The libselinux selinux_set_mapping() implementation was never updated
to handle unknown classes/permissions based on the policy handle_unknown
flag. Update it and the internal mapping functions to gracefully
handle unknown classes/permissions. Add a security_reject_unknown()
interface to expose the corresponding selinuxfs node and use it when
creating a mapping to decide whether to fail immediately or proceed.
This enables dbus-daemon and XSELinux, which use selinux_set_mapping(),
to continue working with the dummy policy or other policies that lack
their userspace class/permission definitions as long as the policy
was built with -U allow.
Signed-off-by: Stephen Smalley <sds@xxxxxxxxxxxxx>
---
libselinux/include/selinux/selinux.h | 5 +-
libselinux/src/compute_av.c | 16 +++++--
libselinux/src/mapping.c | 71 ++++++++++++++++++++++------
libselinux/src/mapping.h | 4 +-
libselinux/src/reject_unknown.c | 40 ++++++++++++++++
libselinux/src/selinux_internal.h | 1 +
6 files changed, 117 insertions(+), 20 deletions(-)
create mode 100644 libselinux/src/reject_unknown.c
diff --git a/libselinux/include/selinux/selinux.h b/libselinux/include/selinux/selinux.h
index 01201eee..a34d54fc 100644
--- a/libselinux/include/selinux/selinux.h
+++ b/libselinux/include/selinux/selinux.h
@@ -328,7 +328,10 @@ extern int security_getenforce(void);
/* Set the enforce flag value. */
extern int security_setenforce(int value);
-/* Get the behavior for undefined classes/permissions */
+/* Get the load-time behavior for undefined classes/permissions */
+extern int security_reject_unknown(void);
+
+/* Get the runtime behavior for undefined classes/permissions */
extern int security_deny_unknown(void);
/* Get the checkreqprot value */
diff --git a/libselinux/src/compute_av.c b/libselinux/src/compute_av.c
index 1d05e7b6..d5741637 100644
--- a/libselinux/src/compute_av.c
+++ b/libselinux/src/compute_av.c
@@ -20,6 +20,7 @@ int security_compute_av_flags_raw(const char * scon,
char *buf;
size_t len;
int fd, ret;
+ security_class_t kclass;
if (!selinux_mnt) {
errno = ENOENT;
@@ -38,8 +39,9 @@ int security_compute_av_flags_raw(const char * scon,
goto out;
}
+ kclass = unmap_class(tclass);
snprintf(buf, len, "%s %s %hu %x", scon, tcon,
- unmap_class(tclass), unmap_perm(tclass, requested));
+ kclass, unmap_perm(tclass, requested));
ret = write(fd, buf, strlen(buf));
if (ret < 0)
@@ -60,9 +62,15 @@ int security_compute_av_flags_raw(const char * scon,
} else if (ret < 6)
avd->flags = 0;
- /* If tclass invalid, kernel sets avd according to deny_unknown flag */
- if (tclass != 0)
- map_decision(tclass, avd);
+ /*
+ * If the tclass could not be mapped to a kernel class at all, the
+ * kernel will have already set avd according to the
+ * handle_unknown flag and we do not need to do anything further.
+ * Otherwise, we must map the permissions within the returned
+ * avd to the userspace permission values.
+ */
+ if (kclass != 0)
+ map_decision(tclass, avd, !security_deny_unknown());
ret = 0;
out2:
diff --git a/libselinux/src/mapping.c b/libselinux/src/mapping.c
index f205804b..892f887e 100644
--- a/libselinux/src/mapping.c
+++ b/libselinux/src/mapping.c
@@ -8,7 +8,9 @@
#include <stdarg.h>
#include <selinux/selinux.h>
#include <selinux/avc.h>
+#include "callbacks.h"
#include "mapping.h"
+#include "selinux_internal.h"
/*
* Class and permission mappings
@@ -33,6 +35,9 @@ selinux_set_mapping(struct security_class_mapping *map)
size_t size = sizeof(struct selinux_mapping);
security_class_t i, j;
unsigned k;
+ bool print_unknown_handle = false;
+ bool reject = (security_reject_unknown() == 1);
+ bool deny = (security_deny_unknown() == 1);
free(current_mapping);
current_mapping = NULL;
@@ -62,8 +67,16 @@ selinux_set_mapping(struct security_class_mapping *map)
struct selinux_mapping *p_out = current_mapping + j;
p_out->value = string_to_security_class(p_in->name);
- if (!p_out->value)
- goto err2;
+ if (!p_out->value) {
+ selinux_log(SELINUX_INFO,
+ "SELinux: Class %s not defined in policy.\n",
+ p_in->name);
+ if (reject)
+ goto err2;
+ p_out->num_perms = 0;
+ print_unknown_handle = true;
+ continue;
+ }
k = 0;
while (p_in->perms[k]) {
@@ -74,13 +87,24 @@ selinux_set_mapping(struct security_class_mapping *map)
}
p_out->perms[k] = string_to_av_perm(p_out->value,
p_in->perms[k]);
- if (!p_out->perms[k])
- goto err2;
+ if (!p_out->perms[k]) {
