apparmor: Add support for attaching profiles via xattr, presence and value

Make it possible to tie Apparmor profiles to the presence of one or more
extended attributes, and optionally their values. An example usecase for
this is to automatically transition to a more privileged Apparmor profile
if an executable has a valid IMA signature, which can then be appraised
by the IMA subsystem.

Signed-off-by: Matthew Garrett <mjg59@google.com>
Signed-off-by: John Johansen <john.johansen@canonical.com>

1 files changed, 76 insertions, 9 deletions

diff --git a/security/apparmor/policy_unpack.c b/security/apparmor/policy_unpack.c
index 40c8dc617b13..98d019185e57 100644
--- a/security/apparmor/policy_unpack.c
+++ b/security/apparmor/policy_unpack.c
@@ -203,6 +203,15 @@ static bool inbounds(struct aa_ext *e, size_t size)
 	return (size <= e->end - e->pos);
 }
 
+static void *kvmemdup(const void *src, size_t len)
+{
+	void *p = kvmalloc(len, GFP_KERNEL);
+
+	if (p)
+		memcpy(p, src, len);
+	return p;
+}
+
 /**
  * aa_u16_chunck - test and do bounds checking for a u16 size based chunk
  * @e: serialized data read head (NOT NULL)
@@ -522,6 +531,68 @@ fail:
 	return 0;
 }
 
+static bool unpack_xattrs(struct aa_ext *e, struct aa_profile *profile)
+{
+	void *pos = e->pos;
+
+	if (unpack_nameX(e, AA_STRUCT, "xattrs")) {
+		int i, size;
+
+		size = unpack_array(e, NULL);
+		profile->xattr_count = size;
+		profile->xattrs = kcalloc(size, sizeof(char *),
+						GFP_KERNEL);
+		if (!profile->xattrs)
+			goto fail;
+		for (i = 0; i < size; i++) {
+			if (!unpack_strdup(e, &profile->xattrs[i], NULL))
+				goto fail;
+		}
+		if (!unpack_nameX(e, AA_ARRAYEND, NULL))
+			goto fail;
+		if (!unpack_nameX(e, AA_STRUCTEND, NULL))
+			goto fail;
+	}
+
+	if (unpack_nameX(e, AA_STRUCT, "xattr_values")) {
+		int i, size;
+
+		size = unpack_array(e, NULL);
+
+		/* Must be the same number of xattr values as xattrs */
+		if (size != profile->xattr_count)
+			goto fail;
+
+		profile->xattr_lens = kcalloc(size, sizeof(size_t),
+						    GFP_KERNEL);
+		if (!profile->xattr_lens)
+			goto fail;
+
+		profile->xattr_values = kcalloc(size, sizeof(char *),
+						      GFP_KERNEL);
+		if (!profile->xattr_values)
+			goto fail;
+
+		for (i = 0; i < size; i++) {
+			profile->xattr_lens[i] = unpack_blob(e,
+					      &profile->xattr_values[i], NULL);
+			profile->xattr_values[i] =
+				kvmemdup(profile->xattr_values[i],
+					 profile->xattr_lens[i]);
+		}
+
+		if (!unpack_nameX(e, AA_ARRAYEND, NULL))
+			goto fail;
+		if (!unpack_nameX(e, AA_STRUCTEND, NULL))
+			goto fail;
+	}
+	return 1;
+
+fail:
+	e->pos = pos;
+	return 0;
+}
+
 static bool unpack_rlimits(struct aa_ext *e, struct aa_profile *profile)
 {
 	void *pos = e->pos;
@@ -556,15 +627,6 @@ fail:
 	return 0;
 }
 
-static void *kvmemdup(const void *src, size_t len)
-{
-	void *p = kvmalloc(len, GFP_KERNEL);
-
-	if (p)
-		memcpy(p, src, len);
-	return p;
-}
-
 static u32 strhash(const void *data, u32 len, u32 seed)
 {
 	const char * const *key = data;
@@ -719,6 +781,11 @@ static struct aa_profile *unpack_profile(struct aa_ext *e, char **ns_name)
 			goto fail;
 	}
 
+	if (!unpack_xattrs(e, profile)) {
+		info = "failed to unpack profile xattrs";
+		goto fail;
+	}
+
 	if (!unpack_rlimits(e, profile)) {
 		info = "failed to unpack profile rlimits";
 		goto fail;