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Move temporary keys for pairing/verification into separate structure 

Confirmed pairing and verification continue to works as expected.
This commit is contained in:
Gregg 2024-05-11 13:29:07 -05:00
parent e0ec162938
commit 3643506d89
2 changed files with 22 additions and 30 deletions
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40
src/HAP.cpp
View File

@ -447,8 +447,7 @@ int HAPClient::postPairSetupURL(uint8_t *content, size_t len){
// Note the SALT and INFO text fields used by HKDF to create this Session Key are NOT the same as those for creating iosDeviceX.
// The iosDeviceX HKDF calculations are separate and will be performed further below with the SALT and INFO as specified in the HAP docs.
TempBuffer<uint8_t> sessionKey(crypto_box_PUBLICKEYBYTES); // temporary space - used only in this block
HKDF::create(sessionKey,srp->K,64,"Pair-Setup-Encrypt-Salt","Pair-Setup-Encrypt-Info"); // create SessionKey
HKDF::create(temp.sessionKey,srp->K,64,"Pair-Setup-Encrypt-Salt","Pair-Setup-Encrypt-Info"); // create SessionKey
LOG2("------- DECRYPTING SUB-TLVS -------\n");
@ -456,7 +455,7 @@ int HAPClient::postPairSetupURL(uint8_t *content, size_t len){
TempBuffer<uint8_t> decrypted(itEncryptedData->getLen()-crypto_aead_chacha20poly1305_IETF_ABYTES); // temporary storage for decrypted data
if(crypto_aead_chacha20poly1305_ietf_decrypt(decrypted, NULL, NULL, *itEncryptedData, itEncryptedData->getLen(), NULL, 0, (unsigned char *)"\x00\x00\x00\x00PS-Msg05", sessionKey)==-1){
if(crypto_aead_chacha20poly1305_ietf_decrypt(decrypted, NULL, NULL, *itEncryptedData, itEncryptedData->getLen(), NULL, 0, (unsigned char *)"\x00\x00\x00\x00PS-Msg05", temp.sessionKey)==-1){
LOG0("\n*** ERROR: Exchange-Request Authentication Failed\n\n");
responseTLV.add(kTLVType_Error,tagError_Authentication); // set Error=Authentication
tlvRespond(responseTLV); // send response to client
@ -534,7 +533,7 @@ int HAPClient::postPairSetupURL(uint8_t *content, size_t len){
itEncryptedData=responseTLV.add(kTLVType_EncryptedData,subPack.len()+crypto_aead_chacha20poly1305_IETF_ABYTES,NULL); //create blank EncryptedData TLV with space for subTLV + Authentication Tag
crypto_aead_chacha20poly1305_ietf_encrypt(*itEncryptedData,NULL,subPack,subPack.len(),NULL,0,NULL,(unsigned char *)"\x00\x00\x00\x00PS-Msg06",sessionKey);
crypto_aead_chacha20poly1305_ietf_encrypt(*itEncryptedData,NULL,subPack,subPack.len(),NULL,0,NULL,(unsigned char *)"\x00\x00\x00\x00PS-Msg06",temp.sessionKey);
LOG2("---------- END SUB-TLVS! ----------\n");
@ -611,16 +610,14 @@ int HAPClient::postPairVerifyURL(uint8_t *content, size_t len){
return(0);
}
publicCurveKey=(uint8_t *)HS_MALLOC(crypto_box_PUBLICKEYBYTES); // temporary space - will be deleted at end of verification process
TempBuffer<uint8_t> secretCurveKey(crypto_box_SECRETKEYBYTES); // temporary space - used only in this block
crypto_box_keypair(publicCurveKey,secretCurveKey); // generate Accessory's random Curve25519 Public/Secret Key Pair
crypto_box_keypair(temp.publicCurveKey,secretCurveKey); // generate Accessory's random Curve25519 Public/Secret Key Pair
iosCurveKey=(uint8_t *)HS_MALLOC(crypto_box_PUBLICKEYBYTES); // temporary space - will be deleted at end of verification process
memcpy(iosCurveKey,*itPublicKey,crypto_box_PUBLICKEYBYTES); // save Controller's Curve25519 Public Key
memcpy(temp.iosCurveKey,*itPublicKey,crypto_box_PUBLICKEYBYTES); // save Controller's Curve25519 Public Key
// concatenate Accessory's Curve25519 Public Key, Accessory's Pairing ID, and Controller's Curve25519 Public Key into accessoryInfo
