From 40fcaabfaa2c865471cc5fb1fab04106bc3ec611 Mon Sep 17 00:00:00 2001

From: William Brown <firstyear@redhat.com>

Date: Thu, 18 Jan 2018 11:27:58 +1000

Subject: [PATCH] Ticket bz1525628 - invalid password migration causes unauth

 bind

Bug Description:  Slapi_ct_memcmp expects both inputs to be

at LEAST size n. If they are not, we only compared UP to n.

Invalid migrations of passwords (IE {CRYPT}XX) would create

a pw which is just salt and no hash. ct_memcmp would then

only verify the salt bits and would allow the authentication.

This relies on an administrative mistake both of allowing

password migration (nsslapd-allow-hashed-passwords) and then

subsequently migrating an INVALID password to the server.

Fix Description:  slapi_ct_memcmp now access n1, n2 size

and will FAIL if they are not the same, but will still compare

n bytes, where n is the "longest" memory, to the first byte

of the other to prevent length disclosure of the shorter

value (generally the mis-migrated password)

https://bugzilla.redhat.com/show_bug.cgi?id=1525628

Author: wibrown

Review by: ???

Signed-off-by: Mark Reynolds <mreynolds@redhat.com>

---

 .../bz1525628_ct_memcmp_invalid_hash_test.py       | 56 ++++++++++++++++++++++

 ldap/servers/plugins/pwdstorage/clear_pwd.c        |  4 +-

 ldap/servers/plugins/pwdstorage/crypt_pwd.c        |  4 +-

 ldap/servers/plugins/pwdstorage/md5_pwd.c          |  4 +-

 ldap/servers/plugins/pwdstorage/sha_pwd.c          | 16 +++++--

 ldap/servers/plugins/pwdstorage/smd5_pwd.c         |  2 +-

 ldap/servers/slapd/ch_malloc.c                     | 36 ++++++++++++--

 ldap/servers/slapd/slapi-plugin.h                  |  2 +-

 8 files changed, 108 insertions(+), 16 deletions(-)

 create mode 100644 dirsrvtests/tests/suites/password/bz1525628_ct_memcmp_invalid_hash_test.py

diff --git a/dirsrvtests/tests/suites/password/bz1525628_ct_memcmp_invalid_hash_test.py b/dirsrvtests/tests/suites/password/bz1525628_ct_memcmp_invalid_hash_test.py

new file mode 100644

index 000000000..2f38384a1

--- /dev/null

+++ b/dirsrvtests/tests/suites/password/bz1525628_ct_memcmp_invalid_hash_test.py

@@ -0,0 +1,56 @@

+# --- BEGIN COPYRIGHT BLOCK ---

+# Copyright (C) 2018 Red Hat, Inc.

+# All rights reserved.

+#

+# License: GPL (version 3 or any later version).

+# See LICENSE for details.

+# --- END COPYRIGHT BLOCK ---

+#

+

+import ldap

+import pytest

+import logging

+from lib389.topologies import topology_st

+from lib389._constants import PASSWORD, DEFAULT_SUFFIX

+

+from lib389.idm.user import UserAccounts, TEST_USER_PROPERTIES

+

+logging.getLogger(__name__).setLevel(logging.DEBUG)

+log = logging.getLogger(__name__)

+

+def test_invalid_hash_fails(topology_st):

+    """When given a malformed hash from userpassword migration

+    slapi_ct_memcmp would check only to the length of the shorter

+    field. This affects some values where it would ONLY verify

+    the salt is valid, and thus would allow any password to bind.

+

+    :id: 8131c029-7147-47db-8d03-ec5db2a01cfb

+    :setup: Standalone Instance

+    :steps:

+        1. Create a user

+        2. Add an invalid password hash (truncated)

+        3. Attempt to bind

+    :expectedresults:

+        1. User is added

+        2. Invalid pw hash is added

+        3. Bind fails

+    """

+    log.info("Running invalid hash test")

+

+    # Allow setting raw password hashes for migration.

+    topology_st.standalone.config.set('nsslapd-allow-hashed-passwords', 'on')

+

+    users = UserAccounts(topology_st.standalone, DEFAULT_SUFFIX)

+    user = users.create(properties=TEST_USER_PROPERTIES)

+    user.set('userPassword', '{CRYPT}XX')

+

+    # Attempt to bind. This should fail.

