From f345805c73c294db42452ae966c48fbc36c48006 Mon Sep 17 00:00:00 2001

From: Petr Spacek <pspacek@redhat.com>

Date: Fri, 20 Jul 2012 14:55:43 +0200

Subject: [PATCH] Fix and harden DNS-to-LDAP name conversion. Fixes

 CVE-2012-3429.

Signed-off-by: Petr Spacek <pspacek@redhat.com>

---

 src/ldap_convert.c | 44 +++++++++++++++++++++++++++++++++-----------

 1 file changed, 33 insertions(+), 11 deletions(-)

diff --git a/src/ldap_convert.c b/src/ldap_convert.c

index 6b4e321..3352c57 100644

--- a/src/ldap_convert.c

+++ b/src/ldap_convert.c

@@ -192,16 +192,23 @@ cleanup:

 }

 /**

+ * WARNING! This function is used to mangle input from network

+ *          and it is security sensitive.

+ *

  * Convert a string from DNS escaping to LDAP escaping.

  * The Input string dns_str is expected to be the result of dns_name_tostring().

  * The DNS label can contain any binary data as described in

  * http://tools.ietf.org/html/rfc2181#section-11 .

  *

- * DNS escaping uses form   "\123" = ASCII value 123 (decimal)

+ * DNS escaping uses 2 forms: (see dns_name_totext2() in bind/lib/dns/name.c)

+ *     form "\123" = ASCII value 123 (decimal)

+ *     form "\$" = character '$' is escaped with '\'

+ *     WARNING! Some characters are not escaped at all (e.g. ',').

+ *

  * LDAP escaping users form "\7b"  = ASCII value 7b (hexadecimal)

  *

- * Input (DNS escaped) example  : _aaa,bbb\255\000ccc.555.ddd-eee

- * Output (LDAP escaped) example: _aaa\2cbbb\ff\00ccc.555.ddd-eee

+ * Input  (DNS escaped)  example: \$.\255_aaa,bbb\127\000ccc.555.ddd-eee

+ * Output (LDAP escaped) example: \24.\ff_aaa\2cbbb\7f\00ccc.555.ddd-eee

  *

  * The DNS to text functions from ISC libraries do not convert certain

  * characters (e.g. ","). This function converts \123 form to \7b form in all

@@ -248,13 +255,23 @@ dns_to_ldap_dn_escape(isc_mem_t *mctx, const char const * dns_str, char ** ldap_

 			}

 			if (dns_str[dns_idx] != '\\') { /* not nice raw value, e.g. ',' */

 				ascii_val = dns_str[dns_idx];

-			} else { /* not nice value in DNS \123 decimal format */

-				/* check if input length <= expected size */

-				REQUIRE (dns_str_len > dns_idx + 3); /* this problem should never happen */

-				ascii_val = 100 * (dns_str[dns_idx + 1] - '0')

-						+ 10 * (dns_str[dns_idx + 2] - '0')

-						+ (dns_str[dns_idx + 3] - '0');

-				dns_idx += 3;

+			} else { /* DNS escaped value, it starts with '\' */

+				if (!(dns_idx + 1 < dns_str_len)) {

+					CHECK(DNS_R_BADESCAPE); /* this problem should never happen */

+				}

+				if (isdigit(dns_str[dns_idx + 1])) { /* \123 decimal format */

+					/* check if input length <= expected size */

+					if (!(dns_idx + 3 < dns_str_len)) {

+						CHECK(DNS_R_BADESCAPE); /* this problem should never happen */

+					}

+					ascii_val = 100 * (dns_str[dns_idx + 1] - '0')

+							+ 10 * (dns_str[dns_idx + 2] - '0')

+							+ (dns_str[dns_idx + 3] - '0');

+					dns_idx += 3;

+				} else { /* \$ single char format */

+					ascii_val = dns_str[dns_idx + 1];

+					dns_idx += 1;

+				}

 			}

 			/* LDAP uses \xy escaping. "xy" represent two hexadecimal digits.*/

 			/* TODO: optimize to bit mask & rotate & dec->hex table? */

@@ -272,8 +289,13 @@ dns_to_ldap_dn_escape(isc_mem_t *mctx, const char const * dns_str, char ** ldap_

 	return ISC_R_SUCCESS;

 cleanup:

-	if (*ldap_name)

+	if (result == DNS_R_BADESCAPE)

+		log_bug("improperly escaped DNS string: '%s'", dns_str);

+

+	if (*ldap_name) {

 		isc_mem_free(mctx, *ldap_name);

+		*ldap_name = NULL;

+	}

 	return result;

 }

-- 

1.7.11.2