Try all history keys to decrypt password history

A database created prior to 1.3 will have multiple password history
keys, and kadmin prior to 1.8 won't necessarily choose the first one.
So if there are multiple keys, we have to try them all.  If none of
the keys can decrypt a password history entry, don't fail the password
change operation; it's not worth it without positive evidence of
password reuse.

(back ported from commit 2782e80a12bccd920fa71e23166ac97c4470a637)

ticket: 7180 (new)
version_fixed: 1.8.7
status: resolved

diff --git a/src/lib/kadm5/server_internal.h b/src/lib/kadm5/server_internal.h
index 3276b2727ee82cc26fa924e2f3ca3239aff134a2..a55f802c459481846dfac6b47b665dca3fc3491d 100644 (file)
--- a/src/lib/kadm5/server_internal.h
+++ b/src/lib/kadm5/server_internal.h
@@ -74,8 +74,10 @@ krb5_error_code     kdb_init_master(kadm5_server_handle_t handle,
 krb5_error_code     kdb_init_hist(kadm5_server_handle_t handle,
                                   char *r);
 krb5_error_code     kdb_get_hist_key(kadm5_server_handle_t handle,
-                                     krb5_keyblock *hist_keyblock,
-                                     krb5_kvno *hist_kvno);
+                                     krb5_keyblock **keyblocks_out,
+                                     krb5_kvno *kvno_out);
+void                kdb_free_keyblocks(kadm5_server_handle_t handle,
+                                       krb5_keyblock *keyblocks);
 krb5_error_code     kdb_get_entry(kadm5_server_handle_t handle,
                                   krb5_principal principal, krb5_db_entry *kdb,
                                   osa_princ_ent_rec *adb);

diff --git a/src/lib/kadm5/srv/server_kdb.c b/src/lib/kadm5/srv/server_kdb.c
index 337c1422c10265845c5487518aed127ad57cee36..4106092de453e972c89d8ca80537a4a27e924580 100644 (file)
--- a/src/lib/kadm5/srv/server_kdb.c
+++ b/src/lib/kadm5/srv/server_kdb.c
@@ -177,26 +177,20 @@ done:
 }
 
 /*
- * Function: kdb_get_hist_key
- *
- * Purpose: Fetches the current history key
- *
- * Arguments:
- *
- *      handle          (r) kadm5 api server handle
- *      hist_keyblock   (w) keyblock to fill in with history key
- *      hist_kvno       (w) kvno to fill in with history kvno
- *
- * Effects: This function looks up the history principal and retrieves the
- * current history key and version.
+ * Fetch the current history key(s), creating the history principal if
+ * necessary.  Database created since krb5 1.3 will have only one key, but
+ * databases created before that may have multiple keys (of the same kvno)
+ * and we need to try them all.  History keys will be returned in a list
+ * terminated by an entry with enctype 0.
  */
 krb5_error_code
-kdb_get_hist_key(kadm5_server_handle_t handle, krb5_keyblock *hist_keyblock,
-                 krb5_kvno *hist_kvno)
+kdb_get_hist_key(kadm5_server_handle_t handle, krb5_keyblock **keyblocks_out,
+                 krb5_kvno *kvno_out)
 {
     krb5_error_code ret;
     krb5_db_entry kdb;
-    krb5_keyblock *mkey;
+    krb5_keyblock *mkey, *kblist = NULL;
+    krb5_int16 i;
 
     ret = kdb_get_entry(handle, hist_princ, &kdb, NULL);
     if (ret)
@@ -214,18 +208,40 @@ kdb_get_hist_key(kadm5_server_handle_t handle, krb5_keyblock *hist_keyblock,
     if (ret)
         goto done;
 
-    ret = krb5_dbekd_decrypt_key_data(handle->context, mkey,
-                                      &kdb.key_data[0], hist_keyblock, NULL);
-    if (ret)
+    kblist = k5alloc((kdb.n_key_data + 1) * sizeof(*kblist), &ret);
+    if (kblist == NULL)
         goto done;
+    for (i = 0; i < kdb.n_key_data; i++) {
+        ret = krb5_dbekd_decrypt_key_data(handle->context, mkey,
+                                          &kdb.key_data[i], &kblist[i],
+                                          NULL);
+        if (ret)
+            goto done;
+    }
 
-    *hist_kvno = kdb.key_data[0].key_data_kvno;
+    *keyblocks_out = kblist;
+    kblist = NULL;
+    *kvno_out = kdb.key_data[0].key_data_kvno;
 
 done:
     kdb_free_entry(handle, &kdb, NULL);
+    kdb_free_keyblocks(handle, kblist);
     return ret;
 }
 
