diff --git a/qrexec-lib/libqrexec-utils.h b/qrexec-lib/libqrexec-utils.h
index b4f3204..9b03caf 100644
--- a/qrexec-lib/libqrexec-utils.h
+++ b/qrexec-lib/libqrexec-utils.h
@@ -42,6 +42,8 @@ void *buffer_data(struct buffer *b);
 void do_fork_exec(const char *cmdline, int *pid, int *stdin_fd, int *stdout_fd,
 		  int *stderr_fd);
 void wait_for_vchan_or_argfd(libvchan_t *vchan, int max, fd_set * rdset, fd_set * wrset);
+int read_vchan_all(libvchan_t *vchan, void *data, size_t size);
+int write_vchan_all(libvchan_t *vchan, void *data, size_t size);
 int read_all(int fd, void *buf, int size);
 int write_all(int fd, const void *buf, int size);
 void fix_fds(int fdin, int fdout, int fderr);
diff --git a/qrexec-lib/txrx-vchan.c b/qrexec-lib/txrx-vchan.c
index b3d252e..c552b84 100644
--- a/qrexec-lib/txrx-vchan.c
+++ b/qrexec-lib/txrx-vchan.c
@@ -74,3 +74,29 @@ void wait_for_vchan_or_argfd(libvchan_t *ctrl, int max, fd_set * rdset, fd_set *
 	}
 	while (wait_for_vchan_or_argfd_once(ctrl, max, rdset, wrset) == 0);
 }
+
+int write_vchan_all(libvchan_t *vchan, void *data, size_t size) {
+    int pos, ret;
+
+    pos = 0;
+    while (pos < size) {
+        ret = libvchan_write(vchan, data+pos, size-pos);
+        if (ret < 0)
+            return 0;
+        pos += ret;
+    }
+    return 1;
+}
+
+int read_vchan_all(libvchan_t *vchan, void *data, size_t size) {
+    int pos, ret;
+
+    pos = 0;
+    while (pos < size) {
+        ret = libvchan_read(vchan, data+pos, size-pos);
+        if (ret < 0)
+            return 0;
+        pos += ret;
+    }
+    return 1;
+}