Avoid allocating zero key_data structures

When we allocate space for an array of key_data structures, make sure
we allocate at least one, so we don't spuriously fail on platforms
where malloc(0) returns NULL.  Where we use malloc, use k5calloc
instead.  Where we use krb5_db_alloc or realloc, just allocate an
extra entry.

2 files changed, 20 insertions, 21 deletions

diff --git a/src/lib/kadm5/srv/svr_principal.c b/src/lib/kadm5/srv/svr_principal.c
index 6c7a2c0d5..2bb871166 100644
--- a/src/lib/kadm5/srv/svr_principal.c
+++ b/src/lib/kadm5/srv/svr_principal.c
@@ -941,11 +941,10 @@ kadm5_get_principal(void *server_handle, krb5_principal principal,
     if (mask & KADM5_KEY_DATA) {
         entry->n_key_data = kdb->n_key_data;
         if(entry->n_key_data) {
-            entry->key_data = malloc(entry->n_key_data*sizeof(krb5_key_data));
-            if (entry->key_data == NULL) {
-                ret = ENOMEM;
+            entry->key_data = k5calloc(entry->n_key_data,
+                                       sizeof(krb5_key_data), &ret);
+            if (entry->key_data == NULL)
                 goto done;
-            }
         } else
             entry->key_data = NULL;
 
@@ -1070,14 +1069,14 @@ int create_history_entry(krb5_context context,
                          krb5_keyblock *hist_key, int n_key_data,
                          krb5_key_data *key_data, osa_pw_hist_ent *hist)
 {
-    int i, ret;
+    krb5_error_code ret;
     krb5_keyblock key;
     krb5_keysalt salt;
+    int i;
 
-    hist->key_data = (krb5_key_data*)malloc(n_key_data*sizeof(krb5_key_data));
+    hist->key_data = k5calloc(n_key_data, sizeof(krb5_key_data), &ret);
     if (hist->key_data == NULL)
-        return ENOMEM;
-    memset(hist->key_data, 0, n_key_data*sizeof(krb5_key_data));
+        return ret;
 
     for (i = 0; i < n_key_data; i++) {
         ret = krb5_dbe_decrypt_key_data(context, NULL, &key_data[i], &key,
@@ -1999,8 +1998,10 @@ kadm5_setkey_principal_3(void *server_handle,
         old_key_data = NULL;
     }
 
-    kdb->key_data = (krb5_key_data*)krb5_db_alloc(handle->context, NULL, (n_keys+n_old_keys)
-                                                  *sizeof(krb5_key_data));
+    /* Allocate one extra key_data to avoid allocating 0 bytes. */
+    kdb->key_data = krb5_db_alloc(handle->context, NULL,
+                                  (n_keys + n_old_keys + 1) *
+                                  sizeof(krb5_key_data));
     if (kdb->key_data == NULL) {
         ret = ENOMEM;
         goto done;
@@ -2330,8 +2331,9 @@ kadm5_purgekeys(void *server_handle,
     old_keydata = kdb->key_data;
     n_old_keydata = kdb->n_key_data;
     kdb->n_key_data = 0;
+    /* Allocate one extra key_data to avoid allocating 0 bytes. */
     kdb->key_data = krb5_db_alloc(handle->context, NULL,
-                                  n_old_keydata * sizeof(krb5_key_data));
+                                  (n_old_keydata + 1) * sizeof(krb5_key_data));
     if (kdb->key_data == NULL) {
         ret = ENOMEM;
         goto done;
diff --git a/src/lib/kdb/kdb_convert.c b/src/lib/kdb/kdb_convert.c
index f08d4233b..ee3e984ec 100644
--- a/src/lib/kdb/kdb_convert.c
+++ b/src/lib/kdb/kdb_convert.c
@@ -589,6 +589,7 @@ ulog_conv_2dbentry(krb5_context context, krb5_db_entry **entry,
     krb5_error_code ret;
     unsigned int prev_n_keys = 0;
     krb5_boolean is_add;
+    void *newptr;
 
     *entry = NULL;
 
@@ -687,15 +688,12 @@ ulog_conv_2dbentry(krb5_context context, krb5_db_entry **entry,
             if (is_add)
                 ent->key_data = NULL;
 
-            ent->key_data = (krb5_key_data *)realloc(ent->key_data,
-                                                     (ent->n_key_data *
-                                                      sizeof (krb5_key_data)));
-            /* XXX Memory leak: Old key data in
-               records eliminated by resizing to
-               smaller size.  */
-            if (ent->key_data == NULL)
-                /* XXX Memory leak: old storage.  */
-                return (ENOMEM);
+            /* Allocate one extra key data to avoid allocating zero bytes. */
+            newptr = realloc(ent->key_data, (ent->n_key_data + 1) *
+                             sizeof(krb5_key_data));
+            if (newptr == NULL)
+                return ENOMEM;
+            ent->key_data = newptr;
 
 /* BEGIN CSTYLED */
             for (j = prev_n_keys; j < ent->n_key_data; j++) {
@@ -713,7 +711,6 @@ ulog_conv_2dbentry(krb5_context context, krb5_db_entry **entry,
                 }
 
                 for (cnt = 0; cnt < kp->key_data_ver; cnt++) {
-                    void *newptr;
                     kp->key_data_type[cnt] =  (krb5_int16)kv->k_enctype.k_enctype_val[cnt];
                     kp->key_data_length[cnt] = (krb5_int16)kv->k_contents.k_contents_val[cnt].utf8str_t_len;
                     newptr = realloc(kp->key_data_contents[cnt],