Re: [PATCH] audit: Add cmdline to taskinfo output

William Roberts
2013-10-29T23:24:04Z

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On Tue, Oct 29, 2013 at 1:25 PM, William Roberts
<bill.c.roberts@gmail.com>wrote:

>
>
>
> On Tue, Oct 29, 2013 at 12:55 PM, Steve Grubb <sgrubb@redhat.com> wrote:
>
>> On Tuesday, October 29, 2013 12:12:29 PM William Roberts wrote:
>> > > > to small for most package names, and
>> > > > already contains the VM command. I really have no information of
>> what
>> > > > Android App has created the issue.
>> > >
>> > > This is true for all arches. Usually you can have it pretty narrowly
>> > > defined to
>> > > where you have a pretty good guess between 2 or 3 apps with the same
>> root
>> > > name. But in your case its totally named wrong.
>> >
>> > I could set the title via prctl and PR_SET_NAME, but again I would be
>> > limited at 16 bytes, at least with cmdline I am limited at a page.
>>
>> A page would be a problem for audit records. What I see is a NULL
>> terminated
>> list of arguments which the program name is argv[0]. So, you'd want to
>> grab
>> that one. Butyou could have something in there with PATH_MAX and
>> whitespaces
>> which would be excessively long.
>>
>> > As a simple example, a basic example from samsung gets truncated.
>> >
>> > com.samsung.myapp
>> >
>> > > > Solution:
>> > > > Get the proc cmdline info (not trust worthy, but can help debugging
>> > >
>> > > Android)
>> > >
>> > > > type=1300 msg=audit(1383068585.326:205): arch=40000028 syscall=5
>> > >
>> > > per=840000
>> > >
>> > > > success=yes exit=38 a0=74d86d34 a1=20241 a2=180 a3=74d86d0c items=1
>> > > > ppid=296 pid=1378 auid=4294967295 uid=1027 gid=1027 euid=1027
>> suid=1027
>> > > > fsuid=1027 egid=1027 sgid=1027 fsgid=1027 tty=(none) ses=4294967295
>> > > > comm=4173796E635461736B202331 exe="/system/bin/app_process"
>> > > > cmdline="com.android.nfc" subj=u:r:nfc:s0 key=(null)
>> > > >
>> > > > Now I know it was the NFC app
>> > >
>> > > What do you get on x86_64 auditing a shell or python script with your
>> same
>> > > patch? Also, does cmdline potentially include arguments?
>> >
>> > I would have to get back to you on this, but whatever is set in
>> > /proc/<pid>/cmdline shows up here, which means
>> > it could have arguments etc.
>>
>> The reason I'm asking is that it might be better for all arches to
>> switch. All
>> have the 16 character limit. But we would only want argv[0] and not the
>> arguments.
>>
>> -Steve
>>
>
> I guess i'm thinking about how can I access the smallest set of data that
> I need to get the information I want.... however, wouldn't argv[0]
> typically be the vm name...
> <vm> <program>
> And on Android, to make it even more of a pain.... A VM is already
> running, that then forks itself and then invokes the classloader, so their
> is no
> explicit exec.
>
> I guess I could just set the comm field explicitly via the packagename
> when the classloader loads the value, but I was hoping for something more
> generic that would
> let me get larger package names then 16.
>
>
I made the change of setting the comm field from within the VM, but its
less then ideal... that 16char limitation is a pain. In Android Java Land,
some of the packages that get run can be quite large. Also, current APIs in
Javaland
already change this...

Also, a more generic solution would be desired.

Lets look at what happens:
type=SYSCALL msg=audit(10/29/2013 15:16:08.185:177) : arch=unknown elf
type(40000028) syscall=fstat per=840000 success=yes exit=38 a0=7432ed34
a1=20241 a2=180 a3=7432ed0c items=1 ppid=322 pid=1432 auid=unset
uid=unknown(1027) gid=unknown(1027) euid=unknown(1027) suid=unknown(1027)
fsuid=unknown(1027) egid=unknown(1027) sgid=unknown(1027)
fsgid=unknown(1027) tty=(none) ses=4294967295 comm=AsyncTask #1
exe=/system/bin/app_process cmdline="com.android.nfc" subj=u:r:nfc:s0
key=(null)

Here the nfc task has an async task, that async task api sets the cmd field
when it attaches a thread to the VM....

type=1300 msg=audit(1383088554.170:322): arch=40000028 syscall=54
per=840000 success=yes exit=0 a0=a a1=c0186201 a2=be985430 a3=be98542c
items=0 ppid=321 pid=1181 auid=4294967295 uid=10036 gid=10036 euid=10036
suid=10036 fsuid=10036 egid=10036 sgid=10036 fsgid=10036 tty=(none)
ses=4294967295 comm="putmethod.latin" exe="/system/bin/app_process"
cmdline="com.android.inputmethod.latin" subj=u:r:shared_app:s0 key=(null)

Again... the comm field got cut off and now I have no idea again. I think
exe= in the audit logs is essentially arg[0]... so thats not going to work
here, and I don't think I can change that value from userspace as its not
logged with untrusted string, which is a good indication its mutable from
userspace.

Why dont I just limit the size of what is displayed on cmdline to something
like 128 or 256?

Eventually some limit has to be set, whether its PAGE_SIZE or not..their
will always be an argument of "too much memory". But its also important to
note its off by default, you have to turn it on, so most desktop instances
will leave it off, whilst I will dynamically enable it as needed.

Thanks again for your review and help, I appreciate it.

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