TempBuffer<uint8_t> accessoryInfo(publicCurveKey,crypto_box_PUBLICKEYBYTES,accessory.ID,hap_accessory_IDBYTES,iosCurveKey,crypto_box_PUBLICKEYBYTES,NULL);
TempBuffer<uint8_t> accessoryInfo(temp.publicCurveKey,crypto_box_PUBLICKEYBYTES,accessory.ID,hap_accessory_IDBYTES,temp.iosCurveKey,crypto_box_PUBLICKEYBYTES,NULL);
subTLV.add(kTLVType_Identifier,hap_accessory_IDBYTES,accessory.ID); // set Identifier subTLV record as Accessory's Pairing ID
auto itSignature=subTLV.add(kTLVType_Signature,crypto_sign_BYTES,NULL); // create blank Signature subTLV
@ -634,19 +631,17 @@ int HAPClient::postPairVerifyURL(uint8_t *content, size_t len){
TempBuffer<uint8_t> subPack(subTLV.pack_size()); // create sub-TLV by packing Identifier and Signature TLV records together
subTLV.pack(subPack);
sharedCurveKey=(uint8_t *)HS_MALLOC(crypto_box_PUBLICKEYBYTES); // temporary space - will be deleted at end of verification process
crypto_scalarmult_curve25519(sharedCurveKey,secretCurveKey,iosCurveKey); // generate Shared-Secret Curve25519 Key from Accessory's Curve25519 Secret Key and Controller's Curve25519 Public Key
crypto_scalarmult_curve25519(temp.sharedCurveKey,secretCurveKey,temp.iosCurveKey); // generate Shared-Secret Curve25519 Key from Accessory's Curve25519 Secret Key and Controller's Curve25519 Public Key
sessionKey=(uint8_t *)HS_MALLOC(crypto_box_PUBLICKEYBYTES); // temporary space - will be deleted at end of verification process
HKDF::create(sessionKey,sharedCurveKey,crypto_box_PUBLICKEYBYTES,"Pair-Verify-Encrypt-Salt","Pair-Verify-Encrypt-Info"); // create Session Curve25519 Key from Shared-Secret Curve25519 Key using HKDF-SHA-512
HKDF::create(temp.sessionKey,temp.sharedCurveKey,crypto_box_PUBLICKEYBYTES,"Pair-Verify-Encrypt-Salt","Pair-Verify-Encrypt-Info"); // create Session Curve25519 Key from Shared-Secret Curve25519 Key using HKDF-SHA-512
auto itEncryptedData=responseTLV.add(kTLVType_EncryptedData,subPack.len()+crypto_aead_chacha20poly1305_IETF_ABYTES,NULL); // create blank EncryptedData subTLV
crypto_aead_chacha20poly1305_ietf_encrypt(*itEncryptedData,NULL,subPack,subPack.len(),NULL,0,NULL,(unsigned char *)"\x00\x00\x00\x00PV-Msg02",sessionKey); // encrypt data with Session Curve25519 Key and padded nonce="PV-Msg02"
auto itEncryptedData=responseTLV.add(kTLVType_EncryptedData,subPack.len()+crypto_aead_chacha20poly1305_IETF_ABYTES,NULL); // create blank EncryptedData subTLV
crypto_aead_chacha20poly1305_ietf_encrypt(*itEncryptedData,NULL,subPack,subPack.len(),NULL,0,NULL,(unsigned char *)"\x00\x00\x00\x00PV-Msg02",temp.sessionKey); // encrypt data with Session Curve25519 Key and padded nonce="PV-Msg02"
LOG2("---------- END SUB-TLVS! ----------\n");
responseTLV.add(kTLVType_State,pairState_M2); // set State=<M2>
responseTLV.add(kTLVType_PublicKey,crypto_box_PUBLICKEYBYTES,publicCurveKey); // set PublicKey to Accessory's Curve25519 Public Key
responseTLV.add(kTLVType_PublicKey,crypto_box_PUBLICKEYBYTES,temp.publicCurveKey); // set PublicKey to Accessory's Curve25519 Public Key
tlvRespond(responseTLV); // send response to client
}
@ -670,7 +665,7 @@ int HAPClient::postPairVerifyURL(uint8_t *content, size_t len){
TempBuffer<uint8_t> decrypted((*itEncryptedData).getLen()-crypto_aead_chacha20poly1305_IETF_ABYTES); // temporary storage for decrypted data
if(crypto_aead_chacha20poly1305_ietf_decrypt(decrypted, NULL, NULL, *itEncryptedData, itEncryptedData->getLen(), NULL, 0, (unsigned char *)"\x00\x00\x00\x00PV-Msg03", sessionKey)==-1){
if(crypto_aead_chacha20poly1305_ietf_decrypt(decrypted, NULL, NULL, *itEncryptedData, itEncryptedData->getLen(), NULL, 0, (unsigned char *)"\x00\x00\x00\x00PV-Msg03", temp.sessionKey)==-1){
