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Message-ID: <20200409215056.qa5uso6rr57y4joo@madcap2.tricolour.ca>
Date: Thu, 9 Apr 2020 17:50:56 -0400
From: Richard Guy Briggs <rgb@...hat.com>
To: Vladis Dronov <vdronov@...hat.com>
Cc: Casey Schaufler <casey@...aufler-ca.com>,
Paul Moore <paul@...l-moore.com>,
Eric Paris <eparis@...hat.com>, linux-audit@...hat.com,
James Morris <jmorris@...ei.org>,
"Serge E . Hallyn" <serge@...lyn.com>,
linux-security-module@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH ghak96] audit: set cwd in audit context for file-related
LSM audit records
On 2020-04-02 12:31, Vladis Dronov wrote:
> Hello, Casey, all,
>
> ----- Original Message -----
> > From: "Casey Schaufler" <casey@...aufler-ca.com>
> > Subject: Re: [PATCH ghak96] audit: set cwd in audit context for file-related LSM audit records
> >
> > On 4/2/2020 7:13 AM, Vladis Dronov wrote:
> > > Set a current working directory in an audit context for the following
> > > record
> > > types in dump_common_audit_data(): LSM_AUDIT_DATA_PATH,
> > > LSM_AUDIT_DATA_FILE,
> > > LSM_AUDIT_DATA_IOCTL_OP, LSM_AUDIT_DATA_DENTRY, LSM_AUDIT_DATA_INODE so a
> > > separate CWD record is emitted later.
> > >
> > > Link: https://github.com/linux-audit/audit-kernel/issues/96
> >
> > I don't have a problem with the patch, but it sure would be nice
> > if you explained why these events "could use a CWD record".
>
> (adding Richard Guy Briggs <rgb@...hat.com> which I should have been done earlier)
>
> I would agree, adding "cwd=" field in the LSM record itself is simpler to me.
We already have a CWD record to record this information. It usually
accompanies an AUDIT_PATH record, but the intent is that it accompanies
any event that has filesystem pathnames in path= or name= fields in
records to help understand the command's context relative to the
filesystem.
> Unfortunately, all I can say for now is "The intent was a separate CWD record,
> that is already defined" requirement from the ghak#96 issue.
>
> Richard, could you, please, clarify since you've posted this requirement in
> the ghak#96's description?
>
> > > Signed-off-by: Vladis Dronov <vdronov@...hat.com>
> > > ---
> > > out-of-commit-message-note:
> > >
> > > Hello,
> > > Honestly, I'm not sure about "if (!context->in_syscall)" check in
> > > __audit_getcwd(). It was copied from __audit_getname() and I do
> > > not quite understand why it is there and if __audit_getcwd() needs
> > > it. If you have an idea on this, could you please, tell?
> > >
> > > include/linux/audit.h | 9 ++++++++-
> > > kernel/auditsc.c | 17 +++++++++++++++++
> > > security/lsm_audit.c | 5 +++++
> > > 3 files changed, 30 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/include/linux/audit.h b/include/linux/audit.h
> > > index f9ceae57ca8d..b4306abc5891 100644
> > > --- a/include/linux/audit.h
> > > +++ b/include/linux/audit.h
> > > @@ -268,7 +268,7 @@ extern void __audit_syscall_entry(int major, unsigned
> > > long a0, unsigned long a1,
> > > extern void __audit_syscall_exit(int ret_success, long ret_value);
> > > extern struct filename *__audit_reusename(const __user char *uptr);
> > > extern void __audit_getname(struct filename *name);
> > > -
> > > +extern void __audit_getcwd(void);
> > > extern void __audit_inode(struct filename *name, const struct dentry
> > > *dentry,
> > > unsigned int flags);
> > > extern void __audit_file(const struct file *);
> > > @@ -327,6 +327,11 @@ static inline void audit_getname(struct filename
> > > *name)
> > > if (unlikely(!audit_dummy_context()))
> > > __audit_getname(name);
> > > }
> > > +static inline void audit_getcwd(void)
> > > +{
> > > + if (unlikely(!audit_dummy_context()))
> > > + __audit_getcwd();
> > > +}
> > > static inline void audit_inode(struct filename *name,
> > > const struct dentry *dentry,
> > > unsigned int aflags) {
> > > @@ -545,6 +550,8 @@ static inline struct filename *audit_reusename(const
> > > __user char *name)
> > > }
> > > static inline void audit_getname(struct filename *name)
> > > { }
> > > +static inline void audit_getcwd(void)
> > > +{ }
> > > static inline void __audit_inode(struct filename *name,
> > > const struct dentry *dentry,
> > > unsigned int flags)
> > > diff --git a/kernel/auditsc.c b/kernel/auditsc.c
> > > index 814406a35db1..16316032ef9f 100644
> > > --- a/kernel/auditsc.c
> > > +++ b/kernel/auditsc.c
> > > @@ -1890,6 +1890,23 @@ void __audit_getname(struct filename *name)
> > > get_fs_pwd(current->fs, &context->pwd);
> > > }
> > >
> > > +/**
> > > + * __audit_getcwd - set a current working directory
> > > + *
> > > + * Set a current working directory of an audited process for this context.
