diff options
Diffstat (limited to 'readpass.c')
| -rw-r--r-- | readpass.c | 332 |
1 files changed, 332 insertions, 0 deletions
diff --git a/readpass.c b/readpass.c new file mode 100644 index 0000000..b52f3d6 --- /dev/null +++ b/readpass.c @@ -0,0 +1,332 @@ +/* $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 { + 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 && + ((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); +} |