[PATCH 1/2] checkmodule: add support for specifying module policy version

[Gary Tierney <gary.tierney@fastmail.com>]

Currently checkpolicy can produce binary policies for earlier policy versions
to provide support for building policies on one machine and loading/analyzing
them on another machine with an earlier version of the kernel or libsepol,
respectively. However, checkmodule was lacking this capability.

This commit adds an identical `-c` flag that can be passed to checkmodule that
will build a modular policy file of the specified version.

Signed-off-by: Gary Tierney <gary.tierney@fastmail.com>
---
 checkpolicy/checkmodule.8 |  5 ++++-
 checkpolicy/checkmodule.c | 29 +++++++++++++++++++++++++++--
 2 files changed, 31 insertions(+), 3 deletions(-)

diff --git a/checkpolicy/checkmodule.8 b/checkpolicy/checkmodule.8
index cf76591c24d0..e55582f30ec0 100644
--- a/checkpolicy/checkmodule.8
+++ b/checkpolicy/checkmodule.8
@@ -38,7 +38,7 @@ Generate a non-base policy module.
 Enable the MLS/MCS support when checking and compiling the policy module.
 .TP
 .B \-V,\-\-version
- Show policy versions created by this program.  Note that you cannot currently build older versions.
+Show policy versions created by this program.
 .TP
 .B \-o,\-\-output filename
 Write a binary policy module file to the specified filename.
@@ -47,6 +47,9 @@ and will not generate a binary module at all.
 .TP
 .B \-U,\-\-handle-unknown <action>
 Specify how the kernel should handle unknown classes or permissions (deny, allow or reject).
+.TP
+.B \-c policyvers
+Specify the policy version, defaults to the latest.
 
 .SH EXAMPLE
 .nf
diff --git a/checkpolicy/checkmodule.c b/checkpolicy/checkmodule.c
index 8edc1f8c7bbd..3bb9e5a4a6b3 100644
--- a/checkpolicy/checkmodule.c
+++ b/checkpolicy/checkmodule.c
@@ -142,6 +142,8 @@ static __attribute__((__noreturn__)) void usage(const char *progname)
 	printf("  -m         build a policy module instead of a base module\n");
 	printf("  -M         enable MLS policy\n");
 	printf("  -o FILE    write module to FILE (else just check syntax)\n");
+	printf("  -c VERSION build a policy module targeting a modular policy version (%d-%d)\n",
+	       MOD_POLICYDB_VERSION_MIN, MOD_POLICYDB_VERSION_MAX);
 	exit(1);
 }
 
@@ -163,7 +165,7 @@ int main(int argc, char **argv)
 		{NULL, 0, NULL, 0}
 	};
 
-	while ((ch = getopt_long(argc, argv, "ho:bVU:mMC", long_options, NULL)) != -1) {
+	while ((ch = getopt_long(argc, argv, "ho:bVU:mMCc:", long_options, NULL)) != -1) {
 		switch (ch) {
 		case 'h':
 			usage(argv[0]);
@@ -194,7 +196,6 @@ int main(int argc, char **argv)
 			usage(argv[0]);
 		case 'm':
 			policy_type = POLICY_MOD;
-			policyvers = MOD_POLICYDB_VERSION_MAX;
 			break;
 		case 'M':
 			mlspol = 1;
@@ -202,6 +203,30 @@ int main(int argc, char **argv)
 		case 'C':
 			cil = 1;
 			break;
+		case 'c': {
+			long int n;
+			errno = 0;
+			n = strtol(optarg, NULL, 10);
+
+			if (errno) {
+				fprintf(stderr,
+					"Invalid policyvers specified: %s\n",
+					optarg);
+				usage(argv[0]);
+			}
+
+			if (n < MOD_POLICYDB_VERSION_MIN
+			    || n > MOD_POLICYDB_VERSION_MAX) {
+				fprintf(stderr,
+					"policyvers value %ld not in range %d-%d\n",
+					n, MOD_POLICYDB_VERSION_MIN,
+					MOD_POLICYDB_VERSION_MAX);
+				usage(argv[0]);
+			}
+
+			policyvers = n;
+			break;
+		}
 		default:
 			usage(argv[0]);
 		}
-- 
2.17.2