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-rw-r--r--plugins/sudoers/check.c325
1 files changed, 325 insertions, 0 deletions
diff --git a/plugins/sudoers/check.c 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 <timestamp.h>
+
+/*
+ * 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 ctx->user.pw or ctx->runas.pw.
+ */
+static struct passwd *
+get_authpw(struct sudoers_context *ctx, unsigned 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(ctx->user.pw);
+ pw = ctx->user.pw;
+ } else {
+ if (def_rootpw) {
+ if ((pw = sudo_getpwuid(ROOT_UID)) == NULL) {
+ log_warningx(ctx, SLOG_SEND_MAIL, N_("unknown uid %u"),
+ ROOT_UID);
+ }
+ } else if (def_runaspw) {
+ if ((pw = sudo_getpwnam(def_runas_default)) == NULL) {
+ log_warningx(ctx, SLOG_SEND_MAIL,
+ N_("unknown user %s"), def_runas_default);
+ }
+ } else if (def_targetpw) {
+ if (ctx->runas.pw->pw_name == NULL) {
+ /* This should never be NULL as we fake up the passwd struct */
+ log_warningx(ctx, SLOG_RAW_MSG, N_("unknown uid %u"),
+ (unsigned int) ctx->runas.pw->pw_uid);
+ } else {
+ sudo_pw_addref(ctx->runas.pw);
+ pw = ctx->runas.pw;
+ }
+ } else {
+ sudo_pw_addref(ctx->user.pw);
+ pw = ctx->user.pw;
+ }
+ }
+
+ debug_return_ptr(pw);
+}
+
+/*
+ * Returns AUTH_SUCCESS if the user successfully authenticates,
+ * AUTH_FAILURE if not or AUTH_ERROR on error.
+ */
+int
+check_user(struct sudoers_context *ctx, unsigned int validated,
+ unsigned int mode)
+{
+ struct getpass_closure closure = { 0 };
+ struct sudo_conv_callback callback;
+ int status = TS_ERROR;
+ int ret = AUTH_ERROR;
+ bool exempt = false;
+ char *prompt;
+ debug_decl(check_user, SUDOERS_DEBUG_AUTH);
+
+ /*
+ * In intercept mode, only check the user if configured to do so.
+ * We already have a session so no need to init the auth subsystem.
+ */
+ if (ISSET(ctx->mode, MODE_POLICY_INTERCEPTED)) {
+ if (!def_intercept_authenticate) {
+ debug_return_int(AUTH_SUCCESS);
+ }
+ }
+
+ /*
+ * Init authentication system regardless of whether we need a password.
+ * Required for proper PAM session support.
+ */
+ if ((closure.auth_pw = get_authpw(ctx, mode)) == NULL)
+ debug_return_int(AUTH_ERROR);
+ if (sudo_auth_init(ctx, closure.auth_pw, mode) != AUTH_SUCCESS) {
+ sudo_pw_delref(closure.auth_pw);
+ debug_return_int(AUTH_ERROR);
+ }
+ closure.ctx = ctx;
+
+ /*
+ * 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(ctx)) {
+ sudo_debug_printf(SUDO_DEBUG_INFO, "%s: %s", __func__,
+ !def_authenticate ? "authentication disabled" :
+ "user exempt from authentication");
+ exempt = true;
+ ret = AUTH_SUCCESS;
+ goto done;
+ }
+ if (ctx->user.uid == 0 || (ctx->user.uid == ctx->runas.pw->pw_uid &&
+ (ctx->runas.gr == NULL ||
+ user_in_group(ctx->user.pw, ctx->runas.gr->gr_name)))) {
+#ifdef HAVE_SELINUX
+ if (ctx->runas.role == NULL && ctx->runas.type == NULL)
+#endif
+#ifdef HAVE_APPARMOR
+ if (ctx->runas.apparmor_profile == NULL)
+#endif
+#ifdef HAVE_PRIV_SET
+ if (ctx->runas.privs == NULL && ctx->runas.limitprivs == NULL)
+#endif
+ {
+ sudo_debug_printf(SUDO_DEBUG_INFO,
+ "%s: user running command as self", __func__);
+ ret = AUTH_SUCCESS;
+ goto done;
+ }
+ }
+
+ /* Construct callback for getpass function. */
+ memset(&callback, 0, sizeof(callback));
+ callback.version = SUDO_CONV_CALLBACK_VERSION;
+ callback.closure = &closure;
+
+ /* 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(ctx);
+ if (closure.cookie != NULL) {
