Some initial work on key2root: everything but authentication and keyfile forwarding

Signed-off-by: Mattias Andrée <maandree@kth.se>

1 files changed, 203 insertions, 2 deletions

diff --git a/key2root.c b/key2root.c
index 69b7dc6..5a152ab 100644
--- a/key2root.c
+++ b/key2root.c
@@ -1,18 +1,164 @@
 /* See LICENSE file for copyright and license details. */
+#include <sys/mman.h>
+#include <errno.h>
+#include <pwd.h>
 #include <stdio.h>
 #include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
 
 #include "arg.h"
 
 
+#define EXIT_AUTH   124
+#define EXIT_ERROR  125
+#define EXIT_EXEC   126
+#define EXIT_NOENT  127
+
+
 char *argv0;
 
+/* Keep list in sync with asroot(8)'s list */
+static const char *env_whitelist[] = {
+	"DISPLAY=",
+	"WAYLAND_DISPLAY=",
+	"PATH=",
+	"TERM=",
+	"COLORTERM=",
+	"XAUTHORITY=",
+	"LANG=",
+	"LANGUAGE=",
+	"LOCALE=",
+	"LC_CTYPE=",
+	"LC_NUMERIC=",
+	"LC_TIME=",
+	"LC_COLLATE=",
+	"LC_MONETARY=",
+	"LC_MESSAGES=",
+	"LC_PAPER=",
+	"LC_NAME=",
+	"LC_ADDRESS=",
+	"LC_TELEPHONE=",
+	"LC_MEASUREMENT=",
+	"LC_IDENTIFICATION=",
+	"LC_ALL=",
+	"LOCPATH=",
+	"NLSPATH=",
+	"TZ=",
+	"TZDIR=",
+	"SDL_VIDEO_FULLSCREEN_DISPLAY=",
+	"EDITOR=",
+	"VISUAL=",
+	"BROWSER=",
+	"DESKTOP_SESSION=",
+	"LS_COLORS=",
+	"GTK_THEME=",
+	"QT_STYLE_OVERRIDE=",
+	"PWD=",
+	"OLDPWD=",
+	"JAVA_HOME=",
+	"_JAVA_AWT_WM_NONREPARENTING=",
+	"_JAVA_OPTIONS=",
+	"MAIN_ALSA_MIXER=",
+	"MAIN_ALSA_CARD=",
+	"XDG_SEAT=",
+	"XDG_SESSION_TYPE=",
+	"XDG_SESSION_CLASS=",
+	"XDG_VTNR=",
+	"XDG_SESSION_ID=",
+	"XDG_DATA_DIRS=",
+	"XDG_CONFIG_DIRS=",
+	"MANPATH=",
+	"INFODIR=",
+	"PAGER=",
+	"ftp_proxy=",
+	"http_proxy=",
+	NULL
+};
+
 
