1 /* SPDX-License-Identifier: BSD-2-Clause */ 2 /* 3 * Privilege Separation for dhcpcd, control proxy 4 * Copyright (c) 2006-2020 Roy Marples <roy@marples.name> 5 * All rights reserved 6 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions 9 * are met: 10 * 1. Redistributions of source code must retain the above copyright 11 * notice, this list of conditions and the following disclaimer. 12 * 2. Redistributions in binary form must reproduce the above copyright 13 * notice, this list of conditions and the following disclaimer in the 14 * documentation and/or other materials provided with the distribution. 15 * 16 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 17 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 19 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 20 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 21 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 22 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 23 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26 * SUCH DAMAGE. 27 */ 28 29 #include <errno.h> 30 #include <stdlib.h> 31 #include <string.h> 32 33 #include "dhcpcd.h" 34 #include "control.h" 35 #include "eloop.h" 36 #include "logerr.h" 37 #include "privsep.h" 38 39 static int 40 ps_ctl_startcb(void *arg) 41 { 42 struct dhcpcd_ctx *ctx = arg; 43 sa_family_t af; 44 45 if (ctx->options & DHCPCD_MASTER) { 46 setproctitle("[control proxy]"); 47 af = AF_UNSPEC; 48 } else { 49 setproctitle("[control proxy] %s%s%s", 50 ctx->ifv[0], 51 ctx->options & DHCPCD_IPV4 ? " [ip4]" : "", 52 ctx->options & DHCPCD_IPV6 ? " [ip6]" : ""); 53 if ((ctx->options & 54 (DHCPCD_IPV4 | DHCPCD_IPV6)) == DHCPCD_IPV4) 55 af = AF_INET; 56 else if ((ctx->options & 57 (DHCPCD_IPV4 | DHCPCD_IPV6)) == DHCPCD_IPV6) 58 af = AF_INET6; 59 else 60 af = AF_UNSPEC; 61 } 62 63 ctx->ps_control_pid = getpid(); 64 65 return control_start(ctx, 66 ctx->options & DHCPCD_MASTER ? NULL : *ctx->ifv, af); 67 } 68 69 static ssize_t 70 ps_ctl_recvmsgcb(void *arg, struct ps_msghdr *psm, __unused struct msghdr *msg) 71 { 72 struct dhcpcd_ctx *ctx = arg; 73 74 if (psm->ps_cmd != PS_CTL_EOF) { 75 errno = ENOTSUP; 76 return -1; 77 } 78 79 if (ctx->ps_control_client != NULL) 80 ctx->ps_control_client = NULL; 81 return 0; 82 } 83 84 static void 85 ps_ctl_recvmsg(void *arg) 86 { 87 struct dhcpcd_ctx *ctx = arg; 88 89 if (ps_recvpsmsg(ctx, ctx->ps_control_fd, ps_ctl_recvmsgcb, ctx) == -1) 90 logerr(__func__); 91 } 92 93 ssize_t 94 ps_ctl_handleargs(struct fd_list *fd, char *data, size_t len) 95 { 96 97 /* Make any change here in dhcpcd.c as well. */ 98 if (strncmp(data, "--version", 99 MIN(strlen("--version"), len)) == 0) { 100 return control_queue(fd, UNCONST(VERSION), 101 strlen(VERSION) + 1); 102 } else if (strncmp(data, "--getconfigfile", 103 MIN(strlen("--getconfigfile"), len)) == 0) { 104 return control_queue(fd, UNCONST(fd->ctx->cffile), 105 strlen(fd->ctx->cffile) + 1); 106 } else if (strncmp(data, "--listen", 107 MIN(strlen("--listen"), len)) == 0) { 108 fd->flags |= FD_LISTEN; 109 return 0; 110 } 111 112 if (fd->ctx->ps_control_client != NULL && 113 fd->ctx->ps_control_client != fd) 114 { 115 logerrx("%s: cannot handle another client", __func__); 116 return 0; 117 } 118 return 1; 119 } 120 121 static ssize_t 122 ps_ctl_dispatch(void *arg, struct ps_msghdr *psm, struct msghdr *msg) 123 { 124 struct dhcpcd_ctx *ctx = arg; 125 struct iovec *iov = msg->msg_iov; 126 struct fd_list *fd; 127 unsigned int fd_flags = FD_SENDLEN; 128 129 switch (psm->ps_flags) { 130 case PS_CTL_PRIV: 131 break; 132 case PS_CTL_UNPRIV: 133 fd_flags |= FD_UNPRIV; 134 break; 135 } 136 137 switch (psm->ps_cmd) { 138 case PS_CTL: 139 if (msg->msg_iovlen != 1) { 140 errno = EINVAL; 141 return -1; 142 } 143 if (ctx->ps_control_client != NULL) { 144 logerrx("%s: cannot handle another