+ if (timestamp_lock(closure.cookie, closure.auth_pw)) {
+ status = timestamp_status(closure.cookie, closure.auth_pw);
+ }
+ }
+ }
+
+ switch (status) {
+ 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 = AUTH_SUCCESS;
+ break;
+ }
+ sudo_debug_printf(SUDO_DEBUG_INFO,
+ "%s: check user flag overrides time stamp", __func__);
+ FALLTHROUGH;
+
+ default:
+ if (ISSET(mode, MODE_NONINTERACTIVE) && !def_noninteractive_auth) {
+ validated |= FLAG_NO_USER_INPUT;
+ log_auth_failure(ctx, validated, 0);
+ goto done;
+ }
+
+ /* Expand any escapes in the prompt. */
+ prompt = expand_prompt(ctx,
+ ctx->user.prompt ? ctx->user.prompt : def_passprompt,
+ closure.auth_pw->pw_name);
+ if (prompt == NULL)
+ goto done;
+
+ ret = verify_user(ctx, closure.auth_pw, prompt, validated, &callback);
+ if (ret == AUTH_SUCCESS && closure.lectured)
+ (void)set_lectured(ctx); /* lecture error not fatal */
+ free(prompt);
+ break;
+ }
+
+done:
+ if (ret == AUTH_SUCCESS) {
+ /* The approval function may disallow a user post-authentication. */
+ ret = sudo_auth_approval(ctx, 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 == AUTH_SUCCESS && ISSET(validated, VALIDATE_SUCCESS)) {
+ if (ISSET(mode, MODE_UPDATE_TICKET) && status != TS_ERROR)
+ (void)timestamp_update(closure.cookie, closure.auth_pw);
+ }
+ }
+ timestamp_close(closure.cookie);
+ sudo_auth_cleanup(ctx, closure.auth_pw, !ISSET(validated, VALIDATE_SUCCESS));
+ 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.
+ */
+void
+display_lecture(struct sudo_conv_callback *callback)
+{
+ struct getpass_closure *closure;
+ struct sudo_conv_message msg[2];
+ struct sudo_conv_reply repl[2];
+ char buf[BUFSIZ];
+ struct stat sb;
+ ssize_t nread;
+ int fd, msgcount = 1;
+ debug_decl(lecture, SUDOERS_DEBUG_AUTH);
+
+ if (callback == NULL || (closure = callback->closure) == NULL)
+ debug_return;
+
+ if (closure->lectured)
+ debug_return;
+
+ if (def_lecture == never ||
+ (def_lecture == once && already_lectured(closure->ctx)))
+ debug_return;
+
+ 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[0].msg_type = SUDO_CONV_ERROR_MSG|SUDO_CONV_PREFER_TTY;
+ msg[0].msg = buf;
+ sudo_conv(1, msg, repl, NULL);
+ }
+ if (nread == 0) {
+ close(fd);
+ goto done;
+ }
+ log_warning(closure->ctx, SLOG_RAW_MSG,
+ N_("error reading lecture file %s"), def_lecture_file);
+ } else {
+ log_warningx(closure->ctx, SLOG_RAW_MSG,
+ N_("ignoring lecture file %s: not a regular file"),
+ def_lecture_file);
+ }
+ } else {
+ log_warning(closure->ctx, SLOG_RAW_MSG|SLOG_NO_STDERR,
+ N_("unable to open %s"), def_lecture_file);
+ }
+ if (fd != -1)
+ close(fd);
+ }
+
+ /* Default sudo lecture. */
+ msg[0].msg_type = SUDO_CONV_ERROR_MSG|SUDO_CONV_PREFER_TTY;
+ msg[0].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");
+ if (!def_pwfeedback) {
+ msg[1].msg_type = SUDO_CONV_ERROR_MSG|SUDO_CONV_PREFER_TTY;
+ msg[1].msg = _("For security reasons, the password you type will not be visible.\n\n");
+ msgcount++;
+ }
+ sudo_conv(msgcount, msg, repl, NULL);
+
+done:
+ closure->lectured = true;
+ debug_return;
+}
+
+/*
+ * Checks if the user is exempt from supplying a password.
+ */
+bool
+user_is_exempt(const struct sudoers_context *ctx)
+{
+ bool ret = false;
+ debug_decl(user_is_exempt, SUDOERS_DEBUG_AUTH);
+
+ if (def_exempt_group) {
+ if (user_in_group(ctx->user.pw, def_exempt_group))
+ ret = true;
+ }
+ debug_return_bool(ret);
+}
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