 static void
 usage(void)
 {
 	fprintf(stderr, "usage: %s [-k key-name] [-e] command [argument] ...\n", argv0);
-	exit(125);
+	exit(EXIT_ERROR);
+}
+
+
+static char **
+set_environ(void)
+{
+	char **new_environ;
+	size_t i, j, n, len;
+	struct passwd *pw;
+
+	new_environ = calloc(sizeof(env_whitelist) / sizeof(*env_whitelist) + 5, sizeof(*env_whitelist));
+	if (!new_environ) {
+		fprintf(stderr, "%s: calloc %zu %zu: %s\n",
+			argv0, sizeof(env_whitelist) / sizeof(*env_whitelist) + 5, sizeof(*env_whitelist), strerror(errno));
+		exit(EXIT_ERROR);
+	}
+	for (i = 0, n = 0; env_whitelist[i]; i++) {
+		len = strlen(env_whitelist[i]);
+		for (j = 0; environ[j]; j++) {
+			if (!strncmp(environ[j], env_whitelist[i], len)) {
+				new_environ[n++] = environ[j];
+				break;
+			}
+		}
+	}
+
+	errno = 0;
+	pw = getpwuid(0);
+	if (!pw) {
+		if (errno)
+			fprintf(stderr, "%s: getpwuid 0: %s\n", argv0, strerror(errno));
+		else
+			fprintf(stderr, "%s: cannot find root user\n", argv0);
+		exit(EXIT_ERROR);
+	}
+
+	if (pw->pw_dir && *pw->pw_dir) {
+		len = strlen(pw->pw_dir);
+		len += sizeof("HOME=");
+		new_environ[n] = malloc(len);
+		if (!new_environ[n])
+			fprintf(stderr, "%s: malloc %zu: %s\n", argv0, len, strerror(errno));
+		stpcpy(stpcpy(new_environ[n++], "HOME="), pw->pw_dir);
+	}
+	if (pw->pw_name && *pw->pw_name) {
+		len = strlen(pw->pw_name);
+		len += sizeof("LOGNAME=");
+		new_environ[n] = malloc(len);
+		if (!new_environ[n])
+			fprintf(stderr, "%s: malloc %zu: %s\n", argv0, len, strerror(errno));
+		stpcpy(stpcpy(new_environ[n++], "LOGNAME="), pw->pw_name);
+
+		len -= sizeof("LOGNAME=");
+		len += sizeof("USER=");
+		new_environ[n] = malloc(len);
+		if (!new_environ[n])
+			fprintf(stderr, "%s: malloc %zu: %s\n", argv0, len, strerror(errno));
+		stpcpy(stpcpy(new_environ[n++], "USER="), pw->pw_name);
+
+		len -= sizeof("USER=");
+		len += sizeof("MAIL=/var/spool/mail/");
+		new_environ[n] = malloc(len);
+		if (!new_environ[n])
+			fprintf(stderr, "%s: malloc %zu: %s\n", argv0, len, strerror(errno));
+		stpcpy(stpcpy(new_environ[n++], "MAIL=/var/spool/mail/"), pw->pw_name);
+	}
+	if (pw->pw_shell && *pw->pw_shell) {
+		len = strlen(pw->pw_shell);
+		len += sizeof("SHELL=");
+		new_environ[n] = malloc(len);
+		if (!new_environ[n])
+			fprintf(stderr, "%s: malloc %zu: %s\n", argv0, len, strerror(errno));
+		stpcpy(stpcpy(new_environ[n++], "SHELL="), pw->pw_shell);
+	}
+	new_environ[n] = NULL;
+
+	return new_environ;
 }
 
 
@@ -20,7 +166,12 @@ int
 main(int argc, char *argv[])
 {
 	int keep_env = 0;
+	char **new_environ = NULL;
 	const char *key_name = NULL;
+	char *key = NULL, *key_new;
+	size_t key_len = 0;
+	size_t key_size = 0;
+	ssize_t r;
 
 	ARGBEGIN {
 	case 'e':
@@ -38,5 +189,55 @@ main(int argc, char *argv[])
 	if (!argc)
 		usage();
 
-	return 0;
+	if (mlockall(MCL_CURRENT | MCL_FUTURE)) {
+		fprintf(stderr, "%s: mlockall MCL_CURRENT|MCL_FUTURE: %s\n", argv0, strerror(errno));
+		exit(EXIT_ERROR);
+	}
+
+	for (;;) {
+		if (key_len == key_size) {
+			key_new = malloc(key_size += 1024);
+			if (!key_new) {
+				explicit_bzero(key, key_len);
+				fprintf(stderr, "%s: malloc: %s\n", argv0, strerror(errno));
+				exit(EXIT_ERROR);
+			}
+			memcpy(key_new, key, key_len);
+			explicit_bzero(key, key_len);
+			free(key);
+			key = key_new;
+		}
+		r = read(STDIN_FILENO, &key[key_len], key_size - key_len);
+		if (r <= 0) {
+			if (!r)
+				break;
+			explicit_bzero(key, key_len);
+			fprintf(stderr, "%s: read <stdin>: %s\n", argv0, strerror(errno));
+			exit(EXIT_ERROR);
+		}
+		key_len += (size_t)r;
+	}
+
+	/* TODO authenticate */
+	/* TODO forward */
+
+	explicit_bzero(key, key_len);
+
+	if (!keep_env)
+		new_environ = set_environ();
+
+	if (setgid(0)) {
+		fprintf(stderr, "%s: setgid 0: %s\n", argv0, strerror(errno));
+		exit(EXIT_ERROR);
+	}
+	if (setuid(0)) {
+		fprintf(stderr, "%s: setuid 0: %s\n", argv0, strerror(errno));
+		exit(EXIT_ERROR);
+	}
+
+	if (new_environ)
+		environ = new_environ;
+	execvp(argv[0], argv);
+	fprintf(stderr, "%s: execvpe %s: %s\n", argv0, argv[0], strerror(errno));
+	return errno == ENOENT ? EXIT_NOENT : EXIT_EXEC;
 }