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/* $OpenBSD: readpass.c,v 1.50 2014/02/02 03:44:31 djm Exp $ */
/*
* Copyright (c) 2001 Markus Friedl. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include "includes.h"
#include <sys/types.h>
#include <sys/wait.h>
#include <errno.h>
#include <fcntl.h>
#ifdef HAVE_PATHS_H
# include <paths.h>
#endif
#include <signal.h>
#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include "xmalloc.h"
#include "misc.h"
#include "pathnames.h"
#include "log.h"
#include "ssh.h"
#include "uidswap.h"
static char *
ssh_askpass(char *askpass, const char *msg)
{
pid_t pid, ret;
size_t len;
char *pass;
int p[2], status;
char buf[1024];
void (*osigchld)(int);
if (fflush(stdout) != 0)
error("ssh_askpass: fflush: %s", strerror(errno));
if (askpass == NULL)
fatal("internal error: askpass undefined");
if (pipe(p) < 0) {
error("ssh_askpass: pipe: %s", strerror(errno));
return NULL;
}
osigchld = signal(SIGCHLD, SIG_DFL);
if ((pid = fork()) < 0) {
error("ssh_askpass: fork: %s", strerror(errno));
signal(SIGCHLD, osigchld);
return NULL;
}
if (pid == 0) {
permanently_drop_suid(getuid());
close(p[0]);
if (dup2(p[1], STDOUT_FILENO) < 0)
fatal("ssh_askpass: dup2: %s", strerror(errno));
execlp(askpass, askpass, msg, (char *) 0);
fatal("ssh_askpass: exec(%s): %s", askpass, strerror(errno));
}
close(p[1]);
len = 0;
do {
ssize_t r = read(p[0], buf + len, sizeof(buf) - 1 - len);
if (r == -1 && errno == EINTR)
continue;
if (r <= 0)
break;
len += r;
} while (sizeof(buf) - 1 - len > 0);
buf[len] = '\0';
close(p[0]);
while ((ret = waitpid(pid, &status, 0)) < 0)
if (errno != EINTR)
break;
signal(SIGCHLD, osigchld);
if (ret == -1 || !WIFEXITED(status) || WEXITSTATUS(status) != 0) {
explicit_bzero(buf, sizeof(buf));
return NULL;
}
buf[strcspn(buf, "\r\n")] = '\0';
pass = xstrdup(buf);
explicit_bzero(buf, sizeof(buf));
return pass;
}
/*
* Reads a passphrase from /dev/tty with echo turned off/on. Returns the
* passphrase (allocated with xmalloc). Exits if EOF is encountered. If
* RP_ALLOW_STDIN is set, the passphrase will be read from stdin if no
* tty is available
*/
char *
read_passphrase(const char *prompt, int flags)
{
char *askpass = NULL, *ret, buf[1024];
int rppflags, use_askpass = 0, ttyfd;
rppflags = (flags & RP_ECHO) ? RPP_ECHO_ON : RPP_ECHO_OFF;
if (flags & RP_USE_ASKPASS)
use_askpass = 1;
else if (flags & RP_ALLOW_STDIN) {
if (!isatty(STDIN_FILENO)) {
debug("read_passphrase: stdin is not a tty");
use_askpass = 1;
}
} else {
rppflags |= RPP_REQUIRE_TTY;
ttyfd = open(_PATH_TTY, O_RDWR);
if (ttyfd >= 0)
close(ttyfd);
else {
debug("read_passphrase: can't open %s: %s", _PATH_TTY,
strerror(errno));
use_askpass = 1;
}
}
if ((flags & RP_USE_ASKPASS) && getenv("DISPLAY") == NULL)
return (flags & RP_ALLOW_EOF) ? NULL : xstrdup("");
if (use_askpass && getenv("DISPLAY")) {
if (getenv(SSH_ASKPASS_ENV))
askpass = getenv(SSH_ASKPASS_ENV);
else
askpass = _PATH_SSH_ASKPASS_DEFAULT;
if ((ret = ssh_askpass(askpass, prompt)) == NULL)
if (!(flags & RP_ALLOW_EOF))
return xstrdup("");
return ret;
}
if (readpassphrase(prompt, buf, sizeof buf, rppflags) == NULL) {
if (flags & RP_ALLOW_EOF)
return NULL;
return xstrdup("");
}
ret = xstrdup(buf);
explicit_bzero(buf, sizeof(buf));
return ret;
}
int
ask_permission(const char *fmt, ...)
{
va_list args;
char *p, prompt[1024];
int allowed = 0;
va_start(args, fmt);
vsnprintf(prompt, sizeof(prompt), fmt, args);
va_end(args);
p = read_passphrase(prompt, RP_USE_ASKPASS|RP_ALLOW_EOF);
if (p != NULL) {
/*
* Accept empty responses and responses consisting
* of the word "yes" as affirmative.
*/
if (*p == '\0' || *p == '\n' ||
strcasecmp(p, "yes") == 0)
allowed = 1;
free(p);
}
return (allowed);
}
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