From 750cc1136d054b77e84cd55be5fbe0e8ad0174e8 Mon Sep 17 00:00:00 2001
From: James Carter <jwcart2@gmail.com>
Date: Mon, 15 Mar 2021 11:09:37 -0400
Subject: [PATCH] checkpolicy: Do not automatically upgrade when using "-b"
 flag

When reading a binary policy, do not automatically change the version
to the max policy version supported by libsepol or, if specified, the
value given using the "-c" flag.

If the binary policy version is less than or equal to version 23
(POLICYDB_VERSION_PERMISSIVE) than do not automatically upgrade the
policy and if a policy version is specified by the "-c" flag, only set
the binary policy to the specified version if it is lower than the
current version.

If the binary policy version is greater than version 23 than it should
be set to the maximum version supported by libsepol or, if specified,
the value given by the "-c" flag.

The reason for this change is that policy versions 20
(POLICYDB_VERSION_AVTAB) to 23 have a more primitive support for type
attributes where the datums are not written out, but they exist in the
type_attr_map. This means that when the binary policy is read by
libsepol, there will be gaps in the type_val_to_struct and
p_type_val_to_name arrays and policy rules can refer to those gaps.
Certain libsepol functions like sepol_kernel_policydb_to_conf() and
sepol_kernel_policydb_to_cil() do not support this behavior and need
to be able to identify these policies. Policies before version 20 do not
support attributes at all and can be handled by all libsepol functions.

Signed-off-by: James Carter <jwcart2@gmail.com>
---
 checkpolicy/checkpolicy.c | 19 +++++++++++++++----
 1 file changed, 15 insertions(+), 4 deletions(-)

diff --git a/checkpolicy/checkpolicy.c b/checkpolicy/checkpolicy.c
index 5841c5c4c196..acf1eac41559 100644
--- a/checkpolicy/checkpolicy.c
+++ b/checkpolicy/checkpolicy.c
@@ -106,7 +106,7 @@ static int handle_unknown = SEPOL_DENY_UNKNOWN;
 static const char *txtfile = "policy.conf";
 static const char *binfile = "policy";
 
-unsigned int policyvers = POLICYDB_VERSION_MAX;
+unsigned int policyvers = 0;
 
 static __attribute__((__noreturn__)) void usage(const char *progname)
 {
@@ -515,7 +515,8 @@ int main(int argc, char **argv)
 	}
 
 	if (show_version) {
-		printf("%d (compatibility range %d-%d)\n", policyvers,
+		printf("%d (compatibility range %d-%d)\n",
+			   policyvers ? policyvers : POLICYDB_VERSION_MAX ,
 		       POLICYDB_VERSION_MAX, POLICYDB_VERSION_MIN);
 		exit(0);
 	}
@@ -588,6 +589,16 @@ int main(int argc, char **argv)
 				exit(1);
 			}
 		}
+
+		if (policydbp->policyvers <= POLICYDB_VERSION_PERMISSIVE) {
+			if (policyvers > policydbp->policyvers) {
+				fprintf(stderr, "Binary policies with version <= %u cannot be upgraded\n", POLICYDB_VERSION_PERMISSIVE);
+			} else if (policyvers) {
+				policydbp->policyvers = policyvers;
+			}
+		} else {
+			policydbp->policyvers = policyvers ? policyvers : POLICYDB_VERSION_MAX;
+		}
 	} else {
 		if (conf) {
 			fprintf(stderr, "Can only generate policy.conf from binary policy\n");
@@ -629,6 +640,8 @@ int main(int argc, char **argv)
 			policydb_destroy(policydbp);
 			policydbp = &policydb;
 		}
+
+		policydbp->policyvers = policyvers ? policyvers : POLICYDB_VERSION_MAX;
 	}
 
 	if (policydb_load_isids(&policydb, &sidtab))
@@ -654,8 +667,6 @@ int main(int argc, char **argv)
 			}
 		}
 
-		policydb.policyvers = policyvers;
-
 		if (!cil) {
 			if (!conf) {
 				policydb.policy_type = POLICY_KERN;
-- 
2.32.0