* Re: [PATCH ghak109 V1] audit: link integrity evm_write_xattrs record to syscall event
2019-03-21 0:50 ` Richard Guy Briggs
@ 2019-03-21 1:03 ` Paul Moore
2019-03-26 15:11 ` Mimi Zohar
2019-03-26 15:22 ` Steve Grubb
2 siblings, 0 replies; 10+ messages in thread
From: Paul Moore @ 2019-03-21 1:03 UTC (permalink / raw)
To: Richard Guy Briggs
Cc: linux-integrity, linux-security-module, Linux-Audit Mailing List,
LKML, sgrubb, omosnace, Eric Paris, Serge Hallyn, zohar, mjg59
On Wed, Mar 20, 2019 at 8:50 PM Richard Guy Briggs <rgb@redhat.com> wrote:
> On 2019-03-20 19:48, Paul Moore wrote:
> > On Sat, Mar 16, 2019 at 8:10 AM Richard Guy Briggs <rgb@redhat.com> wrote:
> > > In commit fa516b66a1bf ("EVM: Allow runtime modification of the set of
> > > verified xattrs"), the call to audit_log_start() is missing a context to
> > > link it to an audit event. Since this event is in user context, add
> > > the process' syscall context to the record.
> > >
> > > In addition, the orphaned keyword "locked" appears in the record.
> > > Normalize this by changing it to "xattr=(locked)".
> > >
> > > Please see the github issue
> > > https://github.com/linux-audit/audit-kernel/issues/109
> > >
> > > Signed-off-by: Richard Guy Briggs <rgb@redhat.com>
> > > ---
> > > security/integrity/evm/evm_secfs.c | 5 +++--
> > > 1 file changed, 3 insertions(+), 2 deletions(-)
...
> > > @@ -222,7 +223,7 @@ static ssize_t evm_write_xattrs(struct file *file, const char __user *buf,
> > > inode_lock(inode);
> > > err = simple_setattr(evm_xattrs, &newattrs);
> > > inode_unlock(inode);
> > > - audit_log_format(ab, "locked");
> > > + audit_log_format(ab, "xattr=(locked)");
> >
> > Two things come to mind:
> >
> > * While we can clearly trust the string above, should we be logging
> > the xattr field value as an untrusted string so it is consistent with
> > how we record other xattr names?
>
> That would be a question for Steve.
Yep, that's who I wanted to hear from, it's not really something I
expected you to answer Richard. I vaguely remember something about
Steve's audit libs being able to handle both trusted and untrusted
value strings for a given field, but I could have confused "able to
handle" with "don't care".
--
paul moore
www.paul-moore.com
^ permalink raw reply [flat|nested] 10+ messages in thread* Re: [PATCH ghak109 V1] audit: link integrity evm_write_xattrs record to syscall event
2019-03-21 0:50 ` Richard Guy Briggs
2019-03-21 1:03 ` Paul Moore
@ 2019-03-26 15:11 ` Mimi Zohar
2019-03-26 15:22 ` Steve Grubb
2 siblings, 0 replies; 10+ messages in thread
From: Mimi Zohar @ 2019-03-26 15:11 UTC (permalink / raw)
To: Richard Guy Briggs, Paul Moore
Cc: linux-integrity, linux-security-module, Linux-Audit Mailing List,
LKML, sgrubb, omosnace, mjg59
On Wed, 2019-03-20 at 20:50 -0400, Richard Guy Briggs wrote:
> On 2019-03-20 19:48, Paul Moore wrote:
> > On Sat, Mar 16, 2019 at 8:10 AM Richard Guy Briggs <rgb@redhat.com> wrote:
> > > In commit fa516b66a1bf ("EVM: Allow runtime modification of the set of
> > > verified xattrs"), the call to audit_log_start() is missing a context to
> > > link it to an audit event. Since this event is in user context, add
> > > the process' syscall context to the record.
> > >
> > > In addition, the orphaned keyword "locked" appears in the record.
> > > Normalize this by changing it to "xattr=(locked)".
