--- trunk/1.6.x/ccs-patch/README.ccs 2008/02/26 08:37:13 1006 +++ trunk/1.6.x/ccs-patch/README.ccs 2008/05/09 03:14:27 1194 @@ -1,7 +1,7 @@ Notes for TOMOYO Linux project This is a handy Mandatory Access Control patch for Linux kernels. -This patch is released under the GPL. +This patch is released under the GPLv2. Project URL: http://tomoyo.sourceforge.jp/ @@ -1146,11 +1146,11 @@ Fix 2008/02/05 - @ Use find_task_by_vpid() instead of find_task_pid(). + @ Use find_task_by_vpid() instead of find_task_by_pid(). Kernel 2.6.24 introduced PID namespace. To search PID given from userland, the kernel needs to use - find_task_by_vpid() instead of find_task_pid(). + find_task_by_vpid() instead of find_task_by_pid(). Fix 2008/02/14 @@ -1203,3 +1203,228 @@ I made "(current->uid == 0 && current->euid == 0)" requirement optional. If this requirement is disabled, only "conventional DAC permission checks" and "/proc/ccs/manager checks" are used. + +Fix 2008/02/29 + + @ Add sleep_on_violation feature. + + Some exploit codes (e.g. trans2open for Samba) continue running + until it achieves the purpose of the exploit code (e.g. invoke /bin/sh). + + If such code is injected due to buffer overflow but the kernel + rejects the request, it triggers infinite "Permission denied" loop. + As a result, the CPU usage becomes 100% and gives bad effects to + the rest of processes. + This is a side effect of rejecting the request from the exploit code + which wouldn't happen if the request from the exploit code was granted. + + To avoid such CPU consumption, I added a penalty that forcibly + sleeps for specified period when a request is rejected. + + This penalty doesn't work if the exploit code does nothing but + continue running, but I think most exploit code's purpose is + to start some program rather than to slow down the target system. + + @ Add alt_exec feature. + + Since TOMOYO Linux's approach is "know all essential requests in advance + and create policy that permits only them", you can regard anomalous + requests as attacks (if you want to do so). + + Common MAC implementations merely reject requests that violate policy. + But I added a special handler for execve() to TOMOYO Linux. + + This handler is triggered when a process requested to execute a program + but the request was rejected by the policy. + This handler executes a program specified by the administrator + instead of a program requested by the process. + + Most attackers attempt to execute /bin/sh to start something malicious. + Attackers execute an exploit code using buffer overflow vulnerability + to steal control of a process. But this handler can get back control + if an exploit code requests execve() that is not permitted by policy. + + By default, this handler does nothing (i.e. merely reject execve() + request). You can specify any program to start what you want to do. + + You can redirect attackers to somewhere else (e.g. honey pot). + This makes it possible to act your Linux box as an on-demand honey pot + while keeping regular services for your usage. + + You can collect information of the attacker (e.g. IP address) and + update firewall configuration. + + You can silently terminate a process who requested execve() + that is not permitted by policy. + +Fix 2008/03/03 + + @ Add "force_alt_exec" keyword. + + To be able to fully utilize "alt_exec" feature, + I added "force_alt_exec" keyword so that + all execute requests are replaced by the execute request of a program + specified by alt_exec feature. + + If this keyword is specified for a domain, the domain no longer + executes any programs regardless of the mode of file access control + (i.e. the domain won't execute even if MAC_FOR_FILE=0 ). + Instead, the domain executes the program specified by alt_exec feature + and the program specified by alt_exec feature validates the execute + request and executes it if it is appropriate to execute. + + If you can tolerate that there is no chance to return an error code + to the caller to tell the execute request was rejected, + this is more flexible approach than in-kernel execve() parameter + checking because we can do argv[] and envp[] checking easily. + +Fix 2008/03/04 + + @ Use string for access control mode. + + An integer expression for access control mode sometimes confuses + administrators because profile number is also an integer expression. + To avoid confusion between profile number and access control mode, + I introduced a string expression for access control mode. + + Modes which take an integer between 0 and 3. + + 0 -> disabled + 1 -> learning + 2 -> permissive + 3 -> enforcing + + Modes which take 0 or 1. + + 0 -> disabled + 1 -> enabled + +Fix 2008/03/10 + + @ Rename "force_alt_exec" keyword to "execute_handler". + + To be able to use different programs for validating execve() parameters, + I moved the