+/* Free all keyblocks in a list (terminated by a keyblock with enctype 0). */
+void
+kdb_free_keyblocks(kadm5_server_handle_t handle, krb5_keyblock *keyblocks)
+{
+    krb5_keyblock *kb;
+
+    if (keyblocks == NULL)
+        return;
+    for (kb = keyblocks; kb->enctype != 0; kb++)
+        krb5_free_keyblock_contents(handle->context, kb);
+    free(keyblocks);
+}
+
 /*
  * Function: kdb_get_entry
  *

diff --git a/src/lib/kadm5/srv/svr_principal.c b/src/lib/kadm5/srv/svr_principal.c
index c9a6881d94c22c08309d173b7a20499280d0f78d..f1739196be184a17940d2f039589df6d440c95e2 100644 (file)
--- a/src/lib/kadm5/srv/svr_principal.c
+++ b/src/lib/kadm5/srv/svr_principal.c
@@ -968,12 +968,13 @@ done:
 static kadm5_ret_t
 check_pw_reuse(krb5_context context,
                krb5_keyblock *mkey,
-               krb5_keyblock *hist_keyblock,
+               krb5_keyblock *hist_keyblocks,
                int n_new_key_data, krb5_key_data *new_key_data,
                unsigned int n_pw_hist_data, osa_pw_hist_ent *pw_hist_data)
 {
     int x, y, z;
-    krb5_keyblock newkey, histkey;
+    krb5_keyblock newkey, histkey, *kb;
+    krb5_key_data *key_data;
     krb5_error_code ret;
 
     for (x = 0; x < n_new_key_data; x++) {
@@ -985,23 +986,22 @@ check_pw_reuse(krb5_context context,
             return(ret);
         for (y = 0; y < n_pw_hist_data; y++) {
             for (z = 0; z < pw_hist_data[y].n_key_data; z++) {
-                ret = krb5_dbekd_decrypt_key_data(context,
-                                                  hist_keyblock,
-                                                  &pw_hist_data[y].key_data[z],
-                                                  &histkey, NULL);
-                if (ret)
-                    return(ret);
-
-                if ((newkey.length == histkey.length) &&
-                    (newkey.enctype == histkey.enctype) &&
-                    (memcmp(newkey.contents, histkey.contents,
-                            histkey.length) == 0)) {
+                for (kb = hist_keyblocks; kb->enctype != 0; kb++) {
+                    key_data = &pw_hist_data[y].key_data[z];
+                    ret = krb5_dbekd_decrypt_key_data(context, kb, key_data,
+                                                      &histkey, NULL);
+                    if (ret)
+                        continue;
+                    if (newkey.length == histkey.length &&
+                        newkey.enctype == histkey.enctype &&
+                        memcmp(newkey.contents, histkey.contents,
+                               histkey.length) == 0) {
+                        krb5_free_keyblock_contents(context, &histkey);
+                        krb5_free_keyblock_contents(context, &newkey);
+                        return KADM5_PASS_REUSE;
+                    }
                     krb5_free_keyblock_contents(context, &histkey);
-                    krb5_free_keyblock_contents(context, &newkey);
-
-                    return(KADM5_PASS_REUSE);
                 }
-                krb5_free_keyblock_contents(context, &histkey);
             }
         }
         krb5_free_keyblock_contents(context, &newkey);
@@ -1349,7 +1349,7 @@ kadm5_chpass_principal_3(void *server_handle,
     int                         have_pol = 0;
     kadm5_server_handle_t       handle = server_handle;
     osa_pw_hist_ent             hist;
-    krb5_keyblock               *act_mkey, hist_keyblock;
+    krb5_keyblock               *act_mkey, *hist_keyblocks = NULL;
     krb5_kvno                   act_kvno, hist_kvno;
 
     CHECK_HANDLE(server_handle);
@@ -1358,7 +1358,6 @@ kadm5_chpass_principal_3(void *server_handle,
 
     hist_added = 0;
     memset(&hist, 0, sizeof(hist));
-    memset(&hist_keyblock, 0, sizeof(hist_keyblock));
 
     if (principal == NULL || password == NULL)
         return EINVAL;
@@ -1430,18 +1429,18 @@ kadm5_chpass_principal_3(void *server_handle,
         }
 #endif
 
-        ret = kdb_get_hist_key(handle, &hist_keyblock, &hist_kvno);
+        ret = kdb_get_hist_key(handle, &hist_keyblocks, &hist_kvno);
         if (ret)
             goto done;
 
         ret = create_history_entry(handle->context,
-                                   act_mkey, &hist_keyblock,
+                                   act_mkey, &hist_keyblocks[0],
                                    kdb_save.n_key_data,
                                    kdb_save.key_data, &hist);
         if (ret)
             goto done;
 
-        ret = check_pw_reuse(handle->context, act_mkey, &hist_keyblock,
+        ret = check_pw_reuse(handle->context, act_mkey, hist_keyblocks,
                              kdb.n_key_data, kdb.key_data,
                              1, &hist);
         if (ret)
@@ -1451,7 +1450,7 @@ kadm5_chpass_principal_3(void *server_handle,
             /* If hist_kvno has changed since the last password change, we
              * can't check the history. */
             if (adb.admin_history_kvno == hist_kvno) {
-                ret = check_pw_reuse(handle->context, act_mkey, &hist_keyblock,
+                ret = check_pw_reuse(handle->context, act_mkey, hist_keyblocks,
                                      kdb.n_key_data, kdb.key_data,
                                      adb.old_key_len, adb.old_keys);
                 if (ret)
@@ -1524,7 +1523,7 @@ done:
     kdb_free_entry(handle, &kdb, &adb);
     kdb_free_entry(handle, &kdb_save, NULL);
     krb5_db_free_principal(handle->context, &kdb, 1);
-    krb5_free_keyblock_contents(handle->context, &hist_keyblock);
+    kdb_free_keyblocks(handle, hist_keyblocks);
 
     if (have_pol && (ret2 = kadm5_free_policy_ent(handle->lhandle, &pol))
         && !ret)