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Message-ID: <CAFftDdpmqCOv6Ed9CvEUV_QF5F6HrLOUHQHL8Bdfjxa1Z8uowA@mail.gmail.com>
Date: Tue, 11 Feb 2014 09:47:06 -0800
From: William Roberts <bill.c.roberts@...il.com>
To: Richard Guy Briggs <rgb@...hat.com>
Cc: "linux-audit@...hat.com" <linux-audit@...hat.com>,
"linux-mm@...ck.org" <linux-mm@...ck.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"viro@...iv.linux.org.uk" <viro@...iv.linux.org.uk>,
akpm@...ux-foundation.org, Stephen Smalley <sds@...ho.nsa.gov>,
William Roberts <wroberts@...sys.com>
Subject: Re: [PATCH v5 3/3] audit: Audit proc/<pid>/cmdline aka proctitle
The most up to date patches were v6. The difference between v5 and v6
is rtrim(). Did you not want the rtrim?
Most things end with null bytes, this helps prevent hex-escaping when
not needed.
v6 - adds rtrim
http://marc.info/?l=linux-kernel&m=139093195718315&w=2
http://marc.info/?l=linux-kernel&m=139093196518317&w=2
http://marc.info/?l=linux-kernel&m=139093197518332&w=2
Bill
On Tue, Feb 11, 2014 at 9:25 AM, William Roberts
<bill.c.roberts@...il.com> wrote:
> On Tue, Feb 11, 2014 at 8:36 AM, Richard Guy Briggs <rgb@...hat.com> wrote:
>> On 14/02/06, William Roberts wrote:
>>> During an audit event, cache and print the value of the process's
>>> proctitle value (proc/<pid>/cmdline). This is useful in situations
>>> where processes are started via fork'd virtual machines where the
>>> comm field is incorrect. Often times, setting the comm field still
>>> is insufficient as the comm width is not very wide and most
>>> virtual machine "package names" do not fit. Also, during execution,
>>> many threads have their comm field set as well. By tying it back to
>>> the global cmdline value for the process, audit records will be more
>>> complete in systems with these properties. An example of where this
>>> is useful and applicable is in the realm of Android. With Android,
>>> their is no fork/exec for VM instances. The bare, preloaded Dalvik
>>> VM listens for a fork and specialize request. When this request comes
>>> in, the VM forks, and the loads the specific application (specializing).
>>> This was done to take advantage of COW and to not require a load of
>>> basic packages by the VM on very app spawn. When this spawn occurs,
>>> the package name is set via setproctitle() and shows up in procfs.
>>> Many of these package names are longer then 16 bytes, the historical
>>> width of task->comm. Having the cmdline in the audit records will
>>> couple the application back to the record directly. Also, on my
>>> Debian development box, some audit records were more useful then
>>> what was printed under comm.
>>>
>>> The cached proctitle is tied to the life-cycle of the audit_context
>>> structure and is built on demand.
>>>
>>> Proctitle is controllable by userspace, and thus should not be trusted.
>>> It is meant as an aid to assist in debugging. The proctitle event is
>>> emitted during syscall audits, and can be filtered with auditctl.
>>>
>>> Example:
>>> type=AVC msg=audit(1391217013.924:386): avc: denied { getattr } for pid=1971 comm="mkdir" name="/" dev="selinuxfs" ino=1 scontext=system_u:system_r:consolekit_t:s0-s0:c0.c255 tcontext=system_u:object_r:security_t:s0 tclass=filesystem
>>> type=SYSCALL msg=audit(1391217013.924:386): arch=c000003e syscall=137 success=yes exit=0 a0=7f019dfc8bd7 a1=7fffa6aed2c0 a2=fffffffffff4bd25 a3=7fffa6aed050 items=0 ppid=1967 pid=1971 auid=4294967295 uid=0 gid=0 euid=0 suid=0 fsuid=0 egid=0 sgid=0 fsgid=0 tty=(none) ses=4294967295 comm="mkdir" exe="/bin/mkdir" subj=system_u:system_r:consolekit_t:s0-s0:c0.c255 key=(null)
>>> type=UNKNOWN[1327] msg=audit(1391217013.924:386): proctitle=6D6B646972002D70002F7661722F72756E2F636F6E736F6C65
>>>
>>> Signed-off-by: William Roberts <wroberts@...sys.com>
>>
>> Signed-off-by: Richard Guy Briggs <rgb@...hat.com>
>>
>> Though, I would prefer to see the size of the proctitle copy buffer
>> dynamically allocated based on the size of the original rather than
>> pinned at 128.