location to specify the program's pathname from profile + to domain policy. + + The "execute_handler" keyword takes one pathname which is + invoked whenever execve() request is issued. Thus, any "allow_execute" + keywords in a domain with "execute_handler" are ignored. + This keyword is designed for validating expected/desirable execve() + requests in userspace, although there is no way to tell the caller + that the execve() request was rejected. + + @ Rename "alt_exec" keyword to "denied_execute_handler". + + The "denied_execute_handler" keyword takes one pathname which is + invoked only when execve() request was rejected. In other words, + this program is invoked only when the following conditions are met. + + (1) None of "allow_execute" keywords in the domain matched. + (2) The execve() request was rejected in enforcing mode. + (3) "execute_handler" keyword is not used by the domain. + + This keyword is designed for handling unexpected/undesirable execve() + requests, to redirect the process issuing such requests to somewhere. + +Fix 2008/03/18 + + @ Fix wrong/redundant locks in pre-vfs functions. + + lock_kernel()/unlock_kernel() in pre_vfs_rename() were redundant for + 2.6 kernels. + + Locking order in pre_vfs_link() and pre_vfs_unlink() for 2.4 kernels + after 2.4.33 were different from before 2.4.32 . + +Fix 2008/03/28 + + @ Disable execute handler loop. + + To be able to use "execute_handler" in a "keep_domain" domain, + ignore "execute_handler" and "denied_execute_handler" keywords + if the current process is executing programs specified by + "execute_handler" or "denied_execute_handler" keyword. + + This exception is needed to avoid infinite execute handler loop. + If a domain has both "keep_domain" and "execute_handler", + any execute request by that domain is handled by an execute handler, + and the execute handler attempts to process original execute request. + But the original execute request is handled by the same execute handler + unless the execute handler ignores "execute_handler". + + @ Update coding style. + + I rewrote the code to pass scripts/checkpatch.pl as much as possible. + Function names were changed to use only lower letters. + +Version 1.6.0 2008/04/01 Feature enhancement release. + +Fix 2008/04/14 + + @ Fix "Compilation failures" and "Initialization ordering bugs" + with kernels before 2.4.30/2.6.11 . + + 2.6 kernels before 2.6.9 didn't have include/linux/hardirq.h , + resulting compilation error at #include . + I added #elif condition. + + CentOS 4.6's 2.6.9 kernel calls do_execve() before initialization of + ccs_alloc(), resulting NULL pointer dereference. + I changed __initcall to core_initcall. + + CentOS 4.6's 2.6.9 kernel backported kzalloc() from 2.6.14 , + resulting compilation error at kzalloc(). + I modified prototype of kzalloc(). + +Fix 2008/04/20 + + @ Fix "Compilation failures" with kernels before 2.4.30/2.6.11 . + + Turbolinux 10 Server's 2.6.8 kernel backported kzalloc() as an inlined + function, resulting compilation error at kzalloc(). + I converted kzalloc() from an inlined function into a macro. + +Fix 2008/04/21 + + @ Add workaround for gcc 3.2.2's inline bug. + + RedHat Linux 9's gcc 3.2.2 generated a bad code + if ((var_of_u8 & 0x000000BF) & 0x80000000) { } + where the expected code is + if ((var_of_u8 & 0xBF) & 0x80) { } + when embedding ccs_acl_type2() into print_entry(), + resulting runtime BUG(). + I added the expected code explicitly as a workaround. + +Fix 2008/05/06 + + @ Add memory quota. + + 1.5.x returns -ENOMEM when FindNextDomain() failed to create a new + domain, but I forgot to return -ENOMEM when find_next_domain() failed to + create a new domain. + + A domain is automatically created by find_next_domain() only if + the domain for the requested program doesn't exist. + This behavior is for the administrator's convenience. + The administrator needn't to know how many domains are needed for running + the whole programs in the system beforehand when developing the policy. + But the administrator does not want the kernel to reject execution of the + requested program when developing the policy. + + So, I think it is better to grant execution of programs even if + find_next_domain() failed to create a new domain than reject execution. + Thus, I decided not to return -ENOMEM when find_next_domain() failed to + create a new domain. This exception breaks the domain transition rules, + so I print "transition_failed" warning in /proc/ccs/domain_policy + when this exception happened. + + Also, to prevent the system from being halted by unexpectedly allocating + all kernel memory for the policy, I added memory quota. + This quota is configurable via /proc/ccs/meminfo like + + echo Shared: 1048576 > /proc/ccs/meminfo + echo Private: 1048576 > /proc/ccs/meminfo + +Version 1.6.1 2008/05/10 Bug fix release.