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-rw-r--r--plugins/sudoers/check.c373
1 files changed, 373 insertions, 0 deletions
diff --git a/plugins/sudoers/check.c b/plugins/sudoers/check.c
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+++ b/plugins/sudoers/check.c
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+/*
+ * SPDX-License-Identifier: ISC
+ *
+ * Copyright (c) 1993-1996,1998-2005, 2007-2018
+ * Todd C. Miller <Todd.Miller@sudo.ws>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ *
+ * Sponsored in part by the Defense Advanced Research Projects
+ * Agency (DARPA) and Air Force Research Laboratory, Air Force
+ * Materiel Command, USAF, under agreement number F39502-99-1-0512.
+ */
+
+/*
+ * This is an open source non-commercial project. Dear PVS-Studio, please check it.
+ * PVS-Studio Static Code Analyzer for C, C++ and C#: http://www.viva64.com
+ */
+
+#include <config.h>
+
+#include <sys/types.h> /* for ssize_t */
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <time.h>
+#include <errno.h>
+#include <pwd.h>
+#include <grp.h>
+
+#include "sudoers.h"
+#include "check.h"
+
+static bool display_lecture(int);
+static struct passwd *get_authpw(int);
+
+struct getpass_closure {
+ int tstat;
+ void *cookie;
+ struct passwd *auth_pw;
+};
+
+/*
+ * Called when getpass is suspended so we can drop the lock.
+ */
+static int
+getpass_suspend(int signo, void *vclosure)
+{
+ struct getpass_closure *closure = vclosure;
+
+ timestamp_close(closure->cookie);
+ closure->cookie = NULL;
+ return 0;
+}
+
+/*
+ * Called when getpass is resumed so we can reacquire the lock.
+ */
+static int
+getpass_resume(int signo, void *vclosure)
+{
+ struct getpass_closure *closure = vclosure;
+
+ closure->cookie = timestamp_open(user_name, user_sid);
+ if (closure->cookie == NULL)
+ return -1;
+ if (!timestamp_lock(closure->cookie, closure->auth_pw))
+ return -1;
+ return 0;
+}
+
+/*
+ * Returns true if the user successfully authenticates, false if not
+ * or -1 on fatal error.
+ */
+static int
+check_user_interactive(int validated, int mode, struct getpass_closure *closure)
+{
+ struct sudo_conv_callback cb, *callback = NULL;
+ int ret = -1;
+ char *prompt;
+ bool lectured;
+ debug_decl(check_user_interactive, SUDOERS_DEBUG_AUTH);
+
+ /* Open, lock and read time stamp file if we are using it. */
+ if (!ISSET(mode, MODE_IGNORE_TICKET)) {
+ /* Open time stamp file and check its status. */
+ closure->cookie = timestamp_open(user_name, user_sid);
+ if (timestamp_lock(closure->cookie, closure->auth_pw))
+ closure->tstat = timestamp_status(closure->cookie, closure->auth_pw);
+
+ /* Construct callback for getpass function. */
+ memset(&cb, 0, sizeof(cb));
+ cb.version = SUDO_CONV_CALLBACK_VERSION;
+ cb.closure = closure;
+ cb.on_suspend = getpass_suspend;
+ cb.on_resume = getpass_resume;
+ callback = &cb;
+ }
+
+ switch (closure->tstat) {
+ case TS_FATAL:
+ /* Fatal error (usually setuid failure), unsafe to proceed. */
+ goto done;
+
+ case TS_CURRENT:
+ /* Time stamp file is valid and current. */
+ if (!ISSET(validated, FLAG_CHECK_USER)) {
+ ret = true;
+ break;
+ }
+ sudo_debug_printf(SUDO_DEBUG_INFO,
+ "%s: check user flag overrides time stamp", __func__);
+ FALLTHROUGH;
+
+ default:
+ /* Bail out if we are non-interactive and a password is required */
+ if (ISSET(mode, MODE_NONINTERACTIVE)) {
+ validated |= FLAG_NON_INTERACTIVE;
+ log_auth_failure(validated, 0);
+ goto done;
+ }
+
+ /* XXX - should not lecture if askpass helper is being used. */
+ lectured = display_lecture(closure->tstat);
+
+ /* Expand any escapes in the prompt. */
+ prompt = expand_prompt(user_prompt ? user_prompt : def_passprompt,
+ closure->auth_pw->pw_name);
+ if (prompt == NULL)
+ goto done;
+
+ ret = verify_user(closure->auth_pw, prompt, validated, callback);
+ if (ret == true && lectured)
+ (void)set_lectured(); /* lecture error not fatal */
+ free(prompt);
+ break;
+ }
+
+done:
+ debug_return_int(ret);
+}
+
+/*
+ * Returns true if the user successfully authenticates, false if not
+ * or -1 on error.
