1 /* $OpenBSD: readpass.c,v 1.71 2024/03/30 04:27:44 djm Exp $ */ 2 /* 3 * Copyright (c) 2001 Markus Friedl. All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 15 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 16 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 17 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 18 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 19 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 20 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 21 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 22 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 23 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 24 */ 25 26 #include <sys/types.h> 27 #include <sys/wait.h> 28 29 #include <errno.h> 30 #include <fcntl.h> 31 #include <paths.h> 32 #include <readpassphrase.h> 33 #include <signal.h> 34 #include <stdarg.h> 35 #include <stdio.h> 36 #include <stdlib.h> 37 #include <string.h> 38 #include <unistd.h> 39 40 #include "xmalloc.h" 41 #include "misc.h" 42 #include "pathnames.h" 43 #include "log.h" 44 #include "ssh.h" 45 #include "uidswap.h" 46 47 static char * 48 ssh_askpass(char *askpass, const char *msg, const char *env_hint) 49 { 50 pid_t pid, ret; 51 size_t len; 52 char *pass; 53 int p[2], status; 54 char buf[1024]; 55 void (*osigchld)(int); 56 57 if (fflush(stdout) != 0) 58 error_f("fflush: %s", strerror(errno)); 59 if (askpass == NULL) 60 fatal("internal error: askpass undefined"); 61 if (pipe(p) == -1) { 62 error_f("pipe: %s", strerror(errno)); 63 return NULL; 64 } 65 osigchld = ssh_signal(SIGCHLD, SIG_DFL); 66 if ((pid = fork()) == -1) { 67 error_f("fork: %s", strerror(errno)); 68 ssh_signal(SIGCHLD, osigchld); 69 return NULL; 70 } 71 if (pid == 0) { 72 close(p[0]); 73 if (dup2(p[1], STDOUT_FILENO) == -1) 74 fatal_f("dup2: %s", strerror(errno)); 75 if (env_hint != NULL) 76 setenv("SSH_ASKPASS_PROMPT", env_hint, 1); 77 execlp(askpass, askpass, msg, (char *)NULL); 78 fatal_f("exec(%s): %s", askpass, strerror(errno)); 79 } 80 close(p[1]); 81 82 len = 0; 83 do { 84 ssize_t r = read(p[0], buf + len, sizeof(buf) - 1 - len); 85 86 if (r == -1 && errno == EINTR) 87 continue; 88 if (r <= 0) 89 break; 90 len += r; 91 } while (sizeof(buf) - 1 - len > 0); 92 buf[len] = '\0'; 93 94 close(p[0]); 95 while ((ret = waitpid(pid, &status, 0)) == -1) 96 if (errno != EINTR) 97 break; 98 ssh_signal(SIGCHLD, osigchld); 99 if (ret == -1 || !WIFEXITED(status) || WEXITSTATUS(status) != 0) { 100 explicit_bzero(buf, sizeof(buf)); 101 return NULL; 102 } 103 104 buf[strcspn(buf, "\r\n")] = '\0'; 105 pass = xstrdup(buf); 106 explicit_bzero(buf, sizeof(buf)); 107 return pass; 108 } 109 110 /* private/internal read_passphrase flags */ 111 #define RP_ASK_PERMISSION 0x8000 /* pass hint to askpass for confirm UI */ 112 113 /* 114 * Reads a passphrase from /dev/tty with echo turned off/on. Returns the 115 * passphrase (allocated with xmalloc). Exits if EOF is encountered. If 116 * RP_ALLOW_STDIN is set, the passphrase will be read from stdin if no 117 * tty is or askpass program is available 118 */ 119 char * 120 read_passphrase(const char *prompt, int flags) 121 { 122 char cr = '\r', *askpass = NULL, *ret, buf[1024]; 123 int rppflags, ttyfd, use_askpass = 0, allow_askpass = 0; 124 const char *askpass_hint = NULL; 125 const char *s; 126 127 if (((s = getenv("DISPLAY")) != NULL && *s != '\0') || 128 ((s = getenv("WAYLAND_DISPLAY")) != NULL && *s != '\0')) 129 allow_askpass = 1; 130 if ((s = getenv(SSH_ASKPASS_REQUIRE_ENV)) != NULL) { 131 if (strcasecmp(s, "force") == 0) { 132 use_askpass = 1; 133 allow_askpass = 1; 134 } else if (strcasecmp(s, "prefer") == 0) 135 use_askpass = allow_askpass; 136 else if (strcasecmp(s, "never") == 0) 137 allow_askpass = 0; 138 } 139 140 rppflags = (flags & RP_ECHO) ? RPP_ECHO_ON : RPP_ECHO_OFF; 141 if (use_askpass) 142 debug_f("requested to askpass"); 143 else if (flags & RP_USE_ASKPASS) 144 use_askpass = 1; 145 else if (flags & RP_ALLOW_STDIN) { 146 if (!isatty(STDIN_FILENO)) { 147 debug_f("stdin is not a tty"); 148 use_askpass = 1; 149 } 150 } else { 151 rppflags |= RPP_REQUIRE_TTY; 152 ttyfd = open(_PATH_TTY, O_RDWR); 153 if (ttyfd >= 0) { 154 /* 155 * If we're on a tty, ensure that show the prompt at 156 * the beginning of the line. This will hopefully 157 * clobber any password characters the user has 158 * optimistically typed before echo is disabled. 