From edfc79c2ab492d9e147da0c34bd1a2a68df43a72 Mon Sep 17 00:00:00 2001
From: Sam Anthony <sam@samanthony.xyz>
Date: Fri, 11 Apr 2025 13:55:54 -0400
Subject: handshake sending side

---
 handshake.go | 49 +++++++++++++++++++++++++++++++++++++++++++++++++
 main.go      | 14 +++++++++-----
 2 files changed, 58 insertions(+), 5 deletions(-)
 create mode 100644 handshake.go

diff --git a/handshake.go b/handshake.go
new file mode 100644
index 0000000..bbd100c
--- /dev/null
+++ b/handshake.go
@@ -0,0 +1,49 @@
+package main
+
+import (
+	"golang/org/x/sync/errgroup"
+
+	"key"
+)
+
+// handshake exchanges public keys with a remote host.
+// The user is asked to verify the fingerprint of the received key
+// before it is saved in the known hosts file.
+func handshake(rhost string) error {
+	logf("initiating handshake with %s...", rhost)
+	var group errgroup.Group
+	group.Go(handshakeSend(rhost))
+	group.Go(handshakeRecv(rhost))
+	return group.Wait()
+}
+
+// handshakeSend sends the local public key to a remote host.
+func handshakeSend(rhost string) error {
+	pubkey, err := key.LoadPublicKey()
+	if err != nil {
+		return err
+	}
+
+	raddr := net.JoinHostPort(rhost, port)
+	logf("connecting to %s...", raddr)
+	conn, err := net.Dial(network, raddr)
+	if err != nil {
+		return err
+	}
+	defer conn.Close()
+	logf("connected to %s", raddr)
+
+	if _, err := conn.Write(pubkey[:]); err != nil {
+		return err
+	}
+
+	logf("sent public key to %s", rhost)
+	return nil
+}
+
+// handshakeRecv receives the public key of a remote host.
+// The user is asked to verify the fingerprint of the key before
+// it is saved to the known hosts file.
+func handshakeRecv(rhost string) error {
+	// TODO
+}
diff --git a/main.go b/main.go
index d2d942b..906bfb6 100644
--- a/main.go
+++ b/main.go
@@ -16,18 +16,22 @@ const (
 )
 
 var (
-	r     = flag.Bool("r", false, "receive")
-	rhost = flag.String("s", "", "send to remote host")
+	recvFlag = flag.Bool("r", false, "receive")
+	sendHost = flag.String("s", "", "send to remote host")
 )
 
 func main() {
 	flag.Parse()
-	if *r {
+	if *handshakeHost {
+		if err := handshake(*handshakeHost); err != nil {
+			eprintf("%v\n", err)
+		}
+	} else if *recvFlag {
 		if err := recv(); err != nil {
 			eprintf("%v\n", err)
 		}
-	} else if *rhost != "" {
-		if err := send(*rhost); err != nil {
+	} else if *sendHost != "" {
+		if err := send(*sendHost); err != nil {
 			eprintf("%v\n", err)
 		}
 	} else {
-- 
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