1 /* $OpenBSD: readpass.c,v 1.51 2015/12/11 00:20:04 mmcc 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 permanently_drop_suid(getuid()); 76 close(p[0]); 77 if (dup2(p[1], STDOUT_FILENO) < 0) 78 fatal("ssh_askpass: dup2: %s", strerror(errno)); 79 execlp(askpass, askpass, msg, (char *)NULL); 80 fatal("ssh_askpass: exec(%s): %s", askpass, strerror(errno)); 81 } 82 close(p[1]); 83 84 len = 0; 85 do { 86 ssize_t r = read(p[0], buf + len, sizeof(buf) - 1 - len); 87 88 if (r == -1 && errno == EINTR) 89 continue; 90 if (r <= 0) 91 break; 92 len += r; 93 } while (sizeof(buf) - 1 - len > 0); 94 buf[len] = '\0'; 95 96 close(p[0]); 97 while ((ret = waitpid(pid, &status, 0)) < 0) 98 if (errno != EINTR) 99 break; 100 signal(SIGCHLD, osigchld); 101 if (ret == -1 || !WIFEXITED(status) || WEXITSTATUS(status) != 0) { 102 explicit_bzero(buf, sizeof(buf)); 103 return NULL; 104 } 105 106 buf[strcspn(buf, "\r\n")] = '\0'; 107 pass = xstrdup(buf); 108 explicit_bzero(buf, sizeof(buf)); 109 return pass; 110 } 111 112 /* 113 * Reads a passphrase from /dev/tty with echo turned off/on. Returns the 114 * passphrase (allocated with xmalloc). Exits if EOF is encountered. If 115 * RP_ALLOW_STDIN is set, the passphrase will be read from stdin if no 116 * tty is available 117 */ 118 char * 119 read_passphrase(const char *prompt, int flags) 120 { 121 char *askpass = NULL, *ret, buf[1024]; 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 close(ttyfd); 137 else { 138 debug("read_passphrase: can't open %s: %s", _PATH_TTY, 139 strerror(errno)); 140 use_askpass = 1; 141 } 142 } 143 144 if ((flags & RP_USE_ASKPASS) && getenv("DISPLAY") == NULL) 145 return (flags & RP_ALLOW_EOF) ? NULL : xstrdup(""); 146 147 if (use_askpass && getenv("DISPLAY")) { 148 if (getenv(SSH_ASKPASS_ENV)) 149 askpass = getenv(SSH_ASKPASS_ENV); 150 else 151 askpass = _PATH_SSH_ASKPASS_DEFAULT; 152 if ((ret = ssh_askpass(askpass, prompt)) == NULL) 153 if (!(flags & RP_ALLOW_EOF)) 154 return xstrdup(""); 155 return ret; 156 } 157 158 if (readpassphrase(prompt, buf, sizeof buf, rppflags) == NULL) { 159 if (flags & RP_ALLOW_EOF) 160 return NULL; 161 return xstrdup(""); 162 } 163 164 ret = xstrdup(buf); 165 explicit_bzero(buf, sizeof(buf)); 166 return ret; 167 } 168 169 int 170 ask_permission(const char *fmt, ...) 171 { 172 va_list args; 173 char *p, prompt[1024]; 174 int allowed = 0; 175 176 va_start(args, fmt); 177 vsnprintf(prompt, sizeof(prompt), fmt, args); 178 va_end(args); 179 180 p = read_passphrase(prompt, RP_USE_ASKPASS|RP_ALLOW_EOF); 181 if (p != NULL) { 182 /* 183 * Accept empty responses and responses consisting 184 * of the word "yes" as affirmative. 185 */ 186 if (*p == '\0' || *p == '\n' || 187 strcasecmp(p, "yes") == 0) 188 allowed = 1; 189 free(p); 190 } 191 192 return (allowed); 193 } 194