I submit the patch again, according to patch submission convension.
This patch enables to accept percent-encoded object names as forth argument of /selinux/create interface to avoid possible bugs when we give an object name including whitespace or multibutes.
E.g) if and when a userspace object manager tries to create a new object
named as "resolve.conf but fake", it shall give this name as the forth
argument of the /selinux/create. But sscanf() logic in kernel space
fetches only the part earlier than the first whitespace.
In this case, selinux may unexpectedly answer a default security context
configured to "resolve.conf", but it is bug.
Although I could not test this patch on named TYPE_TRANSITION rules actually, But debug printk() message seems to me the logic works correctly.
I assume the libselinux provides an interface to apply this logic transparently, so nothing shall not be changed from the viewpoint of application.
Signed-off-by: KaiGai Kohei <kohei.kaigai@xxxxxxxxxxxx>
---
security/selinux/selinuxfs.c | 38 +++++++++++++++++++++++++++++++++++++-
1 files changed, 37 insertions(+), 1 deletions(-)
diff --git a/security/selinux/selinuxfs.c b/security/selinux/selinuxfs.c index 973f5a4..4fde279 100644
--- a/security/selinux/selinuxfs.c
+++ b/security/selinux/selinuxfs.c
@@ -28,6 +28,7 @@
#include <linux/percpu.h>
#include <linux/audit.h>
#include <linux/uaccess.h>
+#include <linux/ctype.h>
/* selinuxfs pseudo filesystem for exporting the security policy API.
Based on the proc code and the fs/nfsd/nfsctl.c code. */ @@ -750,6 +751,15 @@ out:
return length;
}
+static inline int hexcode_to_int(int code) {
+ if (code == '\0' || !isxdigit(code))
+ return -1;
+ if (isdigit(code))
+ return code - '0';
+ return tolower(code) - 'a' + 10;
+}
+
static ssize_t sel_write_create(struct file *file, char *buf, size_t size) {
char *scon = NULL, *tcon = NULL;
@@ -784,8 +794,34 @@ static ssize_t sel_write_create(struct file *file, char *buf, size_t size)
nargs = sscanf(buf, "%s %s %hu %s", scon, tcon, &tclass, namebuf);
if (nargs < 3 || nargs > 4)
goto out;
- if (nargs == 4)
+ if (nargs == 4) {
+ /*
+ * If and when the name of new object to be queried contains
+ * either whitespace or multibyte characters, they shall be
+ * encoded based on the percentage-encoding rule.
+ * If not encoded, the sscanf logic picks up only left-half
+ * of the supplied name; splitted by a whitespace unexpectedly.
+ */
+ char *r, *w;
+ int c1, c2;
+
+ r = w = namebuf;
+ do {
+ c1 = *r++;
+ if (c1 == '+')
+ c1 = ' ';
+ else if (c1 == '%') {
+ if ((c1 = hexcode_to_int(*r++)) < 0)
+ goto out;
+ if ((c2 = hexcode_to_int(*r++)) < 0)
+ goto out;
+ c1 = (c1 << 4) | c2;
+ }
+ *w++ = c1;
+ } while (c1 != '\0');
+
objname = namebuf;
+ }
length = security_context_to_sid(scon, strlen(scon) + 1, &ssid);
if (length)
--
NEC Europe Ltd, SAP Global Competence Center
KaiGai Kohei <kohei.kaigai@xxxxxxxxxxxx>
--
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