From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ee0-f41.google.com (mail-ee0-f41.google.com [74.125.83.41]) by kanga.kvack.org (Postfix) with ESMTP id 4CE936B003B for ; Tue, 11 Feb 2014 12:25:46 -0500 (EST) Received: by mail-ee0-f41.google.com with SMTP id e51so3225959eek.0 for ; Tue, 11 Feb 2014 09:25:45 -0800 (PST) Received: from mail-wi0-x22d.google.com (mail-wi0-x22d.google.com [2a00:1450:400c:c05::22d]) by mx.google.com with ESMTPS id k3si33342853eep.246.2014.02.11.09.25.44 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Tue, 11 Feb 2014 09:25:44 -0800 (PST) Received: by mail-wi0-f173.google.com with SMTP id hn9so4835369wib.0 for ; Tue, 11 Feb 2014 09:25:44 -0800 (PST) MIME-Version: 1.0 In-Reply-To: <20140211163629.GM18807@madcap2.tricolour.ca> References: <1391710528-23481-1-git-send-email-wroberts@tresys.com> <1391710528-23481-3-git-send-email-wroberts@tresys.com> <20140211163629.GM18807@madcap2.tricolour.ca> Date: Tue, 11 Feb 2014 09:25:44 -0800 Message-ID: Subject: Re: [PATCH v5 3/3] audit: Audit proc//cmdline aka proctitle From: William Roberts Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Sender: owner-linux-mm@kvack.org List-ID: To: Richard Guy Briggs Cc: "linux-audit@redhat.com" , "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" , "viro@zeniv.linux.org.uk" , akpm@linux-foundation.org, Stephen Smalley , William Roberts On Tue, Feb 11, 2014 at 8:36 AM, Richard Guy Briggs wrote: > On 14/02/06, William Roberts wrote: >> During an audit event, cache and print the value of the process's >> proctitle value (proc//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=3DAVC msg=3Daudit(1391217013.924:386): avc: denied { getattr } fo= r pid=3D1971 comm=3D"mkdir" name=3D"/" dev=3D"selinuxfs" ino=3D1 scontext= =3Dsystem_u:system_r:consolekit_t:s0-s0:c0.c255 tcontext=3Dsystem_u:object_= r:security_t:s0 tclass=3Dfilesystem >> type=3DSYSCALL msg=3Daudit(1391217013.924:386): arch=3Dc000003e syscall= =3D137 success=3Dyes exit=3D0 a0=3D7f019dfc8bd7 a1=3D7fffa6aed2c0 a2=3Dffff= fffffff4bd25 a3=3D7fffa6aed050 items=3D0 ppid=3D1967 pid=3D1971 auid=3D4294= 967295 uid=3D0 gid=3D0 euid=3D0 suid=3D0 fsuid=3D0 egid=3D0 sgid=3D0 fsgid= =3D0 tty=3D(none) ses=3D4294967295 comm=3D"mkdir" exe=3D"/bin/mkdir" subj= =3Dsystem_u:system_r:consolekit_t:s0-s0:c0.c255 key=3D(null) >> type=3DUNKNOWN[1327] msg=3Daudit(1391217013.924:386): proctitle=3D6D6B6= 46972002D70002F7661722F72756E2F636F6E736F6C65 >> >> Signed-off-by: William Roberts > > Signed-off-by: Richard Guy Briggs > > 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 ch= ains */ >> #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 >> #include >> #include >> +#include >> >> #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_conte= xt(struct task_struct *tsk, >> return context; >> } >> >> +static inline void audit_proctitle_free(struct audit_context *context) >> +{ >> + kfree(context->proctitle.value); >> + context->proctitle.value =3D NULL; >> + context->proctitle.len =3D 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_c= ontext *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 *co= ntext, int *call_panic) >> audit_log_end(ab); >> } >> >> +static inline int audit_proctitle_rtrim(char *proctitle, int len) >> +{ >> + char *end =3D proctitle + len - 1; >> + while (end > proctitle && !isprint(*end)) >> + end--; >> + >> + /* catch the case where proctitle is only 1 non-print character */ >> + len =3D end - proctitle + 1; >> + len -=3D isprint(proctitle[len-1]) =3D=3D 0; >> + return len; >> +} >> + >> +static void audit_log_proctitle(struct task_struct *tsk, >> + struct audit_context *context) >> +{ >> + int res; >> + char *buf; >> + char *msg =3D "(null)"; >> + int len =3D strlen(msg); >> + struct audit_buffer *ab; >> + >> + ab =3D audit_log_start(context, GFP_KERNEL, AUDIT_PROCTITLE); >> + if (!ab) >> + return; /* audit_panic or being filtered */ >> + >> + audit_log_format(ab, "proctitle=3D"); >> + >> + /* Not cached */ >> + if (!context->proctitle.value) { >> + buf =3D kmalloc(MAX_PROCTITLE_AUDIT_LEN, GFP_KERNEL); >> + if (!buf) >> + goto out; >> + /* Historically called this from procfs naming */ >> + res =3D get_cmdline(tsk, buf, MAX_PROCTITLE_AUDIT_LEN); >> + if (res =3D=3D 0) { >> + kfree(buf); >> + goto out; >> + } >> + res =3D audit_proctitle_rtrim(buf, res); >> + if (res =3D=3D 0) { >> + kfree(buf); >> + goto out; >> + } >> + context->proctitle.value =3D buf; >> + context->proctitle.len =3D res; >> + } >> + msg =3D context->proctitle.value; >> + len =3D 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_s= truct *tsk) >> { >> int i, call_panic =3D 0; >> @@ -1388,6 +1453,8 @@ static void audit_log_exit(struct audit_context *c= ontext, 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 finishe= d */ >> ab =3D audit_log_start(context, GFP_KERNEL, AUDIT_EOE); >> if (ab) >> -- >> 1.7.9.5 >> > > - RGB > > -- > Richard Guy Briggs > Senior Software Engineer, Kernel Security, AMER ENG Base Operating System= s, Red Hat > Remote, Ottawa, Canada > Voice: +1.647.777.2635, Internal: (81) 32635, Alt: +1.613.693.0684x3545 --=20 Respectfully, William C Roberts -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. 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