+    with pytest.raises(ldap.INVALID_CREDENTIALS):

+        user.bind(PASSWORD)

+    with pytest.raises(ldap.INVALID_CREDENTIALS):

+        user.bind('XX')

+    with pytest.raises(ldap.INVALID_CREDENTIALS):

+        user.bind('{CRYPT}XX')

+

+    log.info("PASSED")

+

diff --git a/ldap/servers/plugins/pwdstorage/clear_pwd.c b/ldap/servers/plugins/pwdstorage/clear_pwd.c

index f5e6f9d4c..3d340752d 100644

--- a/ldap/servers/plugins/pwdstorage/clear_pwd.c

+++ b/ldap/servers/plugins/pwdstorage/clear_pwd.c

@@ -39,7 +39,7 @@ clear_pw_cmp(const char *userpwd, const char *dbpwd)

          * However, even if the first part of userpw matches dbpwd, but len !=, we

          * have already failed anyawy. This prevents substring matching.

          */

-        if (slapi_ct_memcmp(userpwd, dbpwd, len_dbp) != 0) {

+        if (slapi_ct_memcmp(userpwd, dbpwd, len_user, len_dbp) != 0) {

             result = 1;

         }

     } else {

@@ -51,7 +51,7 @@ clear_pw_cmp(const char *userpwd, const char *dbpwd)

          * dbpwd to itself. We have already got result == 1 if we are here, so we are

          * just trying to take up time!

          */

-        if (slapi_ct_memcmp(dbpwd, dbpwd, len_dbp)) {

+        if (slapi_ct_memcmp(dbpwd, dbpwd, len_dbp, len_dbp)) {

             /* Do nothing, we have the if to fix a coverity check. */

         }

     }

diff --git a/ldap/servers/plugins/pwdstorage/crypt_pwd.c b/ldap/servers/plugins/pwdstorage/crypt_pwd.c

index 3bd226581..0dccd1b51 100644

--- a/ldap/servers/plugins/pwdstorage/crypt_pwd.c

+++ b/ldap/servers/plugins/pwdstorage/crypt_pwd.c

@@ -65,13 +65,13 @@ crypt_close(Slapi_PBlock *pb __attribute__((unused)))

 int

 crypt_pw_cmp(const char *userpwd, const char *dbpwd)

 {

-    int rc;

+    int32_t rc;

     char *cp;

     PR_Lock(cryptlock);

     /* we use salt (first 2 chars) of encoded password in call to crypt() */

     cp = crypt(userpwd, dbpwd);

     if (cp) {

-        rc = slapi_ct_memcmp(dbpwd, cp, strlen(dbpwd));

+        rc = slapi_ct_memcmp(dbpwd, cp, strlen(dbpwd), strlen(cp));

     } else {

         rc = -1;

     }

diff --git a/ldap/servers/plugins/pwdstorage/md5_pwd.c b/ldap/servers/plugins/pwdstorage/md5_pwd.c

index 1e2cf58e7..2c2aacaa6 100644

--- a/ldap/servers/plugins/pwdstorage/md5_pwd.c

+++ b/ldap/servers/plugins/pwdstorage/md5_pwd.c

@@ -30,7 +30,7 @@

 int

 md5_pw_cmp(const char *userpwd, const char *dbpwd)

 {

-    int rc = -1;

+    int32_t rc = -1;

     char *bver;

     PK11Context *ctx = NULL;

     unsigned int outLen;

@@ -57,7 +57,7 @@ md5_pw_cmp(const char *userpwd, const char *dbpwd)

     bver = NSSBase64_EncodeItem(NULL, (char *)b2a_out, sizeof b2a_out, &binary_item);

     /* bver points to b2a_out upon success */

     if (bver) {

-        rc = slapi_ct_memcmp(bver, dbpwd, strlen(dbpwd));

+        rc = slapi_ct_memcmp(bver, dbpwd, strlen(dbpwd), strlen(bver));

     } else {

         slapi_log_err(SLAPI_LOG_PLUGIN, MD5_SUBSYSTEM_NAME,

                       "Could not base64 encode hashed value for password compare");

diff --git a/ldap/servers/plugins/pwdstorage/sha_pwd.c b/ldap/servers/plugins/pwdstorage/sha_pwd.c

index 1fbe0bc82..381b31d7c 100644

--- a/ldap/servers/plugins/pwdstorage/sha_pwd.c

+++ b/ldap/servers/plugins/pwdstorage/sha_pwd.c

@@ -49,7 +49,7 @@ sha_pw_cmp(const char *userpwd, const char *dbpwd, unsigned int shaLen)

     char userhash[MAX_SHA_HASH_SIZE];

     char quick_dbhash[MAX_SHA_HASH_SIZE + SHA_SALT_LENGTH + 3];

     char *dbhash = quick_dbhash;

-    struct berval salt;

+    struct berval salt = {0};

     PRUint32 hash_len;

     unsigned int secOID;

     char *schemeName;

@@ -122,9 +122,19 @@ sha_pw_cmp(const char *userpwd, const char *dbpwd, unsigned int shaLen)

     /* the proof is in the comparison... */

     if (hash_len >= shaLen) {

-        result = slapi_ct_memcmp(userhash, dbhash, shaLen);

+        /*

+         * This say "if the hash has a salt IE >, OR if they are equal, check the hash component ONLY.

