Fix Sparkle auto-update: inject SUPublicEDKey into Info.plist via PlistBuddy (#15)

Root cause: INFOPLIST_KEY_ build setting prefix only works for Apple-recognized
keys (CF*, NS*, LS*), not custom keys like SUPublicEDKey. The key was never
being added to Info.plist, so generate_appcast silently skipped EdDSA signing
(no public key in app = nothing to match against).

Fix:
- Derive public key from private key at build time using CryptoKit
- Use PlistBuddy to inject SUPublicEDKey and SUFeedURL after build
- Add sign_update fallback in appcast script if generate_appcast skips signing
- Add base64 padding normalization for key handling

.github/workflows/release.yml

@@ -63,11 +63,32 @@ jobs:
           mkdir -p "$CACHE_DIR"
           echo "SWIFTPM_CACHE_PATH=$CACHE_DIR" >> "$GITHUB_ENV"
 
+      - name: Derive Sparkle public key from private key
+        env:
+          SPARKLE_PRIVATE_KEY: ${{ secrets.SPARKLE_PRIVATE_KEY }}
+        run: |
+          if [ -z "$SPARKLE_PRIVATE_KEY" ]; then
+            echo "Missing SPARKLE_PRIVATE_KEY secret" >&2
+            exit 1
+          fi
+          DERIVED_PUBLIC_KEY=$(swift scripts/derive_sparkle_public_key.swift "$SPARKLE_PRIVATE_KEY")
+          echo "Derived Sparkle public key: $DERIVED_PUBLIC_KEY"
+          echo "SPARKLE_PUBLIC_KEY=$DERIVED_PUBLIC_KEY" >> "$GITHUB_ENV"
+
       - name: Build app (Release)
         run: |
-          xcodebuild -scheme cmux -configuration Release -derivedDataPath build CODE_SIGNING_ALLOWED=NO SPARKLE_PUBLIC_KEY="${SPARKLE_PUBLIC_KEY}" build
-        env:
-          SPARKLE_PUBLIC_KEY: ${{ secrets.SPARKLE_PUBLIC_KEY }}
+          xcodebuild -scheme cmux -configuration Release -derivedDataPath build CODE_SIGNING_ALLOWED=NO build
+
+      - name: Inject Sparkle keys into Info.plist
+        run: |
+          APP_PLIST="build/Build/Products/Release/cmuxterm.app/Contents/Info.plist"
+          echo "Adding SUPublicEDKey to Info.plist..."
+          /usr/libexec/PlistBuddy -c "Add :SUPublicEDKey string ${SPARKLE_PUBLIC_KEY}" "$APP_PLIST"
+          echo "Adding SUFeedURL to Info.plist..."
+          /usr/libexec/PlistBuddy -c "Add :SUFeedURL string https://github.com/manaflow-ai/cmuxterm/releases/latest/download/appcast.xml" "$APP_PLIST"
+          echo "Verifying:"
+          /usr/libexec/PlistBuddy -c "Print :SUPublicEDKey" "$APP_PLIST"
+          /usr/libexec/PlistBuddy -c "Print :SUFeedURL" "$APP_PLIST"
 
       - name: Import signing cert
         env:

scripts/derive_sparkle_public_key.swift

@@ -0,0 +1,39 @@
+#!/usr/bin/env swift
+import CryptoKit
+import Foundation
+
+// Derives the Ed25519 public key from a Sparkle private key (base64-encoded).
+// Supports both new format (32-byte seed) and old format (96-byte key+pub).
+
+guard CommandLine.arguments.count > 1 else {
+    fputs("Usage: derive_sparkle_public_key.swift <base64-private-key>\n", stderr)
+    exit(1)
+}
+
+// Pad base64 string if needed (Sparkle keys may be stored without padding)
+var b64 = CommandLine.arguments[1]
+while b64.count % 4 != 0 {
+    b64 += "="
+}
+guard let data = Data(base64Encoded: b64) else {
+    fputs("Error: invalid base64 input\n", stderr)
+    exit(1)
+}
+
+if data.count == 32 {
+    // New format: 32-byte Ed25519 seed
+    do {
+        let privateKey = try Curve25519.Signing.PrivateKey(rawRepresentation: data)
+        print(privateKey.publicKey.rawRepresentation.base64EncodedString())
+    } catch {
+        fputs("Error deriving key: \(error)\n", stderr)
+        exit(1)
+    }
+} else if data.count == 96 {
+    // Old format: 64-byte private key + 32-byte public key
+    let pubKeyData = data[64...]
+    print(pubKeyData.base64EncodedString())
+} else {
+    fputs("Error: unexpected key length \(data.count) (expected 32 or 96)\n", stderr)
+    exit(1)
+}