>
> Not as good as it originally seems as this could be a whole page,
> which would result in 2*PAGE_SIZE if hex escaped back to
> userspace. A tuneable interface could be added in the future if its needed.
>
>>
>>> ---
>>> include/uapi/linux/audit.h | 1 +
>>> kernel/audit.h | 6 ++++
>>> kernel/auditsc.c | 67 ++++++++++++++++++++++++++++++++++++++++++++
>>> 3 files changed, 74 insertions(+)
>>>
>>> diff --git a/include/uapi/linux/audit.h b/include/uapi/linux/audit.h
>>> index 2d48fe1..4315ee9 100644
>>> --- a/include/uapi/linux/audit.h
>>> +++ b/include/uapi/linux/audit.h
>>> @@ -109,6 +109,7 @@
>>> #define AUDIT_NETFILTER_PKT 1324 /* Packets traversing netfilter chains */
>>> #define AUDIT_NETFILTER_CFG 1325 /* Netfilter chain modifications */
>>> #define AUDIT_SECCOMP 1326 /* Secure Computing event */
>>> +#define AUDIT_PROCTITLE 1327 /* Proctitle emit event */
>>>
>>> #define AUDIT_AVC 1400 /* SE Linux avc denial or grant */
>>> #define AUDIT_SELINUX_ERR 1401 /* Internal SE Linux Errors */
>>> diff --git a/kernel/audit.h b/kernel/audit.h
>>> index 57cc64d..38c967d 100644
>>> --- a/kernel/audit.h
>>> +++ b/kernel/audit.h
>>> @@ -106,6 +106,11 @@ struct audit_names {
>>> bool should_free;
>>> };
>>>
>>> +struct audit_proctitle {
>>> + int len; /* length of the cmdline field. */
>>> + char *value; /* the cmdline field */
>>> +};
>>> +
>>> /* The per-task audit context. */
>>> struct audit_context {
>>> int dummy; /* must be the first element */
>>> @@ -202,6 +207,7 @@ struct audit_context {
>>> } execve;
>>> };
>>> int fds[2];
>>> + struct audit_proctitle proctitle;
>>>
>>> #if AUDIT_DEBUG
>>> int put_count;
>>> diff --git a/kernel/auditsc.c b/kernel/auditsc.c
>>> index 10176cd..e342eb0 100644
>>> --- a/kernel/auditsc.c
>>> +++ b/kernel/auditsc.c
>>> @@ -68,6 +68,7 @@
>>> #include <linux/capability.h>
>>> #include <linux/fs_struct.h>
>>> #include <linux/compat.h>
>>> +#include <linux/ctype.h>
>>>
>>> #include "audit.h"
>>>
>>> @@ -79,6 +80,9 @@
>>> /* no execve audit message should be longer than this (userspace limits) */
>>> #define MAX_EXECVE_AUDIT_LEN 7500
>>>
>>> +/* max length to print of cmdline/proctitle value during audit */
>>> +#define MAX_PROCTITLE_AUDIT_LEN 128
>>> +
>>> /* number of audit rules */
>>> int audit_n_rules;
>>>
>>> @@ -842,6 +846,13 @@ static inline struct audit_context *audit_get_context(struct task_struct *tsk,
>>> return context;
>>> }
>>>
>>> +static inline void audit_proctitle_free(struct audit_context *context)
>>> +{
>>> + kfree(context->proctitle.value);
>>> + context->proctitle.value = NULL;
>>> + context->proctitle.len = 0;
>>> +}
>>> +
>>> static inline void audit_free_names(struct audit_context *context)
>>> {
>>> struct audit_names *n, *next;
