1 /* $OpenBSD: readpass.c,v 1.47 2006/08/03 03:34:42 deraadt 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 <stdarg.h> 34 #include <stdio.h> 35 #include <stdlib.h> 36 #include <string.h> 37 #include <unistd.h> 38 39 #include "xmalloc.h" 40 #include "misc.h" 41 #include "pathnames.h" 42 #include "log.h" 43 #include "ssh.h" 44 #include "uidswap.h" 45 46 static char * 47 ssh_askpass(char *askpass, const char *msg) 48 { 49 pid_t pid; 50 size_t len; 51 char *pass; 52 int p[2], status, ret; 53 char buf[1024]; 54 55 if (fflush(stdout) != 0) 56 error("ssh_askpass: fflush: %s", strerror(errno)); 57 if (askpass == NULL) 58 fatal("internal error: askpass undefined"); 59 if (pipe(p) < 0) { 60 error("ssh_askpass: pipe: %s", strerror(errno)); 61 return NULL; 62 } 63 if ((pid = fork()) < 0) { 64 error("ssh_askpass: fork: %s", strerror(errno)); 65 return NULL; 66 } 67 if (pid == 0) { 68 permanently_drop_suid(getuid()); 69 close(p[0]); 70 if (dup2(p[1], STDOUT_FILENO) < 0) 71 fatal("ssh_askpass: dup2: %s", strerror(errno)); 72 execlp(askpass, askpass, msg, (char *) 0); 73 fatal("ssh_askpass: exec(%s): %s", askpass, strerror(errno)); 74 } 75 close(p[1]); 76 77 len = ret = 0; 78 do { 79 ret = read(p[0], buf + len, sizeof(buf) - 1 - len); 80 if (ret == -1 && errno == EINTR) 81 continue; 82 if (ret <= 0) 83 break; 84 len += ret; 85 } while (sizeof(buf) - 1 - len > 0); 86 buf[len] = '\0'; 87 88 close(p[0]); 89 while (waitpid(pid, &status, 0) < 0) 90 if (errno != EINTR) 91 break; 92 93 if (!WIFEXITED(status) || WEXITSTATUS(status) != 0) { 94 memset(buf, 0, sizeof(buf)); 95 return NULL; 96 } 97 98 buf[strcspn(buf, "\r\n")] = '\0'; 99 pass = xstrdup(buf); 100 memset(buf, 0, sizeof(buf)); 101 return pass; 102 } 103 104 /* 105 * Reads a passphrase from /dev/tty with echo turned off/on. Returns the 106 * passphrase (allocated with xmalloc). Exits if EOF is encountered. If 107 * RP_ALLOW_STDIN is set, the passphrase will be read from stdin if no 108 * tty is available 109 */ 110 char * 111 read_passphrase(const char *prompt, int flags) 112 { 113 char *askpass = NULL, *ret, buf[1024]; 114 int rppflags, use_askpass = 0, ttyfd; 115 116 rppflags = (flags & RP_ECHO) ? RPP_ECHO_ON : RPP_ECHO_OFF; 117 if (flags & RP_USE_ASKPASS) 118 use_askpass = 1; 119 else if (flags & RP_ALLOW_STDIN) { 120 if (!isatty(STDIN_FILENO)) { 121 debug("read_passphrase: stdin is not a tty"); 122 use_askpass = 1; 123 } 124 } else { 125 rppflags |= RPP_REQUIRE_TTY; 126 ttyfd = open(_PATH_TTY, O_RDWR); 127 if (ttyfd >= 0) 128 close(ttyfd); 129 else { 130 debug("read_passphrase: can't open %s: %s", _PATH_TTY, 131 strerror(errno)); 132 use_askpass = 1; 133 } 134 } 135 136 if ((flags & RP_USE_ASKPASS) && getenv("DISPLAY") == NULL) 137 return (flags & RP_ALLOW_EOF) ? NULL : xstrdup(""); 138 139 if (use_askpass && getenv("DISPLAY")) { 140 if (getenv(SSH_ASKPASS_ENV)) 141 askpass = getenv(SSH_ASKPASS_ENV); 142 else 143 askpass = _PATH_SSH_ASKPASS_DEFAULT; 144 if ((ret = ssh_askpass(askpass, prompt)) == NULL) 145 if (!(flags & RP_ALLOW_EOF)) 146 return xstrdup(""); 147 return ret; 148 } 149 150 if (readpassphrase(prompt, buf, sizeof buf, rppflags) == NULL) { 151 if (flags & RP_ALLOW_EOF) 152 return NULL; 153 return xstrdup(""); 154 } 155 156 ret = xstrdup(buf); 157 memset(buf, 'x', sizeof buf); 158 return ret; 159 } 160 161 int 162 ask_permission(const char *fmt, ...) 163 { 164 va_list args; 165 char *p, prompt[1024]; 166 int allowed = 0; 167 168 va_start(args, fmt); 169 vsnprintf(prompt, sizeof(prompt), fmt, args); 170 va_end(args); 171 172 p = read_passphrase(prompt, RP_USE_ASKPASS|RP_ALLOW_EOF); 173 if (p != NULL) { 174 /* 175 * Accept empty responses and responses consisting 176 * of the word "yes" as affirmative. 177 */ 178 if (*p == '\0' || *p == '\n' || 179 strcasecmp(p, "yes") == 0) 180 allowed = 1; 181 xfree(p); 182 } 183 184 return (allowed); 185 } 186