+ */
+int
+check_user(int validated, int mode)
+{
+ struct getpass_closure closure = { TS_ERROR };
+ int ret = -1;
+ bool exempt = false;
+ debug_decl(check_user, SUDOERS_DEBUG_AUTH);
+
+ /*
+ * Init authentication system regardless of whether we need a password.
+ * Required for proper PAM session support.
+ */
+ if ((closure.auth_pw = get_authpw(mode)) == NULL)
+ goto done;
+ if (sudo_auth_init(closure.auth_pw) == -1)
+ goto done;
+
+ /*
+ * Don't prompt for the root passwd or if the user is exempt.
+ * If the user is not changing uid/gid, no need for a password.
+ */
+ if (!def_authenticate || user_is_exempt()) {
+ sudo_debug_printf(SUDO_DEBUG_INFO, "%s: %s", __func__,
+ !def_authenticate ? "authentication disabled" :
+ "user exempt from authentication");
+ exempt = true;
+ ret = true;
+ goto done;
+ }
+ if (user_uid == 0 || (user_uid == runas_pw->pw_uid &&
+ (!runas_gr || user_in_group(sudo_user.pw, runas_gr->gr_name)))) {
+#ifdef HAVE_SELINUX
+ if (user_role == NULL && user_type == NULL)
+#endif
+#ifdef HAVE_PRIV_SET
+ if (runas_privs == NULL && runas_limitprivs == NULL)
+#endif
+ {
+ sudo_debug_printf(SUDO_DEBUG_INFO,
+ "%s: user running command as self", __func__);
+ ret = true;
+ goto done;
+ }
+ }
+
+ ret = check_user_interactive(validated, mode, &closure);
+
+done:
+ if (ret == true) {
+ /* The approval function may disallow a user post-authentication. */
+ ret = sudo_auth_approval(closure.auth_pw, validated, exempt);
+
+ /*
+ * Only update time stamp if user validated and was approved.
+ * Failure to update the time stamp is not a fatal error.
+ */
+ if (ret == true && closure.tstat != TS_ERROR) {
+ if (ISSET(validated, VALIDATE_SUCCESS))
+ (void)timestamp_update(closure.cookie, closure.auth_pw);
+ }
+ }
+ timestamp_close(closure.cookie);
+ sudo_auth_cleanup(closure.auth_pw, !ISSET(validated, VALIDATE_SUCCESS));
+ if (closure.auth_pw != NULL)
+ sudo_pw_delref(closure.auth_pw);
+
+ debug_return_int(ret);
+}
+
+/*
+ * Display sudo lecture (standard or custom).
+ * Returns true if the user was lectured, else false.
