Re: [PATCH ghak109 V1] audit: link integrity evm_write_xattrs record to syscall event

On 2019-03-20 19:48, Paul Moore wrote: > On Sat, Mar 16, 2019 at 8:10 AM Richard Guy Briggs <rgb(a)redhat.com&gt;

> > 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(a)redhat.com&gt; > > --- > > > > 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. > paul moore - RGB -- Richard Guy Briggs <rgb(a)redhat.com&gt; 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