1 /* SPDX-License-Identifier: BSD-2-Clause */ 2 /* 3 * Privilege Separation for dhcpcd, control proxy 4 * Copyright (c) 2006-2023 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(struct ps_process *psp) 41 { 42 struct dhcpcd_ctx *ctx = psp->psp_ctx; 43 sa_family_t af; 44 45 if (ctx->options & DHCPCD_MANAGER) { 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 return control_start(ctx, 64 ctx->options & DHCPCD_MANAGER ? NULL : *ctx->ifv, af); 65 } 66 67 static void 68 ps_ctl_recvmsg(void *arg, unsigned short events) 69 { 70 struct ps_process *psp = arg; 71 72 if (ps_recvpsmsg(psp->psp_ctx, psp->psp_fd, events, NULL, NULL) == -1) 73 logerr(__func__); 74 } 75 76 ssize_t 77 ps_ctl_handleargs(struct fd_list *fd, char *data, size_t len) 78 { 79 80 /* Make any change here in dhcpcd.c as well. */ 81 if (strncmp(data, "--version", 82 MIN(strlen("--version"), len)) == 0) { 83 return control_queue(fd, UNCONST(VERSION), 84 strlen(VERSION) + 1); 85 } else if (strncmp(data, "--getconfigfile", 86 MIN(strlen("--getconfigfile"), len)) == 0) { 87 return control_queue(fd, UNCONST(fd->ctx->cffile), 88 strlen(fd->ctx->cffile) + 1); 89 } else if (strncmp(data, "--listen", 90 MIN(strlen("--listen"), len)) == 0) { 91 fd->flags |= FD_LISTEN; 92 return 0; 93 } 94 95 if (fd->ctx->ps_control_client != NULL && 96 fd->ctx->ps_control_client != fd) 97 { 98 logerrx("%s: cannot handle another client", __func__); 99 return 0; 100 } 101 return 1; 102 } 103 104 static ssize_t 105 ps_ctl_dispatch(void *arg, struct ps_msghdr *psm, struct msghdr *msg) 106 { 107 struct dhcpcd_ctx *ctx = arg; 108 struct iovec *iov = msg->msg_iov; 109 struct fd_list *fd; 110 unsigned int fd_flags = FD_SENDLEN; 111 112 switch (psm->ps_flags) { 113 case PS_CTL_PRIV: 114 break; 115 case PS_CTL_UNPRIV: 116 fd_flags |= FD_UNPRIV; 117 break; 118 } 119 120 switch (psm->ps_cmd) { 121 case PS_CTL: 122 if (msg->msg_iovlen != 1) { 123 errno = EINVAL; 124 return -1; 125 } 126 if (ctx->ps_control_client != NULL) { 127 logerrx("%s: cannot handle another client", __func__); 128 return 0; 129 } 130 fd = control_new(ctx, ctx->ps_ctl->psp_work_fd, fd_flags); 131 if (fd == NULL) 132 return -1; 133 ctx->ps_control_client = fd; 134 control_recvdata(fd, iov->iov_base, iov->iov_len); 135 break; 136 case PS_CTL_EOF: 137 ctx->ps_control_client = NULL; 138 break; 139 default: 140 errno = ENOTSUP; 141 return -1; 142 } 143 return 0; 144 } 145 146 static void 147 ps_ctl_dodispatch(void *arg, unsigned short events) 148 { 149 struct ps_process *psp = arg; 150 151 if (ps_recvpsmsg(psp->psp_ctx, psp->psp_fd, events, 152 ps_ctl_dispatch, psp->psp_ctx) == -1) 153 logerr(__func__); 154 } 155 156 static void 157 ps_ctl_recv(void *arg, unsigned short events) 158 { 159 struct dhcpcd_ctx *ctx = arg; 160 char buf[BUFSIZ]; 161 ssize_t len; 162 163 if (!(events & (ELE_READ | ELE_HANGUP))) 164 logerrx("%s: unexpected event 0x%04x", __func__, events); 165 166 if (events & ELE_READ) { 167 len = read(ctx->ps_ctl->psp_work_fd, buf, sizeof(buf)); 168 if (len == -1) 169 logerr("%s: read", __func__); 170 else if (len == 0) 171 // FIXME: Why does this happen? 