client", __func__); 145 return 0; 146 } 147 fd = control_new(ctx, ctx->ps_control_data_fd, fd_flags); 148 if (fd == NULL) 149 return -1; 150 ctx->ps_control_client = fd; 151 control_recvdata(fd, iov->iov_base, iov->iov_len); 152 break; 153 case PS_CTL_EOF: 154 control_free(ctx->ps_control_client); 155 break; 156 default: 157 errno = ENOTSUP; 158 return -1; 159 } 160 return 0; 161 } 162 163 static void 164 ps_ctl_dodispatch(void *arg) 165 { 166 struct dhcpcd_ctx *ctx = arg; 167 168 if (ps_recvpsmsg(ctx, ctx->ps_control_fd, ps_ctl_dispatch, ctx) == -1) 169 logerr(__func__); 170 } 171 172 static void 173 ps_ctl_recv(void *arg) 174 { 175 struct dhcpcd_ctx *ctx = arg; 176 char buf[BUFSIZ]; 177 ssize_t len; 178 179 errno = 0; 180 len = read(ctx->ps_control_data_fd, buf, sizeof(buf)); 181 if (len == -1 || len == 0) { 182 logerr("%s: read", __func__); 183 eloop_exit(ctx->eloop, EXIT_FAILURE); 184 return; 185 } 186 if (ctx->ps_control_client == NULL) /* client disconnected */ 187 return; 188 errno = 0; 189 if (control_queue(ctx->ps_control_client, buf, (size_t)len) == -1) 190 logerr("%s: control_queue", __func__); 191 } 192 193 static void 194 ps_ctl_listen(void *arg) 195 { 196 struct dhcpcd_ctx *ctx = arg; 197 char buf[BUFSIZ]; 198 ssize_t len; 199 struct fd_list *fd; 200 201 errno = 0; 202 len = read(ctx->ps_control->fd, buf, sizeof(buf)); 203 if (len == -1 || len == 0) { 204 logerr("%s: read", __func__); 205 eloop_exit(ctx->eloop, EXIT_FAILURE); 206 return; 207 } 208 209 /* Send to our listeners */ 210 TAILQ_FOREACH(fd, &ctx->control_fds, next) { 211 if (!(fd->flags & FD_LISTEN)) 212 continue; 213 if (control_queue(fd, buf, (size_t)len)== -1) 214 logerr("%s: control_queue", __func__); 215 } 216 } 217 218 pid_t 219 ps_ctl_start(struct dhcpcd_ctx *ctx) 220 { 221 int data_fd[2], listen_fd[2]; 222 pid_t pid; 223 224 if (xsocketpair(AF_UNIX, SOCK_STREAM | SOCK_CXNB, 0, data_fd) == -1 || 225 xsocketpair(AF_UNIX, SOCK_STREAM | SOCK_CXNB, 0, listen_fd) == -1) 226 return -1; 227 #ifdef PRIVSEP_RIGHTS 228 if (ps_rights_limit_fdpair(data_fd) == -1 || 229 ps_rights_limit_fdpair(listen_fd) == -1) 230 return -1; 231 #endif 232 233 pid = ps_dostart(ctx, &ctx->ps_control_pid, &ctx->ps_control_fd, 234 ps_ctl_recvmsg, ps_ctl_dodispatch, ctx, 235 ps_ctl_startcb, NULL, 236 PSF_DROPPRIVS); 237 238 if (pid == -1) 239 return -1; 240 else if (pid != 0) { 241 ctx->ps_control_data_fd = data_fd[1]; 242 close(data_fd[0]); 243 ctx->ps_control = control_new(ctx, 244 listen_fd[1], FD_SENDLEN | FD_LISTEN); 245 if (ctx->ps_control == NULL) 246 return -1; 247 close(listen_fd[0]); 248 return pid; 249 } 250 251 ctx->ps_control_data_fd = data_fd[0]; 252 close(data_fd[1]); 253 if (eloop_event_add(ctx->eloop, ctx->ps_control_data_fd, 254 ps_ctl_recv, ctx) == -1) 255 return -1; 256 257 ctx->ps_control = control_new(ctx, 258 listen_fd[0], 0); 259 close(listen_fd[1]); 260 if (ctx->ps_control == NULL) 261 return -1; 262 if (eloop_event_add(ctx->eloop, ctx->ps_control->fd, 263 ps_ctl_listen, ctx) == -1) 264 return -1; 265 266 ps_entersandbox("stdio inet", NULL); 267 return 0; 268 } 269 270 int 271 ps_ctl_stop(struct dhcpcd_ctx *ctx) 272 { 273 274 return ps_dostop(ctx, &ctx->ps_control_pid, &ctx->ps_control_fd); 275 } 276 277 ssize_t 278 ps_ctl_sendargs(struct fd_list *fd, void *data, size_t len) 279 { 280 struct dhcpcd_ctx *ctx = fd->ctx; 281 282 if (ctx->ps_control_client != NULL && ctx->ps_control_client != fd) 283 logerrx("%s: cannot deal with another client", __func__); 284 ctx->ps_control_client = fd; 285 return ps_sendcmd(ctx, ctx->ps_control_fd, PS_CTL, 286 fd->flags & FD_UNPRIV ? PS_CTL_UNPRIV : PS_CTL_PRIV, 287 data, len); 288 } 289 290 ssize_t 291 ps_ctl_sendeof(struct fd_list *fd) 292 { 293 struct dhcpcd_ctx *ctx = fd->ctx; 294 295 return ps_sendcmd(ctx, ctx->ps_control_fd, PS_CTL_EOF, 0, NULL, 0); 296 } 297