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Add an ACL list for users connecting to the tmux socket. Users may be forbidden
from attaching, forced to attach read-only, or allowed to attach read-write. A new command, server-access, configures the list. tmux gets the user using getpeereid(3) of the client socket. Users must still configure file system permissions manually.
This commit is contained in:
Nicholas Marriott
182
server-acl.c
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182
server-acl.c
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/* $OpenBSD$ */
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/*
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* Copyright (c) 2021 Holland Schutte, Jayson Morberg
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* Copyright (c) 2021 Dallas Lyons <dallasdlyons@gmail.com>
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*
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* Permission to use, copy, modify, and distribute this software for any
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* purpose with or without fee is hereby granted, provided that the above
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* copyright notice and this permission notice appear in all copies.
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*
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* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
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* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
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* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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* WHATSOEVER RESULTING FROM LOSS OF MIND, USE, DATA OR PROFITS, WHETHER
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* IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING
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* OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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*/
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#include <sys/types.h>
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#include <sys/stat.h>
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#include <sys/socket.h>
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#include <ctype.h>
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#include <pwd.h>
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#include <stdlib.h>
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#include <string.h>
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#include <unistd.h>
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#include "tmux.h"
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struct server_acl_user {
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uid_t uid;
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int flags;
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#define SERVER_ACL_READONLY 0x1
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RB_ENTRY(server_acl_user) entry;
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};
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static int
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server_acl_cmp(struct server_acl_user *user1, struct server_acl_user *user2)
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{
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if (user1->uid < user2->uid)
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return -1;
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return user1->uid > user2->uid;
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}
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RB_HEAD(server_acl_entries, server_acl_user) server_acl_entries;
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RB_GENERATE_STATIC(server_acl_entries, server_acl_user, entry, server_acl_cmp);
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/* Initialize server_acl tree. */
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void
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server_acl_init(void)
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{
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RB_INIT(&server_acl_entries);
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if (getuid() != 0)
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server_acl_user_allow(0);
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server_acl_user_allow(getuid());
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}
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/* Find user entry. */
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struct server_acl_user*
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server_acl_user_find(uid_t uid)
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{
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struct server_acl_user find = { .uid = uid };
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return RB_FIND(server_acl_entries, &server_acl_entries, &find);
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}
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/* Display the tree. */
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void
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server_acl_display(struct cmdq_item *item)
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{
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struct server_acl_user *loop;
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struct passwd *pw;
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const char *name;
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RB_FOREACH(loop, server_acl_entries, &server_acl_entries) {
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if (loop->uid == 0)
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continue;
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if ((pw = getpwuid(loop->uid)) != NULL)
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name = pw->pw_name;
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else
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name = "unknown";
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if (loop->flags == SERVER_ACL_READONLY)
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cmdq_print(item, "%s (R)", name);
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else
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cmdq_print(item, "%s (W)", name);
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}
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}
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/* Allow a user. */
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void
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server_acl_user_allow(uid_t uid)
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{
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struct server_acl_user *user;
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user = server_acl_user_find(uid);
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if (user == NULL) {
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user = xcalloc(1, sizeof *user);
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user->uid = uid;
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RB_INSERT(server_acl_entries, &server_acl_entries, user);
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}
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}
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/* Deny a user (remove from the tree). */
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void
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server_acl_user_deny(uid_t uid)
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{
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struct server_acl_user *user;
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user = server_acl_user_find(uid);
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if (user != NULL) {
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RB_REMOVE(server_acl_entries, &server_acl_entries, user);
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free(user);
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}
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}
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/* Allow this user write access. */
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void
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server_acl_user_allow_write(uid_t uid)
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{
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struct server_acl_user *user;
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struct client *c;
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user = server_acl_user_find(uid);
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if (user == NULL)
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return;
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user->flags &= ~SERVER_ACL_READONLY;
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TAILQ_FOREACH(c, &clients, entry) {
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uid = proc_get_peer_uid(c->peer);
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if (uid != (uid_t)-1 && uid == user->uid)
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c->flags &= ~CLIENT_READONLY;
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}
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}
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/* Deny this user write access. */
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void
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server_acl_user_deny_write(uid_t uid)
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{
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struct server_acl_user *user;
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struct client *c;
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user = server_acl_user_find(uid);
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if (user == NULL)
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return;
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user->flags |= SERVER_ACL_READONLY;
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TAILQ_FOREACH(c, &clients, entry) {
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uid = proc_get_peer_uid(c->peer);
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if (uid == user->uid && uid == user->uid)
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c->flags |= CLIENT_READONLY;
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}
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}
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/*
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* Check if the client's UID exists in the ACL list and if so, set as read only
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* if needed. Return false if the user does not exist.
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*/
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int
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server_acl_join(struct client *c)
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{
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struct server_acl_user *user;
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uid_t uid = proc_get_peer_uid(c->peer);
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user = server_acl_user_find(uid);
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if (user == NULL)
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return (0);
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if (user->flags & SERVER_ACL_READONLY)
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c->flags |= CLIENT_READONLY;
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return (1);
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}
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/* Get UID for user entry. */
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uid_t
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server_acl_get_uid(struct server_acl_user *user)
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{
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return (user->uid);
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}
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