--- res/res_config_ldap.c.orig  2009-08-10 15:30:55.000000000 -0400
+++ res/res_config_ldap.c       2009-09-15 06:25:44.000000000 -0400
@@ -1181,7 +1181,9 @@
 
        /* Create the modification array with the parameter/value pairs we were given, 
         * if there are several parameters with the same name, we collect them into 
-        * one parameter/value pair and delimit them with a semicolon */
+        * one parameter/value pair and delimit them with a semicolon.
+        * For Bug 15895 - handle both a single null value (delete the parameter) and
+        * a series of null values (create multiple semicolon-delimited null values) */
        newparam = va_arg(ap, const char *);
        newparam = convert_attribute_name_to_ldap(table_config, newparam);
        newval = va_arg(ap, const char *);
@@ -1199,19 +1201,32 @@
        ldap_mods[0]->mod_type = ast_calloc(sizeof(char), strlen(newparam) + 1);
        strcpy(ldap_mods[0]->mod_type, newparam);
 
-       ldap_mods[0]->mod_values = ast_calloc(sizeof(char), 2);
-       ldap_mods[0]->mod_values[0] = ast_calloc(sizeof(char), strlen(newval) + 1);
-       strcpy(ldap_mods[0]->mod_values[0], newval);
-
+       ldap_mods[0]->mod_values = ast_calloc(sizeof(char **), 1);
+       if (newval[0]==0) {
+               ldap_mods[0]->mod_values[0] = 0; /* Null pointer to delete from LDAP */
+       } else {
+               ldap_mods[0]->mod_values[0] = ast_calloc(sizeof(char), strlen(newval) + 1);
+               strcpy(ldap_mods[0]->mod_values[0], newval);
+       }
        while ((newparam = va_arg(ap, const char *))) {
                newparam = convert_attribute_name_to_ldap(table_config, newparam);
                newval = va_arg(ap, const char *);
                mod_exists = 0;
 
                for (i = 0; i < mods_size - 1; i++) {
-                       if (ldap_mods[i]&& !strcmp(ldap_mods[i]->mod_type, newparam)) {
-                               /* We have the parameter allready, adding the value as a semicolon delimited value */
-                               ldap_mods[i]->mod_values[0] = ast_realloc(ldap_mods[i]->mod_values[0], sizeof(char) * (strlen(ldap_mods[i]->mod_values[0]) + strlen(newval) + 2));
+                       if (ldap_mods[i] && !strcmp(ldap_mods[i]->mod_type, newparam)) {
+                               /* We have the parameter already; add the value as a semicolon delimited value.
+                                  If the new parameter is null, just add a semicolon.
+                                  If the old parameter was null, we need the storage we didn't get before. */
+                               if (ldap_mods[i]->mod_values[0]==0) {
+                                       /* Previously null, so do initial allocation not done before */
+                                       ldap_mods[i]->mod_values[0] = ast_calloc(sizeof(char), 1);
+                               } else {
+                                       /* A value was already there.  Increase storage to the length of the
+                                          current value plus the length of the new value plus the semicolon
+                                          and the null string terminator */
+                                       ldap_mods[i]->mod_values[0] = ast_realloc(ldap_mods[i]->mod_values[0], sizeof(char) * (strlen(ldap_mods[i]->mod_values[0]) + strlen(newval) + 2));
+                               }
                                strcat(ldap_mods[i]->mod_values[0], ";");
                                strcat(ldap_mods[i]->mod_values[0], newval);
                                mod_exists = 1;
@@ -1231,9 +1246,14 @@
                        ldap_mods[mods_size - 2]->mod_type = ast_calloc(sizeof(char), strlen(newparam) + 1);
                        strcpy(ldap_mods[mods_size - 2]->mod_type, newparam);
 
-                       ldap_mods[mods_size - 2]->mod_values = ast_calloc(sizeof(char *), 2);
-                       ldap_mods[mods_size - 2]->mod_values[0] = ast_calloc(sizeof(char), strlen(newval) + 1);
-                       strcpy(ldap_mods[mods_size - 2]->mod_values[0], newval);
+                       ldap_mods[mods_size - 2]->mod_values = ast_calloc(sizeof(char **), 1);
+
+                       if (newval[0]==0) {
+                               ldap_mods[mods_size -2]->mod_values[0] = 0;
+                       } else {
+                             ldap_mods[mods_size - 2]->mod_values[0] = ast_calloc(sizeof(char), strlen(newval) + 1);
+                             strcpy(ldap_mods[mods_size - 2]->mod_values[0], newval);
+                       }
                }
        }
        /* freeing ldap_mods further down */