> > >
> > > Please see the github issue
> > > https://github.com/linux-audit/audit-kernel/issues/109
> > >
> > > Signed-off-by: Richard Guy Briggs <rgb@redhat.com>
> > > ---
> > > security/integrity/evm/evm_secfs.c | 5 +++--
> > > 1 file changed, 3 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/security/integrity/evm/evm_secfs.c b/security/integrity/evm/evm_secfs.c
> > > index 015aea8fdf1e..4171d174e9da 100644
> > > --- a/security/integrity/evm/evm_secfs.c
> > > +++ b/security/integrity/evm/evm_secfs.c
> > > @@ -192,7 +192,8 @@ static ssize_t evm_write_xattrs(struct file *file, const char __user *buf,
> > > if (count > XATTR_NAME_MAX)
> > > return -E2BIG;
> > >
> > > - ab = audit_log_start(NULL, GFP_KERNEL, AUDIT_INTEGRITY_EVM_XATTR);
> > > + ab = audit_log_start(audit_context(), GFP_KERNEL,
> > > + AUDIT_INTEGRITY_EVM_XATTR);
> >
> > This part is fine.
> >
> > > if (!ab)
> > > return -ENOMEM;
> > >
> > > @@ -222,7 +223,7 @@ static ssize_t evm_write_xattrs(struct file *file, const char __user *buf,
> > > inode_lock(inode);
> > > err = simple_setattr(evm_xattrs, &newattrs);
> > > inode_unlock(inode);
> > > - audit_log_format(ab, "locked");
> > > + audit_log_format(ab, "xattr=(locked)");
> >
> > Two things come to mind:
> >
> > * While we can clearly trust the string above, should we be logging
> > the xattr field value as an untrusted string so it is consistent with
> > how we record other xattr names?
>
> That would be a question for Steve.
>
> > * I'm not sure you can ever have parens in a xattr (I would hope not),
> > but if we are going to use the xattr field, perhaps we should simply
> > stick with the name as provided (".") so we don't ever run afoul of
> > xattr names? I'm curious to hear what the IMA/EVM folks think of
> > this.
>
> The legal xaddr names start with XATTR_SECURITY_PREFIX which is
> "security." so there is no danger of collision with legal names, but I
> suppose someone could try to use "(locked)" as a name which would look
> identical but fail with a different res= number. I think I prefer your
> idea of printing the given value verbatim.
I really don't have a preference - "locked", "(locked)", "." or "(.)".
Any of them is fine.
Thanks!
Mimi
^ permalink raw reply [flat|nested] 10+ messages in thread* Re: [PATCH ghak109 V1] audit: link integrity evm_write_xattrs record to syscall event
2019-03-21 0:50 ` Richard Guy Briggs
2019-03-21 1:03 ` Paul Moore
2019-03-26 15:11 ` Mimi Zohar
@ 2019-03-26 15:22 ` Steve Grubb
2019-03-26 15:29 ` Mimi Zohar
2 siblings, 1 reply; 10+ messages in thread
From: Steve Grubb @ 2019-03-26 15:22 UTC (permalink / raw)
To: Richard Guy Briggs
Cc: Paul Moore, linux-integrity, linux-security-module,
Linux-Audit Mailing List, LKML, omosnace, Eric Paris,
Serge Hallyn, zohar, mjg59
On Wednesday, March 20, 2019 8:50:08 PM EDT Richard Guy Briggs wrote:
> On 2019-03-20 19:48, Paul Moore wrote:
> > On Sat, Mar 16, 2019 at 8:10 AM Richard Guy Briggs <rgb@redhat.com>
wrote:
> > > In commit fa516b66a1bf ("EVM: Allow runtime modification of the set of
> > > verified xattrs"), the call to audit_log_start() is missing a context
> > > to
> > > link it to an audit event. Since this event is in user context, add
> > > the process' syscall context to the record.
> > >
> > > In addition, the orphaned keyword "locked" appears in the record.
> > > Normalize this by changing it to "xattr=(locked)".
