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Notes for TOMOYO Linux project |
Notes for TOMOYO Linux project |
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| 3 |
This is a handy Mandatory Access Control patch for Linux kernels. |
This is a handy Mandatory Access Control patch for Linux kernels. |
| 4 |
This patch is released under the GPL. |
This patch is released under the GPLv2. |
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| 6 |
Project URL: http://tomoyo.sourceforge.jp/ |
Project URL: http://tomoyo.sourceforge.jp/ |
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| 933 |
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| 934 |
@ Fix ReadAddressGroupPolicy() bug. |
@ Fix ReadAddressGroupPolicy() bug. |
| 935 |
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| 936 |
ReadAddressGroupPolicy() fails if both "path_group" and "address_group" are used |
ReadAddressGroupPolicy() fails if both "path_group" and "address_group" |
| 937 |
because I forgot to set "head->read_var1 = NULL". |
are used because I forgot to set "head->read_var1 = NULL". |
| 938 |
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| 939 |
Fix 2007/07/10 |
Fix 2007/07/10 |
| 940 |
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| 949 |
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| 950 |
@ Remove mount-flags manipulation. |
@ Remove mount-flags manipulation. |
| 951 |
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| 952 |
Until now, administrator is permitted to turn on/off specific mount options |
Until now, administrator is permitted to turn on/off specific mount |
| 953 |
regardless of mount options passed to kernel. |
options regardless of mount options passed to kernel. |
| 954 |
I removed this feature because "exact option matching" sounds better than |
I removed this feature because "exact option matching" sounds better than |
| 955 |
"automatic option enabler/disabler". |
"automatic option enabler/disabler". |
| 956 |
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| 957 |
@ Remove /proc/ccs/info/mapping . |
@ Remove /proc/ccs/info/mapping . |
| 958 |
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| 959 |
I removed /proc/ccs/info/mapping because nobody seems to use this feature. |
I removed /proc/ccs/info/mapping because nobody seems to use this |
| 960 |
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feature. |
| 961 |
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| 962 |
@ Call external policy loader automatically. |
@ Call external policy loader automatically. |
| 963 |
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| 981 |
can handle interactive operations by opening /dev/console . |
can handle interactive operations by opening /dev/console . |
| 982 |
Now, there is no difference between init=/sbin/ccs-init and |
Now, there is no difference between init=/sbin/ccs-init and |
| 983 |
call_usermodehelper("/sbin/ccs-init"), and users no longer need to |
call_usermodehelper("/sbin/ccs-init"), and users no longer need to |
| 984 |
add init=/sbin/ccs-init parameter to load policy before /sbin/init starts. |
add init=/sbin/ccs-init parameter to load policy before /sbin/init |
| 985 |
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starts. |
| 986 |
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| 987 |
Fix 2007/08/14 |
Fix 2007/08/14 |
| 988 |
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| 1103 |
To my surprise, "mount --bind source dest" accepts |
To my surprise, "mount --bind source dest" accepts |
| 1104 |
not only "both source and dest are directory" |
not only "both source and dest are directory" |
| 1105 |
but also "both source and dest are non-directory". |
but also "both source and dest are non-directory". |
| 1106 |
I was rejecting if dest is not a derectory in AddMountACL(). |
I was rejecting if dest is not a directory in AddMountACL(). |
| 1107 |
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| 1108 |
@ Change log format. |
@ Change log format. |
| 1109 |
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| 1110 |
Profile number and mode is added in audit logs. |
Profile number and mode is added in audit logs. |
| 1111 |
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| 1112 |
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Fix 2008/01/03 |
| 1113 |
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| 1114 |
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@ Change directive for file's read/write/execute permission. |
| 1115 |
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| 1116 |
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Directives for file's read/write/execute permissions were |
| 1117 |
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4/2/1 respectively. But for easier understanding, they are now |
| 1118 |
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replaced by read/write/execute (e.g. "allow_read" instead of "4"). |
| 1119 |
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But for easier inputting, 4/2/1 are still accepted instead of |
| 1120 |
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allow_read/allow_write/allow_execute respectively. |
| 1121 |
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| 1122 |
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@ Change internal data structure. |
| 1123 |
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| 1124 |
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Since I don't have more than 16 types of file permissions, |
| 1125 |
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I combined them using bit-fields. |
| 1126 |
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| 1127 |
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Each entry had a field for conditional permission support. |
| 1128 |
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But since this field is unlikely used, I separated the field from |
| 1129 |
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common part. |
| 1130 |
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| 1131 |
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These changes will reduce memory used by policy. |
| 1132 |
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| 1133 |
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Fix 2008/01/15 |
| 1134 |
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| 1135 |
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@ Add ptrace() hook. |
| 1136 |
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| 1137 |
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To prevent attackers from controlling important processes using |
| 1138 |
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ptrace(), I added a hook for ptrace(). |
| 1139 |
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Most programs (except strace(1) and gdb(1)) won't use ptrace(2). |
| 1140 |
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| 1141 |
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@ Fix sleep condition check in CheckSocketRecvDatagramPermission(). |
| 1142 |
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| 1143 |
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It seems that correct method to use is in_atomic() |
| 1144 |
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rather than in_interrupt() because in_atomic() returns nonzero |
