From df17a1224a3406f57477bcd372c61e04c0e5a5bb Mon Sep 17 00:00:00 2001
From: Greg Hudson <ghudson@mit.edu>
Date: Fri, 8 Jan 2016 12:45:25 -0500
Subject: [PATCH 1/3] Verify decoded kadmin C strings [CVE-2015-8629]

In xdr_nullstring(), check that the decoded string is terminated with
a zero byte and does not contain any internal zero bytes.

CVE-2015-8629:

In all versions of MIT krb5, an authenticated attacker can cause
kadmind to read beyond the end of allocated memory by sending a string
without a terminating zero byte.  Information leakage may be possible
for an attacker with permission to modify the database.

    CVSSv2 Vector: AV:N/AC:H/Au:S/C:P/I:N/A:N/E:POC/RL:OF/RC:C

ticket: 8341 (new)
target_version: 1.14-next
target_version: 1.13-next
tags: pullup
---
 src/lib/kadm5/kadm_rpc_xdr.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/src/lib/kadm5/kadm_rpc_xdr.c b/src/lib/kadm5/kadm_rpc_xdr.c
index 2bef858..ba67084 100644
--- a/src/lib/kadm5/kadm_rpc_xdr.c
+++ b/src/lib/kadm5/kadm_rpc_xdr.c
@@ -64,7 +64,14 @@ bool_t xdr_nullstring(XDR *xdrs, char **objp)
 		    return FALSE;
 	       }
 	  }
-	  return (xdr_opaque(xdrs, *objp, size));
+	  if (!xdr_opaque(xdrs, *objp, size))
+		  return FALSE;
+	  /* Check that the unmarshalled bytes are a C string. */
+	  if ((*objp)[size - 1] != '\0')
+		  return FALSE;
+	  if (memchr(*objp, '\0', size - 1) != NULL)
+		  return FALSE;
+	  return TRUE;
 
      case XDR_ENCODE:
 	  if (size != 0)
-- 
2.7.0.rc3