Info: Version 1.3 is available.
Last modified: $Date: 2011-11-20 09:56:56 +0900 (Sun, 20 Nov 2011) $
There are no limitations for distributions. But since it is impossible to cover all distributions, this manual covers "RedHat Linux 9", "Fedora Core 3" and "Debian Sarge".
The size of policy files gets smaller by uninstalling unnecessary applications. You should know what application you want to run on the system.
To compile kernel, see TOMOYO Linux kernel compilation.
To compile tools, run the following commands.
cd /root/ # Download source of tools for TOMOYO Linux. wget -O ccs-tools-1.2-20060903.tar.gz 'http://sourceforge.jp/frs/redir.php?m=jaist&f=/tomoyo/21579/ccs-tools-1.2-20060903.tar.gz' # Extract. tar -zxf ccs-tools-1.2-20060903.tar.gz # Compile. make -sC ccstools/ |
Boot with TOMOYO Linux kernel, and check the system works properly.
After you confirmed the system works properly, save the content of /proc/ccs/status as /root/security/status.txt . This file contains the topics controllable for this kernel. This file is used as a hint when creating profiles (described later).
mkdir -p /root/security cat /proc/ccs/status > /root/security/status.txt |
Please use normal kernel for operations in this chapter.
If you use TOMOYO Linux's kernel, /root/ccstools/savepolicy will be executed on shutdown and modifications you made on /root/security/exception_policy.txt will be lost.
TOMOYO Linux doesn't have default policy files distributed with softwares. Administrators need to create policy files using "accept mode".
The example policies are available to help your understanding. You may use these examples as a guide, but you MUST NOT use these examples as default policies.
Create /root/security/manager.txt and list up programs that are allowed to update policies via /proc/ccs/ interface.
Specifically, "loadpolicy" that reloads policy, "editpolicy" that edits policy, "setlevel" that changes control level, "ld-watch" that updates globally readable files, "ccs-queryd" that grants access requests interactively.
cat > /root/security/manager.txt << EOF /root/ccstools/loadpolicy /root/ccstools/editpolicy /root/ccstools/setlevel /root/ccstools/ld-watch /root/ccstools/ccs-queryd EOF |
To save on-memory policies onto disk just before power off, modify the shutdown script to run /root/ccstools/savepolicy . Actual locations to modify depends on distributions. In many cases, since the final program invoked in the shutdown script under /etc/init.d/ directory is the program to power off, save on-memory policies just before the invocation of the program.
If you are using RedHat Linux 9 or Fedora Core 3, modify as follows.
/etc/rc.d/init.d/halt | |
Before | After |
exec $command $HALTARGS |
/root/ccstools/savepolicy exec $command $HALTARGS |
If you are using Debian Sarge, modify as follows. To create and include domains for executing halt/reboot among the domain policy, run halt/reboot once before invoking savepolicy.
/etc/init.d/halt | /etc/init.d/reboot | ||
Before | After | Before | After |
halt -d -f -i $poweroff $hddown |
halt --help 2> /dev/null /root/ccstools/savepolicy halt -d -f -i $poweroff $hddown |
reboot -d -f -i |
reboot --help 2> /dev/null /root/ccstools/savepolicy reboot -d -f -i |
TOMOYO Linux can perform several MACs besides MAC for files, but to reduce the load of policy managements, you can disable MACs you think unnecessary.
You can switch the MACs and their initial control status by creating several profiles and specifying the profile index number at kernel command line. Specifically, the parameter CCS=$INDEX (where $INDEX is an integer) given in the kernel command line corresponds to the profile /root/security/profile$INDEX.txt to use.
Refer the descriptions below and create profiles for "accept mode", "permissive mode", "enforce mode". Only topics included in /root/security/status.txt are configurable. The topics included in /root/security/status.txt vary depending on the kernel configuration.
