fix: handle invalid signatureKeyPublic types in sender-key-state AND fix handling chain key objects for skmsg group message decryption (#1760)

* fix: handle invalid signatureKeyPublic types in sender-key-state

- added extra check to ensure signatureKeyPublic is either a base64 string or a Buffer
- fallback to empty buffer when unexpected object type is received
- prevents ERR_INVALID_ARG_TYPE error in Buffer.from

* fix: lint

* adjusted based on  @jlucaso1 recommmendation

* fix: handle chain key objects for skmsg group message decryption

previously, some sender chain keys were stored or retrieved as plain objects
(e.g. { '0': 85, '1': 100, ... }) instead of Buffers. this caused
"ERR_INVALID_ARG_TYPE" during initial decryption of skmsg group messages.

this fixes any chain key object is converted to a proper Buffer
before being passed to SenderChainKey.

* fix: add more robust checks and fallbacks

* hacky fix(sender-key-state): normalize signing pubkey as Buffer with 0x05 prefix

a little hacky fix that ensures getSigningKeyPublic always returns a proper Buffer to satisfy libsignal.
adds a fallback to prepend 0x05 when only a 32-byte key is present, avoiding
"Invalid public key" errors and TS type issues around Uint8Array vs Buffer.

src/Signal/Group/sender-chain-key.ts

@@ -10,12 +10,14 @@ export class SenderChainKey {
 
 	constructor(iteration: number, chainKey: any) {
 		this.iteration = iteration
-		if (chainKey instanceof Buffer) {
+		if (Buffer.isBuffer(chainKey)) {
 			this.chainKey = chainKey
 		} else if (chainKey instanceof Uint8Array) {
 			this.chainKey = Buffer.from(chainKey)
+		} else if (chainKey && typeof chainKey === 'object') {
+			this.chainKey = Buffer.from(Object.values(chainKey))
 		} else {
-			this.chainKey = Buffer.from(chainKey || [])
+			this.chainKey = Buffer.alloc(0)
 		}
 	}
 

src/Signal/Group/sender-key-state.ts

@@ -30,17 +30,25 @@ export class SenderKeyState {
 	constructor(
 		id?: number | null,
 		iteration?: number | null,
-		chainKey?: Uint8Array | null,
-		signatureKeyPair?: { public: Uint8Array; private: Uint8Array } | null,
-		signatureKeyPublic?: Uint8Array | null,
-		signatureKeyPrivate?: Uint8Array | null,
+		chainKey?: Uint8Array | null | string,
+		signatureKeyPair?: { public: Uint8Array | string; private: Uint8Array | string } | null,
+		signatureKeyPublic?: Uint8Array | string | null,
+		signatureKeyPrivate?: Uint8Array | string | null,
 		senderKeyStateStructure?: SenderKeyStateStructure | null
 	) {
+		const toBuffer = (val: any) => {
+			if (!val) return Buffer.alloc(0)
+			if (typeof val === 'string') return Buffer.from(val, 'base64')
+			if (val instanceof Uint8Array || Array.isArray(val)) return Buffer.from(val)
+			return Buffer.alloc(0)
+		}
+
 		if (senderKeyStateStructure) {
-			if (!Array.isArray(senderKeyStateStructure.senderMessageKeys)) {
-				this.senderKeyStateStructure = { ...senderKeyStateStructure, senderMessageKeys: [] }
-			} else {
-				this.senderKeyStateStructure = senderKeyStateStructure
+			this.senderKeyStateStructure = {
+				...senderKeyStateStructure,
+				senderMessageKeys: Array.isArray(senderKeyStateStructure.senderMessageKeys)
+					? senderKeyStateStructure.senderMessageKeys
+					: []
 			}
 		} else {
 			if (signatureKeyPair) {
@@ -52,19 +60,12 @@ export class SenderKeyState {
 
 			const senderChainKeyStructure: SenderChainKeyStructure = {
 				iteration: iteration || 0,
-				seed: chainKey || Buffer.alloc(0)
+				seed: chainKey ? toBuffer(chainKey) : Buffer.alloc(0)
 			}
 
 			const signingKeyStructure: SenderSigningKeyStructure = {
-				public:
-					typeof signatureKeyPublic === 'string'
-						? Buffer.from(signatureKeyPublic, 'base64')
-						: signatureKeyPublic || Buffer.alloc(0)
-			}
-
-			if (signatureKeyPrivate) {
-				signingKeyStructure.private =
-					typeof signatureKeyPrivate === 'string' ? Buffer.from(signatureKeyPrivate, 'base64') : signatureKeyPrivate
+				public: toBuffer(signatureKeyPublic),
+				private: signatureKeyPrivate ? toBuffer(signatureKeyPrivate) : undefined
 			}
 
 			this.senderKeyStateStructure = {
@@ -95,16 +96,29 @@ export class SenderKeyState {
 	}
 
 	public getSigningKeyPublic(): Buffer {
-		const publicKey = this.senderKeyStateStructure.senderSigningKey.public
-		if (publicKey instanceof Buffer) {
-			return publicKey
-		} else if (publicKey instanceof Uint8Array) {
-			return Buffer.from(publicKey)
-		} else if (typeof publicKey === 'string') {
-			return Buffer.from(publicKey, 'base64')
+		let key = this.senderKeyStateStructure.senderSigningKey.public
+
+		// normalize into Buffer
+		if (!(key instanceof Buffer)) {
+			if (key instanceof Uint8Array) {
+				key = Buffer.from(key)
+			} else if (typeof key === 'string') {
+				key = Buffer.from(key, 'base64')
+			} else {
+				key = Buffer.from(key || [])
+			}
 		}
 
-		return Buffer.from(publicKey || [])
+		const publicKey = key as Buffer
+
+		if (publicKey.length === 32) {
+			const fixed = Buffer.alloc(33)
+			fixed[0] = 0x05
+			publicKey.copy(fixed, 1)
+			return fixed
+		}
+
+		return publicKey
 	}
 
 	public getSigningKeyPrivate(): Buffer | undefined {