Annotation of src/usr.bin/ssh/readpass.c, Revision 1.59
1.59 ! djm 1: /* $OpenBSD: readpass.c,v 1.58 2019/11/27 05:00:17 djm Exp $ */
1.1 deraadt 2: /*
1.26 markus 3: * Copyright (c) 2001 Markus Friedl. All rights reserved.
1.8 deraadt 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: *
1.26 markus 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.
1.6 deraadt 24: */
1.35 stevesk 25:
26: #include <sys/types.h>
27: #include <sys/wait.h>
1.19 markus 28:
1.42 stevesk 29: #include <errno.h>
1.40 stevesk 30: #include <fcntl.h>
1.34 stevesk 31: #include <paths.h>
1.19 markus 32: #include <readpassphrase.h>
1.48 djm 33: #include <signal.h>
1.41 stevesk 34: #include <stdarg.h>
1.46 stevesk 35: #include <stdio.h>
1.45 stevesk 36: #include <stdlib.h>
1.44 stevesk 37: #include <string.h>
1.43 stevesk 38: #include <unistd.h>
1.1 deraadt 39:
40: #include "xmalloc.h"
1.29 djm 41: #include "misc.h"
1.15 markus 42: #include "pathnames.h"
43: #include "log.h"
44: #include "ssh.h"
1.38 markus 45: #include "uidswap.h"
1.15 markus 46:
1.18 itojun 47: static char *
1.16 mouring 48: ssh_askpass(char *askpass, const char *msg)
1.15 markus 49: {
1.48 djm 50: pid_t pid, ret;
1.15 markus 51: size_t len;
1.23 markus 52: char *pass;
1.48 djm 53: int p[2], status;
1.15 markus 54: char buf[1024];
1.48 djm 55: void (*osigchld)(int);
1.15 markus 56:
57: if (fflush(stdout) != 0)
1.59 ! djm 58: error("%s: fflush: %s", __func__, strerror(errno));
1.15 markus 59: if (askpass == NULL)
60: fatal("internal error: askpass undefined");
1.54 deraadt 61: if (pipe(p) == -1) {
1.59 ! djm 62: error("%s: pipe: %s", __func__, strerror(errno));
1.28 markus 63: return NULL;
1.21 markus 64: }
1.48 djm 65: osigchld = signal(SIGCHLD, SIG_DFL);
1.54 deraadt 66: if ((pid = fork()) == -1) {
1.59 ! djm 67: error("%s: fork: %s", __func__, strerror(errno));
1.48 djm 68: signal(SIGCHLD, osigchld);
1.28 markus 69: return NULL;
1.21 markus 70: }
1.15 markus 71: if (pid == 0) {
72: close(p[0]);
1.54 deraadt 73: if (dup2(p[1], STDOUT_FILENO) == -1)
1.59 ! djm 74: fatal("%s: dup2: %s", __func__, strerror(errno));
1.56 djm 75: setenv("SSH_ASKPASS_PROMPT", "confirm", 1); /* hint to UI */
1.51 mmcc 76: execlp(askpass, askpass, msg, (char *)NULL);
1.59 ! djm 77: fatal("%s: exec(%s): %s", __func__, askpass, strerror(errno));
1.15 markus 78: }
79: close(p[1]);
1.24 djm 80:
1.48 djm 81: len = 0;
1.24 djm 82: do {
1.48 djm 83: ssize_t r = read(p[0], buf + len, sizeof(buf) - 1 - len);
84:
85: if (r == -1 && errno == EINTR)
1.24 djm 86: continue;
1.48 djm 87: if (r <= 0)
1.24 djm 88: break;
1.48 djm 89: len += r;
1.24 djm 90: } while (sizeof(buf) - 1 - len > 0);
91: buf[len] = '\0';
92:
1.15 markus 93: close(p[0]);
1.54 deraadt 94: while ((ret = waitpid(pid, &status, 0)) == -1)
1.15 markus 95: if (errno != EINTR)