Name | Control | Accept mode supported |
MAC_FOR_FILE | File Access | Yes |
MAX_ACCEPT_FILES | Limits the max number of file ACL entries that are automatically appended during accept mode | - |
MAX_GRANT_LOG | Limits the max number of grant logs that the kernel can hold | - |
MAX_REJECT_LOG | Limits the max number of reject logs that the kernel can hold | - |
TOMOYO_VERBOSE | Dump domain policy violation messages to syslog | - |
MAX_ENFORCE_GRACE | Wait before rejecting access request when the request violates policy in enforce mode | - |
You can give the following values for MAX_ACCEPT_FILES
Value | Meaning |
any integer | The max number of file ACL entries that are automatically appended during accept mode. The default is given at the kernel compilation time. |
You can give the following values for MAX_GRANT_LOG and MAX_REJECT_LOG
Value | Meaning |
any integer | The max number of logs that the kernel can hold. The default is given at the kernel compilation time. You may give 0 if you don't need logs. |
You can give the following values for TOMOYO_VERBOSE
Value | Meaning |
0 | Don't dump domain policy violation messages. |
1 | Dump domain policy violation messages. |
You can give the following values for MAX_ENFORCE_GRACE
Value | Meaning |
any integer | The max grace time in seconds. If the administrator tells the kernel not to reject the request that violated policy in enforce mode, the request will be granted. |
You can give the following values for all but listed above.
Value | Meaning |
0 | Disabled. Works as if regular kernel. |
1 | Accept mode. Not rejected if the request violates policy. Automatically appended to policy. |
2 | Permissive mode. Not rejected if the request violates policy. Not appended to policy automatically. |
3 | Enforce mode. Rejected if the request violates policy. |
Register pathnames with patterns that likely exists on all Linux systems.
Register pathnames with patterns using the "file_pattern" directive in /root/security/exception_policy.txt .
When a file operation are performed and the requested pathname matches to a patterned pathname registered with "file_pattern" directive, policy is generated using patterned pathnames.
The following is the guideline.
TOMOYO Linux needs more patterned pathnames depending on the applications installed and their configurations. You can add missing patterned pathnames after running the system.
Register files that are allowed to be read by all programs.
Register pathnames using the "allow_read" directive in /root/security/exception_policy.txt . No patterns allowed.
When a read access is requested and the requested pathname matches to a pathname registered with "allow_read" directive, the read access is granted without checking domain policy.
The following is the guideline.
Register programs that initializes the domain transition history.
Register programs using the "initializer" directive in /root/security/exception_policy.txt . No patterns allowed.
When a program that is registered with "initializer" directive is executed, the program runs just under the <kernel> domain.
The following is the guideline.
Since it is impossible to append to policy automatically for programs that triggers power failure, specify domains that are used by such programs as trusted.
Actual program that involves power failure depends on distributions. In many cases, the final command invoked by shutdown scripts located under /etc/init.d/ directory is the program to trigger power failure.
A shell script is included that performs the operations described above. Create /root/security/exception_policy.txt based on the candidates shown by executing /root/ccstools/make_exception.sh . You have to review the content of the file because automatically generated file may contain redundant or dangerous entries.
Register domain for /usr/sbin/logrotate as "initializer" in the exception policy because you run logrotate from the command line (not from cron) to learn necessary permissions.
initializer /usr/sbin/logrotate |
Jobs that read/write so many programs could be removed from cron jobs.
For example, /etc/cron.daily/prelink for Fedora Core 3 and later reads/writes many programs, and this makes policy files larger. Moreover, it is not desirable to allow read/write permissions to executable files.
I think that it is enough executing /usr/sbin/prelink once after updating packages from the trusted domain, without executing /usr/sbin/prelink everyday from cron. Therefore, you can remove from cron jobs as follows.
mv /etc/cron.daily/prelink /usr/sbin/prelink.cron |
Register domain for /usr/sbin/anacron as "initializer" in the exception policy because you run anacron from the command line to learn necessary permissions.
initializer /usr/sbin/anacron |
Register domain for /usr/bin/run-parts as "initializer" in the exception policy because anacron runs /usr/bin/run-parts .
initializer /usr/bin/run-parts |
Register domain for /usr/bin/run-parts as "initializer" in the exception policy because cron runs /usr/bin/run-parts .
initializer /usr/bin/run-parts |
Open /etc/crontab and modify to run cron jobs for 5 minutes interval. 1 minute interval is too short to finish previous cron job, therefore you need to make appropriate interval.
