Annotation of src/usr.bin/ssh/readpass.c, Revision 1.71
1.71 ! djm 1: /* $OpenBSD: readpass.c,v 1.70 2022/05/27 04:27:49 dtucker 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 *
1.60 djm 48: ssh_askpass(char *askpass, const char *msg, const char *env_hint)
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)
1.65 djm 58: error_f("fflush: %s", strerror(errno));
1.15 markus 59: if (askpass == NULL)
60: fatal("internal error: askpass undefined");
1.54 deraadt 61: if (pipe(p) == -1) {
1.65 djm 62: error_f("pipe: %s", strerror(errno));
1.28 markus 63: return NULL;
1.21 markus 64: }
1.61 dtucker 65: osigchld = ssh_signal(SIGCHLD, SIG_DFL);
1.54 deraadt 66: if ((pid = fork()) == -1) {
1.65 djm 67: error_f("fork: %s", strerror(errno));
1.61 dtucker 68: ssh_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)
1.65 djm 74: fatal_f("dup2: %s", strerror(errno));
1.60 djm 75: if (env_hint != NULL)
76: setenv("SSH_ASKPASS_PROMPT", env_hint, 1);
1.51 mmcc 77: execlp(askpass, askpass, msg, (char *)NULL);
1.65 djm 78: fatal_f("exec(%s): %s", askpass, strerror(errno));
1.15 markus 79: }
80: close(p[1]);
1.24 djm 81:
1.48 djm 82: len = 0;
1.24 djm 83: do {
1.48 djm 84: ssize_t r = read(p[0], buf + len, sizeof(buf) - 1 - len);
85:
86: if (r == -1 && errno == EINTR)
1.24 djm 87: continue;
1.48 djm 88: if (r <= 0)
1.24 djm 89: break;
1.48 djm 90: len += r;
1.24 djm 91: } while (sizeof(buf) - 1 - len > 0);
92: buf[len] = '\0';
93:
1.15 markus 94: close(p[0]);
1.54 deraadt 95: while ((ret = waitpid(pid, &status, 0)) == -1)
1.15 markus 96: if (errno != EINTR)
97: break;
1.61 dtucker 98: ssh_signal(SIGCHLD, osigchld);
1.48 djm 99: if (ret == -1 || !WIFEXITED(status) || WEXITSTATUS(status) != 0) {
1.50 djm 100: explicit_bzero(buf, sizeof(buf));
1.28 markus 101: return NULL;
102: }
103:
1.23 markus 104: buf[strcspn(buf, "\r\n")] = '\0';
1.15 markus 105: pass = xstrdup(buf);
1.50 djm 106: explicit_bzero(buf, sizeof(buf));
1.15 markus 107: return pass;
108: }
109:
1.60 djm 110: /* private/internal read_passphrase flags */
111: #define RP_ASK_PERMISSION 0x8000 /* pass hint to askpass for confirm UI */
112:
1.7 markus 113: /*
1.19 markus 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
1.69 djm 117: * tty is or askpass program is available
1.12 markus 118: */
1.5 markus 119: char *
1.19 markus 120: read_passphrase(const char *prompt, int flags)
1.1 deraadt 121: {
1.53 tb 122: char cr = '\r', *askpass = NULL, *ret, buf[1024];
1.62 djm 123: int rppflags, ttyfd, use_askpass = 0, allow_askpass = 0;
1.60 djm 124: const char *askpass_hint = NULL;
1.62 djm 125: const char *s;
126:
1.71 ! djm 127: if (((s = getenv("DISPLAY")) != NULL && *s != '\0') ||
! 128: ((s = getenv("WAYLAND_DISPLAY")) != NULL && *s != '\0'))
! 129: allow_askpass = 1;
1.62 djm 130: if ((s = getenv(SSH_ASKPASS_REQUIRE_ENV)) != NULL) {
131: if (strcasecmp(s, "force") == 0) {
132: use_askpass = 1;
133: allow_askpass = 1;
134: } else if (strcasecmp(s, "prefer") == 0)
135: use_askpass = allow_askpass;
136: else if (strcasecmp(s, "never") == 0)
137: allow_askpass = 0;
138: }
1.15 markus 139:
1.19 markus 140: rppflags = (flags & RP_ECHO) ? RPP_ECHO_ON : RPP_ECHO_OFF;
1.62 djm 141: if (use_askpass)
1.65 djm 142: debug_f("requested to askpass");
1.62 djm 143: else if (flags & RP_USE_ASKPASS)
1.30 djm 144: use_askpass = 1;
145: else if (flags & RP_ALLOW_STDIN) {
1.33 markus 146: if (!isatty(STDIN_FILENO)) {
1.69 djm 147: debug_f("stdin is not a tty");
1.15 markus 148: use_askpass = 1;
1.33 markus 149: }
1.15 markus 150: } else {
1.19 markus 151: rppflags |= RPP_REQUIRE_TTY;
1.25 markus 152: ttyfd = open(_PATH_TTY, O_RDWR);
1.53 tb 153: if (ttyfd >= 0) {
154: /*
155: * If we're on a tty, ensure that show the prompt at
156: * the beginning of the line. This will hopefully
157: * clobber any password characters the user has
158: * optimistically typed before echo is disabled.
