1 files changed, 263 insertions, 0 deletions
diff --git a/gasroot-setuid.c b/gasroot-setuid.c
new file mode 100644
index 0000000..b699b32
--- /dev/null
+++ b/gasroot-setuid.c
@@ -0,0 +1,263 @@
+/* See LICENSE file for copyright and license details. */
+#include "common.h"
+
+
+static const char *
+get_expected(void)
+{
+	struct passwd *pwd;
+	struct spwd *shdw;
+	const char *expected;
+
+	errno = 0;
+	pwd = getpwuid(getuid());
+	if (!pwd || !pwd->pw_name || !*pwd->pw_name) {
+		if (errno)
+			fprintf(stderr, "%s: getpwuid: %s\n", argv0, strerror(errno));
+		else
+			fprintf(stderr, "%s: your user does not exist\n", argv0);
+		exit(EXIT_ERROR);
+	}
+
+	shdw = getspnam(pwd->pw_name);
+	if (!shdw || !shdw->sp_pwdp) {
+		if (errno)
+			fprintf(stderr, "%s: getspnam: %s\n", argv0, strerror(errno));
+		else
+			fprintf(stderr, "%s: your user does not have a shadow entry\n", argv0);
+		exit(EXIT_ERROR);
+	}
+
+	expected = shdw->sp_pwdp;
+
+	if (!*expected) {
+		fprintf(stderr, "%s: your user does not have a password\n", argv0);
+		exit(EXIT_ERROR);
+	} else if (expected[expected[0] == '!'] == '*' || expected[expected[0] == '!'] == 'x') {
+		fprintf(stderr, "%s: login to your account is disabled\n", argv0);
+		exit(EXIT_ERROR);
+	} else if (expected[0] == '!') {
+		fprintf(stderr, "%s: your account is currently locked\n", argv0);
+		exit(EXIT_ERROR);
+	}
+
+	return expected;
+}
+
+
+static void
+set_environ(void)
+{
+	char *str;
+	size_t len;
+	struct passwd *pw;
+
+	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);
+	}
+
+	libenv_select_variable_list((const char **)(void *)environ, LIBENV_SU_SAFE, LIBENV_END);
+
+	if (pw->pw_dir && *pw->pw_dir) {
+		if (setenv("HOME", pw->pw_dir, 1))
+			fprintf(stderr, "%s: setenv HOME %s 1: %s\n", argv0, pw->pw_dir, strerror(errno));
+	}
+	if (pw->pw_name && *pw->pw_name) {
+		if (setenv("LOGNAME", pw->pw_name, 1))
+			fprintf(stderr, "%s: setenv LOGNAME %s 1: %s\n", argv0, pw->pw_name, strerror(errno));
+
+		if (setenv("USER", pw->pw_name, 1))
+			fprintf(stderr, "%s: setenv USER %s 1: %s\n", argv0, pw->pw_name, strerror(errno));
+
+		len = sizeof("/var/spool/mail/") + strlen(pw->pw_name);
+		str = malloc(len);
+		if (!str)
+			fprintf(stderr, "%s: malloc %zu: %s\n", argv0, len, strerror(errno));
+		stpcpy(stpcpy(str, "/var/spool/mail/"), pw->pw_name);
+		if (setenv("MAIL", str, 1))
+			fprintf(stderr, "%s: setenv MAIL %s 1: %s\n", argv0, str, strerror(errno));
+		free(str);
+	}
+	if (pw->pw_shell && *pw->pw_shell) {
+		if (setenv("SHELL", pw->pw_shell, 1))
+			fprintf(stderr, "%s: setenv SHELL %s 1: %s\n", argv0, pw->pw_shell, strerror(errno));
+	}
+}
+
+
+static int
+get_passphrase_fd(void)
+{
+	const char *env;
+	long int r;
+	char *end;
+	int fd, value;
+
+	env = getenv("GASROOT_PASSFD");
+	if (!env) {
+		fprintf(stderr, "%s: GASROOT_PASSFD environment variable not set\n", argv0);
+		exit(EXIT_ERROR);
+	}
+
+	if (!isdigit(env[0])) {
+	invalid:
+		fprintf(stderr, "%s: GASROOT_PASSFD environment variable is improperly configured\n", argv0);
+		exit(EXIT_ERROR);
+	}
+
+	errno = 0;
+	r = strtol(env, &end, 10);
+	if (errno || (*end && *end != ':') || r < 0)