96: break;
1.48 djm 97: signal(SIGCHLD, osigchld);
98: if (ret == -1 || !WIFEXITED(status) || WEXITSTATUS(status) != 0) {
1.50 djm 99: explicit_bzero(buf, sizeof(buf));
1.28 markus 100: return NULL;
101: }
102:
1.23 markus 103: buf[strcspn(buf, "\r\n")] = '\0';
1.15 markus 104: pass = xstrdup(buf);
1.50 djm 105: explicit_bzero(buf, sizeof(buf));
1.15 markus 106: return pass;
107: }
108:
1.7 markus 109: /*
1.19 markus 110: * Reads a passphrase from /dev/tty with echo turned off/on. Returns the
111: * passphrase (allocated with xmalloc). Exits if EOF is encountered. If
112: * RP_ALLOW_STDIN is set, the passphrase will be read from stdin if no
113: * tty is available
1.12 markus 114: */
1.5 markus 115: char *
1.19 markus 116: read_passphrase(const char *prompt, int flags)
1.1 deraadt 117: {
1.53 tb 118: char cr = '\r', *askpass = NULL, *ret, buf[1024];
1.19 markus 119: int rppflags, use_askpass = 0, ttyfd;
1.15 markus 120:
1.19 markus 121: rppflags = (flags & RP_ECHO) ? RPP_ECHO_ON : RPP_ECHO_OFF;
1.30 djm 122: if (flags & RP_USE_ASKPASS)
123: use_askpass = 1;
124: else if (flags & RP_ALLOW_STDIN) {
1.33 markus 125: if (!isatty(STDIN_FILENO)) {
1.32 dtucker 126: debug("read_passphrase: stdin is not a tty");
1.15 markus 127: use_askpass = 1;
1.33 markus 128: }
1.15 markus 129: } else {
1.19 markus 130: rppflags |= RPP_REQUIRE_TTY;
1.25 markus 131: ttyfd = open(_PATH_TTY, O_RDWR);
1.53 tb 132: if (ttyfd >= 0) {
133: /*
134: * If we're on a tty, ensure that show the prompt at
135: * the beginning of the line. This will hopefully
136: * clobber any password characters the user has
137: * optimistically typed before echo is disabled.
138: */
139: (void)write(ttyfd, &cr, 1);
1.15 markus 140: close(ttyfd);
1.53 tb 141: } else {
1.32 dtucker 142: debug("read_passphrase: can't open %s: %s", _PATH_TTY,
143: strerror(errno));
1.15 markus 144: use_askpass = 1;
1.32 dtucker 145: }
1.15 markus 146: }
1.30 djm 147:
148: if ((flags & RP_USE_ASKPASS) && getenv("DISPLAY") == NULL)
149: return (flags & RP_ALLOW_EOF) ? NULL : xstrdup("");
1.15 markus 150:
151: if (use_askpass && getenv("DISPLAY")) {
152: if (getenv(SSH_ASKPASS_ENV))
153: askpass = getenv(SSH_ASKPASS_ENV);
154: else
155: askpass = _PATH_SSH_ASKPASS_DEFAULT;
1.28 markus 156: if ((ret = ssh_askpass(askpass, prompt)) == NULL)
157: if (!(flags & RP_ALLOW_EOF))
158: return xstrdup("");
159: return ret;
1.15 markus 160: }
161:
1.27 markus 162: if (readpassphrase(prompt, buf, sizeof buf, rppflags) == NULL) {
163: if (flags & RP_ALLOW_EOF)
164: return NULL;
1.20 markus 165: return xstrdup("");
1.27 markus 166: }
1.19 markus 167:
168: ret = xstrdup(buf);
1.50 djm 169: explicit_bzero(buf, sizeof(buf));
1.19 markus 170: return ret;
1.31 djm 171: }
172:
173: int
174: ask_permission(const char *fmt, ...)