> > >
> > > Please see the github issue
> > > https://github.com/linux-audit/audit-kernel/issues/109
> > >
> > > Signed-off-by: Richard Guy Briggs <rgb@redhat.com>
> > > ---
> > >
> > > security/integrity/evm/evm_secfs.c | 5 +++--
> > > 1 file changed, 3 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/security/integrity/evm/evm_secfs.c
> > > b/security/integrity/evm/evm_secfs.c index 015aea8fdf1e..4171d174e9da
> > > 100644
> > > --- a/security/integrity/evm/evm_secfs.c
> > > +++ b/security/integrity/evm/evm_secfs.c
> > > @@ -192,7 +192,8 @@ static ssize_t evm_write_xattrs(struct file *file,
> > > const char __user *buf,> >
> > > if (count > XATTR_NAME_MAX)
> > >
> > > return -E2BIG;
> > >
> > > - ab = audit_log_start(NULL, GFP_KERNEL,
> > > AUDIT_INTEGRITY_EVM_XATTR);
> > > + ab = audit_log_start(audit_context(), GFP_KERNEL,
> > > + AUDIT_INTEGRITY_EVM_XATTR);
> >
> > This part is fine.
> >
> > > if (!ab)
> > >
> > > return -ENOMEM;
> > >
> > > @@ -222,7 +223,7 @@ static ssize_t evm_write_xattrs(struct file *file,
> > > const char __user *buf,> >
> > > inode_lock(inode);
> > > err = simple_setattr(evm_xattrs, &newattrs);
> > > inode_unlock(inode);
> > >
> > > - audit_log_format(ab, "locked");
> > > + audit_log_format(ab, "xattr=(locked)");
> >
> > Two things come to mind:
> >
> > * While we can clearly trust the string above, should we be logging
> > the xattr field value as an untrusted string so it is consistent with
> > how we record other xattr names?
>
> That would be a question for Steve.
All fields with the same name must be represented the same way. If one
instance is untrusted, every instance of the same keyword must be untrusted.
-Steve
> > * I'm not sure you can ever have parens in a xattr (I would hope not),
> > but if we are going to use the xattr field, perhaps we should simply
> > stick with the name as provided (".") so we don't ever run afoul of
> > xattr names? I'm curious to hear what the IMA/EVM folks think of
> > this.
>
> The legal xaddr names start with XATTR_SECURITY_PREFIX which is
> "security." so there is no danger of collision with legal names, but I
> suppose someone could try to use "(locked)" as a name which would look
> identical but fail with a different res= number. I think I prefer your
> idea of printing the given value verbatim.
>
> > paul moore
>
> - RGB
>
> --
> Richard Guy Briggs <rgb@redhat.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
^ permalink raw reply [flat|nested] 10+ messages in thread* Re: [PATCH ghak109 V1] audit: link integrity evm_write_xattrs record to syscall event
2019-03-26 15:22 ` Steve Grubb
@ 2019-03-26 15:29 ` Mimi Zohar
2019-03-26 16:14 ` Richard Guy Briggs
0 siblings, 1 reply; 10+ messages in thread
From: Mimi Zohar @ 2019-03-26 15:29 UTC (permalink / raw)
To: Steve Grubb, Richard Guy Briggs
Cc: Paul Moore, linux-integrity, linux-security-module,
Linux-Audit Mailing List, LKML, omosnace, Eric Paris,
Serge Hallyn, mjg59
On Tue, 2019-03-26 at 11:22 -0400, Steve Grubb wrote:
> > > > --- a/security/integrity/evm/evm_secfs.c
> > > > +++ b/security/integrity/evm/evm_secfs.c
> > > > @@ -192,7 +192,8 @@ static ssize_t evm_write_xattrs(struct file *file,
> > > > const char __user *buf,> >
> > > > if (count > XATTR_NAME_MAX)
> > > >
> > > > return -E2BIG;
> > > >
> > > > - ab = audit_log_start(NULL, GFP_KERNEL,
> > > > AUDIT_INTEGRITY_EVM_XATTR);
> > > > + ab = audit_log_start(audit_context(), GFP_KERNEL,
> > > > + AUDIT_INTEGRITY_EVM_XATTR);
> > >
> > > This part is fine.
