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