From c956e49d44545ebc0d8455ff8903cc3e40d7547a Mon Sep 17 00:00:00 2001
From: Sam Anthony <sam@samanthony.xyz>
Date: Mon, 14 Apr 2025 19:13:50 -0400
Subject: store signature verification key in known hosts file

---
 hosts/hosts.go | 101 +++++++++++++++++++++++++++++++++++++--------------------
 1 file changed, 65 insertions(+), 36 deletions(-)

(limited to 'hosts')

diff --git a/hosts/hosts.go b/hosts/hosts.go
index 23883e2..3dc3f33 100644
--- a/hosts/hosts.go
+++ b/hosts/hosts.go
@@ -6,41 +6,46 @@ import (
 	"errors"
 	"fmt"
 	"github.com/adrg/xdg"
-	"net"
 	"net/netip"
 	"os"
 	"path/filepath"
+	"slices"
 	"strings"
+
+	"git.samanthony.xyz/hose/key"
+	"git.samanthony.xyz/hose/util"
 )
 
 var knownHostsFile = filepath.Join(xdg.DataHome, "hose", "known_hosts")
 
-// Set sets the public key of a remote host.
-// It replaces or creates an entry in the known hosts file.
-func Set(hostport net.Addr, pubkey [32]byte) error {
-	host, _, err := net.SplitHostPort(hostport.String())
-	if err != nil {
-		return err
-	}
-	addr, err := netip.ParseAddr(host)
-	if err != nil {
-		return err
-	}
+type Host struct {
+	netip.Addr       // address.
+	key.BoxPublicKey // public encryption key.
+	key.SigPublicKey // public signature verification key.
+}
 
+// Add adds or replaces an entry in the known hosts file.
+func Add(host Host) error {
 	hosts, err := Load()
 	if err != nil {
 		return err
 	}
 
-	hosts[addr] = pubkey
+	i, ok := slices.BinarySearchFunc(hosts, host, cmpHost)
+	if ok {
+		util.Logf("replacing host %q in known hosts file")
+		hosts[i] = host
+	} else {
+		hosts = slices.Insert(hosts, i, host)
+	}
 
 	return Store(hosts)
 }
 
-// Load loads the set of known hosts and their associated public keys
-// from disc.
-func Load() (map[netip.Addr][32]byte, error) {
-	hosts := make(map[netip.Addr][32]byte)
+// Load loads the set of known hosts from disc.
+// The returned list is sorted.
+func Load() ([]Host, error) {
+	hosts := make([]Host, 0)
 
 	f, err := os.Open(knownHostsFile)
 	if errors.Is(err, os.ErrNotExist) {
@@ -52,53 +57,77 @@ func Load() (map[netip.Addr][32]byte, error) {
 
 	scanner := bufio.NewScanner(f)
 	for line := 1; scanner.Scan(); line++ {
-		host, pubkey, err := parseHostKeyPair(scanner.Text())
+		host, err := parseHost(scanner.Text())
 		if err != nil {
 			return hosts, fmt.Errorf("error parsing known hosts file: %s:%d: %v", knownHostsFile, line, err)
 		}
-		if _, ok := hosts[host]; ok {
+		i, ok := slices.BinarySearchFunc(hosts, host, cmpHost)
+		if ok {
 			return hosts, fmt.Errorf("duplicate entry in known hosts file: %s", host)
 		}
-		hosts[host] = pubkey
+		hosts = slices.Insert(hosts, i, host)
 	}
 	return hosts, scanner.Err()
 }
 
-// parseHostKeyPair parses a line of the known hosts file.
-func parseHostKeyPair(s string) (netip.Addr, [32]byte, error) {
+// parseHost parses a line of the known hosts file.
+func parseHost(s string) (Host, error) {
 	fields := strings.Fields(s)
-	if len(fields) != 2 {
-		return netip.Addr{}, [32]byte{}, fmt.Errorf("expected 2 fields; got %d", len(fields))
+	if len(fields) != 3 {
+		return Host{}, fmt.Errorf("expected 3 fields; got %d", len(fields))
 	}
 
 	addr, err := netip.ParseAddr(fields[0])
 	if err != nil {
-		return netip.Addr{}, [32]byte{}, err
+		return Host{}, err
 	}
 
-	var key [32]byte
-	if hex.DecodedLen(len(fields[1])) != len(key) {
-		return netip.Addr{}, [32]byte{}, fmt.Errorf("malformed key: %s", fields[1])
+	var boxPubKey key.BoxPublicKey
+	if hex.DecodedLen(len(fields[1])) != len(boxPubKey) {
+		return Host{}, fmt.Errorf("malformed box public key: %s", fields[1])
 	}
-	if _, err := hex.Decode(key[:], []byte(fields[1])); err != nil {
-		return netip.Addr{}, [32]byte{}, err
+	if _, err := hex.Decode(boxPubKey[:], []byte(fields[1])); err != nil {
+		return Host{}, err
 	}
 
-	return addr, key, nil
+	var sigPubKey key.SigPublicKey
+	if hex.DecodedLen(len(fields[2])) != len(sigPubKey) {
+		return Host{}, fmt.Errorf("malformed signature public key: %s", fields[2])
+	}
+	if _, err := hex.Decode(sigPubKey[:], []byte(fields[2])); err != nil {
+		return Host{}, err
+	}
+
+	return Host{addr, boxPubKey, sigPubKey}, nil
 }
 
-// Store stores the set of known hosts and their associated public keys
-// to disc. It overwrites the entire file.
-func Store(hosts map[netip.Addr][32]byte) error {
+// Store stores the set of known hosts to disc. It overwrites the entire file.
+func Store(hosts []Host) error {
+	slices.SortFunc(hosts, cmpHost)
+
 	f, err := os.Create(knownHostsFile)
 	if err != nil {
 		return err
 	}
 	defer f.Close()
 
-	for host, key := range hosts {
-		fmt.Fprintf(f, "%s %x\n", host, key)
+	for _, host := range hosts {
+		fmt.Fprintf(f, "%s\n", host)
 	}
 
 	return nil
 }
+
+func cmpHost(a, b Host) int {
+	if x := a.Addr.Compare(b.Addr); x != 0 {
+		return x
+	}
+	if x := a.BoxPublicKey.Compare(b.BoxPublicKey); x != 0 {
+		return x
+	}
+	return a.SigPublicKey.Compare(b.SigPublicKey)
+}
+
+func (h Host) String() string {
+	return fmt.Sprintf("%s %x %x", h.Addr, h.BoxPublicKey, h.SigPublicKey)
+}
-- 
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