1 /* $NetBSD: readpass.c,v 1.9 2017/04/18 18:41:46 christos Exp $ */ 2 /* $OpenBSD: readpass.c,v 1.51 2015/12/11 00:20:04 mmcc 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 1.9 2017/04/18 18:41:46 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) 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("ssh_askpass: fflush: %s", strerror(errno)); 63 if (askpass == NULL) 64 fatal("internal error: askpass undefined"); 65 if (pipe(p) < 0) { 66 error("ssh_askpass: pipe: %s", strerror(errno)); 67 return NULL; 68 } 69 osigchld = signal(SIGCHLD, SIG_DFL); 70 if ((pid = fork()) < 0) { 71 error("ssh_askpass: fork: %s", strerror(errno)); 72 signal(SIGCHLD, osigchld); 73 return NULL; 74 } 75 if (pid == 0) { 76 permanently_drop_suid(getuid()); 77 close(p[0]); 78 if (dup2(p[1], STDOUT_FILENO) < 0) 79 fatal("ssh_askpass: dup2: %s", strerror(errno)); 80 execlp(askpass, askpass, msg, (char *)NULL); 81 fatal("ssh_askpass: exec(%s): %s", askpass, strerror(errno)); 82 } 83 close(p[1]); 84 85 len = 0; 86 do { 87 ssize_t r = read(p[0], buf + len, sizeof(buf) - 1 - len); 88 89 if (r == -1 && errno == EINTR) 90 continue; 91 if (r <= 0) 92 break; 93 len += r; 94 } while (sizeof(buf) - 1 - len > 0); 95 buf[len] = '\0'; 96 97 close(p[0]); 98 while ((ret = waitpid(pid, &status, 0)) < 0) 99 if (errno != EINTR) 100 break; 101 signal(SIGCHLD, osigchld); 102 if (ret == -1 || !WIFEXITED(status) || WEXITSTATUS(status) != 0) { 103 explicit_bzero(buf, sizeof(buf)); 104 return NULL; 105 } 106 107 buf[strcspn(buf, "\r\n")] = '\0'; 108 pass = xstrdup(buf); 109 explicit_bzero(buf, sizeof(buf)); 110 return pass; 111 } 112 113 /* 114 * Reads a passphrase from /dev/tty with echo turned off/on. Returns the 115 * passphrase (allocated with xmalloc). Exits if EOF is encountered. If 116 * RP_ALLOW_STDIN is set, the passphrase will be read from stdin if no 117 * tty is available 118 */ 119 char * 120 read_passphrase(const char *prompt, int flags) 121 { 122 const char *askpass = NULL; 123 char *ret, buf[1024]; 124 int rppflags, use_askpass = 0, ttyfd; 125 126 rppflags = (flags & RP_ECHO) ? RPP_ECHO_ON : RPP_ECHO_OFF; 127 if (flags & RP_USE_ASKPASS) 128 use_askpass = 1; 129 else if (flags & RP_ALLOW_STDIN) { 130 if (!isatty(STDIN_FILENO)) { 131 debug("read_passphrase: stdin is not a tty"); 132 use_askpass = 1; 133 } 134 } else { 135 rppflags |= RPP_REQUIRE_TTY; 136 ttyfd = open(_PATH_TTY, O_RDWR); 137 if (ttyfd >= 0) 138 close(ttyfd); 139 else { 140 debug("read_passphrase: can't open %s: %s", _PATH_TTY, 141 strerror(errno)); 142 use_askpass = 1; 143 } 144 } 145 146 if ((flags & RP_USE_ASKPASS) && getenv("DISPLAY") == NULL) 147 return (flags & RP_ALLOW_EOF) ? NULL : xstrdup(""); 148 149 if (use_askpass && getenv("DISPLAY")) { 150 if (getenv(SSH_ASKPASS_ENV)) 151 askpass = getenv(SSH_ASKPASS_ENV); 152 else 153 askpass = _PATH_SSH_ASKPASS_DEFAULT; 154 if ((ret = ssh_askpass(askpass, prompt)) == NULL) 155 if (!(flags & RP_ALLOW_EOF)) 156 return xstrdup(""); 157 return ret; 158 } 159 160 if (readpassphrase(prompt, buf, sizeof buf, rppflags) == NULL) { 161 if (flags & RP_ALLOW_EOF) 162 return NULL; 163 return xstrdup(""); 164 } 165 166 ret = xstrdup(buf); 167 explicit_bzero(buf, sizeof(buf)); 168 return ret; 169 } 170 171 int 172 ask_permission(const char *fmt, ...) 173 { 174 va_list args; 175 char *p, prompt[1024]; 176 int allowed = 0; 177 178 va_start(args, fmt); 179 vsnprintf(prompt, sizeof(prompt), fmt, args); 180 va_end(args); 181 182 p = read_passphrase(prompt, RP_USE_ASKPASS|RP_ALLOW_EOF); 183 if (p != NULL) { 184 /* 185 * Accept empty responses and responses consisting 186 * of the word "yes" as affirmative. 187 */ 188 if (*p == '\0' || *p == '\n' || 189 strcasecmp(p, "yes") == 0) 190 allowed = 1; 191 free(p); 192 } 193 194 return (allowed); 195 } 196