Before | After |
SHELL=/bin/bash PATH=/sbin:/bin:/usr/sbin:/usr/bin MAILTO=root HOME=/ # run-parts 01 * * * * root run-parts /etc/cron.hourly 02 4 * * * root run-parts /etc/cron.daily 22 4 * * 0 root run-parts /etc/cron.weekly 42 4 1 * * root run-parts /etc/cron.monthly |
SHELL=/bin/bash PATH=/sbin:/bin:/usr/sbin:/usr/bin MAILTO=root HOME=/ # run-parts */5 * * * * root run-parts /etc/cron.hourly */5 * * * * root run-parts /etc/cron.daily */5 * * * * root run-parts /etc/cron.weekly */5 * * * * root run-parts /etc/cron.monthly |
Be sure to undo /etc/crontab after you have finished generating policies.
The /root/security/exception_policy.txt generated by the procedure above is for "Strict Policy". If you want to use TOMOYO Linux for "Targeted Policy", modify /root/security/exception_policy.txt in the following way.
Add the following 3 lines. If /sbin/modprobe and/or /sbin/hotplug are symbolic links, give the dereferenced pathnames.
trust_domain <kernel> /sbin/init trust_domain <kernel> /sbin/modprobe trust_domain <kernel> /sbin/hotplug |
Exclude lines that begins with "initializer" directive and that you want to disable Mandatory Access Controls on the program specified with "initializer" directive. For example, if you want to enable Mandatory Access Controls on /usr/sbin/httpd and programs invoked by /usr/sbin/httpd , remove all lines that starts with "initializer" directive but the following 3 lines.
initializer /usr/sbin/httpd initializer /sbin/modprobe initializer /sbin/hotplug |
By these steps, /usr/sbin/httpd and programs invoked by /usr/sbin/httpd run in the "<kernel> /usr/sbin/httpd" domain and its child domains and are protected by Mandatory Access Controls. Other programs run in one of the "<kernel> /sbin/init" "<kernel> /sbin/modprobe" "<kernel> /sbin/hotplug" domain and are not protected by Mandatory Access Controls.
Boot with TOMOYO Linux kernel with the profile number for accept mode to CCS= parameter. Give the parameter "TOMOYO_NOLOAD" to the kernel command line for the first time to skip reading domain policy. If the parameter "TOMOYO_NOLOAD" is given, the domain policy file (domain_policy.txt) won't get loaded. (Therefore, choose TOMOYO Linux kernel with TOMOYO_NOLOAD parameter and the profile number for accept mode to CCS= parameter.)
Do a series of operations you want to allow.
Repeat several times, for all access patterns may not be recorded by single operations.
Also, there are operations that are done only startup and shutdown, repeat reboot for several times.
When you are running with accept mode, you may find messages in the following format.
TOMOYO-WARNING: Domain '<kernel> ...' has so many ACLs to hold. Stopped auto-append mode. |
This message tells you that the safeguard for this program is activated to prevent memory consumption and dull response since this program accessed so many files. When the safeguard is activated, file ACLs for that domain are no longer appended automatically.
To deal with this message, you need to edit ACLs manually.
For example, if the following message appeared, you need to reduce the number of file ACLs for <kernel> /usr/sbin/hald using appropriate pathname patterns.
TOMOYO-WARNING: Domain '<kernel> /usr/sbin/hald' has so many ACLs to hold. Stopped auto-append mode. |
You can edit policies using /root/ccstools/editpolicy .
Run logrotate from the command line to learn necessary permissions. To run logrotate jobs regardless of the system clock, use -f option.
/usr/sbin/logrotate -f /etc/logrotate.conf |
Repeat several times, for all access patterns may not be recorded by single operations.
Run anacron from the command line to learn necessary permissions. To run anacron jobs regardless of the system clock, use -d -f -n options.
anacron -dfn |
Repeat several times, for all access patterns may not be recorded by single operations.
Reboot with normal kernel.
Run the following command to find pathnames that are likely temporary, and make appropriate patterns and register in /root/security/exception_policy.txt using "file_pattern" directive.
/root/ccstools/findtemp < /root/security/domain_policy.txt | sort | uniq |
Guidelines for temporary pathnames are "Multiple pathnames that differs only last 6 letters", "Multiple pathnames that differs only numerical part" and so on.
