blob: 974d67f0bfa64cd0b08359dbfc53d98bd98ecf2e [file] [log] [blame]
/* $OpenBSD: readpass.c,v 1.61 2020/01/23 07:10:22 dtucker 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, const char *env_hint)
{
pid_t pid, ret;
size_t len;
char *pass;
int p[2], status;
char buf[1024];
void (*osigchld)(int);
if (fflush(stdout) != 0)
error("%s: fflush: %s", __func__, strerror(errno));
if (askpass == NULL)
fatal("internal error: askpass undefined");
if (pipe(p) == -1) {
error("%s: pipe: %s", __func__, strerror(errno));
return NULL;
}
osigchld = ssh_signal(SIGCHLD, SIG_DFL);
if ((pid = fork()) == -1) {
error("%s: fork: %s", __func__, strerror(errno));
ssh_signal(SIGCHLD, osigchld);
return NULL;
}
if (pid == 0) {
close(p[0]);
if (dup2(p[1], STDOUT_FILENO) == -1)
fatal("%s: dup2: %s", __func__, strerror(errno));
if (env_hint != NULL)
setenv("SSH_ASKPASS_PROMPT", env_hint, 1);
execlp(askpass, askpass, msg, (char *)NULL);
fatal("%s: exec(%s): %s", __func__, 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)) == -1)
if (errno != EINTR)
break;
ssh_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;
}
/* private/internal read_passphrase flags */
#define RP_ASK_PERMISSION 0x8000 /* pass hint to askpass for confirm UI */
/*
* 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 cr = '\r', *askpass = NULL, *ret, buf[1024];
int rppflags, use_askpass = 0, ttyfd;
const char *askpass_hint = NULL;
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) {
/*
* If we're on a tty, ensure that show the prompt at
* the beginning of the line. This will hopefully
* clobber any password characters the user has
* optimistically typed before echo is disabled.
*/
(void)write(ttyfd, &cr, 1);
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 ((flags & RP_ASK_PERMISSION) != 0)
askpass_hint = "confirm";
if ((ret = ssh_askpass(askpass, prompt, askpass_hint)) == 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|RP_ASK_PERMISSION);
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);
}
struct notifier_ctx {
pid_t pid;
void (*osigchld)(int);
};
struct notifier_ctx *
notify_start(int force_askpass, const char *fmt, ...)
{
va_list args;
char *prompt = NULL;
int devnull;
pid_t pid;
void (*osigchld)(int);
const char *askpass;
struct notifier_ctx *ret;
va_start(args, fmt);
xvasprintf(&prompt, fmt, args);
va_end(args);
if (fflush(NULL) != 0)
error("%s: fflush: %s", __func__, strerror(errno));
if (!force_askpass && isatty(STDERR_FILENO)) {
(void)write(STDERR_FILENO, "\r", 1);
(void)write(STDERR_FILENO, prompt, strlen(prompt));
(void)write(STDERR_FILENO, "\r\n", 2);
free(prompt);
return NULL;
}
if ((askpass = getenv("SSH_ASKPASS")) == NULL)
askpass = _PATH_SSH_ASKPASS_DEFAULT;
if (getenv("DISPLAY") == NULL || *askpass == '\0') {
debug3("%s: cannot notify", __func__);
free(prompt);
return NULL;
}
osigchld = ssh_signal(SIGCHLD, SIG_DFL);
if ((pid = fork()) == -1) {
error("%s: fork: %s", __func__, strerror(errno));
ssh_signal(SIGCHLD, osigchld);
free(prompt);
return NULL;
}
if (pid == 0) {
if ((devnull = open(_PATH_DEVNULL, O_RDWR)) == -1)
fatal("%s: open %s", __func__, strerror(errno));
if (dup2(devnull, STDIN_FILENO) == -1 ||
dup2(devnull, STDOUT_FILENO) == -1)
fatal("%s: dup2: %s", __func__, strerror(errno));
closefrom(STDERR_FILENO + 1);
setenv("SSH_ASKPASS_PROMPT", "none", 1); /* hint to UI */
execlp(askpass, askpass, prompt, (char *)NULL);
error("%s: exec(%s): %s", __func__, askpass, strerror(errno));
_exit(1);
/* NOTREACHED */
}
if ((ret = calloc(1, sizeof(*ret))) == NULL) {
kill(pid, SIGTERM);
fatal("%s: calloc failed", __func__);
}
ret->pid = pid;
ret->osigchld = osigchld;
free(prompt);
return ret;
}
void
notify_complete(struct notifier_ctx *ctx)
{
int ret;
if (ctx == NULL || ctx->pid <= 0) {
free(ctx);
return;
}
kill(ctx->pid, SIGTERM);
while ((ret = waitpid(ctx->pid, NULL, 0)) == -1) {
if (errno != EINTR)
break;
}
if (ret == -1)
fatal("%s: waitpid: %s", __func__, strerror(errno));
ssh_signal(SIGCHLD, ctx->osigchld);
free(ctx);
}