+ */
+static bool
+display_lecture(int status)
+{
+ struct sudo_conv_message msg;
+ struct sudo_conv_reply repl;
+ char buf[BUFSIZ];
+ struct stat sb;
+ ssize_t nread;
+ int fd;
+ debug_decl(lecture, SUDOERS_DEBUG_AUTH);
+
+ if (def_lecture == never ||
+ (def_lecture == once && already_lectured(status)))
+ debug_return_bool(false);
+
+ memset(&msg, 0, sizeof(msg));
+ memset(&repl, 0, sizeof(repl));
+
+ if (def_lecture_file) {
+ fd = open(def_lecture_file, O_RDONLY|O_NONBLOCK);
+ if (fd != -1 && fstat(fd, &sb) == 0) {
+ if (S_ISREG(sb.st_mode)) {
+ (void) fcntl(fd, F_SETFL, fcntl(fd, F_GETFL, 0) & ~O_NONBLOCK);
+ while ((nread = read(fd, buf, sizeof(buf) - 1)) > 0) {
+ buf[nread] = '\0';
+ msg.msg_type = SUDO_CONV_ERROR_MSG|SUDO_CONV_PREFER_TTY;
+ msg.msg = buf;
+ sudo_conv(1, &msg, &repl, NULL);
+ }
+ close(fd);
+ if (nread == -1) {
+ log_warning(SLOG_RAW_MSG,
+ N_("error reading lecture file %s"), def_lecture_file);
+ debug_return_bool(false);
+ }
+ debug_return_bool(true);
+ } else {
+ log_warningx(SLOG_RAW_MSG,
+ N_("ignoring lecture file %s: not a regular file"),
+ def_lecture_file);
+ }
+ } else {
+ log_warning(SLOG_RAW_MSG|SLOG_NO_STDERR, N_("unable to open %s"),
+ def_lecture_file);
+ }
+ if (fd != -1)
+ close(fd);
+ }
+
+ /* Default sudo lecture. */
+ msg.msg_type = SUDO_CONV_ERROR_MSG|SUDO_CONV_PREFER_TTY;
+ msg.msg = _("\n"
+ "We trust you have received the usual lecture from the local System\n"
+ "Administrator. It usually boils down to these three things:\n\n"
+ " #1) Respect the privacy of others.\n"
+ " #2) Think before you type.\n"
+ " #3) With great power comes great responsibility.\n\n");
+ sudo_conv(1, &msg, &repl, NULL);
+ debug_return_bool(true);
+}
+
+/*
+ * Checks if the user is exempt from supplying a password.
+ */
+bool
+user_is_exempt(void)
+{
+ bool ret = false;
+ debug_decl(user_is_exempt, SUDOERS_DEBUG_AUTH);
+
+ if (def_exempt_group)
+ ret = user_in_group(sudo_user.pw, def_exempt_group);
+ debug_return_bool(ret);
+}
+
+/*
+ * Get passwd entry for the user we are going to authenticate as.
+ * By default, this is the user invoking sudo. In the most common
+ * case, this matches sudo_user.pw or runas_pw.
+ */
+static struct passwd *
+get_authpw(int mode)
+{
+ struct passwd *pw = NULL;
+ debug_decl(get_authpw, SUDOERS_DEBUG_AUTH);
+
+ if (ISSET(mode, (MODE_CHECK|MODE_LIST))) {
+ /* In list mode we always prompt for the user's password. */
+ sudo_pw_addref(sudo_user.pw);
+ pw = sudo_user.pw;
+ } else {
+ if (def_rootpw) {
+ if ((pw = sudo_getpwuid(ROOT_UID)) == NULL) {
+ log_warningx(SLOG_SEND_MAIL, N_("unknown uid: %u"), ROOT_UID);
+ }
+ } else if (def_runaspw) {
+ if ((pw = sudo_getpwnam(def_runas_default)) == NULL) {
+ log_warningx(SLOG_SEND_MAIL,
+ N_("unknown user: %s"), def_runas_default);
+ }
+ } else if (def_targetpw) {
+ if (runas_pw->pw_name == NULL) {
+ /* This should never be NULL as we fake up the passwd struct */
+ log_warningx(SLOG_RAW_MSG, N_("unknown uid: %u"),
+ (unsigned int) runas_pw->pw_uid);
+ } else {
+ sudo_pw_addref(runas_pw);
+ pw = runas_pw;
+ }
+ } else {
+ sudo_pw_addref(sudo_user.pw);
+ pw = sudo_user.pw;
+ }
+ }
+
+ debug_return_ptr(pw);
+}
+
+/*
+ * Returns true if the specified shell is allowed by /etc/shells, else false.
+ */
+bool
+check_user_shell(const struct passwd *pw)
+{
+ const char *shell;
+ debug_decl(check_user_shell, SUDOERS_DEBUG_AUTH);
+
+ if (!def_runas_check_shell)
+ debug_return_bool(true);
+
+ sudo_debug_printf(SUDO_DEBUG_INFO,
+ "%s: checking /etc/shells for %s", __func__, pw->pw_shell);
+
+ setusershell();
+ while ((shell = getusershell()) != NULL) {
+ if (strcmp(shell, pw->pw_shell) == 0)
+ debug_return_bool(true);
+ }
+ endusershell();
+
+ debug_return_bool(false);
+}
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