/* $OpenBSD: readpass.c,v 1.71 2024/03/30 04:27:44 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, 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 && *s != '\0') ||
            ((s = getenv("WAYLAND_DISPLAY")) != NULL && *s != '\0'))
                allow_askpass = 1;
        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 {
                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_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 && getenv("WAYLAND_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);
}