scripts/sparkle_generate_appcast.sh

@@ -37,18 +37,38 @@ xcodebuild \
   CODE_SIGNING_ALLOWED=NO \
   build >/dev/null
 
+echo "Building Sparkle sign_update tool..."
+xcodebuild \
+  -project "$work_dir/Sparkle/Sparkle.xcodeproj" \
+  -scheme sign_update \
+  -configuration Release \
+  -derivedDataPath "$work_dir/build" \
+  CODE_SIGNING_ALLOWED=NO \
+  build >/dev/null
+
 generate_appcast="$work_dir/build/Build/Products/Release/generate_appcast"
+sign_update="$work_dir/build/Build/Products/Release/sign_update"
+
 if [[ ! -x "$generate_appcast" ]]; then
   echo "generate_appcast binary not found at $generate_appcast" >&2
   exit 1
 fi
+if [[ ! -x "$sign_update" ]]; then
+  echo "sign_update binary not found at $sign_update" >&2
+  exit 1
+fi
 
 archives_dir="$work_dir/archives"
 mkdir -p "$archives_dir"
 cp "$DMG_PATH" "$archives_dir/$(basename "$DMG_PATH")"
 
 key_file="$work_dir/sparkle_ed_key"
-printf "%s" "$SPARKLE_PRIVATE_KEY" > "$key_file"
+# Ensure base64 padding (keys may be stored without trailing '=')
+padded_key="$SPARKLE_PRIVATE_KEY"
+while (( ${#padded_key} % 4 != 0 )); do
+  padded_key="${padded_key}="
+done
+printf "%s" "$padded_key" > "$key_file"
 
 "$generate_appcast" \
   --ed-key-file "$key_file" \
@@ -61,5 +81,40 @@ if [[ ! -f "$archives_dir/appcast.xml" ]]; then
   exit 1
 fi
 
+# Check if generate_appcast added the edSignature. If not, use sign_update
+# to sign the DMG and inject the signature. generate_appcast silently skips
+# signing when the public key derived from the private key doesn't match the
+# SUPublicEDKey in the app's Info.plist.
+if ! grep -q 'sparkle:edSignature' "$archives_dir/appcast.xml"; then
+  echo "Warning: generate_appcast did not add edSignature. Using sign_update fallback..."
+  SIGNATURE=$("$sign_update" -p --ed-key-file "$key_file" "$DMG_PATH")
+  DMG_LENGTH=$(stat -f%z "$DMG_PATH")
+  echo "  EdDSA signature: ${SIGNATURE:0:20}..."
+  echo "  DMG length: $DMG_LENGTH"
+
+  # Inject sparkle:edSignature and correct length into the enclosure element
+  python3 -c "
+import sys
+xml = open('$archives_dir/appcast.xml').read()
+sig = '$SIGNATURE'
+length = '$DMG_LENGTH'
+# Add edSignature to enclosure
+xml = xml.replace(
+    'type=\"application/octet-stream\"',
+    'sparkle:edSignature=\"' + sig + '\" length=\"' + length + '\" type=\"application/octet-stream\"'
+)
+open('$archives_dir/appcast.xml', 'w').write(xml)
+print('  Injected edSignature into appcast.xml')
+"
+fi
+
 cp "$archives_dir/appcast.xml" "$OUT_PATH"
 echo "Generated appcast at $OUT_PATH"
+
+# Verify the appcast has a signature
+if grep -q 'sparkle:edSignature' "$OUT_PATH"; then
+  echo "Verified: appcast contains sparkle:edSignature"
+else
+  echo "ERROR: appcast is missing sparkle:edSignature!" >&2
+  exit 1
+fi