>>> @@ -955,6 +966,7 @@ static inline void audit_free_context(struct audit_context *context)
>>> audit_free_aux(context);
>>> kfree(context->filterkey);
>>> kfree(context->sockaddr);
>>> + audit_proctitle_free(context);
>>> kfree(context);
>>> }
>>>
>>> @@ -1271,6 +1283,59 @@ static void show_special(struct audit_context *context, int *call_panic)
>>> audit_log_end(ab);
>>> }
>>>
>>> +static inline int audit_proctitle_rtrim(char *proctitle, int len)
>>> +{
>>> + char *end = proctitle + len - 1;
>>> + while (end > proctitle && !isprint(*end))
>>> + end--;
>>> +
>>> + /* catch the case where proctitle is only 1 non-print character */
>>> + len = end - proctitle + 1;
>>> + len -= isprint(proctitle[len-1]) == 0;
>>> + return len;
>>> +}
>>> +
>>> +static void audit_log_proctitle(struct task_struct *tsk,
>>> + struct audit_context *context)
>>> +{
>>> + int res;
>>> + char *buf;
>>> + char *msg = "(null)";
>>> + int len = strlen(msg);
>>> + struct audit_buffer *ab;
>>> +
>>> + ab = audit_log_start(context, GFP_KERNEL, AUDIT_PROCTITLE);
>>> + if (!ab)
>>> + return; /* audit_panic or being filtered */
>>> +
>>> + audit_log_format(ab, "proctitle=");
>>> +
>>> + /* Not cached */
>>> + if (!context->proctitle.value) {
>>> + buf = kmalloc(MAX_PROCTITLE_AUDIT_LEN, GFP_KERNEL);
>>> + if (!buf)
>>> + goto out;
>>> + /* Historically called this from procfs naming */
>>> + res = get_cmdline(tsk, buf, MAX_PROCTITLE_AUDIT_LEN);
>>> + if (res == 0) {
>>> + kfree(buf);
>>> + goto out;
>>> + }
>>> + res = audit_proctitle_rtrim(buf, res);
>>> + if (res == 0) {
>>> + kfree(buf);
>>> + goto out;
>>> + }
>>> + context->proctitle.value = buf;
>>> + context->proctitle.len = res;
>>> + }
>>> + msg = context->proctitle.value;
>>> + len = context->proctitle.len;
>>> +out:
>>> + audit_log_n_untrustedstring(ab, msg, len);
>>> + audit_log_end(ab);
>>> +}
>>> +
>>> static void audit_log_exit(struct audit_context *context, struct task_struct *tsk)
>>> {
>>> int i, call_panic = 0;
>>> @@ -1388,6 +1453,8 @@ static void audit_log_exit(struct audit_context *context, struct task_struct *ts
>>> audit_log_name(context, n, NULL, i++, &call_panic);
>>> }
>>>
>>> + audit_log_proctitle(tsk, context);
>>> +
>>> /* Send end of event record to help user space know we are finished */
>>> ab = audit_log_start(context, GFP_KERNEL, AUDIT_EOE);
>>> if (ab)
>>> --
>>> 1.7.9.5
>>>
>>
>> - RGB
>>
>> --
>> Richard Guy Briggs <rbriggs@...hat.com>
>> Senior Software Engineer, Kernel Security, AMER ENG Base Operating Systems, Red Hat
>> Remote, Ottawa, Canada
>> Voice: +1.647.777.2635, Internal: (81) 32635, Alt: +1.613.693.0684x3545
>
>
>
> --
> Respectfully,
>
> William C Roberts
--
Respectfully,
William C Roberts
--
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