readpass.c - third_party/openssh-portable - Git at Google

 /* $OpenBSD: readpass.c,v 1.70 2022/05/27 04:27:49 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_f("fflush: %s", strerror(errno));
 	if (askpass == NULL)
 		fatal("internal error: askpass undefined");
 	if (pipe(p) == -1) {
 		error_f("pipe: %s", strerror(errno));
 		return NULL;
 	}
 	osigchld = ssh_signal(SIGCHLD, SIG_DFL);
 	if ((pid = fork()) == -1) {
 		error_f("fork: %s", strerror(errno));
 		ssh_signal(SIGCHLD, osigchld);
 		return NULL;
 	}
 	if (pid == 0) {
 		close(p[0]);
 		if (dup2(p[1], STDOUT_FILENO) == -1)
 			fatal_f("dup2: %s", strerror(errno));
 		if (env_hint != NULL)
 			setenv("SSH_ASKPASS_PROMPT", env_hint, 1);
 		execlp(askpass, askpass, msg, (char *)NULL);
 		fatal_f("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)) == -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 or askpass program is available
  */
 char *
 read_passphrase(const char *prompt, int flags)
 {
 	char cr = '\r', *askpass = NULL, *ret, buf[1024];
 	int rppflags, ttyfd, use_askpass = 0, allow_askpass = 0;
 	const char *askpass_hint = NULL;
 	const char *s;

 	if ((s = getenv("DISPLAY")) != NULL)
 		allow_askpass = *s != '\0';
 	if ((s = getenv(SSH_ASKPASS_REQUIRE_ENV)) != NULL) {
 		if (strcasecmp(s, "force") == 0) {
 			use_askpass = 1;
 			allow_askpass = 1;
 		} else if (strcasecmp(s, "prefer") == 0)
 			use_askpass = allow_askpass;
 		else if (strcasecmp(s, "never") == 0)
 			allow_askpass = 0;
 	}

 	rppflags = (flags & RP_ECHO) ? RPP_ECHO_ON : RPP_ECHO_OFF;
 	if (use_askpass)
 		debug_f("requested to askpass");
 	else if (flags & RP_USE_ASKPASS)
 		use_askpass = 1;
 	else if (flags & RP_ALLOW_STDIN) {
 		if (!isatty(STDIN_FILENO)) {
 			debug_f("stdin is not a tty");
 			use_askpass = 1;
 		}
 	} else {
 #ifndef __Fuchsia__
 		rppflags |= RPP_REQUIRE_TTY;
 #endif  // __Fuchsia__
 		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_f("can't open %s: %s", _PATH_TTY,
 			    strerror(errno));
 			use_askpass = 1;
 		}
 	}

 	if ((flags & RP_USE_ASKPASS) && !allow_askpass)
 		return (flags & RP_ALLOW_EOF) ? NULL : xstrdup("");

 	if (use_askpass && allow_askpass) {
 		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);
 }

 static void
 writemsg(const char *msg)
 {
 	(void)write(STDERR_FILENO, "\r", 1);
 	(void)write(STDERR_FILENO, msg, strlen(msg));
 	(void)write(STDERR_FILENO, "\r\n", 2);
 }

 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;
 	pid_t pid = -1;
 	void (*osigchld)(int) = NULL;
 	const char *askpass, *s;
 	struct notifier_ctx *ret = NULL;

 	va_start(args, fmt);
 	xvasprintf(&prompt, fmt, args);
 	va_end(args);

