1 /* $NetBSD: readpass.c,v 1.19 2024/07/08 22:33:44 christos Exp $ */ 2 /* $OpenBSD: readpass.c,v 1.71 2024/03/30 04:27:44 djm Exp $ */ 3 4 /* 5 * Copyright (c) 2001 Markus Friedl. 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 ``AS IS'' AND ANY EXPRESS OR 17 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 18 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 19 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 20 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 21 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 22 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 23 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 24 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 25 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 26 */ 27 28 #include "includes.h" 29 __RCSID("$NetBSD: readpass.c,v 1.19 2024/07/08 22:33:44 christos Exp $"); 30 #include <sys/types.h> 31 #include <sys/wait.h> 32 33 #include <errno.h> 34 #include <fcntl.h> 35 #include <paths.h> 36 #include <readpassphrase.h> 37 #include <signal.h> 38 #include <stdarg.h> 39 #include <stdio.h> 40 #include <stdlib.h> 41 #include <string.h> 42 #include <unistd.h> 43 44 #include "xmalloc.h" 45 #include "misc.h" 46 #include "pathnames.h" 47 #include "log.h" 48 #include "ssh.h" 49 #include "uidswap.h" 50 51 static char * 52 ssh_askpass(const char *askpass, const char *msg, const char *env_hint) 53 { 54 pid_t pid, ret; 55 size_t len; 56 char *pass; 57 int p[2], status; 58 char buf[1024]; 59 void (*osigchld)(int); 60 61 if (fflush(stdout) != 0) 62 error_f("fflush: %s", strerror(errno)); 63 if (askpass == NULL) 64 fatal("internal error: askpass undefined"); 65 if (pipe(p) == -1) { 66 error_f("pipe: %s", strerror(errno)); 67 return NULL; 68 } 69 osigchld = ssh_signal(SIGCHLD, SIG_DFL); 70 if ((pid = fork()) == -1) { 71 error_f("fork: %s", strerror(errno)); 72 ssh_signal(SIGCHLD, osigchld); 73 return NULL; 74 } 75 if (pid == 0) { 76 close(p[0]); 77 if (dup2(p[1], STDOUT_FILENO) == -1) 78 fatal_f("dup2: %s", strerror(errno)); 79 if (env_hint != NULL) 80 setenv("SSH_ASKPASS_PROMPT", env_hint, 1); 81 execlp(askpass, askpass, msg, (char *)NULL); 82 fatal_f("exec(%s): %s", askpass, strerror(errno)); 83 } 84 close(p[1]); 85 86 len = 0; 87 do { 88 ssize_t r = read(p[0], buf + len, sizeof(buf) - 1 - len); 89 90 if (r == -1 && errno == EINTR) 91 continue; 92 if (r <= 0) 93 break; 94 len += r; 95 } while (sizeof(buf) - 1 - len > 0); 96 buf[len] = '\0'; 97 98 close(p[0]); 99 while ((ret = waitpid(pid, &status, 0)) == -1) 100 if (errno != EINTR) 101 break; 102 ssh_signal(SIGCHLD, osigchld); 103 if (ret == -1 || !WIFEXITED(status) || WEXITSTATUS(status) != 0) { 104 explicit_bzero(buf, sizeof(buf)); 105 return NULL; 106 } 107 108 buf[strcspn(buf, "\r\n")] = '\0'; 109 pass = xstrdup(buf); 110 explicit_bzero(buf, sizeof(buf)); 111 return pass; 112 } 113 114 /* private/internal read_passphrase flags */ 115 #define RP_ASK_PERMISSION 0x8000 /* pass hint to askpass for confirm UI */ 116 117 /* 118 * Reads a passphrase from /dev/tty with echo turned off/on. Returns the 119 * passphrase (allocated with xmalloc). Exits if EOF is encountered. If 120 * RP_ALLOW_STDIN is set, the passphrase will be read from stdin if no 121 * tty is or askpass program is available 122 */ 123 char * 124 read_passphrase(const char *prompt, int flags) 125 { 126 char cr = '\r', *ret, buf[1024]; 127 int rppflags, ttyfd, use_askpass = 0, allow_askpass = 0; 128 const char *askpass_hint = NULL, *askpass = NULL; 129 const char *s; 130 131 if (((s = getenv("DISPLAY")) != NULL && *s != '\0') || 132 ((s = getenv("WAYLAND_DISPLAY")) != NULL && *s != '\0')) 133 allow_askpass = 1; 134 if ((s = getenv(SSH_ASKPASS_REQUIRE_ENV)) != NULL) { 135 if (strcasecmp(s, "force") == 0) { 136 use_askpass = 1; 137 allow_askpass = 1; 138 } else if (strcasecmp(s, "prefer") == 0) 139 use_askpass = allow_askpass; 140 else if (strcasecmp(s, "never") == 0) 141 allow_askpass = 0; 142 } 143 144 rppflags = (flags & RP_ECHO) ? RPP_ECHO_ON : RPP_ECHO_OFF; 145 if (use_askpass) 146 debug_f("requested to askpass"); 147 else if (flags & RP_USE_ASKPASS) 148 use_askpass = 1; 149 else if (flags & RP_ALLOW_STDIN) { 150 if (!isatty(STDIN_FILENO)) { 151 debug_f("stdin is not a tty"); 152 use_askpass = 1; 153 } 154 } else { 155 rppflags |= RPP_REQUIRE_TTY; 156 ttyfd = open(_PATH_TTY, O_RDWR); 157 if (ttyfd >= 0) { 158 /* 159 * If we're on a tty, ensure that show the prompt at 160 * the beginning of the line. This will hopefully 161 * clobber any password characters the user has 162 * optimistically typed before echo is disabled. 163 */ 164 (void)write(ttyfd, &cr, 1); 165 close(ttyfd); 166 } else { 167 debug_f("can't open %s: %s", _PATH_TTY, 168 strerror(errno)); 169 use_askpass = 1; 170 } 171 } 172 173 if ((flags & RP_USE_ASKPASS) && !allow_askpass) 174 return (flags & RP_ALLOW_EOF) ? NULL : xstrdup(""); 175 176 if (use_askpass && allow_askpass) { 177 if (getenv(SSH_ASKPASS_ENV)) 178 askpass = getenv(SSH_ASKPASS_ENV); 179 else 180 askpass = _PATH_SSH_ASKPASS_DEFAULT; 181 if ((flags & RP_ASK_PERMISSION) != 0) 182 askpass_hint = "confirm"; 183 if ((ret = ssh_askpass(askpass, prompt, askpass_hint)) == NULL) 184 if (!(flags & RP_ALLOW_EOF)) 185 return xstrdup(""); 186 return ret; 187 } 188 189 if (readpassphrase(prompt, buf, sizeof buf, rppflags) == NULL) { 190 if (flags & RP_ALLOW_EOF) 191 return NULL; 192 return xstrdup(""); 193 } 194 195 ret = xstrdup(buf); 196 explicit_bzero(buf, sizeof(buf)); 197 return ret; 198 } 199 200 int 201 ask_permission(const char *fmt, ...) 202 { 203 va_list args; 204 char *p, prompt[1024]; 205 int allowed = 0; 206 207 va_start(args, fmt); 208 vsnprintf(prompt, sizeof(prompt), fmt, args); 209 va_end(args); 210 211 p = read_passphrase(prompt, 212 RP_USE_ASKPASS|RP_ALLOW_EOF|RP_ASK_PERMISSION); 213 if (p != NULL) { 214 /* 215 * Accept empty responses and responses consisting 216 * of the word "yes" as affirmative. 