An example of patterned pathnames is shown below. These patterned pathnames may not exist or exist in other location depending on the applications installed and their configurations.
Add "initializer" and "allow_read" if you want to add.
Add "trust_domain" if you want some domains for (for example) maintenances.
If you are sure you found all patterns, recreate the domain policy from the beginning. Give the parameter "TOMOYO_NOLOAD" to the kernel command line for the first time to skip reading domain policy.
Reboot with normal Linux kernel.
Append access permissions for files that are not necessarily accessed in the accept mode such as WWW contents for WWW service to /root/security/domain_policy.txt .
The following example allows /usr/sbin/httpd to read files in the /var/www/html/ directory.
<kernel> /usr/sbin/httpd 4 /var/www/html/\* 4 /var/www/html/\*/\* 4 /var/www/html/\*/\*/\* 4 /var/www/html/\*/\*/\*/\* 4 /var/www/html/\*/\*/\*/\*/\* |
In the same way, modify access permissions for files using patterns that should be grouped. The following example shows /usr/sbin/smbd should handle all log files equally.
Before | After |
<kernel> /usr/sbin/smbd 2 /var/log/samba/host1.log 2 /var/log/samba/host2.log 2 /var/log/samba/host3.log 2 /var/log/samba/host4.log 2 /var/log/samba/host5.log |
<kernel> /usr/sbin/smbd 2 /var/log/samba/\*.log |
TOMOYO Linux 1.2 supports conditional ACLs. By using this feature, you can control system's user ID based access control.
If you want to protect non-anonymous FTP service, by adding conditions in the following manner, you can forbid access to directories outside the user's home directory. To reduce damages when it is cracked, it is recommended that you should expose directories only under specific (such as "ftp") directory rather than exposing whole of home directories. If you use vsftpd, you can give like the following way.
Before |
<kernel> /usr/sbin/vsftpd 6 /home/\*/ftp/\* 6 /home/\*/ftp/\*/\* 6 /home/\*/ftp/\*/\*/\* 6 /home/\*/ftp/\*/\*/\*/\* allow_mkdir /home/\*/ftp/\*/ allow_mkdir /home/\*/ftp/\*/\*/ allow_mkdir /home/\*/ftp/\*/\*/\*/ allow_rmdir /home/\*/ftp/\*/ allow_rmdir /home/\*/ftp/\*/\*/ allow_rmdir /home/\*/ftp/\*/\*/\*/ allow_create /home/\*/ftp/\* allow_create /home/\*/ftp/\*/\* allow_create /home/\*/ftp/\*/\*/\* allow_create /home/\*/ftp/\*/\*/\*/\* allow_truncate /home/\*/ftp/\* allow_truncate /home/\*/ftp/\*/\* allow_truncate /home/\*/ftp/\*/\*/\* allow_truncate /home/\*/ftp/\*/\*/\*/\* allow_unlink /home/\*/ftp/\* allow_unlink /home/\*/ftp/\*/\* allow_unlink /home/\*/ftp/\*/\*/\* allow_unlink /home/\*/ftp/\*/\*/\*/\* allow_rename /home/\*/ftp/\* /home/\*/ftp/\* allow_rename /home/\*/ftp/\*/\* /home/\*/ftp/\*/\* allow_rename /home/\*/ftp/\*/\*/\* /home/\*/ftp/\*/\*/\* allow_rename /home/\*/ftp/\*/\*/\*/\* /home/\*/ftp/\*/\*/\*/\* allow_rename /home/\*/ftp/\*/ /home/\*/ftp/\*/ allow_rename /home/\*/ftp/\*/\*/ /home/\*/ftp/\*/\*/ allow_rename /home/\*/ftp/\*/\*/\*/ /home/\*/ftp/\*/\*/\*/ |
After |
