apparmor: fix absroot causing audited secids to begin with =

commit 511f7b5b835726e844a5fc7444c18e4b8672edfd upstream.

AppArmor is prefixing secids that are converted to secctx with the =
to indicate the secctx should only be parsed from an absolute root
POV. This allows catching errors where secctx are reparsed back into
internal labels.

Unfortunately because audit is using secid to secctx conversion this
means that subject and object labels can result in a very unfortunate
== that can break audit parsing.

eg. the subj==unconfined term in the below audit message

type=USER_LOGIN msg=audit(1639443365.233:160): pid=1633 uid=0 auid=1000
ses=3 subj==unconfined msg='op=login id=1000 exe="/usr/sbin/sshd"
hostname=192.168.122.1 addr=192.168.122.1 terminal=/dev/pts/1 res=success'

Fix this by switch the prepending of = to a _. This still works as a
special character to flag this case without breaking audit. Also move
this check behind debug as it should not be needed during normal
operqation.

Fixes: 26b7899510ae ("apparmor: add support for absolute root view based labels")
Reported-by: Casey Schaufler <casey@schaufler-ca.com>
Signed-off-by: John Johansen <john.johansen@canonical.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/security/apparmor/include/lib.h b/security/apparmor/include/lib.h
index 7d27db740bc2f19fae390923ddd87334950c9004..ac5054899f6f4956199d7b9ac5e88b3f3c2523c9 100644 (file)
--- a/security/apparmor/include/lib.h
+++ b/security/apparmor/include/lib.h
@@ -22,6 +22,11 @@
  */
 
 #define DEBUG_ON (aa_g_debug)
+/*
+ * split individual debug cases out in preparation for finer grained
+ * debug controls in the future.
+ */
+#define AA_DEBUG_LABEL DEBUG_ON
 #define dbg_printk(__fmt, __args...) pr_debug(__fmt, ##__args)
 #define AA_DEBUG(fmt, args...)                                         \
        do {                                                            \

diff --git a/security/apparmor/label.c b/security/apparmor/label.c
index 6222fdfebe4e55a905a55ed554f505b9bb34d216..ec13cd2b007a0d114743f44d9bdaf04666c1812c 100644 (file)
--- a/security/apparmor/label.c
+++ b/security/apparmor/label.c
@@ -1632,9 +1632,9 @@ int aa_label_snxprint(char *str, size_t size, struct aa_ns *ns,
        AA_BUG(!str && size != 0);
        AA_BUG(!label);
 
-       if (flags & FLAG_ABS_ROOT) {
+       if (AA_DEBUG_LABEL && (flags & FLAG_ABS_ROOT)) {
                ns = root_ns;
-               len = snprintf(str, size, "=");
+               len = snprintf(str, size, "_");
                update_for_len(total, len, size, str);
        } else if (!ns) {
                ns = labels_ns(label);
@@ -1896,7 +1896,8 @@ struct aa_label *aa_label_strn_parse(struct aa_label *base, const char *str,
        AA_BUG(!str);
 
        str = skipn_spaces(str, n);
-       if (str == NULL || (*str == '=' && base != &root_ns->unconfined->label))
+       if (str == NULL || (AA_DEBUG_LABEL && *str == '_' &&
+                           base != &root_ns->unconfined->label))
                return ERR_PTR(-EINVAL);
 
        len = label_count_strn_entries(str, end - str);