Re: [PATCH ghak8 ALT4 V4 1/3] audit: show partial pathname for entries with anonymous parents

From: Richard Guy Briggs
Date: Fri Feb 16 2018 - 01:04:34 EST

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On 2018-02-15 18:07, Steve Grubb wrote:
> On Monday, February 12, 2018 12:02:21 AM EST Richard Guy Briggs wrote:
> > Tracefs or debugfs were causing hundreds to thousands of null PATH
> > records to be associated with the init_module and finit_module SYSCALL
> > records on a few modules when the following rule was in place for
> > startup:
> > -a always,exit -F arch=x86_64 -S init_module -F key=mod-load
> >
> > This happens because the parent inode is not found in the task's
> > audit_names list and hence treats it as anonymous. This gives us no
> > information other than a numerical device number for a device that may
> > no longer be visible upon log inspeciton, and an inode number.
> >
> > Fill in the partial known pathname from the filesystem mount point to
> > the leaf node on previously null PATH records from entries that have an
> > anonymous parent from the child dentry using dentry_path_raw().
> >
> > Make the dentry argument of __audit_inode_child() non-const so that we
> > can take a reference to it in the case of an anonymous parent with
> > dget() and dget_parent() to be able to later print a partial path from
> > the host filesystem rather than null.
> >
> > Since all we are given is an inode of the parent and the dentry of the
> > child, finding the path from the mount point to the root of the
> > filesystem is more challenging that would involve searching all
> > vfsmounts from "/" until a matching dentry is found for that
> > filesystem's root dentry. Even if one is found, there may be more than
> > one mount point. At this point the gain seems marginal since
> > knowing the filesystem type and path are a significant help in tracking
> > down the source of the PATH records and being able to address them.
> >
> > Sample output:
> > type=PROCTITLE msg=audit(1488317694.446:143):
> > proctitle=2F7362696E2F6D6F6470726F6265002D71002D2D006E66737634 type=PATH
> > msg=audit(1488317694.446:143): item=797
> > name=events/nfs4/nfs4_setclientid/format inode=15969 dev=00:09
> > mode=0100444 ouid=0 ogid=0 rdev=00:00 obj=system_u:object_r:tracefs_t:s0
> > nametype=CREATE cap_fp=0000000000000000 cap_fi=0000000000000000 cap_fe=0
> > cap_fver=0 type=PATH msg=audit(1488317694.446:143): item=796
> > name=events/nfs4/nfs4_setclientid inode=15964 dev=00:09 mode=040755 ouid=0
> > ogid=0 rdev=00:00 obj=system_u:object_r:tracefs_t:s0 nametype=PARENT
> > cap_fp=0000000000000000 cap_fi=0000000000000000 cap_fe=0 cap_fver=0 ...
> > type=PATH msg=audit(1488317694.446:143): item=1 name=events/nfs4
> > inode=15571 dev=00:09 mode=040755 ouid=0 ogid=0 rdev=00:00
> > obj=system_u:object_r:tracefs_t:s0 nametype=CREATE cap_fp=0000000000000000
> > cap_fi=0000000000000000 cap_fe=0 cap_fver=0 type=PATH
> > msg=audit(1488317694.446:143): item=0 name=events inode=119 dev=00:09
> > mode=040755 ouid=0 ogid=0 rdev=00:00 obj=system_u:object_r:tracefs_t:s0
> > nametype=PARENT cap_fp=0000000000000000 cap_fi=0000000000000000 cap_fe=0
> > cap_fver=0 type=KERN_MODULE msg=audit(1488317694.446:143): name="nfsv4"
> > type=SYSCALL msg=audit(1488317694.446:143): arch=c000003e syscall=313
> > success=yes exit=0 a0=1 a1=55d5a35ce106 a2=0 a3=1 items=798 ppid=6 pid=528
> > auid=4294967295 uid=0 gid=0 euid=0 suid=0 fsuid=0 egid=0 sgid=0 fsgid=0
> > tty=(none) ses=4294967295 comm="modprobe" exe="/usr/bin/kmod"
> > subj=system_u:system_r:insmod_t:s0 key="mod-load"
>
> Thanks for the samples, but the event above fails the ausearch-test test
> suite. The "name" field in the PATH record is not properly escaped.