175: {
176: va_list args;
177: char *p, prompt[1024];
178: int allowed = 0;
179:
180: va_start(args, fmt);
181: vsnprintf(prompt, sizeof(prompt), fmt, args);
182: va_end(args);
183:
184: p = read_passphrase(prompt, RP_USE_ASKPASS|RP_ALLOW_EOF);
185: if (p != NULL) {
186: /*
187: * Accept empty responses and responses consisting
188: * of the word "yes" as affirmative.
189: */
190: if (*p == '\0' || *p == '\n' ||
191: strcasecmp(p, "yes") == 0)
192: allowed = 1;
1.49 djm 193: free(p);
1.31 djm 194: }
195:
196: return (allowed);
1.55 djm 197: }
198:
199: struct notifier_ctx {
200: pid_t pid;
201: void (*osigchld)(int);
202: };
203:
204: struct notifier_ctx *
205: notify_start(int force_askpass, const char *fmt, ...)
206: {
207: va_list args;
208: char *prompt = NULL;
209: int devnull;
210: pid_t pid;
211: void (*osigchld)(int);
212: const char *askpass;
213: struct notifier_ctx *ret;
214:
215: va_start(args, fmt);
216: xvasprintf(&prompt, fmt, args);
217: va_end(args);
218:
219: if (fflush(NULL) != 0)
220: error("%s: fflush: %s", __func__, strerror(errno));
221: if (!force_askpass && isatty(STDERR_FILENO)) {
222: (void)write(STDERR_FILENO, "\r", 1);
223: (void)write(STDERR_FILENO, prompt, strlen(prompt));
224: (void)write(STDERR_FILENO, "\r\n", 2);
225: free(prompt);
226: return NULL;
227: }
1.57 djm 228: if ((askpass = getenv("SSH_ASKPASS")) == NULL)
229: askpass = _PATH_SSH_ASKPASS_DEFAULT;
230: if (getenv("DISPLAY") == NULL || *askpass == '\0') {
1.55 djm 231: debug3("%s: cannot notify", __func__);
232: free(prompt);
233: return NULL;
234: }
235: osigchld = signal(SIGCHLD, SIG_DFL);
236: if ((pid = fork()) == -1) {
237: error("%s: fork: %s", __func__, strerror(errno));
238: signal(SIGCHLD, osigchld);
239: free(prompt);
240: return NULL;
241: }
242: if (pid == 0) {
243: if ((devnull = open(_PATH_DEVNULL, O_RDWR)) == -1)
244: fatal("%s: open %s", __func__, strerror(errno));
245: if (dup2(devnull, STDIN_FILENO) == -1 ||
246: dup2(devnull, STDOUT_FILENO) == -1)
247: fatal("%s: dup2: %s", __func__, strerror(errno));
248: closefrom(STDERR_FILENO + 1);
249: setenv("SSH_ASKPASS_PROMPT", "none", 1); /* hint to UI */
250: execlp(askpass, askpass, prompt, (char *)NULL);
1.58 djm 251: error("%s: exec(%s): %s", __func__, askpass, strerror(errno));
252: _exit(1);
1.55 djm 253: /* NOTREACHED */
254: }
255: if ((ret = calloc(1, sizeof(*ret))) == NULL) {
256: kill(pid, SIGTERM);
257: fatal("%s: calloc failed", __func__);
258: }
259: ret->pid = pid;
260: ret->osigchld = osigchld;
261: free(prompt);
262: return ret;
263: }
264:
265: void
266: notify_complete(struct notifier_ctx *ctx)
267: {
268: int ret;
269:
270: if (ctx == NULL || ctx->pid <= 0) {
271: free(ctx);
272: return;
273: }
274: kill(ctx->pid, SIGTERM);
275: while ((ret = waitpid(ctx->pid, NULL, 0)) == -1) {
276: if (errno != EINTR)
277: break;
278: }
279: if (ret == -1)
280: fatal("%s: waitpid: %s", __func__, strerror(errno));
281: signal(SIGCHLD, ctx->osigchld);
282: free(ctx);
1.1 deraadt 283: }
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