apparmor: allow ptrace checks to be finer grained than just capability

Signed-off-by: John Johansen <john.johansen@canonical.com>

security/apparmor/apparmorfs.c

@@ -2086,6 +2086,11 @@ static struct aa_sfs_entry aa_sfs_entry_file[] = {
 	{ }
 };
 
+static struct aa_sfs_entry aa_sfs_entry_ptrace[] = {
+	AA_SFS_FILE_STRING("mask", "read trace"),
+	{ }
+};
+
 static struct aa_sfs_entry aa_sfs_entry_domain[] = {
 	AA_SFS_FILE_BOOLEAN("change_hat",	1),
 	AA_SFS_FILE_BOOLEAN("change_hatv",	1),
@@ -2125,6 +2130,7 @@ static struct aa_sfs_entry aa_sfs_entry_features[] = {
 	AA_SFS_FILE_U64("capability",		VFS_CAP_FLAGS_MASK),
 	AA_SFS_DIR("rlimit",			aa_sfs_entry_rlimit),
 	AA_SFS_DIR("caps",			aa_sfs_entry_caps),
+	AA_SFS_DIR("ptrace",			aa_sfs_entry_ptrace),
 	AA_SFS_DIR("query",			aa_sfs_entry_query),
 	{ }
 };

security/apparmor/include/ipc.h

@@ -21,6 +21,12 @@ struct aa_profile;
 
 #define AA_PTRACE_TRACE		MAY_WRITE
 #define AA_PTRACE_READ		MAY_READ
+#define AA_MAY_BE_TRACED	AA_MAY_APPEND
+#define AA_MAY_BE_READ		AA_MAY_CREATE
+#define PTRACE_PERM_SHIFT	2
+
+#define AA_PTRACE_PERM_MASK (AA_PTRACE_READ | AA_PTRACE_TRACE | \
+			     AA_MAY_BE_READ | AA_MAY_BE_TRACED)
 
 int aa_may_ptrace(struct aa_label *tracer, struct aa_label *tracee,
 		  u32 request);

security/apparmor/ipc.c

@@ -21,20 +21,76 @@
 #include "include/policy.h"
 #include "include/ipc.h"
 
+/**
+ * audit_ptrace_mask - convert mask to permission string
+ * @buffer: buffer to write string to (NOT NULL)
+ * @mask: permission mask to convert
+ */
+static void audit_ptrace_mask(struct audit_buffer *ab, u32 mask)
+{
+	switch (mask) {
+	case MAY_READ:
+		audit_log_string(ab, "read");
+		break;
+	case MAY_WRITE:
+		audit_log_string(ab, "trace");
+		break;
+	case AA_MAY_BE_READ:
+		audit_log_string(ab, "readby");
+		break;
+	case AA_MAY_BE_TRACED:
+		audit_log_string(ab, "tracedby");
+		break;
+	}
+}
+
 /* call back to audit ptrace fields */
 static void audit_ptrace_cb(struct audit_buffer *ab, void *va)
 {
 	struct common_audit_data *sa = va;
 
+	if (aad(sa)->request & AA_PTRACE_PERM_MASK) {
+		audit_log_format(ab, " requested_mask=");
+		audit_ptrace_mask(ab, aad(sa)->request);
+
+		if (aad(sa)->denied & AA_PTRACE_PERM_MASK) {
+			audit_log_format(ab, " denied_mask=");
+			audit_ptrace_mask(ab, aad(sa)->denied);
+		}
+	}
 	audit_log_format(ab, " peer=");
 	aa_label_xaudit(ab, labels_ns(aad(sa)->label), aad(sa)->peer,
 			FLAGS_NONE, GFP_ATOMIC);
 }
 
+/* TODO: conditionals */
+static int profile_ptrace_perm(struct aa_profile *profile,
+			       struct aa_profile *peer, u32 request,
+			       struct common_audit_data *sa)
+{
+	struct aa_perms perms = { };
+
+	/* need because of peer in cross check */
+	if (profile_unconfined(profile) ||
+	    !PROFILE_MEDIATES(profile, AA_CLASS_PTRACE))
+		return 0;
+
+	aad(sa)->peer = &peer->label;
+	aa_profile_match_label(profile, &peer->label, AA_CLASS_PTRACE, request,
+			       &perms);
+	aa_apply_modes_to_perms(profile, &perms);
+	return aa_check_perms(profile, &perms, request, sa, audit_ptrace_cb);
+}
+
 static int cross_ptrace_perm(struct aa_profile *tracer,
 			     struct aa_profile *tracee, u32 request,
 			     struct common_audit_data *sa)
 {
+	if (PROFILE_MEDIATES(tracer, AA_CLASS_PTRACE))
+		return xcheck(profile_ptrace_perm(tracer, tracee, request, sa),
+			      profile_ptrace_perm(tracee, tracer,
+						  request << PTRACE_PERM_SHIFT,
+						  sa));
 	/* policy uses the old style capability check for ptrace */
 	if (profile_unconfined(tracer) || tracer == tracee)
 		return 0;