Re: [PATCH ghak95] audit: Do not log full CWD path on empty relative paths

On Thu, Aug 2, 2018 at 1:45 PM Ondrej Mosnacek <omosnace(a)redhat.com&gt; wrote: > When a relative path has just a single component and we want to emit a > nametype=PARENT record, the current implementation just reports the full > CWD path (which is alrady available in the audit context). > > This is wrong for three reasons: > 1. Wasting log space for redundant data (CWD path is already in the CWD > > record). > > 2. Inconsistency with other PATH records (if a relative PARENT directory > > path contains at least one component, only the verbatim relative path > is logged). > > 3. In some syscalls (e.g. openat(2)) the relative path may not even be > > relative to the CWD, but to another directory specified as a file > descriptor. In that case the logged path is simply plain wrong. > > This patch modifies this behavior to simply report "." in the > aforementioned case, which is equivalent to an "empty" directory path > and can be concatenated with the actual base directory path (CWD or > dirfd from openat(2)-like syscall) once support for its logging is added > later. In the meantime, defaulting to CWD as base directory on relative > paths (as already done by the userspace tools) will be enough to achieve > results equivalent to the current behavior. I tested this patch a little bit with the libauparse library (it has some functions for normalizing paths extracted from the records) and it seems to behave as intended. The userspace functions seem to take a rather crude approach and I think they won't always properly normalize some paths, but that is a separate issue and this patch at least definitely doesn't make it worse.

> See: https://github.com/linux-audit/audit-kernel/issues/95 > > Fixes: 9c937dcc7102 ("[PATCH] log more info for directory entry change > events") Signed-off-by: Ondrej Mosnacek <omosnace(a)redhat.com&gt; > --- > > kernel/audit.c | 9 ++++----- > 1 file changed, 4 insertions(+), 5 deletions(-) > > diff --git a/kernel/audit.c b/kernel/audit.c > index 2a8058764aa6..4f18bd48eb4b 100644 > --- a/kernel/audit.c > +++ b/kernel/audit.c > @@ -2127,28 +2127,27 @@ void audit_log_name(struct audit_context > *context, struct audit_names *n,> > audit_log_format(ab, "item=%d", record_num); > > + audit_log_format(ab, " name="); > > if (path) > > - audit_log_d_path(ab, " name=", path); > + audit_log_d_path(ab, NULL, path); > > else if (n->name) { > > switch (n->name_len) { > > case AUDIT_NAME_FULL: > /* log the full path */ > > - audit_log_format(ab, " name="); > > audit_log_untrustedstring(ab, n->name->name); > break; > > case 0: > /* name was specified as a relative path and the > > * directory component is the cwd */ > > - audit_log_d_path(ab, " name=", &context->pwd); > + audit_log_untrustedstring(ab, "."); > > break; > > default: > /* log the name's directory component */ > > - audit_log_format(ab, " name="); > > audit_log_n_untrustedstring(ab, n->name->name, > > n->name_len); > > } > > } else > > - audit_log_format(ab, " name=(null)"); > + audit_log_format(ab, "(null)"); > > if (n->ino != AUDIT_INO_UNSET) > > audit_log_format(ab, " inode=%lu" > > -- > 2.17.1 -- Ondrej Mosnacek <omosnace at redhat dot com> Associate Software Engineer, Security Technologies Red Hat, Inc.