 	if (fflush(NULL) != 0)
 		error_f("fflush: %s", strerror(errno));
 	if (!force_askpass && isatty(STDERR_FILENO)) {
 		writemsg(prompt);
 		goto out_ctx;
 	}
 	if ((askpass = getenv("SSH_ASKPASS")) == NULL)
 		askpass = _PATH_SSH_ASKPASS_DEFAULT;
 	if (*askpass == '\0') {
 		debug3_f("cannot notify: no askpass");
 		goto out;
 	}
 	if (getenv("DISPLAY") == NULL &&
 	    ((s = getenv(SSH_ASKPASS_REQUIRE_ENV)) == NULL ||
 	    strcmp(s, "force") != 0)) {
 		debug3_f("cannot notify: no display");
 		goto out;
 	}
 	osigchld = ssh_signal(SIGCHLD, SIG_DFL);
 	if ((pid = fork()) == -1) {
 		error_f("fork: %s", strerror(errno));
 		ssh_signal(SIGCHLD, osigchld);
 		free(prompt);
 		return NULL;
 	}
 	if (pid == 0) {
 		if (stdfd_devnull(1, 1, 0) == -1)
 			fatal_f("stdfd_devnull failed");
 		closefrom(STDERR_FILENO + 1);
 		setenv("SSH_ASKPASS_PROMPT", "none", 1); /* hint to UI */
 		execlp(askpass, askpass, prompt, (char *)NULL);
 		error_f("exec(%s): %s", askpass, strerror(errno));
 		_exit(1);
 		/* NOTREACHED */
 	}
  out_ctx:
 	if ((ret = calloc(1, sizeof(*ret))) == NULL) {
 		if (pid != -1)
 			kill(pid, SIGTERM);
 		fatal_f("calloc failed");
 	}
 	ret->pid = pid;
 	ret->osigchld = osigchld;
  out:
 	free(prompt);
 	return ret;
 }

 void
 notify_complete(struct notifier_ctx *ctx, const char *fmt, ...)
 {
 	int ret;
 	char *msg = NULL;
 	va_list args;

 	if (ctx != NULL && fmt != NULL && ctx->pid == -1) {
 		/*
 		 * notify_start wrote to stderr, so send conclusion message
 		 * there too
 		*/
 		va_start(args, fmt);
 		xvasprintf(&msg, fmt, args);
 		va_end(args);
 		writemsg(msg);
 		free(msg);
 	}

 	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_f("waitpid: %s", strerror(errno));
 	ssh_signal(SIGCHLD, ctx->osigchld);
 	free(ctx);
 }
	/* $OpenBSD: readpass.c,v 1.70 2022/05/27 04:27:49 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_f("fflush: %s", strerror(errno));
	if (askpass == NULL)
	fatal("internal error: askpass undefined");
	if (pipe(p) == -1) {
	error_f("pipe: %s", strerror(errno));
	return NULL;
	}
	osigchld = ssh_signal(SIGCHLD, SIG_DFL);
	if ((pid = fork()) == -1) {
	error_f("fork: %s", strerror(errno));
	ssh_signal(SIGCHLD, osigchld);
	return NULL;
	}
	if (pid == 0) {
	close(p[0]);
	if (dup2(p[1], STDOUT_FILENO) == -1)
	fatal_f("dup2: %s", strerror(errno));
	if (env_hint != NULL)
	setenv("SSH_ASKPASS_PROMPT", env_hint, 1);
	execlp(askpass, askpass, msg, (char *)NULL);
	fatal_f("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)) == -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 or askpass program is available
	*/
	char *
	read_passphrase(const char *prompt, int flags)
	{
	char cr = '\r', askpass = NULL, ret, buf[1024];
	int rppflags, ttyfd, use_askpass = 0, allow_askpass = 0;
	const char *askpass_hint = NULL;
	const char *s;

	if ((s = getenv("DISPLAY")) != NULL)
	allow_askpass = *s != '\0';
	if ((s = getenv(SSH_ASKPASS_REQUIRE_ENV)) != NULL) {
	if (strcasecmp(s, "force") == 0) {
	use_askpass = 1;
	allow_askpass = 1;
	} else if (strcasecmp(s, "prefer") == 0)
	use_askpass = allow_askpass;
	else if (strcasecmp(s, "never") == 0)
	allow_askpass = 0;
	}

