read offline info

libi2pd/Identity.cpp

@@ -455,11 +455,49 @@ namespace data
 		memcpy (m_PrivateKey, buf + ret, 256); // private key always 256
 		ret += 256;
 		size_t signingPrivateKeySize = m_Public->GetSigningPrivateKeyLen ();
-		if(signingPrivateKeySize + ret > len) return 0; // overflow
+		if(signingPrivateKeySize + ret > len || signingPrivateKeySize > 128) return 0; // overflow
 		memcpy (m_SigningPrivateKey, buf + ret, signingPrivateKeySize);
 		ret += signingPrivateKeySize;
 		m_Signer = nullptr;
-		CreateSigner ();
+		// check if signing private key is all zeros
+		bool allzeros = true;
+		for (size_t i = 0; i < signingPrivateKeySize; i++)
+			if (m_SigningPrivateKey[i]) 
+			{
+				allzeros = false;
+				break;
+			}
+		if (allzeros)
+		{
+			// offline information
+			const uint8_t * offlineInfo = buf + ret;
+			ret += 4; // expires timestamp
+			SigningKeyType keyType = bufbe16toh (buf + ret); ret += 2; // key type
+			std::unique_ptr<i2p::crypto::Verifier> transientVerifier (IdentityEx::CreateVerifier (keyType));
+			if (!transientVerifier) return 0;
+			auto keyLen = transientVerifier->GetPublicKeyLen ();
+			if (keyLen + ret > len) return 0;
+			transientVerifier->SetPublicKey (buf + ret); ret += keyLen;
+			if (m_Public->GetSignatureLen () + ret > len) return 0;
+			if (!m_Public->Verify (offlineInfo, keyLen + 6, buf + ret)) 
+			{
+				LogPrint (eLogError, "Identity: offline signature verification failed");
+				return 0;
+			}
+			ret += m_Public->GetSignatureLen ();
+			// copy offline signature
+			size_t offlineInfoLen = buf + ret - offlineInfo;
+			m_OfflineSignature.resize (offlineInfoLen);
+			memcpy (m_OfflineSignature.data (), offlineInfo, offlineInfoLen);
+			// override signing private key 
+			signingPrivateKeySize = transientVerifier->GetPrivateKeyLen ();
+			if (signingPrivateKeySize + ret > len || signingPrivateKeySize > 128) return 0;
+			memcpy (m_SigningPrivateKey, buf + ret, signingPrivateKeySize);
+			ret += signingPrivateKeySize;
+			CreateSigner (keyType);
+		}
+		else
+			CreateSigner (m_Public->GetSigningKeyType ());
 		return ret;
 	}
 
@@ -472,6 +510,7 @@ namespace data
 		if(ret + signingPrivateKeySize > len) return 0; // overflow
 		memcpy (buf + ret, m_SigningPrivateKey, signingPrivateKeySize);
 		ret += signingPrivateKeySize;
+		// TODO: implement offline info
 		return ret;
 	}
 
@@ -505,9 +544,17 @@ namespace data
 	}
 
 	void PrivateKeys::CreateSigner () const
+	{
+		if (IsOfflineSignature ())
+			CreateSigner (bufbe16toh (m_OfflineSignature.data () + 4)); // key type
+		else
+			CreateSigner (m_Public->GetSigningKeyType ());
+	}
+	
+	void PrivateKeys::CreateSigner (SigningKeyType keyType) const
 	{
 		if (m_Signer) return;
-		switch (m_Public->GetSigningKeyType ())
+		switch (keyType)
 		{
 			case SIGNING_KEY_TYPE_DSA_SHA1:
 				m_Signer.reset (new i2p::crypto::DSASigner (m_SigningPrivateKey, m_Public->GetStandardIdentity ().signingKey));
@@ -540,6 +587,11 @@ namespace data
 		}
 	}
 
+	size_t PrivateKeys::GetSignatureLen () const
+	{
+		return m_Public->GetSignatureLen ();
+	}
+
 	uint8_t * PrivateKeys::GetPadding()
 	{
 		if(m_Public->GetSigningKeyType () == SIGNING_KEY_TYPE_EDDSA_SHA512_ED25519)

libi2pd/Identity.h

@@ -6,6 +6,7 @@
 #include <string>
 #include <memory>
 #include <atomic>
+#include <vector>
 #include "Base.h"
 #include "Signature.h"
 #include "CryptoKey.h"
@@ -142,6 +143,8 @@ namespace data
 			std::shared_ptr<const IdentityEx> GetPublic () const { return m_Public; };
 			const uint8_t * GetPrivateKey () const { return m_PrivateKey; };
 			const uint8_t * GetSigningPrivateKey () const { return m_SigningPrivateKey; };
+			size_t GetSignatureLen () const; // might not match identity
+			bool IsOfflineSignature () const { return m_OfflineSignature.size () > 0; };
     		uint8_t * GetPadding();
 			void RecalculateIdentHash(uint8_t * buf=nullptr) { m_Public->RecalculateIdentHash(buf); }
 			void Sign (const uint8_t * buf, int len, uint8_t * signature) const;
@@ -162,13 +165,15 @@ namespace data
 		private:
 
 			void CreateSigner () const;
+			void CreateSigner (SigningKeyType keyType) const;
 
 		private:
 
 			std::shared_ptr<IdentityEx> m_Public;
 			uint8_t m_PrivateKey[256];
-			uint8_t m_SigningPrivateKey[1024]; // assume private key doesn't exceed 1024 bytes
+			uint8_t m_SigningPrivateKey[128]; // assume private key doesn't exceed 128 bytes
 			mutable std::unique_ptr<i2p::crypto::Signer> m_Signer;
+			std::vector<uint8_t> m_OfflineSignature; // non zero length, if applicable
 	};
 
 	// kademlia