172 ; 173 else if (ctx->ps_control_client == NULL) 174 logerrx("%s: clientfd #%d disconnected (len=%zd)", 175 __func__, ctx->ps_ctl->psp_work_fd, len); 176 else { 177 errno = 0; 178 if (control_queue(ctx->ps_control_client, 179 buf, (size_t)len) == -1) 180 logerr("%s: control_queue", __func__); 181 } 182 } 183 } 184 185 static void 186 ps_ctl_listen(void *arg, unsigned short events) 187 { 188 struct dhcpcd_ctx *ctx = arg; 189 char buf[BUFSIZ]; 190 ssize_t len; 191 struct fd_list *fd; 192 193 if (!(events & ELE_READ)) 194 logerrx("%s: unexpected event 0x%04x", __func__, events); 195 196 len = read(ctx->ps_control->fd, buf, sizeof(buf)); 197 if (len == -1) { 198 logerr("%s: read", __func__); 199 eloop_exit(ctx->eloop, EXIT_FAILURE); 200 return; 201 } 202 203 /* Send to our listeners */ 204 TAILQ_FOREACH(fd, &ctx->control_fds, next) { 205 if (!(fd->flags & FD_LISTEN)) 206 continue; 207 if (control_queue(fd, buf, (size_t)len)== -1) 208 logerr("%s: control_queue", __func__); 209 } 210 } 211 212 pid_t 213 ps_ctl_start(struct dhcpcd_ctx *ctx) 214 { 215 struct ps_id id = { 216 .psi_ifindex = 0, 217 .psi_cmd = PS_CTL, 218 }; 219 struct ps_process *psp; 220 int data_fd[2], listen_fd[2]; 221 pid_t pid; 222 223 if (xsocketpair(AF_UNIX, SOCK_STREAM | SOCK_CXNB, 0, data_fd) == -1 || 224 xsocketpair(AF_UNIX, SOCK_STREAM | SOCK_CXNB, 0, listen_fd) == -1) 225 return -1; 226 #ifdef PRIVSEP_RIGHTS 227 if (ps_rights_limit_fdpair(data_fd) == -1 || 228 ps_rights_limit_fdpair(listen_fd) == -1) 229 return -1; 230 #endif 231 232 psp = ctx->ps_ctl = ps_newprocess(ctx, &id); 233 strlcpy(psp->psp_name, "control proxy", sizeof(psp->psp_name)); 234 pid = ps_startprocess(psp, ps_ctl_recvmsg, ps_ctl_dodispatch, 235 ps_ctl_startcb, NULL, PSF_DROPPRIVS); 236 237 if (pid == -1) 238 return -1; 239 else if (pid != 0) { 240 psp->psp_work_fd = data_fd[1]; 241 close(data_fd[0]); 242 ctx->ps_control = control_new(ctx, 243 listen_fd[1], FD_SENDLEN | FD_LISTEN); 244 if (ctx->ps_control == NULL) 245 return -1; 246 close(listen_fd[0]); 247 return pid; 248 } 249 250 psp->psp_work_fd = data_fd[0]; 251 close(data_fd[1]); 252 if (eloop_event_add(ctx->eloop, psp->psp_work_fd, ELE_READ, 253 ps_ctl_recv, ctx) == -1) 254 return -1; 255 256 ctx->ps_control = control_new(ctx, listen_fd[0], 0); 257 close(listen_fd[1]); 258 if (ctx->ps_control == NULL) 259 return -1; 260 if (eloop_event_add(ctx->eloop, ctx->ps_control->fd, ELE_READ, 261 ps_ctl_listen, ctx) == -1) 262 return -1; 263 264 ps_entersandbox("stdio inet", NULL); 265 return 0; 266 } 267 268 int 269 ps_ctl_stop(struct dhcpcd_ctx *ctx) 270 { 271 272 return ps_stopprocess(ctx->ps_ctl); 273 } 274 275 ssize_t 276 ps_ctl_sendargs(struct fd_list *fd, void *data, size_t len) 277 { 278 struct dhcpcd_ctx *ctx = fd->ctx; 279 280 if (ctx->ps_control_client != NULL && ctx->ps_control_client != fd) 281 logerrx("%s: cannot deal with another client", __func__); 282 ctx->ps_control_client = fd; 283 return ps_sendcmd(ctx, ctx->ps_ctl->psp_fd, PS_CTL, 284 fd->flags & FD_UNPRIV ? PS_CTL_UNPRIV : PS_CTL_PRIV, 285 data, len); 286 } 287 288 ssize_t 289 ps_ctl_sendeof(struct fd_list *fd) 290 { 291 struct dhcpcd_ctx *ctx = fd->ctx; 292 293 return ps_sendcmd(ctx, ctx->ps_ctl->psp_fd, PS_CTL_EOF, 0, NULL, 0); 294 } 295