- Generalise spawn_command function

3 files changed, 104 insertions, 89 deletions

diff --git a/dbutil.c b/dbutil.c
index 0967ddc..d10a651 100644
--- a/dbutil.c
+++ b/dbutil.c
@@ -389,6 +389,83 @@ 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. */
+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 (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) ||
+			(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]);
+		close(errfds[FDIN]);
+		close(errfds[FDOUT]);
+
+		exec_fn(exec_data);
+		/* not reached */
+		return DROPBEAR_FAILURE;
+	} else {
+		/* parent */
+		close(infds[FDIN]);
+		close(outfds[FDOUT]);
+		close(errfds[FDOUT]);
+
+		setnonblocking(errfds[FDIN]);
+		setnonblocking(outfds[FDIN]);
+		setnonblocking(infds[FDOUT]);
+
+		*ret_pid = pid;
+		*ret_writefd = infds[FDOUT];
+		*ret_readfd = outfds[FDIN];
+		*ret_errfd = errfds[FDIN];
+		return DROPBEAR_SUCCESS;
+	}
+}
+
 /* 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) {
diff --git a/dbutil.h b/dbutil.h
index 856978d..ca09b4a 100644
--- a/dbutil.h
+++ b/dbutil.h
@@ -49,6 +49,8 @@ char * stripcontrol(const char * text);
 unsigned char * getaddrstring(struct sockaddr_storage* addr, int withport);
 int dropbear_listen(const char* address, const char* port,
 		int *socks, unsigned int sockcount, char **errstring, int *maxfd);
+int spawn_command(void(*exec_fn)(void *user_data), void *exec_data,
+		int *writefd, int *readfd, int *errfd, pid_t *pid);
 int connect_remote(const char* remotehost, const char* remoteport,
 		int nonblocking, char ** errstring);
 char* getaddrhostname(struct sockaddr_storage * addr);
diff --git a/svr-chansession.c b/svr-chansession.c
index 364daf0..6c99e70 100644
--- a/svr-chansession.c
+++ b/svr-chansession.c
@@ -47,7 +47,7 @@ static int sessionsignal(struct ChanSess *chansess);
 static int noptycommand(struct Channel *channel, struct ChanSess *chansess);
 static int ptycommand(struct Channel *channel, struct ChanSess *chansess);
 static int sessionwinchange(struct ChanSess *chansess);
-static void execchild(struct ChanSess *chansess);
+static void execchild(void *user_data_chansess);
 static void addchildpid(struct ChanSess *chansess, pid_t pid);
 static void sesssigchild_handler(int val);
 static void closechansess(struct Channel *channel);
@@ -633,102 +633,37 @@ static int sessioncommand(struct Channel *channel, struct ChanSess *chansess,
  * pty.
  * Returns DROPBEAR_SUCCESS or DROPBEAR_FAILURE */
 static int noptycommand(struct Channel *channel, struct ChanSess *chansess) {
-
-	int infds[2];
-	int outfds[2];
-	int errfds[2];
-	pid_t pid;
-	unsigned int i;
-
-	const int FDIN = 0;
-	const int FDOUT = 1;
+	int ret;
 
 	TRACE(("enter noptycommand"))
+	ret = spawn_command(execchild, chansess, 
+			&channel->writefd, &channel->readfd, &channel->errfd,
+			&chansess->pid);
 
-	/* redirect stdin/stdout/stderr */
-	if (pipe(infds) != 0)
-		return DROPBEAR_FAILURE;
-	if (pipe(outfds) != 0)
-		return DROPBEAR_FAILURE;
-	if (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) ||
-			(dup2(errfds[FDOUT], STDERR_FILENO) < 0)) {
-			TRACE(("leave noptycommand: error redirecting FDs"))
-			return DROPBEAR_FAILURE;
-		}
-
-		close(infds[FDOUT]);
-		close(infds[FDIN]);
-		close(outfds[FDIN]);
-		close(outfds[FDOUT]);
-		close(errfds[FDIN]);
-		close(errfds[FDOUT]);
-
-		execchild(chansess);
-		/* not reached */
+	if (ret == DROPBEAR_FAILURE) {
+		return ret;
+	}
 
-	} else {
-		/* parent */
-		TRACE(("continue noptycommand: parent"))
-		chansess->pid = pid;
-		TRACE(("child pid is %d", pid))
+	ses.maxfd = MAX(ses.maxfd, channel->writefd);
+	ses.maxfd = MAX(ses.maxfd, channel->readfd);
+	ses.maxfd = MAX(ses.maxfd, channel->errfd);
 
-		addchildpid(chansess, pid);
+	addchildpid(chansess, chansess->pid);
 
-		if (svr_ses.lastexit.exitpid != -1) {
-			TRACE(("parent side: lastexitpid is %d", svr_ses.lastexit.exitpid))
-			/* The child probably exited and the signal handler triggered
-			 * possibly before we got around to adding the childpid. So we fill
-			 * out its data manually */
-			for (i = 0; i < svr_ses.childpidsize; i++) {
-				if (svr_ses.childpids[i].pid == svr_ses.lastexit.exitpid) {
-					TRACE(("found match for lastexitpid"))
-					svr_ses.childpids[i].chansess->exit = svr_ses.lastexit;
-					svr_ses.lastexit.exitpid = -1;
-				}
+	if (svr_ses.lastexit.exitpid != -1) {
+		TRACE(("parent side: lastexitpid is %d", svr_ses.lastexit.exitpid))
+		/* The child probably exited and the signal handler triggered
+		 * possibly before we got around to adding the childpid. So we fill
+		 * out its data manually */
+		int i;
+		for (i = 0; i < svr_ses.childpidsize; i++) {
+			if (svr_ses.childpids[i].pid == svr_ses.lastexit.exitpid) {
+				TRACE(("found match for lastexitpid"))
+				svr_ses.childpids[i].chansess->exit = svr_ses.lastexit;
+				svr_ses.lastexit.exitpid = -1;
 			}
 		}
-
-		close(infds[FDIN]);
-		close(outfds[FDOUT]);
-		close(errfds[FDOUT]);
-		channel->writefd = infds[FDOUT];
-		channel->readfd = outfds[FDIN];
-		channel->errfd = errfds[FDIN];
-		ses.maxfd = MAX(ses.maxfd, channel->writefd);
-		ses.maxfd = MAX(ses.maxfd, channel->readfd);
-		ses.maxfd = MAX(ses.maxfd, channel->errfd);
-
-		setnonblocking(channel->readfd);
-		setnonblocking(channel->writefd);
-		setnonblocking(channel->errfd);
-
 	}
-#undef FDIN
-#undef FDOUT
 
 	TRACE(("leave noptycommand"))
 	return DROPBEAR_SUCCESS;
@@ -873,12 +808,13 @@ static void addchildpid(struct ChanSess *chansess, pid_t pid) {
 
 /* Clean up, drop to user privileges, set up the environment and execute
  * the command/shell. This function does not return. */
-static void execchild(struct ChanSess *chansess) {
+static void execchild(void *user_data) {
 
 	char *argv[4];
 	char * usershell = NULL;
 	char * baseshell = NULL;
 	unsigned int i;
+	struct ChanSess *chansess = user_data;
 
     /* with uClinux we'll have vfork()ed, so don't want to overwrite the
      * hostkey. can't think of a workaround to clear it */