<kernel> /usr/sbin/vsftpd 6 /home/\*/ftp/\* if task.uid=path1.uid 6 /home/\*/ftp/\*/\* if task.uid=path1.uid 6 /home/\*/ftp/\*/\*/\* if task.uid=path1.uid 6 /home/\*/ftp/\*/\*/\*/\* if task.uid=path1.uid allow_mkdir /home/\*/ftp/\*/ if task.uid=path1.parent.uid allow_mkdir /home/\*/ftp/\*/\*/ if task.uid=path1.parent.uid allow_mkdir /home/\*/ftp/\*/\*/\*/ if task.uid=path1.parent.uid allow_rmdir /home/\*/ftp/\*/ if task.uid=path1.uid allow_rmdir /home/\*/ftp/\*/\*/ if task.uid=path1.uid allow_rmdir /home/\*/ftp/\*/\*/\*/ if task.uid=path1.uid allow_create /home/\*/ftp/\* if task.uid=path1.parent.uid allow_create /home/\*/ftp/\*/\* if task.uid=path1.parent.uid allow_create /home/\*/ftp/\*/\*/\* if task.uid=path1.parent.uid allow_create /home/\*/ftp/\*/\*/\*/\* if task.uid=path1.parent.uid allow_truncate /home/\*/ftp/\* if task.uid=path1.uid allow_truncate /home/\*/ftp/\*/\* if task.uid=path1.uid allow_truncate /home/\*/ftp/\*/\*/\* if task.uid=path1.uid allow_truncate /home/\*/ftp/\*/\*/\*/\* if task.uid=path1.uid allow_unlink /home/\*/ftp/\* if task.uid=path1.uid allow_unlink /home/\*/ftp/\*/\* if task.uid=path1.uid allow_unlink /home/\*/ftp/\*/\*/\* if task.uid=path1.uid allow_unlink /home/\*/ftp/\*/\*/\*/\* if task.uid=path1.uid allow_rename /home/\*/ftp/\* /home/\*/ftp/\* if task.uid=path1.parent.uid task.uid=path2.parent.uid allow_rename /home/\*/ftp/\*/\* /home/\*/ftp/\*/\* if task.uid=path1.parent.uid task.uid=path2.parent.uid allow_rename /home/\*/ftp/\*/\*/\* /home/\*/ftp/\*/\*/\* if task.uid=path1.parent.uid task.uid=path2.parent.uid allow_rename /home/\*/ftp/\*/\*/\*/\* /home/\*/ftp/\*/\*/\*/\* if task.uid=path1.parent.uid task.uid=path2.parent.uid allow_rename /home/\*/ftp/\*/ /home/\*/ftp/\*/ if task.uid=path1.parent.uid task.uid=path2.parent.uid allow_rename /home/\*/ftp/\*/\*/ /home/\*/ftp/\*/\*/ if task.uid=path1.parent.uid task.uid=path2.parent.uid allow_rename /home/\*/ftp/\*/\*/\*/ /home/\*/ftp/\*/\*/\*/ if task.uid=path1.parent.uid task.uid=path2.parent.uid |
If you want to protect Samba service, by adding conditions in the following manner, you can forbid access to directories outside the user's home directory. To reduce damages when it is cracked, it is recommended that you should expose directories only under specific (such as "samba") directory rather than exposing whole of home directories.
Before |
<kernel> /usr/sbin/smbd 6 /home/\*/samba/\* 6 /home/\*/samba/\*/\* 6 /home/\*/samba/\*/\*/\* 6 /home/\*/samba/\*/\*/\*/\* allow_mkdir /home/\*/samba/\*/ allow_mkdir /home/\*/samba/\*/\*/ allow_mkdir /home/\*/samba/\*/\*/\*/ allow_rmdir /home/\*/samba/\*/ allow_rmdir /home/\*/samba/\*/\*/ allow_rmdir /home/\*/samba/\*/\*/\*/ allow_create /home/\*/samba/\* allow_create /home/\*/samba/\*/\* allow_create /home/\*/samba/\*/\*/\* allow_create /home/\*/samba/\*/\*/\*/\* allow_truncate /home/\*/samba/\* allow_truncate /home/\*/samba/\*/\* allow_truncate /home/\*/samba/\*/\*/\* allow_truncate /home/\*/samba/\*/\*/\*/\* allow_unlink /home/\*/samba/\* allow_unlink /home/\*/samba/\*/\* allow_unlink /home/\*/samba/\*/\*/\* allow_unlink /home/\*/samba/\*/\*/\*/\* allow_rename /home/\*/samba/\* /home/\*/samba/\* allow_rename /home/\*/samba/\*/\* /home/\*/samba/\*/\* allow_rename /home/\*/samba/\*/\*/\* /home/\*/samba/\*/\*/\* allow_rename /home/\*/samba/\*/\*/\*/\* /home/\*/samba/\*/\*/\*/\* allow_rename /home/\*/samba/\*/ /home/\*/samba/\*/ allow_rename /home/\*/samba/\*/\*/ /home/\*/samba/\*/\*/ allow_rename /home/\*/samba/\*/\*/\*/ /home/\*/samba/\*/\*/\*/ |
