 |
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@ Allow using patterns for globally readable files. |
| 1468 |
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| 1469 |
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To allow users specify locale specific files to globally readable files, |
| 1470 |
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I relaxed checking in update_globally_readable_entry(). |
| 1471 |
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| 1472 |
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@ Move ALLOW_ENFORCE_GRACE=enabled checking to write_answer(). |
| 1473 |
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| 1474 |
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To allow users use ccs-notifyd without turning ALLOW_ENFORCE_GRACE on, |
| 1475 |
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I moved it from ccs_check_supervisor() to write_answer(). |
| 1476 |
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| 1477 |
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Fix 2008/06/11 |
| 1478 |
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| 1479 |
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@ Remove ALLOW_ENFORCE_GRACE parameter. |
| 1480 |
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| 1481 |
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Since unexpected requests caused by doing software updates can happen |
| 1482 |
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in all profiles, users likely have to write ALLOW_ENFORCE_GRACE=enabled |
| 1483 |
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to all profiles. And it makes meaningless to allow users to selectively |
| 1484 |
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enable specific profile's ALLOW_ENFORCE_GRACE parameter. |
| 1485 |
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So, I removed ALLOW_ENFORCE_GRACE parameter. |
| 1486 |
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Now, the system behaves as if ALLOW_ENFORCE_GRACE=enabled is specified. |
| 1487 |
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The behavior of "delayed enforcing" mode is defined in the following |
| 1488 |
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order. |
| 1489 |
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| 1490 |
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(1) The requests are rejected immediately if nobody is opening |
| 1491 |
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/proc/ccs/query interface. |
| 1492 |
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(2) The requests will be rejected in 10 seconds if somebody other than |
| 1493 |
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ccs-queryd (such as less(1)) is opening /proc/ccs/query interface, |
| 1494 |
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for such process doesn't write dummy decisions. |
| 1495 |
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| 1496 |
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Fix 2008/06/22 |
| 1497 |
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| 1498 |
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@ Pass escaped pathname to audit_execute_handler_log(). |
| 1499 |
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| 1500 |
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I was passing unescaped pathname to audit_execute_handler_log() |
| 1501 |
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which causes /proc/ccs/grant_log contain whitespace characters |
| 1502 |
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if execute handler's pathname contains whitespace characters. |
| 1503 |
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|
| 1504 |
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Version 1.6.2 2008/??/?? Usability enhancement release. |
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