Backport of:

# HG changeset patch
# Parent  7275148cad1f8cd3c350026460acc4d6ad349c3a
sudoedit: do not permit editor arguments to include "--"
We use "--" to separate the editor and arguments from the files to edit.
If the editor arguments include "--", sudo can be tricked into allowing
the user to edit a file not permitted by the security policy.
Thanks to Matthieu Barjole and Victor Cutillas of Synacktiv
(https://synacktiv.com) for finding this bug.

CVE: CVE-2023-22809
Upstream-Staus: Backport [http://archive.ubuntu.com/ubuntu/pool/main/s/sudo/sudo_1.8.31-1ubuntu1.4.debian.tar.xz]
Signed-off-by: Omkar Patil <omkar.patil@kpit.com>

--- a/plugins/sudoers/editor.c
+++ b/plugins/sudoers/editor.c
@@ -56,7 +56,7 @@ resolve_editor(const char *ed, size_t ed
     const char *cp, *ep, *tmp;
     const char *edend = ed + edlen;
     struct stat user_editor_sb;
-    int nargc;
+    int nargc = 0;
     debug_decl(resolve_editor, SUDOERS_DEBUG_UTIL)
 
     /*
@@ -102,6 +102,21 @@ resolve_editor(const char *ed, size_t ed
 	    free(editor_path);
 	    while (nargc--)
 		free(nargv[nargc]);
+	    free(nargv);
+	    debug_return_str(NULL);
+	}
+
+	/*
+	 * We use "--" to separate the editor and arguments from the files
+	 * to edit.  The editor arguments themselves may not contain "--".
+	 */
+	if (strcmp(nargv[nargc], "--") == 0) {
+	    sudo_warnx(U_("ignoring editor: %.*s"), (int)edlen, ed);
+	    sudo_warnx("%s", U_("editor arguments may not contain \"--\""));
+	    errno = EINVAL;
+	    free(editor_path);
+	    while (nargc--)
+		free(nargv[nargc]);
 	    free(nargv);
 	    debug_return_str(NULL);
 	}
--- a/plugins/sudoers/sudoers.c
+++ b/plugins/sudoers/sudoers.c
@@ -616,20 +616,31 @@ sudoers_policy_main(int argc, char * con
 
     /* Note: must call audit before uid change. */
     if (ISSET(sudo_mode, MODE_EDIT)) {
+	const char *env_editor = NULL;
 	int edit_argc;
-	const char *env_editor;
 
 	free(safe_cmnd);
 	safe_cmnd = find_editor(NewArgc - 1, NewArgv + 1, &edit_argc,
 	    &edit_argv, NULL, &env_editor, false);
 	if (safe_cmnd == NULL) {
-	    if (errno != ENOENT)
+	    switch (errno) {
+	    case ENOENT:
+		audit_failure(NewArgc, NewArgv, N_("%s: command not found"),
+		    env_editor ? env_editor : def_editor);
+		sudo_warnx(U_("%s: command not found"),
+		    env_editor ? env_editor : def_editor);
+		goto bad;
+	    case EINVAL:
+		if (def_env_editor && env_editor != NULL) {
+		    /* User tried to do something funny with the editor. */
+		    log_warningx(SLOG_NO_STDERR|SLOG_SEND_MAIL,
+			"invalid user-specified editor: %s", env_editor);
+		    goto bad;
+		}
+		/* FALLTHROUGH */
+	    default:
 		goto done;
-	    audit_failure(NewArgc, NewArgv, N_("%s: command not found"),
-		env_editor ? env_editor : def_editor);
-	    sudo_warnx(U_("%s: command not found"),
-		env_editor ? env_editor : def_editor);
-	    goto bad;
+	    }
 	}
 	if (audit_success(edit_argc, edit_argv) != 0 && !def_ignore_audit_errors)
 	    goto done;
--- a/plugins/sudoers/visudo.c
+++ b/plugins/sudoers/visudo.c
@@ -308,7 +308,7 @@ static char *
 get_editor(int *editor_argc, char ***editor_argv)
 {
     char *editor_path = NULL, **whitelist = NULL;
-    const char *env_editor;
+    const char *env_editor = NULL;
     static char *files[] = { "+1", "sudoers" };
     unsigned int whitelist_len = 0;
     debug_decl(get_editor, SUDOERS_DEBUG_UTIL)
@@ -342,7 +342,11 @@ get_editor(int *editor_argc, char ***edi
     if (editor_path == NULL) {
 	if (def_env_editor && env_editor != NULL) {
 	    /* We are honoring $EDITOR so this is a fatal error. */
-	    sudo_fatalx(U_("specified editor (%s) doesn't exist"), env_editor);
+	    if (errno == ENOENT) {
+		sudo_warnx(U_("specified editor (%s) doesn't exist"),
+		    env_editor);
+	    }
+	    exit(EXIT_FAILURE);
 	}
 	sudo_fatalx(U_("no editor found (editor path = %s)"), def_editor);
     }