217 */ 218 if (*p == '\0' || *p == '\n' || 219 strcasecmp(p, "yes") == 0) 220 allowed = 1; 221 free(p); 222 } 223 224 return (allowed); 225 } 226 227 static void 228 writemsg(const char *msg) 229 { 230 (void)write(STDERR_FILENO, "\r", 1); 231 (void)write(STDERR_FILENO, msg, strlen(msg)); 232 (void)write(STDERR_FILENO, "\r\n", 2); 233 } 234 235 struct notifier_ctx { 236 pid_t pid; 237 void (*osigchld)(int); 238 }; 239 240 struct notifier_ctx * 241 notify_start(int force_askpass, const char *fmt, ...) 242 { 243 va_list args; 244 char *prompt = NULL; 245 pid_t pid = -1; 246 void (*osigchld)(int) = NULL; 247 const char *askpass, *s; 248 struct notifier_ctx *ret = NULL; 249 250 va_start(args, fmt); 251 xvasprintf(&prompt, fmt, args); 252 va_end(args); 253 254 if (fflush(NULL) != 0) 255 error_f("fflush: %s", strerror(errno)); 256 if (!force_askpass && isatty(STDERR_FILENO)) { 257 writemsg(prompt); 258 goto out_ctx; 259 } 260 if ((askpass = getenv("SSH_ASKPASS")) == NULL) 261 askpass = _PATH_SSH_ASKPASS_DEFAULT; 262 if (*askpass == '\0') { 263 debug3_f("cannot notify: no askpass"); 264 goto out; 265 } 266 if (getenv("DISPLAY") == NULL && getenv("WAYLAND_DISPLAY") == NULL && 267 ((s = getenv(SSH_ASKPASS_REQUIRE_ENV)) == NULL || 268 strcmp(s, "force") != 0)) { 269 debug3_f("cannot notify: no display"); 270 goto out; 271 } 272 osigchld = ssh_signal(SIGCHLD, SIG_DFL); 273 if ((pid = fork()) == -1) { 274 error_f("fork: %s", strerror(errno)); 275 ssh_signal(SIGCHLD, osigchld); 276 free(prompt); 277 return NULL; 278 } 279 if (pid == 0) { 280 if (stdfd_devnull(1, 1, 0) == -1) 281 fatal_f("stdfd_devnull failed"); 282 closefrom(STDERR_FILENO + 1); 283 setenv("SSH_ASKPASS_PROMPT", "none", 1); /* hint to UI */ 284 execlp(askpass, askpass, prompt, (char *)NULL); 285 error_f("exec(%s): %s", askpass, strerror(errno)); 286 _exit(1); 287 /* NOTREACHED */ 288 } 289 out_ctx: 290 if ((ret = calloc(1, sizeof(*ret))) == NULL) { 291 if (pid != -1) 292 kill(pid, SIGTERM); 293 fatal_f("calloc failed"); 294 } 295 ret->pid = pid; 296 ret->osigchld = osigchld; 297 out: 298 free(prompt); 299 return ret; 300 } 301 302 void 303 notify_complete(struct notifier_ctx *ctx, const char *fmt, ...) 304 { 305 int ret; 306 char *msg = NULL; 307 va_list args; 308 309 if (ctx != NULL && fmt != NULL && ctx->pid == -1) { 310 /* 311 * notify_start wrote to stderr, so send conclusion message 312 * there too 313 */ 314 va_start(args, fmt); 315 xvasprintf(&msg, fmt, args); 316 va_end(args); 317 writemsg(msg); 318 free(msg); 319 } 320 321 if (ctx == NULL || ctx->pid <= 0) { 322 free(ctx); 323 return; 324 } 325 kill(ctx->pid, SIGTERM); 326 while ((ret = waitpid(ctx->pid, NULL, 0)) == -1) { 327 if (errno != EINTR) 328 break; 329 } 330 if (ret == -1) 331 fatal_f("waitpid: %s", strerror(errno)); 332 ssh_signal(SIGCHLD, ctx->osigchld); 333 free(ctx); 334 } 335