1 /* $NetBSD: readpass.c,v 1.12 2019/04/20 17:16:40 christos Exp $ */ 2 /* $OpenBSD: readpass.c,v 1.53 2019/01/19 04:15:56 tb Exp $ */ 3 /* 4 * Copyright (c) 2001 Markus Friedl. All rights reserved. 5 * 6 * Redistribution and use in source and binary forms, with or without 7 * modification, are permitted provided that the following conditions 8 * are met: 9 * 1. Redistributions of source code must retain the above copyright 10 * notice, this list of conditions and the following disclaimer. 11 * 2. Redistributions in binary form must reproduce the above copyright 12 * notice, this list of conditions and the following disclaimer in the 13 * documentation and/or other materials provided with the distribution. 14 * 15 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 16 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 17 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 18 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 19 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 20 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 21 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 22 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 23 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 24 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 25 */ 26 27 #include "includes.h" 28 __RCSID("$NetBSD: readpass.c,v 1.12 2019/04/20 17:16:40 christos Exp $"); 29 #include <sys/types.h> 30 #include <sys/wait.h> 31 32 #include <errno.h> 33 #include <fcntl.h> 34 #include <paths.h> 35 #include <readpassphrase.h> 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(const 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', *ret, buf[1024]; 121 const char *askpass = NULL; 122 int rppflags, use_askpass = 0, ttyfd; 123 124 rppflags = (flags & RP_ECHO) ? RPP_ECHO_ON : RPP_ECHO_OFF; 125 if (flags & RP_USE_ASKPASS) 126 use_askpass = 1; 127 else if (flags & RP_ALLOW_STDIN) { 128 if (!isatty(STDIN_FILENO)) { 129 debug("read_passphrase: stdin is not a tty"); 130 use_askpass = 1; 131 } 132 } else { 133 rppflags |= RPP_REQUIRE_TTY; 134 ttyfd = open(_PATH_TTY, O_RDWR); 135 if (ttyfd >= 0) { 136 /* 137 * If we're on a tty, ensure that show the prompt at 138 * the beginning of the line. This will hopefully 139 * clobber any password characters the user has 140 * optimistically typed before echo is disabled. 141 */ 142 (void)write(ttyfd, &cr, 1); 143 close(ttyfd); 144 } else { 145 debug("read_passphrase: can't open %s: %s", _PATH_TTY, 146 strerror(errno)); 147 use_askpass = 1; 148 } 149 } 150 151 if ((flags & RP_USE_ASKPASS) && getenv("DISPLAY") == NULL) 152 return (flags & RP_ALLOW_EOF) ? NULL : xstrdup(""); 153 154 if (use_askpass && getenv("DISPLAY")) { 155 if (getenv(SSH_ASKPASS_ENV)) 156 askpass = getenv(SSH_ASKPASS_ENV); 157 else 158 askpass = _PATH_SSH_ASKPASS_DEFAULT; 159 if ((ret = ssh_askpass(askpass, prompt)) == NULL) 160 if (!(flags & RP_ALLOW_EOF)) 161 return xstrdup(""); 162 return ret; 163 } 164 165 if (readpassphrase(prompt, buf, sizeof buf, rppflags) == NULL) { 166 if (flags & RP_ALLOW_EOF) 167 return NULL; 168 return xstrdup(""); 169 } 170 171 ret = xstrdup(buf); 172 explicit_bzero(buf, sizeof(buf)); 173 return ret; 174 } 175 176 int 177 ask_permission(const char *fmt, ...) 178 { 179 va_list args; 180 char *p, prompt[1024]; 181 int allowed = 0; 182 183 va_start(args, fmt); 184 vsnprintf(prompt, sizeof(prompt), fmt, args); 185 va_end(args); 186 187 p = read_passphrase(prompt, RP_USE_ASKPASS|RP_ALLOW_EOF); 188 if (p != NULL) { 189 /* 190 * Accept empty responses and responses consisting 191 * of the word "yes" as affirmative. 192 */ 193 if (*p == '\0' || *p == '\n' || 194 strcasecmp(p, "yes") == 0) 195 allowed = 1; 196 free(p); 197 } 198 199 return (allowed); 200 } 201