> > >
> > > > if (!ab)
> > > >
> > > > return -ENOMEM;
> > > >
> > > > @@ -222,7 +223,7 @@ static ssize_t evm_write_xattrs(struct file *file,
> > > > const char __user *buf,> >
> > > > inode_lock(inode);
> > > > err = simple_setattr(evm_xattrs, &newattrs);
> > > > inode_unlock(inode);
> > > >
> > > > - audit_log_format(ab, "locked");
> > > > + audit_log_format(ab, "xattr=(locked)");
> > >
> > > Two things come to mind:
> > >
> > > * While we can clearly trust the string above, should we be logging
> > > the xattr field value as an untrusted string so it is consistent with
> > > how we record other xattr names?
> >
> > That would be a question for Steve.
>
> All fields with the same name must be represented the same way. If one
> instance is untrusted, every instance of the same keyword must be untrusted.
Normal case:
audit_log_format(ab, "xattr=");
audit_log_untrustedstring(ab, xattr->name);
Ok, so the above audit_log_format() call should be replaced with
audit_log_untrustedstring().
Mimi
^ permalink raw reply [flat|nested] 10+ messages in thread* Re: [PATCH ghak109 V1] audit: link integrity evm_write_xattrs record to syscall event
2019-03-26 15:29 ` Mimi Zohar
@ 2019-03-26 16:14 ` Richard Guy Briggs
2019-03-26 17:42 ` Richard Guy Briggs
0 siblings, 1 reply; 10+ messages in thread
From: Richard Guy Briggs @ 2019-03-26 16:14 UTC (permalink / raw)
To: Mimi Zohar
Cc: Steve Grubb, Paul Moore, linux-integrity, linux-security-module,
Linux-Audit Mailing List, LKML, omosnace, Eric Paris,
Serge Hallyn, mjg59
On 2019-03-26 11:29, Mimi Zohar wrote:
> On Tue, 2019-03-26 at 11:22 -0400, Steve Grubb wrote:
>
> > > > > --- a/security/integrity/evm/evm_secfs.c
> > > > > +++ b/security/integrity/evm/evm_secfs.c
> > > > > @@ -192,7 +192,8 @@ static ssize_t evm_write_xattrs(struct file *file,
> > > > > const char __user *buf,> >
> > > > > if (count > XATTR_NAME_MAX)
> > > > >
> > > > > return -E2BIG;
> > > > >
> > > > > - ab = audit_log_start(NULL, GFP_KERNEL,
> > > > > AUDIT_INTEGRITY_EVM_XATTR);
> > > > > + ab = audit_log_start(audit_context(), GFP_KERNEL,
> > > > > + AUDIT_INTEGRITY_EVM_XATTR);
> > > >
> > > > This part is fine.
> > > >
> > > > > if (!ab)
> > > > >
> > > > > return -ENOMEM;
> > > > >
> > > > > @@ -222,7 +223,7 @@ static ssize_t evm_write_xattrs(struct file *file,
> > > > > const char __user *buf,> >
> > > > > inode_lock(inode);
> > > > > err = simple_setattr(evm_xattrs, &newattrs);
> > > > > inode_unlock(inode);
> > > > >
> > > > > - audit_log_format(ab, "locked");
> > > > > + audit_log_format(ab, "xattr=(locked)");
> > > >
> > > > Two things come to mind:
> > > >
> > > > * While we can clearly trust the string above, should we be logging
> > > > the xattr field value as an untrusted string so it is consistent with
> > > > how we record other xattr names?
> > >
> > > That would be a question for Steve.
> >
> > All fields with the same name must be represented the same way. If one
> > instance is untrusted, every instance of the same keyword must be untrusted.
>
> Normal case:
> audit_log_format(ab, "xattr=");
> audit_log_untrustedstring(ab, xattr->name);
>
> Ok, so the above audit_log_format() call should be replaced with
> audit_log_untrustedstring().
Ok, so I think we can agree on "audit_log_untrustedstring(ab,
"xattr=.");" and simpler yet just print the contents regardless and not
special case this print. V2 coming...