+ selinux_log(SELINUX_INFO,
+ "SELinux: Permission %s in class %s not defined in policy.\n",
+ p_in->perms[k], p_in->name);
+ if (reject)
+ goto err2;
+ print_unknown_handle = true;
+ }
k++;
}
p_out->num_perms = k;
}
+ if (print_unknown_handle)
+ selinux_log(SELINUX_INFO,
+ "SELinux: the above unknown classes and permissions will be %s\n",
+ deny ? "denied" : "allowed");
+
/* Set the mapping size here so the above lookups are "raw" */
current_mapping_size = i;
return 0;
@@ -181,30 +205,49 @@ map_perm(security_class_t tclass, access_vector_t kperm)
}
void
-map_decision(security_class_t tclass, struct av_decision *avd)
+map_decision(security_class_t tclass, struct av_decision *avd,
+ bool allow_unknown)
{
if (tclass < current_mapping_size) {
- unsigned i;
+ struct selinux_mapping *mapping = ¤t_mapping[tclass];
+ unsigned int i, n = mapping->num_perms;
access_vector_t result;
- for (i=0, result=0; i<current_mapping[tclass].num_perms; i++)
- if (avd->allowed & current_mapping[tclass].perms[i])
+ for (i = 0, result = 0; i < n; i++) {
+ if (avd->allowed & mapping->perms[i])
+ result |= 1<<i;
+ if (allow_unknown && !mapping->perms[i])
result |= 1<<i;
+ }
avd->allowed = result;
- for (i=0, result=0; i<current_mapping[tclass].num_perms; i++)
- if (avd->decided & current_mapping[tclass].perms[i])
+ for (i = 0, result = 0; i < n; i++) {
+ if (avd->decided & mapping->perms[i])
+ result |= 1<<i;
+ if (allow_unknown && !mapping->perms[i])
result |= 1<<i;
+ }
avd->decided = result;
- for (i=0, result=0; i<current_mapping[tclass].num_perms; i++)
- if (avd->auditallow & current_mapping[tclass].perms[i])
+ for (i = 0, result = 0; i < n; i++)
+ if (avd->auditallow & mapping->perms[i])
result |= 1<<i;
avd->auditallow = result;
- for (i=0, result=0; i<current_mapping[tclass].num_perms; i++)
- if (avd->auditdeny & current_mapping[tclass].perms[i])
+ for (i = 0, result = 0; i < n; i++) {
+ if (avd->auditdeny & mapping->perms[i])
result |= 1<<i;
+ if (!allow_unknown && !mapping->perms[i])
+ result |= 1<<i;
+ }
+
+ /*
+ * Make sure we audit denials for any permission check
+ * beyond the mapping->num_perms since this indicates
+ * a bug in the object manager.
+ */
+ for (; i < (sizeof(result)*8); i++)
+ result |= 1<<i;
avd->auditdeny = result;
}
}
diff --git a/libselinux/src/mapping.h b/libselinux/src/mapping.h
index 22a4ccaf..12ebb89f 100644
--- a/libselinux/src/mapping.h
+++ b/libselinux/src/mapping.h
@@ -7,6 +7,7 @@
#define _SELINUX_MAPPING_H_
#include <selinux/selinux.h>
+#include <stdbool.h>
/*
* Get real, kernel values from mapped values
@@ -29,6 +30,7 @@ extern access_vector_t
map_perm(security_class_t tclass, access_vector_t kperm);
extern void
-map_decision(security_class_t tclass, struct av_decision *avd);
+map_decision(security_class_t tclass, struct av_decision *avd,
+ bool allow_unknown);
#endif /* _SELINUX_MAPPING_H_ */
diff --git a/libselinux/src/reject_unknown.c b/libselinux/src/reject_unknown.c
new file mode 100644
index 00000000..5c1d3605
--- /dev/null
+++ b/libselinux/src/reject_unknown.c
@@ -0,0 +1,40 @@
+#include <unistd.h>
+#include <sys/types.h>
+#include <fcntl.h>
+#include <stdlib.h>
+#include <errno.h>
+#include <string.h>
+#include "selinux_internal.h"
+#include "policy.h"
+#include <stdio.h>
+#include <limits.h>
+
+int security_reject_unknown(void)
+{
+ int fd, ret, reject_unknown = 0;
+ char path[PATH_MAX];
+ char buf[20];
+
+ if (!selinux_mnt) {
+ errno = ENOENT;
+ return -1;
+ }
+
+ snprintf(path, sizeof(path), "%s/reject_unknown", selinux_mnt);
+ fd = open(path, O_RDONLY | O_CLOEXEC);
+ if (fd < 0)
+ return -1;
+
+ memset(buf, 0, sizeof(buf));
+ ret = read(fd, buf, sizeof(buf) - 1);
+ close(fd);
+ if (ret < 0)
+ return -1;
+
+ if (sscanf(buf, "%d", &reject_unknown) != 1)
+ return -1;
+
+ return reject_unknown;
+}
+
+hidden_def(security_reject_unknown);
diff --git a/libselinux/src/selinux_internal.h b/libselinux/src/selinux_internal.h
index dfc421cc..70b5025d 100644
--- a/libselinux/src/selinux_internal.h
+++ b/libselinux/src/selinux_internal.h
@@ -59,6 +59,7 @@ hidden_proto(selinux_mkload_policy)
hidden_proto(security_getenforce)
hidden_proto(security_setenforce)
hidden_proto(security_deny_unknown)
+ hidden_proto(security_reject_unknown)
hidden_proto(security_get_checkreqprot)
hidden_proto(selinux_boolean_sub)
hidden_proto(selinux_current_policy_path)
--
2.20.1