+         * This is why we repeat shaLen twice, even though it seems odd. If you have a dbhast of ssha

+         * it's len is 28, and the userpw is 20, but 0 - 20 is the sha, and 21-28 is the salt, which

+         * has already been processed into userhash.

+         * The case where dbpwd is truncated is handled above in "invalid base64" arm.

+         */

+        result = slapi_ct_memcmp(userhash, dbhash, shaLen, shaLen);

     } else {

-        result = slapi_ct_memcmp(userhash, dbhash + OLD_SALT_LENGTH, hash_len - OLD_SALT_LENGTH);

+        /* This case is for if the salt is at the START, which only applies to DS40B1 case.

+         * May never be a valid check...

+         */

+        result = slapi_ct_memcmp(userhash, dbhash + OLD_SALT_LENGTH, shaLen, hash_len - OLD_SALT_LENGTH);

     }

 loser:

diff --git a/ldap/servers/plugins/pwdstorage/smd5_pwd.c b/ldap/servers/plugins/pwdstorage/smd5_pwd.c

index a83ac6fa4..cbfc74ff3 100644

--- a/ldap/servers/plugins/pwdstorage/smd5_pwd.c

+++ b/ldap/servers/plugins/pwdstorage/smd5_pwd.c

@@ -82,7 +82,7 @@ smd5_pw_cmp(const char *userpwd, const char *dbpwd)

     PK11_DestroyContext(ctx, 1);

     /* Compare everything up to the salt. */

-    rc = slapi_ct_memcmp(userhash, dbhash, MD5_LENGTH);

+    rc = slapi_ct_memcmp(userhash, dbhash, MD5_LENGTH, MD5_LENGTH);

 loser:

     if (dbhash && dbhash != quick_dbhash)

diff --git a/ldap/servers/slapd/ch_malloc.c b/ldap/servers/slapd/ch_malloc.c

index ef436b3e8..90a2b2c1a 100644

--- a/ldap/servers/slapd/ch_malloc.c

+++ b/ldap/servers/slapd/ch_malloc.c

@@ -336,8 +336,8 @@ slapi_ch_smprintf(const char *fmt, ...)

 /* Constant time memcmp. Does not shortcircuit on failure! */

 /* This relies on p1 and p2 both being size at least n! */

-int

-slapi_ct_memcmp(const void *p1, const void *p2, size_t n)

+int32_t

+slapi_ct_memcmp(const void *p1, const void *p2, size_t n1, size_t n2)

 {

     int result = 0;

     const unsigned char *_p1 = (const unsigned char *)p1;

@@ -347,9 +347,35 @@ slapi_ct_memcmp(const void *p1, const void *p2, size_t n)

         return 2;

     }

-    for (size_t i = 0; i < n; i++) {

-        if (_p1[i] ^ _p2[i]) {

-            result = 1;

+    if (n1 == n2) {

+        for (size_t i = 0; i < n1; i++) {

+            if (_p1[i] ^ _p2[i]) {

+                result = 1;

+            }

+        }

+    } else {

+        const unsigned char *_pa;

+        const unsigned char *_pb;

+        size_t nl;

+        if (n2 > n1) {

+            _pa = _p2;

+            _pb = _p2;

+            nl = n2;

+        } else {

+            _pa = _p1;

+            _pb = _p1;

+            nl = n1;

+        }

+        /* We already fail as n1 != n2 */

+        result = 3;

+        for (size_t i = 0; i < nl; i++) {

+            if (_pa[i] ^ _pb[i]) {

+                /*

+                 * If we don't mutate result here, dead code elimination

+                 * we remove for loop.

+                 */

+                result = 4;

+            }

         }

     }

     return result;

diff --git a/ldap/servers/slapd/slapi-plugin.h b/ldap/servers/slapd/slapi-plugin.h

index 4566202d3..95cdcc0da 100644

--- a/ldap/servers/slapd/slapi-plugin.h

+++ b/ldap/servers/slapd/slapi-plugin.h

@@ -5862,7 +5862,7 @@ char *slapi_ch_smprintf(const char *fmt, ...)

  * \param n length in bytes of the content of p1 AND p2.

  * \return 0 on match. 1 on non-match. 2 on presence of NULL pointer in p1 or p2.

  */

-int slapi_ct_memcmp(const void *p1, const void *p2, size_t n);

+int32_t slapi_ct_memcmp(const void *p1, const void *p2, size_t n1, size_t n2);

 /*

  * syntax plugin routines

-- 

2.13.6