After |
<kernel> /usr/sbin/smbd 6 /home/\*/samba/\* if task.euid=path1.uid 6 /home/\*/samba/\*/\* if task.euid=path1.uid 6 /home/\*/samba/\*/\*/\* if task.euid=path1.uid 6 /home/\*/samba/\*/\*/\*/\* if task.euid=path1.uid allow_mkdir /home/\*/samba/\*/ if task.euid=path1.parent.uid allow_mkdir /home/\*/samba/\*/\*/ if task.euid=path1.parent.uid allow_mkdir /home/\*/samba/\*/\*/\*/ if task.euid=path1.parent.uid allow_rmdir /home/\*/samba/\*/ if task.euid=path1.uid allow_rmdir /home/\*/samba/\*/\*/ if task.euid=path1.uid allow_rmdir /home/\*/samba/\*/\*/\*/ if task.euid=path1.uid allow_create /home/\*/samba/\* if task.euid=path1.parent.uid allow_create /home/\*/samba/\*/\* if task.euid=path1.parent.uid allow_create /home/\*/samba/\*/\*/\* if task.euid=path1.parent.uid allow_create /home/\*/samba/\*/\*/\*/\* if task.euid=path1.parent.uid allow_truncate /home/\*/samba/\* if task.euid=path1.uid allow_truncate /home/\*/samba/\*/\* if task.euid=path1.uid allow_truncate /home/\*/samba/\*/\*/\* if task.euid=path1.uid allow_truncate /home/\*/samba/\*/\*/\*/\* if task.euid=path1.uid allow_unlink /home/\*/samba/\* if task.euid=path1.uid allow_unlink /home/\*/samba/\*/\* if task.euid=path1.uid allow_unlink /home/\*/samba/\*/\*/\* if task.euid=path1.uid allow_unlink /home/\*/samba/\*/\*/\*/\* if task.euid=path1.uid allow_rename /home/\*/samba/\* /home/\*/samba/\* if task.euid=path1.parent.uid task.euid=path2.parent.uid allow_rename /home/\*/samba/\*/\* /home/\*/samba/\*/\* if task.euid=path1.parent.uid task.euid=path2.parent.uid allow_rename /home/\*/samba/\*/\*/\* /home/\*/samba/\*/\*/\* if task.euid=path1.parent.uid task.euid=path2.parent.uid allow_rename /home/\*/samba/\*/\*/\*/\* /home/\*/samba/\*/\*/\*/\* if task.euid=path1.parent.uid task.euid=path2.parent.uid allow_rename /home/\*/samba/\*/ /home/\*/samba/\*/ if task.euid=path1.parent.uid task.euid=path2.parent.uid allow_rename /home/\*/samba/\*/\*/ /home/\*/samba/\*/\*/ if task.euid=path1.parent.uid task.euid=path2.parent.uid allow_rename /home/\*/samba/\*/\*/\*/ /home/\*/samba/\*/\*/\*/ if task.euid=path1.parent.uid task.euid=path2.parent.uid |
If you want to protect SSH service, by adding conditions in the following manner, you can forbid login as user "root".
Before | After |
<kernel> /usr/sbin/sshd 1 /bin/bash |
<kernel> /usr/sbin/sshd 1 /bin/bash if task.uid!=0 task.euid!=0 |
See Conditional permission for available conditions.
Boot with TOMOYO Linux kernel with the profile number for permissive mode to CCS= parameter.
Check that error messages don't appear when you operate you want to allow.
If the system works properly, the installation of TOMOYO Linux is done.
Boot with TOMOYO Linux kernel with the profile number for enforce mode to CCS= parameter.