	rppflags = (flags & RP_ECHO) ? RPP_ECHO_ON : RPP_ECHO_OFF;
	if (use_askpass)
	debug_f("requested to askpass");
	else if (flags & RP_USE_ASKPASS)
	use_askpass = 1;
	else if (flags & RP_ALLOW_STDIN) {
	if (!isatty(STDIN_FILENO)) {
	debug_f("stdin is not a tty");
	use_askpass = 1;
	}
	} else {
	#ifndef __Fuchsia__
	rppflags \|= RPP_REQUIRE_TTY;
	#endif // __Fuchsia__
	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_f("can't open %s: %s", _PATH_TTY,
	strerror(errno));
	use_askpass = 1;
	}
	}

	if ((flags & RP_USE_ASKPASS) && !allow_askpass)
	return (flags & RP_ALLOW_EOF) ? NULL : xstrdup("");

	if (use_askpass && allow_askpass) {
	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);
	}

	static void
	writemsg(const char *msg)
	{
	(void)write(STDERR_FILENO, "\r", 1);
	(void)write(STDERR_FILENO, msg, strlen(msg));
	(void)write(STDERR_FILENO, "\r\n", 2);
	}

	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;
	pid_t pid = -1;
	void (*osigchld)(int) = NULL;
	const char askpass, s;
	struct notifier_ctx *ret = NULL;

	va_start(args, fmt);
	xvasprintf(&prompt, fmt, args);
	va_end(args);

	if (fflush(NULL) != 0)
	error_f("fflush: %s", strerror(errno));
	if (!force_askpass && isatty(STDERR_FILENO)) {
	writemsg(prompt);
	goto out_ctx;
	}
	if ((askpass = getenv("SSH_ASKPASS")) == NULL)
	askpass = _PATH_SSH_ASKPASS_DEFAULT;
	if (*askpass == '\0') {
	debug3_f("cannot notify: no askpass");
	goto out;
	}
	if (getenv("DISPLAY") == NULL &&
	((s = getenv(SSH_ASKPASS_REQUIRE_ENV)) == NULL \|\|
	strcmp(s, "force") != 0)) {
	debug3_f("cannot notify: no display");
	goto out;
	}
	osigchld = ssh_signal(SIGCHLD, SIG_DFL);
	if ((pid = fork()) == -1) {
	error_f("fork: %s", strerror(errno));
	ssh_signal(SIGCHLD, osigchld);
	free(prompt);
	return NULL;
	}
	if (pid == 0) {
	if (stdfd_devnull(1, 1, 0) == -1)
	fatal_f("stdfd_devnull failed");
	closefrom(STDERR_FILENO + 1);
	setenv("SSH_ASKPASS_PROMPT", "none", 1); /* hint to UI */
	execlp(askpass, askpass, prompt, (char *)NULL);
	error_f("exec(%s): %s", askpass, strerror(errno));
	_exit(1);
	/* NOTREACHED */
	}
	out_ctx:
	if ((ret = calloc(1, sizeof(*ret))) == NULL) {
	if (pid != -1)
	kill(pid, SIGTERM);
	fatal_f("calloc failed");
	}
	ret->pid = pid;
	ret->osigchld = osigchld;
	out:
	free(prompt);
	return ret;
	}

	void
	notify_complete(struct notifier_ctx ctx, const char fmt, ...)
	{
	int ret;
	char *msg = NULL;
	va_list args;

	if (ctx != NULL && fmt != NULL && ctx->pid == -1) {
	/*
	* notify_start wrote to stderr, so send conclusion message
	* there too
	*/
	va_start(args, fmt);
	xvasprintf(&msg, fmt, args);
	va_end(args);
	writemsg(msg);
	free(msg);
	}

	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_f("waitpid: %s", strerror(errno));
	ssh_signal(SIGCHLD, ctx->osigchld);
	free(ctx);
	}