+		goto invalid;
+#if INT_MAX < LONG_MAX
+	if (r > INT_MAX)
+		goto invalid;
+#endif
+	fd = (int)r;
+
+	if (getsockopt(fd, SOL_SOCKET, SO_DOMAIN, &value, &(socklen_t){(socklen_t)sizeof(value)})) {
+		if (errno == EBADF)
+			goto invalid;
+		fprintf(stderr, "%s: getsockopt ${GASROOT_PASSFD} SOL_SOCKET SO_DOMAIN: %s\n", argv0, strerror(errno));
+		exit(EXIT_ERROR);
+	}
+	if (value != PF_UNIX)
+		goto invalid;
+
+	if (getsockopt(fd, SOL_SOCKET, SO_TYPE, &value, &(socklen_t){(socklen_t)sizeof(value)})) {
+		if (errno == EBADF)
+			goto invalid;
+		fprintf(stderr, "%s: getsockopt ${GASROOT_PASSFD} SOL_SOCKET SO_TYPE: %s\n", argv0, strerror(errno));
+		exit(EXIT_ERROR);
+	}
+	if (value != SOCK_STREAM)
+		goto invalid;
+
+	if (!*end) {
+		unsetenv("GASROOT_PASSFD");
+	} else if (setenv("GASROOT_PASSFD", &end[1], 1)) {
+		fprintf(stderr, "%s: setenv: %s\n", argv0, strerror(errno));
+		exit(EXIT_ERROR);
+	}
+
+	return fd;
+}
+
+
+static void
+senddata(int fd, const char *text, size_t len)
+{
+	ssize_t r;
+	while (len) {
+		r = send(fd, text, len, 0);
+		if (r < 0) {
+			if (errno == EINTR)
+				continue;
+			fprintf(stderr, "%s: send <graphical interface> %zu 0: %s\n", argv0, len, strerror(errno));
+			exit(EXIT_ERROR);
+		}
+		text = &text[r];
+		len -= (size_t)r;
+	}
+}
+
+
+#define sendtext(FD, TEXT) senddata(FD, TEXT, sizeof(TEXT))
+
+
+static void
+recvtext(int fd, char **bufp, size_t *sizep)
+{
+	size_t len = 0;
+	ssize_t r;
+	do {
+		if (len + 2048UL > *sizep) {
+			*sizep = len + 2048UL;
+			*bufp = realloc(*bufp, *sizep);
+			if (!*bufp) {
+				fprintf(stderr, "%s: realloc %zu: %s\n", argv0, *sizep, strerror(errno));
+				exit(EXIT_ERROR);
+			}
+		}
+	again:
+		r = recv(fd, &(*bufp)[len], *sizep - len, 0);
+		if (r < 0) {
+			if (errno == EINTR)
+				goto again;
+			fprintf(stderr, "%s: recv <graphical interface> %zu 0: %s\n", argv0, *sizep - len, strerror(errno));
+			exit(EXIT_ERROR);
+		} else if (!r) {
+			exit(EXIT_ERROR);
+		}
+		if (memchr(&(*bufp)[len], 0, (size_t)r - 1U)) {
+			fprintf(stderr, "%s: protocol error in communication with graphical interface\n", argv0);
+			exit(EXIT_ERROR);
+		}
+		len += (size_t)r;
+	} while ((*bufp)[len - 1U]);
+}
+
+
+int
+main(int argc, char *argv[])
+{
+	int keep_env = 0;
+	int fd;
+	char *passphrase = NULL;
+	size_t passphrase_size = 0;
+	const char *expected;
+
+	ARGBEGIN {
+	case 'e':
+		keep_env = 1;
+		break;
+	default:
+		usage();
+	} ARGEND;
+
+	if (!argc)
+		usage();
+
+	fd = get_passphrase_fd();
+	expected = get_expected();
+
+	sendtext(fd, "HELLO");
+	for (;;) {
+		recvtext(fd, &passphrase, &passphrase_size);
+		if (!strcmp(crypt(passphrase, expected), expected))
+			break;
+		wipe(passphrase);
+#if RETRY_SLEEP > 0
+		sendtext(fd, "BLOCK");
+		sleep(RETRY_SLEEP);
+#endif
+		sendtext(fd, "RETRY");
+	}
+	wipe(passphrase);
+	free(passphrase);
+
+	sendtext(fd, "OK");
+	close(fd);
+
+	if (!keep_env)
+		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);
+	}
+
+	execvp(argv[0], argv);
+	fprintf(stderr, "%s: execvpe %s: %s\n", argv0, argv[0], strerror(errno));
+	return errno == ENOENT ? EXIT_NOENT : EXIT_EXEC;
+}