> Mimi
- RGB
--
Richard Guy Briggs <rgb@redhat.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
^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [PATCH ghak109 V1] audit: link integrity evm_write_xattrs record to syscall event
2019-03-26 16:14 ` Richard Guy Briggs
@ 2019-03-26 17:42 ` Richard Guy Briggs
2019-03-26 17:55 ` Matthew Garrett
0 siblings, 1 reply; 10+ messages in thread
From: Richard Guy Briggs @ 2019-03-26 17:42 UTC (permalink / raw)
To: Mimi Zohar
Cc: Steve Grubb, Paul Moore, linux-integrity, linux-security-module,
Linux-Audit Mailing List, LKML, omosnace, Eric Paris,
Serge Hallyn, mjg59
On 2019-03-26 12:14, Richard Guy Briggs wrote:
> On 2019-03-26 11:29, Mimi Zohar wrote:
> > On Tue, 2019-03-26 at 11:22 -0400, Steve Grubb wrote:
> >
> > > > > > --- a/security/integrity/evm/evm_secfs.c
> > > > > > +++ b/security/integrity/evm/evm_secfs.c
> > > > > > @@ -192,7 +192,8 @@ static ssize_t evm_write_xattrs(struct file *file,
> > > > > > const char __user *buf,> >
> > > > > > if (count > XATTR_NAME_MAX)
> > > > > >
> > > > > > return -E2BIG;
> > > > > >
> > > > > > - ab = audit_log_start(NULL, GFP_KERNEL,
> > > > > > AUDIT_INTEGRITY_EVM_XATTR);
> > > > > > + ab = audit_log_start(audit_context(), GFP_KERNEL,
> > > > > > + AUDIT_INTEGRITY_EVM_XATTR);
> > > > >
> > > > > This part is fine.
> > > > >
> > > > > > if (!ab)
> > > > > >
> > > > > > return -ENOMEM;
> > > > > >
> > > > > > @@ -222,7 +223,7 @@ static ssize_t evm_write_xattrs(struct file *file,
> > > > > > const char __user *buf,> >
> > > > > > inode_lock(inode);
> > > > > > err = simple_setattr(evm_xattrs, &newattrs);
> > > > > > inode_unlock(inode);
> > > > > >
> > > > > > - audit_log_format(ab, "locked");
> > > > > > + audit_log_format(ab, "xattr=(locked)");
> > > > >
> > > > > Two things come to mind:
> > > > >
> > > > > * While we can clearly trust the string above, should we be logging
> > > > > the xattr field value as an untrusted string so it is consistent with
> > > > > how we record other xattr names?
> > > >
> > > > That would be a question for Steve.
> > >
> > > All fields with the same name must be represented the same way. If one
> > > instance is untrusted, every instance of the same keyword must be untrusted.
> >
> > Normal case:
> > audit_log_format(ab, "xattr=");
> > audit_log_untrustedstring(ab, xattr->name);
> >
> > Ok, so the above audit_log_format() call should be replaced with
> > audit_log_untrustedstring().
>
> Ok, so I think we can agree on "audit_log_untrustedstring(ab,
> "xattr=.");" and simpler yet just print the contents regardless and not
> special case this print. V2 coming...
Ok, what I typed above wasn't quite what I intended... This is what I
meant:
audit_log_format(ab, "xattr=");
audit_log_untrustedstring(ab, ".");
But, I'll just move the normal case above the "." locking detection and
log all cases the same way.
> > Mimi
>
> - RGB
- RGB
--
Richard Guy Briggs <rgb@redhat.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
^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [PATCH ghak109 V1] audit: link integrity evm_write_xattrs record to syscall event
2019-03-26 17:42 ` Richard Guy Briggs
@ 2019-03-26 17:55 ` Matthew Garrett
0 siblings, 0 replies; 10+ messages in thread
From: Matthew Garrett @ 2019-03-26 17:55 UTC (permalink / raw)
To: Richard Guy Briggs
Cc: Mimi Zohar, Steve Grubb, Paul Moore, linux-integrity, LSM List,
Linux-Audit Mailing List, LKML, omosnace, Eric Paris,
Serge Hallyn
On Tue, Mar 26, 2019 at 10:43 AM Richard Guy Briggs <rgb@redhat.com> wrote:
> Ok, what I typed above wasn't quite what I intended... This is what I
> meant:
>
> audit_log_format(ab, "xattr=");
> audit_log_untrustedstring(ab, ".");
>
> But, I'll just move the normal case above the "." locking detection and
> log all cases the same way.
Sounds good to me.
^ permalink raw reply [flat|nested] 10+ messages in thread