[PATCH] libsemanage: set selinux policy root to match semanage root or storename

[Stephen Smalley <sds@tycho.nsa.gov>]

As reported in #109, semodule -p /path/to/policyroot -s minimum -n -B
tries to use /etc/selinux/targeted/booleans.subs_dist.  This is because
it invokes the libselinux selinux_boolean_sub() interface, which uses
the active/installed policy files rather than the libsemanage ones.

To fix, we need to set the selinux policy root when either the semanage
root or the semanage storename is set.  When setting the semanage root,
we need to prepend the semanage root to the selinux policy root.  When
setting the semanage storename, we need to replace the last component
of the selinux policy root with the new storename.

Test:
strace semodule -p ~/policy-root -s minimum -n -B

Before:
openat(AT_FDCWD, "/etc/selinux/targeted/booleans.subs_dist", O_RDONLY|O_CLOEXEC) = 5

After:
openat(AT_FDCWD, "/home/sds/policy-root/etc/selinux/minimum/booleans.subs_dist", O_RDONLY|O_CLOEXEC) = 5

Fixes https://github.com/SELinuxProject/selinux/issues/109

Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>
---
 libsemanage/src/handle.c | 29 ++++++++++++++++++++++++++++-
 1 file changed, 28 insertions(+), 1 deletion(-)

diff --git a/libsemanage/src/handle.c b/libsemanage/src/handle.c
index a6567bd4..c163e553 100644
--- a/libsemanage/src/handle.c
+++ b/libsemanage/src/handle.c
@@ -43,8 +43,21 @@ static char *private_semanage_root = NULL;
 
 int semanage_set_root(const char *root)
 {
+	char *new_selinux_root = NULL;
+
+	asprintf(&new_selinux_root, "%s%s", root, selinux_policy_root());
+	if (!new_selinux_root)
+		return -1;
+	if (selinux_set_policy_root(new_selinux_root) < 0) {
+		free(new_selinux_root);
+		return -1;
+	}
+	free(new_selinux_root);
+
 	free(private_semanage_root);
 	private_semanage_root = strdup(root);
+	if (!private_semanage_root)
+		return -1;
 	return 0;
 }
 
@@ -273,9 +286,23 @@ int semanage_is_connected(semanage_handle_t * sh)
 void semanage_select_store(semanage_handle_t * sh, char *storename,
 			   enum semanage_connect_type storetype)
 {
-
 	assert(sh != NULL);
 
+	char *root = strdup(selinux_policy_root());
+	assert(root);
+	char *end = strrchr(root, '/');
+	assert(end);
+	end++;
+	*end = '\0';
+
+	char *newroot = NULL;
+	asprintf(&newroot, "%s%s", root, storename);
+	assert(newroot);
+	free(root);
+	int rc = selinux_set_policy_root(newroot);
+	assert(rc == 0);
+	free(newroot);
+
 	/* This just sets the storename to what the user requests, no 
 	   verification of existance will be done until connect */
 	free(sh->conf->store_path);
-- 
2.19.1