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/*
* Copyright (c) 2018, Salvatore Sanfilippo <antirez at gmail dot com>
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* * Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* * Neither the name of Redis nor the names of its contributors may be used
* to endorse or promote products derived from this software without
* specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/
#include "server.h"
/* =============================================================================
* Global state for ACLs
* ==========================================================================*/
rax *Users; /* Table mapping usernames to user structures. */
/* =============================================================================
* Helper functions for the rest of the ACL implementation
* ==========================================================================*/
/* Return zero if strings are the same, non-zero if they are not.
* The comparison is performed in a way that prevents an attacker to obtain
* information about the nature of the strings just monitoring the execution
* time of the function.
*
* Note that limiting the comparison length to strings up to 512 bytes we
* can avoid leaking any information about the password length and any
* possible branch misprediction related leak.
*/
int time_independent_strcmp(char *a, char *b) {
char bufa[CONFIG_AUTHPASS_MAX_LEN], bufb[CONFIG_AUTHPASS_MAX_LEN];
/* The above two strlen perform len(a) + len(b) operations where either
* a or b are fixed (our password) length, and the difference is only
* relative to the length of the user provided string, so no information
* leak is possible in the following two lines of code. */
unsigned int alen = strlen(a);
unsigned int blen = strlen(b);
unsigned int j;
int diff = 0;
/* We can't compare strings longer than our static buffers.
* Note that this will never pass the first test in practical circumstances
* so there is no info leak. */
if (alen > sizeof(bufa) || blen > sizeof(bufb)) return 1;
memset(bufa,0,sizeof(bufa)); /* Constant time. */
memset(bufb,0,sizeof(bufb)); /* Constant time. */
/* Again the time of the following two copies is proportional to
* len(a) + len(b) so no info is leaked. */
memcpy(bufa,a,alen);
memcpy(bufb,b,blen);
/* Always compare all the chars in the two buffers without
* conditional expressions. */
for (j = 0; j < sizeof(bufa); j++) {
diff |= (bufa[j] ^ bufb[j]);
}
/* Length must be equal as well. */
diff |= alen ^ blen;
return diff; /* If zero strings are the same. */
}
/* =============================================================================
* Low level ACL API
* ==========================================================================*/
/* Initialization of the ACL subsystem. */
void ACLInit(void) {
Users = raxNew();
}
/* Check the username and password pair and return C_OK if they are valid,
* otherwise C_ERR is returned and errno is set to:
*
* EINVAL: if the username-password do not match.
* ENONENT: if the specified user does not exist at all.
*/
int ACLCheckUserCredentials(robj *username, robj *password) {
/* For now only the "default" user is allowed. When the RCP1 ACLs
* will be implemented multiple usernames will be supproted. */
if (username != NULL && strcmp(username->ptr,"default")) {
errno = ENOENT;
return C_ERR;
}
/* For now we just compare the password with the system wide one. */
if (!time_independent_strcmp(password->ptr, server.requirepass)) {
return C_OK;
} else {
errno = EINVAL;
return C_ERR;
}
}
/* For ACL purposes, every user has a bitmap with the commands that such
* user is allowed to execute. In order to populate the bitmap, every command
* should have an assigned ID (that is used to index the bitmap). This function
* creates such an ID: it uses sequential IDs, reusing the same ID for the same
* command name, so that a command retains the same ID in case of modules that
* are unloaded and later reloaded. */
unsigned long ACLGetCommandID(const char *cmdname) {
static rax *map = NULL;
static unsigned long nextid = 0;
if (map == NULL) map = raxNew();
void *id = raxFind(map,(unsigned char*)cmdname,strlen(cmdname));
if (id != raxNotFound) return (unsigned long)id;
raxInsert(map,(unsigned char*)cmdname,strlen(cmdname),(void*)nextid,NULL);
return nextid++;
}
/* Return an username by its name, or NULL if the user does not exist. */
user *ACLGetUserByName(const char *name, size_t namelen) {
void *myuser = raxFind(Users,(unsigned char*)name,namelen);
if (myuser == raxNotFound) return NULL;
return myuser;
}
/* =============================================================================
* ACL related commands
* ==========================================================================*/
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