1 files changed, 135 insertions, 0 deletions
diff --git a/dbutil.c b/dbutil.c
index b0496cf..0b32182 100644
--- a/dbutil.c
+++ b/dbutil.c
@@ -389,6 +389,141 @@ int connect_remote(const char* remotehost, const char* remoteport,
 	return sock;
 }
 
+/* Sets up a pipe for a, returning three non-blocking file descriptors
+ * and the pid. exec_fn is the function that will actually execute the child process,
+ * it will be run after the child has fork()ed, and is passed exec_data.
+ * If ret_errfd == NULL then stderr will not be captured.
+ * ret_pid can be passed as  NULL to discard the pid. */
+int spawn_command(void(*exec_fn)(void *user_data), void *exec_data,
+		int *ret_writefd, int *ret_readfd, int *ret_errfd, pid_t *ret_pid) {
+	int infds[2];
+	int outfds[2];
+	int errfds[2];
+	pid_t pid;
+
+	const int FDIN = 0;
+	const int FDOUT = 1;
+
+	/* redirect stdin/stdout/stderr */
+	if (pipe(infds) != 0) {
+		return DROPBEAR_FAILURE;
+	}
+	if (pipe(outfds) != 0) {
+		return DROPBEAR_FAILURE;
+	}
+	if (ret_errfd && pipe(errfds) != 0) {
+		return DROPBEAR_FAILURE;
+	}
+
+#ifdef __uClinux__
+	pid = vfork();
+#else
+	pid = fork();
+#endif
+
+	if (pid < 0) {
+		return DROPBEAR_FAILURE;
+	}
+
+	if (!pid) {
+		/* child */
+
+		TRACE(("back to normal sigchld"))
+		/* Revert to normal sigchld handling */
+		if (signal(SIGCHLD, SIG_DFL) == SIG_ERR) {
+			dropbear_exit("signal() error");
+		}
+
+		/* redirect stdin/stdout */
+
+		if ((dup2(infds[FDIN], STDIN_FILENO) < 0) ||
+			(dup2(outfds[FDOUT], STDOUT_FILENO) < 0) ||
+			(ret_errfd && dup2(errfds[FDOUT], STDERR_FILENO) < 0)) {
+			TRACE(("leave noptycommand: error redirecting FDs"))
+			dropbear_exit("child dup2() failure");
+		}
+
+		close(infds[FDOUT]);
+		close(infds[FDIN]);
+		close(outfds[FDIN]);
+		close(outfds[FDOUT]);
+		if (ret_errfd)
+		{
+			close(errfds[FDIN]);
+			close(errfds[FDOUT]);
+		}
+
+		exec_fn(exec_data);
+		/* not reached */
+		return DROPBEAR_FAILURE;
+	} else {
+		/* parent */
+		close(infds[FDIN]);
+		close(outfds[FDOUT]);
+
+		setnonblocking(outfds[FDIN]);
+		setnonblocking(infds[FDOUT]);
+
+		if (ret_errfd) {
+			close(errfds[FDOUT]);
+			setnonblocking(errfds[FDIN]);
+		}
+
+		if (ret_pid) {
+			*ret_pid = pid;
+		}
+
+		*ret_writefd = infds[FDOUT];
+		*ret_readfd = outfds[FDIN];
+		if (ret_errfd) {
+			*ret_errfd = errfds[FDIN];
+		}
+		return DROPBEAR_SUCCESS;
+	}
+}
+
+/* Runs a command with "sh -c". Will close FDs (except stdin/stdout/stderr) and
+ * re-enabled SIGPIPE. If cmd is NULL, will run a login shell.
+ */
+void run_shell_command(const char* cmd, unsigned int maxfd, char* usershell) {
+	char * argv[4];
+	char * baseshell = NULL;
+	unsigned int i;
+
+	baseshell = basename(usershell);
+
+	if (cmd != NULL) {
+		argv[0] = baseshell;
+	} else {
+		/* a login shell should be "-bash" for "/bin/bash" etc */
+		int len = strlen(baseshell) + 2; /* 2 for "-" */
+		argv[0] = (char*)m_malloc(len);
+		snprintf(argv[0], len, "-%s", baseshell);
+	}
+
+	if (cmd != NULL) {
+		argv[1] = "-c";
+		argv[2] = cmd;
+		argv[3] = NULL;
+	} else {
+		/* construct a shell of the form "-bash" etc */
+		argv[1] = NULL;
+	}
+
+	/* Re-enable SIGPIPE for the executed process */
+	if (signal(SIGPIPE, SIG_DFL) == SIG_ERR) {
+		dropbear_exit("signal() error");
+	}
+
+	/* close file descriptors except stdin/stdout/stderr
+	 * Need to be sure FDs are closed here to avoid reading files as root */
+	for (i = 3; i <= maxfd; i++) {
+		m_close(i);
+	}
+
+	execv(usershell, argv);
+}
+
 /* Return a string representation of the socket address passed. The return
  * value is allocated with malloc() */
 unsigned char * getaddrstring(struct sockaddr_storage* addr, int withport) {