| 1145 |
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whenever scheduling is not allowed. |
| 1146 |
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| 1147 |
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Fix 2008/02/05 |
| 1148 |
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| 1149 |
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@ Use find_task_by_vpid() instead of find_task_pid(). |
| 1150 |
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| 1151 |
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Kernel 2.6.24 introduced PID namespace. |
| 1152 |
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To search PID given from userland, the kernel needs to use |
| 1153 |
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find_task_by_vpid() instead of find_task_pid(). |
| 1154 |
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| 1155 |
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Fix 2008/02/14 |
| 1156 |
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| 1157 |
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@ Add execve() parameter checking. |
| 1158 |
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| 1159 |
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Until now, it was impossible to check argv[] and envp[] parameters |
| 1160 |
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passed to execve(). |
| 1161 |
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I expanded conditional permission syntax so that |
| 1162 |
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{ argc, envc, argv[] , envp[] } parameters can be checked if needed. |
| 1163 |
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This will allow administrator permit execution of /bin/sh only when |
| 1164 |
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/bin/sh is invoked in the form of "/bin/sh -c" and environment variable |
| 1165 |
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HOME is set by specifying |
| 1166 |
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| 1167 |
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allow_execute /bin/sh if exec.argv[1]="-c" exec.envp["HOME"]!=NULL |
| 1168 |
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| 1169 |
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in the policy. |
| 1170 |
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This extension will make exploit codes difficult to start /bin/sh because |
| 1171 |
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they unlikely set up environment variables and unlikely specify "-c" |
| 1172 |
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option when invoking /bin/sh , whereas proper functions likely set up |
| 1173 |
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environment variables and likely specify "-c" option. |
| 1174 |
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| 1175 |
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Fix 2008/02/18 |
| 1176 |
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| 1177 |
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@ Add process state checking. |
| 1178 |
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| 1179 |
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Until now, it was impossible to change ACL without executing program. |
| 1180 |
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I added three variables for performing stateful checking within a domain. |
| 1181 |
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You can set current process's state like: |
| 1182 |
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| 1183 |
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allow_network TCP accept @TRUSTED_HOSTS 1024-65535 ; set task.state[0]=1 |
| 1184 |
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allow_network TCP accept @UNTRUSTED_HOSTS 1024-65535 ; set task.state[0]=0 |
| 1185 |
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| 1186 |
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and you can use the state like |
| 1187 |
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| 1188 |
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allow_read /path/to/important/file if task.state[0]=1 |
| 1189 |
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| 1190 |
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in the policy. |
| 1191 |
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The state changes when the request was granted by the MAC's policy, |
| 1192 |
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so please be careful with situations where the state has changed |
| 1193 |
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successfully but the request was not processed because of other reasons |
| 1194 |
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(e.g. out of memory). |
| 1195 |
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| 1196 |
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Fix 2008/02/26 |
| 1197 |
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| 1198 |
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@ Support /proc/ccs/ access by non-root user. |
| 1199 |
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| 1200 |
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Until now, only root user can access /proc/ccs/ interface. |
| 1201 |
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But to permit /proc/ccs/ access by non-root user so that it won't require |
| 1202 |
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ssh login by root user when administrating from remote host, |
| 1203 |
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I made "(current->uid == 0 && current->euid == 0)" requirement optional. |
| 1204 |
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If this requirement is disabled, only "conventional DAC permission |
| 1205 |
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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 |
| 1274 |
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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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| 1292 |
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0 -> disabled |
| 1293 |
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1 -> learning |
| 1294 |
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2 -> permissive |
| 1295 |
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3 -> enforcing |
| 1296 |
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| 1297 |
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Modes which take 0 or 1. |
| 1298 |
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| 1299 |
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0 -> disabled |
| 1300 |
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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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| 1323 |
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(1) None of "allow_execute" keywords in the domain matched. |
| 1324 |
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(2) The execve() request was rejected in enforcing mode. |
| 1325 |
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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/?? Bug fix release. |
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