apparmor: disable showing the mode as part of a secid to secctx

Displaying the mode as part of the seectx takes up unnecessary memory,
makes it so we can't use refcounted secctx so we need to alloc/free on
every conversion from secid to secctx and introduces a space that
could be potentially mishandled by tooling.

Eg. In an audit record we get

  subj_type=firefix (enforce)

Having the mode reported is not necessary, and might even be confusing
eg. when writing an audit rule to match the above record field you
would use

  -F subj_type=firefox

ie. the mode is not included. AppArmor provides ways to find the mode
without reporting as part of the secctx. So disable this by default
before its use is wide spread and we can't. For now we add a sysctl
to control the behavior as we can't guarantee no one is using this.

Acked-by: Andrea Righi <andrea.righi@canonical.com>
Signed-off-by: John Johansen <john.johansen@canonical.com>

diff --git a/security/apparmor/include/secid.h b/security/apparmor/include/secid.h
index 278dff5ecd1f3cdbf8578d7494185e62c5f5e068..a912a5d5d04f5ea89980ab0174c3615ab657b992 100644 (file)
--- a/security/apparmor/include/secid.h
+++ b/security/apparmor/include/secid.h
@@ -21,6 +21,9 @@ struct aa_label;
 /* secid value that matches any other secid */
 #define AA_SECID_WILDCARD 1
 
+/* sysctl to enable displaying mode when converting secid to secctx */
+extern int apparmor_display_secid_mode;
+
 struct aa_label *aa_secid_to_label(u32 secid);
 int apparmor_secid_to_secctx(u32 secid, char **secdata, u32 *seclen);
 int apparmor_secctx_to_secid(const char *secdata, u32 seclen, u32 *secid);

diff --git a/security/apparmor/lsm.c b/security/apparmor/lsm.c
index b1a0f2172a2e7f25b437296b86bf674a1e7875cb..090a20805664949635895df9cfdc270ca58cd9e5 100644 (file)
--- a/security/apparmor/lsm.c
+++ b/security/apparmor/lsm.c
@@ -1764,6 +1764,14 @@ static struct ctl_table apparmor_sysctl_table[] = {
                .mode           = 0600,
                .proc_handler   = apparmor_dointvec,
        },
+       {
+               .procname       = "apparmor_display_secid_mode",
+               .data           = &apparmor_display_secid_mode,
+               .maxlen         = sizeof(int),
+               .mode           = 0600,
+               .proc_handler   = apparmor_dointvec,
+       },
+
        { }
 };
 

diff --git a/security/apparmor/secid.c b/security/apparmor/secid.c
index 3b08942db1f67058e7becb8042805ac0c8ab7c9c..24a0e23f1b2ba305972ed5cc117c93583600d45b 100644 (file)
--- a/security/apparmor/secid.c
+++ b/security/apparmor/secid.c
@@ -31,6 +31,8 @@
 
 static DEFINE_XARRAY_FLAGS(aa_secids, XA_FLAGS_LOCK_IRQ | XA_FLAGS_TRACK_FREE);
 
+int apparmor_display_secid_mode;
+
 /*
  * TODO: allow policy to reserve a secid range?
  * TODO: add secid pinning
@@ -64,6 +66,7 @@ int apparmor_secid_to_secctx(u32 secid, char **secdata, u32 *seclen)
 {
        /* TODO: cache secctx and ref count so we don't have to recreate */
        struct aa_label *label = aa_secid_to_label(secid);
+       int flags = FLAG_VIEW_SUBNS | FLAG_HIDDEN_UNCONFINED | FLAG_ABS_ROOT;
        int len;
 
        AA_BUG(!seclen);
@@ -71,15 +74,15 @@ int apparmor_secid_to_secctx(u32 secid, char **secdata, u32 *seclen)
        if (!label)
                return -EINVAL;
 
+       if (apparmor_display_secid_mode)
+               flags |= FLAG_SHOW_MODE;
+
        if (secdata)
                len = aa_label_asxprint(secdata, root_ns, label,
-                                       FLAG_SHOW_MODE | FLAG_VIEW_SUBNS |
-                                       FLAG_HIDDEN_UNCONFINED | FLAG_ABS_ROOT,
-                                       GFP_ATOMIC);
+                                       flags, GFP_ATOMIC);
        else
-               len = aa_label_snxprint(NULL, 0, root_ns, label,
-                                       FLAG_SHOW_MODE | FLAG_VIEW_SUBNS |
-                                       FLAG_HIDDEN_UNCONFINED | FLAG_ABS_ROOT);
+               len = aa_label_snxprint(NULL, 0, root_ns, label, flags);
+
        if (len < 0)
                return -ENOMEM;