Is the ausearch-test on github yet? Last I see is v0.6 on your rh
people page.

> -Steve
>
> > See: https://github.com/linux-audit/audit-kernel/issues/8
> > Test case: https://github.com/linux-audit/audit-testsuite/issues/42
> >
> > Signed-off-by: Richard Guy Briggs <rgb@xxxxxxxxxx>
> >
> > ---
> > v4:
> > fix fullpath memleak
> > switch from log_format() to audit_log_untrustedstring()
> > remove leading / from pathname relative to unknown mount point
> >
> > v3:
> > fix audit_buffer leak and dname error allocation leak audit_log_name
> > only put audit_name->dentry if it is being replaced
> >
> > v2:
> > deconstify struct dentry*
> > add hex prefix to fstype
> > ---
> > include/linux/audit.h | 8 ++++----
> > kernel/audit.c | 28 +++++++++++++++++++++++++++-
> > kernel/audit.h | 1 +
> > kernel/auditsc.c | 8 +++++++-
> > 4 files changed, 39 insertions(+), 6 deletions(-)
> >
> > diff --git a/include/linux/audit.h b/include/linux/audit.h
> > index af410d9..2020f1d 100644
> > --- a/include/linux/audit.h
> > +++ b/include/linux/audit.h
> > @@ -232,7 +232,7 @@ extern void __audit_inode(struct filename *name, const
> > struct dentry *dentry, unsigned int flags);
> > extern void __audit_file(const struct file *);
> > extern void __audit_inode_child(struct inode *parent,
> > - const struct dentry *dentry,
> > + struct dentry *dentry,
> > const unsigned char type);
> > extern void __audit_seccomp(unsigned long syscall, long signr, int code);
> > extern void __audit_ptrace(struct task_struct *t);
> > @@ -297,7 +297,7 @@ static inline void audit_inode_parent_hidden(struct
> > filename *name, AUDIT_INODE_PARENT | AUDIT_INODE_HIDDEN);
> > }
> > static inline void audit_inode_child(struct inode *parent,
> > - const struct dentry *dentry,
> > + struct dentry *dentry,
> > const unsigned char type) {
> > if (unlikely(!audit_dummy_context()))
> > __audit_inode_child(parent, dentry, type);
> > @@ -481,7 +481,7 @@ static inline void __audit_inode(struct filename *name,
> > unsigned int flags)
> > { }
> > static inline void __audit_inode_child(struct inode *parent,
> > - const struct dentry *dentry,
> > + struct dentry *dentry,
> > const unsigned char type)
> > { }
> > static inline void audit_inode(struct filename *name,
> > @@ -495,7 +495,7 @@ static inline void audit_inode_parent_hidden(struct
> > filename *name, const struct dentry *dentry)
> > { }
> > static inline void audit_inode_child(struct inode *parent,
> > - const struct dentry *dentry,
> > + struct dentry *dentry,
> > const unsigned char type)
> > { }
> > static inline void audit_core_dumps(long signr)
> > diff --git a/kernel/audit.c b/kernel/audit.c
> > index 227db99..0c8d5a8 100644
> > --- a/kernel/audit.c
> > +++ b/kernel/audit.c
> > @@ -72,6 +72,7 @@
> > #include <linux/freezer.h>
> > #include <linux/pid_namespace.h>
> > #include <net/netns/generic.h>
> > +#include <linux/dcache.h>
> >
> > #include "audit.h"
> >
> > @@ -2056,6 +2057,10 @@ void audit_copy_inode(struct audit_names *name,
> > const struct dentry *dentry, name->gid = inode->i_gid;