159: */
160: (void)write(ttyfd, &cr, 1);
1.15 markus 161: close(ttyfd);
1.53 tb 162: } else {
1.69 djm 163: debug_f("can't open %s: %s", _PATH_TTY,
1.32 dtucker 164: strerror(errno));
1.15 markus 165: use_askpass = 1;
1.32 dtucker 166: }
1.15 markus 167: }
1.30 djm 168:
1.62 djm 169: if ((flags & RP_USE_ASKPASS) && !allow_askpass)
1.30 djm 170: return (flags & RP_ALLOW_EOF) ? NULL : xstrdup("");
1.15 markus 171:
1.62 djm 172: if (use_askpass && allow_askpass) {
1.15 markus 173: if (getenv(SSH_ASKPASS_ENV))
174: askpass = getenv(SSH_ASKPASS_ENV);
175: else
176: askpass = _PATH_SSH_ASKPASS_DEFAULT;
1.60 djm 177: if ((flags & RP_ASK_PERMISSION) != 0)
178: askpass_hint = "confirm";
179: if ((ret = ssh_askpass(askpass, prompt, askpass_hint)) == NULL)
1.28 markus 180: if (!(flags & RP_ALLOW_EOF))
181: return xstrdup("");
182: return ret;
1.15 markus 183: }
184:
1.27 markus 185: if (readpassphrase(prompt, buf, sizeof buf, rppflags) == NULL) {
186: if (flags & RP_ALLOW_EOF)
187: return NULL;
1.20 markus 188: return xstrdup("");
1.27 markus 189: }
1.19 markus 190:
191: ret = xstrdup(buf);
1.50 djm 192: explicit_bzero(buf, sizeof(buf));
1.19 markus 193: return ret;
1.31 djm 194: }
195:
196: int
197: ask_permission(const char *fmt, ...)
198: {
199: va_list args;
200: char *p, prompt[1024];
201: int allowed = 0;
202:
203: va_start(args, fmt);
204: vsnprintf(prompt, sizeof(prompt), fmt, args);
205: va_end(args);
206:
1.60 djm 207: p = read_passphrase(prompt,
208: RP_USE_ASKPASS|RP_ALLOW_EOF|RP_ASK_PERMISSION);
1.31 djm 209: if (p != NULL) {
210: /*
211: * Accept empty responses and responses consisting
212: * of the word "yes" as affirmative.
213: */
214: if (*p == '\0' || *p == '\n' ||
215: strcasecmp(p, "yes") == 0)
216: allowed = 1;
1.49 djm 217: free(p);
1.31 djm 218: }
219:
220: return (allowed);
1.55 djm 221: }
222:
1.66 djm 223: static void
224: writemsg(const char *msg)
225: {
226: (void)write(STDERR_FILENO, "\r", 1);
227: (void)write(STDERR_FILENO, msg, strlen(msg));
228: (void)write(STDERR_FILENO, "\r\n", 2);
229: }
230:
1.55 djm 231: struct notifier_ctx {
232: pid_t pid;
233: void (*osigchld)(int);
234: };
235:
236: struct notifier_ctx *
237: notify_start(int force_askpass, const char *fmt, ...)
