1 /* $OpenBSD: readpass.c,v 1.53 2019/01/19 04:15:56 tb 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 "includes.h" 27 28 #include <sys/types.h> 29 #include <sys/wait.h> 30 31 #include <errno.h> 32 #include <fcntl.h> 33 #ifdef HAVE_PATHS_H 34 # include <paths.h> 35 #endif 36 #include <signal.h> 37 #include <stdarg.h> 38 #include <stdio.h> 39 #include <stdlib.h> 40 #include <string.h> 41 #include <unistd.h> 42 43 #include "xmalloc.h" 44 #include "misc.h" 45 #include "pathnames.h" 46 #include "log.h" 47 #include "ssh.h" 48 #include "uidswap.h" 49 50 static char * 51 ssh_askpass(char *askpass, const char *msg) 52 { 53 pid_t pid, ret; 54 size_t len; 55 char *pass; 56 int p[2], status; 57 char buf[1024]; 58 void (*osigchld)(int); 59 60 if (fflush(stdout) != 0) 61 error("ssh_askpass: fflush: %s", strerror(errno)); 62 if (askpass == NULL) 63 fatal("internal error: askpass undefined"); 64 if (pipe(p) < 0) { 65 error("ssh_askpass: pipe: %s", strerror(errno)); 66 return NULL; 67 } 68 osigchld = signal(SIGCHLD, SIG_DFL); 69 if ((pid = fork()) < 0) { 70 error("ssh_askpass: fork: %s", strerror(errno)); 71 signal(SIGCHLD, osigchld); 72 return NULL; 73 } 74 if (pid == 0) { 75 close(p[0]); 76 if (dup2(p[1], STDOUT_FILENO) < 0) 77 fatal("ssh_askpass: dup2: %s", strerror(errno)); 78 execlp(askpass, askpass, msg, (char *)NULL); 79 fatal("ssh_askpass: exec(%s): %s", askpass, strerror(errno)); 80 } 81 close(p[1]); 82 83 len = 0; 84 do { 85 ssize_t r = read(p[0], buf + len, sizeof(buf) - 1 - len); 86 87 if (r == -1 && errno == EINTR) 88 continue; 89 if (r <= 0) 90 break; 91 len += r; 92 } while (sizeof(buf) - 1 - len > 0); 93 buf[len] = '\0'; 94 95 close(p[0]); 96 while ((ret = waitpid(pid, &status, 0)) < 0) 97 if (errno != EINTR) 98 break; 99 signal(SIGCHLD, osigchld); 100 if (ret == -1 || !WIFEXITED(status) || WEXITSTATUS(status) != 0) { 101 explicit_bzero(buf, sizeof(buf)); 102 return NULL; 103 } 104 105 buf[strcspn(buf, "\r\n")] = '\0'; 106 pass = xstrdup(buf); 107 explicit_bzero(buf, sizeof(buf)); 108 return pass; 109 } 110 111 /* 112 * Reads a passphrase from /dev/tty with echo turned off/on. Returns the 113 * passphrase (allocated with xmalloc). Exits if EOF is encountered. If 114 * RP_ALLOW_STDIN is set, the passphrase will be read from stdin if no 115 * tty is available 116 */ 117 char * 118 read_passphrase(const char *prompt, int flags) 119 { 120 char cr = '\r', *askpass = NULL, *ret, buf[1024]; 121 int rppflags, use_askpass = 0, ttyfd; 122 123 rppflags = (flags & RP_ECHO) ? RPP_ECHO_ON : RPP_ECHO_OFF; 124 if (flags & RP_USE_ASKPASS) 125 use_askpass = 1; 126 else if (flags & RP_ALLOW_STDIN) { 127 if (!isatty(STDIN_FILENO)) { 128 debug("read_passphrase: stdin is not a tty"); 129 use_askpass = 1; 130 } 131 } else { 132 rppflags |= RPP_REQUIRE_TTY; 133 ttyfd = open(_PATH_TTY, O_RDWR); 134 if (ttyfd >= 0) { 135 /* 136 * If we're on a tty, ensure that show the prompt at 137 * the beginning of the line. This will hopefully 138 * clobber any password characters the user has 139 * optimistically typed before echo is disabled. 140 */ 141 (void)write(ttyfd, &cr, 1); 142 close(ttyfd); 143 } else { 144 debug("read_passphrase: can't open %s: %s", _PATH_TTY, 145 strerror(errno)); 146 use_askpass = 1; 147 } 148 } 149 150 if ((flags & RP_USE_ASKPASS) && getenv("DISPLAY") == NULL) 151 return (flags & RP_ALLOW_EOF) ? NULL : xstrdup(""); 152 153 if (use_askpass && getenv("DISPLAY")) { 154 if (getenv(SSH_ASKPASS_ENV)) 155 askpass = getenv(SSH_ASKPASS_ENV); 156 else 157 askpass = _PATH_SSH_ASKPASS_DEFAULT; 158 if ((ret = ssh_askpass(askpass, prompt)) == NULL) 159 if (!(flags & RP_ALLOW_EOF)) 160 return xstrdup(""); 161 return ret; 162 } 163 164 if (readpassphrase(prompt, buf, sizeof buf, rppflags) == NULL) { 165 if (flags & RP_ALLOW_EOF) 166 return NULL; 167 return xstrdup(""); 168 } 169 170 ret = xstrdup(buf); 171 explicit_bzero(buf, sizeof(buf)); 172 return ret; 173 } 174 175 int 176 ask_permission(const char *fmt, ...) 177 { 178 va_list args; 179 char *p, prompt[1024]; 180 int allowed = 0; 181 182 va_start(args, fmt); 183 vsnprintf(prompt, sizeof(prompt), fmt, args); 184 va_end(args); 185 186 p = read_passphrase(prompt, RP_USE_ASKPASS|RP_ALLOW_EOF); 187 if (p != NULL) { 188 /* 189 * Accept empty responses and responses consisting 190 * of the word "yes" as affirmative. 191 */ 192 if (*p == '\0' || *p == '\n' || 193 strcasecmp(p, "yes") == 0) 194 allowed = 1; 195 free(p); 196 } 197 198 return (allowed); 199 } 200