> > name->rdev = inode->i_rdev;
> > security_inode_getsecid(inode, &name->osid);
> > + if (name->dentry) {
> > + dput(name->dentry);
> > + name->dentry = NULL;
> > + }
> > audit_copy_fcaps(name, dentry);
> > }
> >
> > @@ -2097,8 +2102,29 @@ void audit_log_name(struct audit_context *context,
> > struct audit_names *n, audit_log_n_untrustedstring(ab, n->name->name,
> > n->name_len);
> > }
> > - } else
> > + } else if (n->dentry) {
> > + char *fullpath;
> > + const char *fullpathp = NULL;
> > +
> > + fullpath = kmalloc(PATH_MAX, GFP_KERNEL);
> > + if (fullpath) {
> > + fullpathp = dentry_path_raw(n->dentry, fullpath, PATH_MAX);
> > + if (IS_ERR(fullpathp)) {
> > + fullpathp = NULL;
> > + } else {
> > + while (*fullpathp == '/')
> > + fullpathp++;
> > + if (*fullpathp == 0)
> > + fullpathp = NULL;
> > + }
> > + }
> > + audit_log_format(ab, " name=");
> > + audit_log_untrustedstring(ab, fullpathp ?: "?");
> > + if (fullpath)
> > + kfree(fullpath);
> > + } else {
> > audit_log_format(ab, " name=(null)");
> > + }
> >
> > if (n->ino != AUDIT_INO_UNSET)
> > audit_log_format(ab, " inode=%lu"
> > diff --git a/kernel/audit.h b/kernel/audit.h
> > index af5bc59..81f6865 100644
> > --- a/kernel/audit.h
> > +++ b/kernel/audit.h
> > @@ -85,6 +85,7 @@ struct audit_names {
> >
> > unsigned long ino;
> > dev_t dev;
> > + struct dentry *dentry;
> > umode_t mode;
> > kuid_t uid;
> > kgid_t gid;
> > diff --git a/kernel/auditsc.c b/kernel/auditsc.c
> > index e80459f..b73ede0 100644
> > --- a/kernel/auditsc.c
> > +++ b/kernel/auditsc.c
> > @@ -75,6 +75,7 @@
> > #include <linux/uaccess.h>
> > #include <linux/fsnotify_backend.h>
> > #include <uapi/linux/limits.h>
> > +#include <linux/dcache.h>
> >
> > #include "audit.h"
> >
> > @@ -882,6 +883,8 @@ static inline void audit_free_names(struct
> > audit_context *context) list_del(&n->list);
> > if (n->name)
> > putname(n->name);
> > + if (n->dentry)
> > + dput(n->dentry);
> > if (n->should_free)
> > kfree(n);
> > }
> > @@ -1862,7 +1865,7 @@ void __audit_file(const struct file *file)
> > * unsuccessful attempts.
> > */
> > void __audit_inode_child(struct inode *parent,
> > - const struct dentry *dentry,
> > + struct dentry *dentry,
> > const unsigned char type)
> > {
> > struct audit_context *context = current->audit_context;
> > @@ -1941,6 +1944,7 @@ void __audit_inode_child(struct inode *parent,
> > if (!n)
> > return;
> > audit_copy_inode(n, NULL, parent);
> > + n->dentry = dget_parent(dentry);
> > }
> >
> > if (!found_child) {
> > @@ -1962,6 +1966,8 @@ void __audit_inode_child(struct inode *parent,
> > audit_copy_inode(found_child, dentry, inode);
> > else
> > found_child->ino = AUDIT_INO_UNSET;
> > + if (!found_parent)
> > + found_child->dentry = dget(dentry);
> > }
> > EXPORT_SYMBOL_GPL(__audit_inode_child);
>
>
>
>

- RGB

--
Richard Guy Briggs <rgb@xxxxxxxxxx>
Sr. S/W Engineer, Kernel Security, Base Operating Systems
Remote, Ottawa, Red Hat Canada
IRC: rgb, SunRaycer
Voice: +1.647.777.2635, Internal: (81) 32635

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