> > > + * Called from security/lsm_audit.c:dump_common_audit_data().
> > > + */
> > > +void __audit_getcwd(void)
> > > +{
> > > + struct audit_context *context = audit_context();
> > > +
> > > + if (!context->in_syscall)
> > > + return;
> > > +
> > > + if (!context->pwd.dentry)
> > > + get_fs_pwd(current->fs, &context->pwd);
> > > +}
> > > +
> > > static inline int audit_copy_fcaps(struct audit_names *name,
> > > const struct dentry *dentry)
> > > {
> > > diff --git a/security/lsm_audit.c b/security/lsm_audit.c
> > > index 2d2bf49016f4..7c555621c2bd 100644
> > > --- a/security/lsm_audit.c
> > > +++ b/security/lsm_audit.c
> > > @@ -241,6 +241,7 @@ static void dump_common_audit_data(struct audit_buffer
> > > *ab,
> > > audit_log_untrustedstring(ab, inode->i_sb->s_id);
> > > audit_log_format(ab, " ino=%lu", inode->i_ino);
> > > }
> > > + audit_getcwd();
> > > break;
> > > }
> > > case LSM_AUDIT_DATA_FILE: {
> > > @@ -254,6 +255,7 @@ static void dump_common_audit_data(struct audit_buffer
> > > *ab,
> > > audit_log_untrustedstring(ab, inode->i_sb->s_id);
> > > audit_log_format(ab, " ino=%lu", inode->i_ino);
> > > }
> > > + audit_getcwd();
> > > break;
> > > }
> > > case LSM_AUDIT_DATA_IOCTL_OP: {
> > > @@ -269,6 +271,7 @@ static void dump_common_audit_data(struct audit_buffer
> > > *ab,
> > > }
> > >
> > > audit_log_format(ab, " ioctlcmd=0x%hx", a->u.op->cmd);
> > > + audit_getcwd();
> > > break;
> > > }
> > > case LSM_AUDIT_DATA_DENTRY: {
> > > @@ -283,6 +286,7 @@ static void dump_common_audit_data(struct audit_buffer
> > > *ab,
> > > audit_log_untrustedstring(ab, inode->i_sb->s_id);
> > > audit_log_format(ab, " ino=%lu", inode->i_ino);
> > > }
> > > + audit_getcwd();
> > > break;
> > > }
> > > case LSM_AUDIT_DATA_INODE: {
> > > @@ -300,6 +304,7 @@ static void dump_common_audit_data(struct audit_buffer
> > > *ab,
> > > audit_log_format(ab, " dev=");
> > > audit_log_untrustedstring(ab, inode->i_sb->s_id);
> > > audit_log_format(ab, " ino=%lu", inode->i_ino);
> > > + audit_getcwd();
> > > break;
> > > }
> > > case LSM_AUDIT_DATA_TASK: {
>
> Best regards,
> Vladis Dronov | Red Hat, Inc. | The Core Kernel | Senior Software Engineer
- RGB
--
Richard Guy Briggs <rgb@...hat.com>
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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