LOG0("\n*** ERROR: Verify Authentication Failed\n\n");
responseTLV.add(kTLVType_State,pairState_M4); // set State=<M4>
responseTLV.add(kTLVType_Error,tagError_Authentication); // set Error=Authentication
@ -713,7 +708,7 @@ int HAPClient::postPairVerifyURL(uint8_t *content, size_t len){
// concatenate Controller's Curve25519 Public Key (from previous step), Controller's Pairing ID, and Accessory's Curve25519 Public Key (from previous step) into iosDeviceInfo
TempBuffer<uint8_t> iosDeviceInfo(iosCurveKey,crypto_box_PUBLICKEYBYTES,tPair->ID,hap_controller_IDBYTES,publicCurveKey,crypto_box_PUBLICKEYBYTES,NULL);
TempBuffer<uint8_t> iosDeviceInfo(temp.iosCurveKey,crypto_box_PUBLICKEYBYTES,tPair->ID,hap_controller_IDBYTES,temp.publicCurveKey,crypto_box_PUBLICKEYBYTES,NULL);
if(crypto_sign_verify_detached(*itSignature, iosDeviceInfo, iosDeviceInfo.len(), tPair->LTPK) != 0){ // verify signature of iosDeviceInfo using Controller's LTPK
LOG0("\n*** ERROR: LPTK Signature Verification Failed\n\n");
@ -728,17 +723,12 @@ int HAPClient::postPairVerifyURL(uint8_t *content, size_t len){
cPair=tPair; // save Controller for this connection slot - connection is now verified and should be encrypted going forward
HKDF::create(a2cKey,sharedCurveKey,32,"Control-Salt","Control-Read-Encryption-Key"); // create AccessoryToControllerKey from (previously-saved) Shared-Secret Curve25519 Key (HAP Section 6.5.2)
HKDF::create(c2aKey,sharedCurveKey,32,"Control-Salt","Control-Write-Encryption-Key"); // create ControllerToAccessoryKey from (previously-saved) Shared-Secret Curve25519 Key (HAP Section 6.5.2)
HKDF::create(a2cKey,temp.sharedCurveKey,32,"Control-Salt","Control-Read-Encryption-Key"); // create AccessoryToControllerKey from (previously-saved) Shared-Secret Curve25519 Key (HAP Section 6.5.2)
HKDF::create(c2aKey,temp.sharedCurveKey,32,"Control-Salt","Control-Write-Encryption-Key"); // create ControllerToAccessoryKey from (previously-saved) Shared-Secret Curve25519 Key (HAP Section 6.5.2)
a2cNonce.zero(); // reset Nonces for this session to zero
c2aNonce.zero();
free(publicCurveKey); // free storage of these temporary variables created in previous step
free(sharedCurveKey);
free(sessionKey);
free(iosCurveKey);
LOG2("\n*** SESSION VERIFICATION COMPLETE *** \n");
}
break;

12
src/HAP.h
View File

@ -96,12 +96,14 @@ struct HAPClient {
boolean isConnected=false; // flag to indicate client is connect
// These temporary Curve25519 keys are generated in the first call to pair-verify and used in the second call to pair-verify so must persist for a short period
uint8_t *publicCurveKey; // Accessory's Curve25519 Public Key
uint8_t *sharedCurveKey; // Shared-Secret Curve25519 Key derived from Accessory's Secret Key and Controller's Public Key
uint8_t *sessionKey; // Session Key Curve25519 (derived with various HKDF calls)
uint8_t *iosCurveKey; // Controller's Curve25519 Public Key
struct tempKeys_t {
uint8_t publicCurveKey[crypto_box_PUBLICKEYBYTES]; // Accessory's Curve25519 Public Key
uint8_t sharedCurveKey[crypto_box_PUBLICKEYBYTES]; // Shared-Secret Curve25519 Key derived from Accessory's Secret Key and Controller's Public Key
uint8_t sessionKey[crypto_box_PUBLICKEYBYTES]; // Session Key Curve25519 (derived with various HKDF calls)
uint8_t iosCurveKey[crypto_box_PUBLICKEYBYTES]; // Controller's Curve25519 Public Key
} temp;
// CurveKey and CurveKey Nonces are created once each new session is verified in /pair-verify. Keys persist for as long as connection is open
uint8_t a2cKey[32]; // AccessoryToControllerKey derived from HKDF-SHA-512 of sharedCurveKey (HAP Section 6.5.2)