159 */ 160 (void)write(ttyfd, &cr, 1); 161 close(ttyfd); 162 } else { 163 debug_f("can't open %s: %s", _PATH_TTY, 164 strerror(errno)); 165 use_askpass = 1; 166 } 167 } 168 169 if ((flags & RP_USE_ASKPASS) && !allow_askpass) 170 return (flags & RP_ALLOW_EOF) ? NULL : xstrdup(""); 171 172 if (use_askpass && allow_askpass) { 173 if (getenv(SSH_ASKPASS_ENV)) 174 askpass = getenv(SSH_ASKPASS_ENV); 175 else 176 askpass = _PATH_SSH_ASKPASS_DEFAULT; 177 if ((flags & RP_ASK_PERMISSION) != 0) 178 askpass_hint = "confirm"; 179 if ((ret = ssh_askpass(askpass, prompt, askpass_hint)) == NULL) 180 if (!(flags & RP_ALLOW_EOF)) 181 return xstrdup(""); 182 return ret; 183 } 184 185 if (readpassphrase(prompt, buf, sizeof buf, rppflags) == NULL) { 186 if (flags & RP_ALLOW_EOF) 187 return NULL; 188 return xstrdup(""); 189 } 190 191 ret = xstrdup(buf); 192 explicit_bzero(buf, sizeof(buf)); 193 return ret; 194 } 195 196 int 197 ask_permission(const char *fmt, ...) 198 { 199 va_list args; 200 char *p, prompt[1024]; 201 int allowed = 0; 202 203 va_start(args, fmt); 204 vsnprintf(prompt, sizeof(prompt), fmt, args); 205 va_end(args); 206 207 p = read_passphrase(prompt, 208 RP_USE_ASKPASS|RP_ALLOW_EOF|RP_ASK_PERMISSION); 209 if (p != NULL) { 210 /* 211 * Accept empty responses and responses consisting 212 * of the word "yes" as affirmative. 213 */ 214 if (*p == '\0' || *p == '\n' || 215 strcasecmp(p, "yes") == 0) 216 allowed = 1; 217 free(p); 218 } 219 220 return (allowed); 221 } 222 223 static void 224 writemsg(const char *msg) 225 { 226 (void)write(STDERR_FILENO, "\r", 1); 227 (void)write(STDERR_FILENO, msg, strlen(msg)); 228 (void)write(STDERR_FILENO, "\r\n", 2); 229 } 230 231 struct notifier_ctx { 232 pid_t pid; 233 void (*osigchld)(int); 234 }; 235 236 struct notifier_ctx * 237 notify_start(int force_askpass, const char *fmt, ...) 238 { 239 va_list args; 240 char *prompt = NULL; 241 pid_t pid = -1; 242 void (*osigchld)(int) = NULL; 243 const char *askpass, *s; 244 struct notifier_ctx *ret = NULL; 245 246 va_start(args, fmt); 247 xvasprintf(&prompt, fmt, args); 248 va_end(args); 249 250 if (fflush(NULL) != 0) 251 error_f("fflush: %s", strerror(errno)); 252 if (!force_askpass && isatty(STDERR_FILENO)) { 253 writemsg(prompt); 254 goto out_ctx; 255 } 256 if ((askpass = getenv("SSH_ASKPASS")) == NULL) 257 askpass = _PATH_SSH_ASKPASS_DEFAULT; 258 if (*askpass == '\0') { 259 debug3_f("cannot notify: no askpass"); 260 goto out; 261 } 262 if (getenv("DISPLAY") == NULL && getenv("WAYLAND_DISPLAY") == NULL && 263 ((s = getenv(SSH_ASKPASS_REQUIRE_ENV)) == NULL || 264 strcmp(s, "force") != 0)) { 265 debug3_f("cannot notify: no display"); 266 goto out; 267 } 268 osigchld = ssh_signal(SIGCHLD, SIG_DFL); 269 if ((pid = fork()) == -1) { 270 error_f("fork: %s", strerror(errno)); 271 ssh_signal(SIGCHLD, osigchld); 272 free(prompt); 273 return NULL; 274 } 275 if (pid == 0) { 276 if (stdfd_devnull(1, 1, 0) == -1) 277 fatal_f("stdfd_devnull failed"); 278 closefrom(STDERR_FILENO + 1); 279 setenv("SSH_ASKPASS_PROMPT", "none", 1); /* hint to UI */ 280 execlp(askpass, askpass, prompt, (char *)NULL); 281 error_f("exec(%s): %s", askpass, strerror(errno)); 282 _exit(1); 283 /* NOTREACHED */ 284 } 285 out_ctx: 286 if ((ret = calloc(1, sizeof(*ret))) == NULL) { 287 if (pid != -1) 288 kill(pid, SIGTERM); 289 fatal_f("calloc failed"); 290 } 291 ret->pid = pid; 292 ret->osigchld = osigchld; 293 out: 294 free(prompt); 295 return ret; 296 } 297 298 void 299 notify_complete(struct notifier_ctx *ctx, const char *fmt, ...) 300 { 301 int ret; 302 char *msg = NULL; 303 va_list args; 304 305 if (ctx != NULL && fmt != NULL && ctx->pid == -1) { 306 /* 307 * notify_start wrote to stderr, so send conclusion message 308 * there too 309 */ 310 va_start(args, fmt); 311 xvasprintf(&msg, fmt, args); 312 va_end(args); 313 writemsg(msg); 314 free(msg); 315 } 316 317 if (ctx == NULL || ctx->pid <= 0) { 318 free(ctx); 319 return; 320 } 321 kill(ctx->pid, SIGTERM); 322 while ((ret = waitpid(ctx->pid, NULL, 0)) == -1) { 323 if (errno != EINTR) 324 break; 325 } 326 if (ret == -1) 327 fatal_f("waitpid: %s", strerror(errno)); 328 ssh_signal(SIGCHLD, ctx->osigchld); 329 free(ctx); 330 } 331