238: {
239: va_list args;
240: char *prompt = NULL;
1.66 djm 241: pid_t pid = -1;
242: void (*osigchld)(int) = NULL;
1.63 djm 243: const char *askpass, *s;
244: struct notifier_ctx *ret = NULL;
1.55 djm 245:
246: va_start(args, fmt);
247: xvasprintf(&prompt, fmt, args);
248: va_end(args);
249:
250: if (fflush(NULL) != 0)
1.65 djm 251: error_f("fflush: %s", strerror(errno));
1.55 djm 252: if (!force_askpass && isatty(STDERR_FILENO)) {
1.66 djm 253: writemsg(prompt);
254: goto out_ctx;
1.55 djm 255: }
1.57 djm 256: if ((askpass = getenv("SSH_ASKPASS")) == NULL)
257: askpass = _PATH_SSH_ASKPASS_DEFAULT;
1.63 djm 258: if (*askpass == '\0') {
1.65 djm 259: debug3_f("cannot notify: no askpass");
1.63 djm 260: goto out;
261: }
1.71 ! djm 262: if (getenv("DISPLAY") == NULL && getenv("WAYLAND_DISPLAY") == NULL &&
1.63 djm 263: ((s = getenv(SSH_ASKPASS_REQUIRE_ENV)) == NULL ||
264: strcmp(s, "force") != 0)) {
1.65 djm 265: debug3_f("cannot notify: no display");
1.63 djm 266: goto out;
1.55 djm 267: }
1.61 dtucker 268: osigchld = ssh_signal(SIGCHLD, SIG_DFL);
1.55 djm 269: if ((pid = fork()) == -1) {
1.65 djm 270: error_f("fork: %s", strerror(errno));
1.61 dtucker 271: ssh_signal(SIGCHLD, osigchld);
1.55 djm 272: free(prompt);
273: return NULL;
274: }
275: if (pid == 0) {
1.64 djm 276: if (stdfd_devnull(1, 1, 0) == -1)
1.65 djm 277: fatal_f("stdfd_devnull failed");
1.55 djm 278: closefrom(STDERR_FILENO + 1);
279: setenv("SSH_ASKPASS_PROMPT", "none", 1); /* hint to UI */
280: execlp(askpass, askpass, prompt, (char *)NULL);
1.65 djm 281: error_f("exec(%s): %s", askpass, strerror(errno));
1.58 djm 282: _exit(1);
1.55 djm 283: /* NOTREACHED */
284: }
1.66 djm 285: out_ctx:
1.55 djm 286: if ((ret = calloc(1, sizeof(*ret))) == NULL) {
1.70 dtucker 287: if (pid != -1)
288: kill(pid, SIGTERM);
1.65 djm 289: fatal_f("calloc failed");
1.55 djm 290: }
291: ret->pid = pid;
292: ret->osigchld = osigchld;
1.63 djm 293: out:
1.55 djm 294: free(prompt);
295: return ret;
296: }
297:
298: void
1.66 djm 299: notify_complete(struct notifier_ctx *ctx, const char *fmt, ...)
1.55 djm 300: {
301: int ret;
1.66 djm 302: char *msg = NULL;
303: va_list args;
304:
1.67 djm 305: if (ctx != NULL && fmt != NULL && ctx->pid == -1) {
1.66 djm 306: /*
307: * notify_start wrote to stderr, so send conclusion message
308: * there too
309: */
310: va_start(args, fmt);
311: xvasprintf(&msg, fmt, args);
312: va_end(args);
313: writemsg(msg);
1.68 claudio 314: free(msg);
1.66 djm 315: }
1.55 djm 316:
317: if (ctx == NULL || ctx->pid <= 0) {
318: free(ctx);
319: return;
320: }
321: kill(ctx->pid, SIGTERM);
322: while ((ret = waitpid(ctx->pid, NULL, 0)) == -1) {
323: if (errno != EINTR)
324: break;
325: }
326: if (ret == -1)
1.65 djm 327: fatal_f("waitpid: %s", strerror(errno));
1.61 dtucker 328: ssh_signal(SIGCHLD, ctx->osigchld);
1.55 djm 329: free(ctx);
1.1 deraadt 330: }
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