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fedora-selinux: Re: Sample Passenger/Rails policy for review

Re: Sample Passenger/Rails policy for review

From: Dominick Grift <domg472_at_nospam>
Date: Thu Aug 19 2010 - 14:03:19 GMT
To: selinux@lists.fedoraproject.org

On 08/19/2010 03:26 PM, Moray Henderson wrote:
> Dominick Grift wrote:
>>> I still get denials when apache starts or stops:
>>>
>>> type=AVC msg=audit(1282212879.945:6710639): avc: denied { fowner }
> for
>>> pid=10440 comm="chmod" capability=3
> scontext=user_u:system_r:httpd_t:s0
>>> tcontext=user_u:system_r:httpd_t:s0 tclass=capability
>>> type=SYSCALL msg=audit(1282212879.945:6710639): arch=40000003
> syscall=15
>>> success=no exit=-1 a0=91d95ec a1=9c0 a2=8051614 a3=0 items=0
> ppid=10439
>>> pid=10440 auid=500 uid=0 gid=0 euid=0 suid=0 fsuid=0 egid=0 sgid=0
>>> fsgid=0 tty=pts0 ses=404 comm="chmod" exe="/bin/chmod"
>>> subj=user_u:system_r:httpd_t:s0 key=(null)
>>> type=AVC msg=audit(1282212879.946:6710640): avc: denied { fowner }
> for
>>> pid=10440 comm="chmod" capability=3
> scontext=user_u:system_r:httpd_t:s0
>>> tcontext=user_u:system_r:httpd_t:s0 tclass=capability
>>> type=SYSCALL msg=audit(1282212879.946:6710640): arch=40000003
> syscall=15
>>> success=no exit=-1 a0=91d96a4 a1=9c0 a2=8051614 a3=0 items=0
> ppid=10439
>>> pid=10440 auid=500 uid=0 gid=0 euid=0 suid=0 fsuid=0 egid=0 sgid=0
>>> fsgid=0 tty=pts0 ses=404 comm="chmod" exe="/bin/chmod"
>>> subj=user_u:system_r:httpd_t:s0 key=(null)
>>
>> So something running in the httpd_t domain wants to change file
>> ownership of some object.
>>
>> Still wondering what is running in the httpd_t domain that ran chmod,
>> and on which object did it run it.
>
> I think I've found it. It's in the mod_passenger library, which is
> currently
>
> -rwxrwxr-x root root system_u:object_r:httpd_modules_t
> /usr/lib/httpd/modules/mod_passenger.so
>
> There are a couple of functions there that deal with creation and
> deletion of FIFOs and mention chmod. As it's loaded by the master
> apache daemon, I didn't think we could tweak its permissions.
> Everything seems to work - is there a problem?

see what happens when you label it with the passenger executable type.
httpd_myapp_script_exec_t.

The problem is that we do not want to have to extend httpd_t policy if
we do not have to.
>
> static void
> createNonWritableFifo(const string &filename) {
> int ret, e;
> bool ignoreChmodErrors = false;
>
> do {
> ret = mkfifo(filename.c_str(), 0);
> } while (ret == -1 && errno == EINTR);
> if (ret == -1) {
> if (errno == EEXIST) {
> /* The FIFO file was likely created by root, but after
> lowering
> * privilege createPassengerTempDir() is called again, and
> this
> * time we won't be able to set permissions. So in this case
> * we'll want to ignore any chmod errors.
> */
> ignoreChmodErrors = geteuid() != 0;
> } else {
> e = errno;
> throw FileSystemException("Cannot create FIFO file " +
> filename,
> e, filename);
> }
> }
>
> do {
> ret = chmod(filename.c_str(), 0);
> } while (ret == -1 && errno == EINTR);
> if (ret == -1 && !ignoreChmodErrors) {
> e = errno;
> throw FileSystemException("Cannot set permissions on file " +
> filename, e, filename);
> }
> }
>
> void
> removeDirTree(const string &path) {
> char command[PATH_MAX + 30];
> int result;
>
> snprintf(command, sizeof(command), "chmod -R u+rwx \"%s\"
> 2>/dev/null", path.c_str());
> command[sizeof(command) - 1] = '\0';
> do {
> result = system(command);
> } while (result == -1 && errno == EINTR);
>
> snprintf(command, sizeof(command), "rm -rf \"%s\"", path.c_str());
> command[sizeof(command) - 1] = '\0';
> do {
> result = system(command);
> } while (result == -1 && errno == EINTR);
> if (result == -1) {
> char message[1024];
> int e = errno;
>
> snprintf(message, sizeof(message) - 1, "Cannot remove directory
> '%s'", path.c_str());
> message[sizeof(message) - 1] = '\0';
> throw FileSystemException(message, e, path);
> }
> }
>
>>> but I can dontaudit those. I've also changed the labelling so that
> only
>>> the passenger executable is labelled with the entry type; all other
>>> passenger files are content type. The policy becomes:
>>>
>>> #### myapp.te ####
>>> policy_module(myapp,1.0)
>>>
>>> apache_content_template(myapp);
>>>
>>> kernel_read_kernel_sysctls(httpd_myapp_script_t);
>>> miscfiles_read_certs(httpd_myapp_script_t);
>>> term_use_all_user_ptys(httpd_myapp_script_t);
>>>
>>> dontaudit httpd_t self:capability { fowner };
>>> allow httpd_t httpd_myapp_script_t:unix_stream_socket
> rw_socket_perms;
>>> allow httpd_t httpd_myapp_script_rw_t:fifo_file manage_file_perms;
>>> allow httpd_t httpd_myapp_script_rw_t:sock_file { setattr unlink };
>>>
>>> allow httpd_myapp_script_t self:capability { chown dac_override
>>> dac_read_search fowner fsetid setgid setuid };
>>> allow httpd_myapp_script_t httpd_t:unix_stream_socket { read write };
>>>
>>> #### myapp.fc ####
>>>
> /usr/lib/ruby/gems/1.9.1/gems/passenger-2.2.15/lib/phusion_passenger/App
>>> licationPoolServerExecutable --
>>> gen_context(system_u:object_r:httpd_myapp_script_exec_t, s0)
>>> /usr/lib/ruby/gems/1.9.1/gems/passenger-2.2.15(/.*)?
>>> gen_context(system_u:object_r:httpd_myapp_content_t, s0)
>>> /usr/local/lib/myapp(/.*)?
>>> gen_context(system_u:object_r:httpd_myapp_content_t, s0)
>>> /var/run/passenger(/.*)?
>>> gen_context(system_u:object_r:httpd_myapp_script_rw_t, s0)
>>>
>>>
>>> Thanks for your reply on the documentation, too. I'll take time to
> work
>>> through it properly.
>
>
> Moray.
> "To err is human. To purr, feline"
>
>
>
>
> --
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> selinux@lists.fedoraproject.org
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