ACL: Make Redis 6 more backward compatible with requirepass.

Note that this as a side effect fixes Sentinel "requirepass" mode.

src/acl.c

@@ -899,16 +899,6 @@ char *ACLSetUserStringError(void) {
     return errmsg;
 }
 
-/* Return the first password of the default user or NULL.
- * This function is needed for backward compatibility with the old
- * directive "requirepass" when Redis supported a single global
- * password. */
-sds ACLDefaultUserFirstPassword(void) {
-    if (listLength(DefaultUser->passwords) == 0) return NULL;
-    listNode *first = listFirst(DefaultUser->passwords);
-    return listNodeValue(first);
-}
-
 /* Initialize the default user, that will always exist for all the process
  * lifetime. */
 void ACLInitDefaultUser(void) {
@@ -925,6 +915,7 @@ void ACLInit(void) {
     UsersToLoad = listCreate();
     ACLLog = listCreate();
     ACLInitDefaultUser();
+    server.requirepass = NULL; /* Only used for backward compatibility. */
 }
 
 /* Check the username and password pair and return C_OK if they are valid,

src/config.c

@@ -411,11 +411,15 @@ void loadServerConfigFromString(char *config) {
                 goto loaderr;
             }
             /* The old "requirepass" directive just translates to setting
-             * a password to the default user. */
+             * a password to the default user. The only thing we do
+             * additionally is to remember the cleartext password in this
+             * case, for backward compatibility with Redis <= 5. */
             ACLSetUser(DefaultUser,"resetpass",-1);
             sds aclop = sdscatprintf(sdsempty(),">%s",argv[1]);
             ACLSetUser(DefaultUser,aclop,sdslen(aclop));
             sdsfree(aclop);
+            sdsfree(server.requirepass);
+            server.requirepass = sdsnew(argv[1]);
         } else if (!strcasecmp(argv[0],"list-max-ziplist-entries") && argc == 2){
             /* DEAD OPTION */
         } else if (!strcasecmp(argv[0],"list-max-ziplist-value") && argc == 2) {
@@ -623,11 +627,15 @@ void configSetCommand(client *c) {
     config_set_special_field("requirepass") {
         if (sdslen(o->ptr) > CONFIG_AUTHPASS_MAX_LEN) goto badfmt;
         /* The old "requirepass" directive just translates to setting
-         * a password to the default user. */
+         * a password to the default user. The only thing we do
+         * additionally is to remember the cleartext password in this
+         * case, for backward compatibility with Redis <= 5. */
         ACLSetUser(DefaultUser,"resetpass",-1);
         sds aclop = sdscatprintf(sdsempty(),">%s",(char*)o->ptr);
         ACLSetUser(DefaultUser,aclop,sdslen(aclop));
         sdsfree(aclop);
+        sdsfree(server.requirepass);
+        server.requirepass = sdsnew(o->ptr);
     } config_set_special_field("save") {
         int vlen, j;
         sds *v = sdssplitlen(o->ptr,sdslen(o->ptr)," ",1,&vlen);
@@ -899,7 +907,7 @@ void configGetCommand(client *c) {
     }
     if (stringmatch(pattern,"requirepass",1)) {
         addReplyBulkCString(c,"requirepass");
-        sds password = ACLDefaultUserFirstPassword();
+        sds password = server.requirepass;
         if (password) {
             addReplyBulkCBuffer(c,password,sdslen(password));
         } else {
@@ -1341,7 +1349,7 @@ void rewriteConfigBindOption(struct rewriteConfigState *state) {
 void rewriteConfigRequirepassOption(struct rewriteConfigState *state, char *option) {
     int force = 1;
     sds line;
-    sds password = ACLDefaultUserFirstPassword();
+    sds password = server.requirepass;
 
     /* If there is no password set, we don't want the requirepass option
      * to be present in the configuration at all. */

src/sentinel.c

@@ -1992,7 +1992,7 @@ void sentinelSendAuthIfNeeded(sentinelRedisInstance *ri, redisAsyncContext *c) {
         auth_pass = ri->master->auth_pass;
         auth_user = ri->master->auth_user;
     } else if (ri->flags & SRI_SENTINEL) {
-        auth_pass = ACLDefaultUserFirstPassword();
+        auth_pass = server.requirepass;
         auth_user = NULL;
     }
 

src/server.h

@@ -1395,6 +1395,9 @@ struct redisServer {
     /* ACLs */
     char *acl_filename;     /* ACL Users file. NULL if not configured. */
     unsigned long acllog_max_len; /* Maximum length of the ACL LOG list. */
+    sds requirepass;        /* Remember the cleartext password set with the
+                               old "requirepass" directive for backward
+                               compatibility with Redis <= 5. */
     /* Assert & bug reporting */
     const char *assert_failed;
     const char *assert_file;