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HAPPairingPairSetup.c
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HAPPairingPairSetup.c
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// Copyright (c) 2015-2019 The HomeKit ADK Contributors
//
// Licensed under the Apache License, Version 2.0 (the “License”);
// you may not use this file except in compliance with the License.
// See [CONTRIBUTORS.md] for the list of HomeKit ADK project authors.
#include "HAP+Internal.h"
static const HAPLogObject logObject = { .subsystem = kHAP_LogSubsystem, .category = "PairingPairSetup" };
void HAPPairingPairSetupResetForSession(HAPAccessoryServerRef* server_, HAPSessionRef* session_) {
HAPPrecondition(server_);
HAPAccessoryServer* server = (HAPAccessoryServer*) server_;
HAPPrecondition(session_);
HAPSession* session = (HAPSession*) session_;
// Reset session-specific Pair Setup procedure state that is stored in shared memory.
if (server->pairSetup.sessionThatIsCurrentlyPairing == session_) {
bool keepSetupInfo = server->pairSetup.keepSetupInfo;
HAPRawBufferZero(&server->pairSetup, sizeof server->pairSetup);
HAPAccessorySetupInfoHandlePairingStop(server_, keepSetupInfo);
}
// Reset session-specific Pair Setup procedure state.
HAPRawBufferZero(&session->state.pairSetup, sizeof session->state.pairSetup);
}
/**
* Pair Setup M1 TLVs.
*/
typedef struct {
HAPTLV* stateTLV; /**< kTLVType_State. */
HAPTLV* methodTLV; /**< kTLVType_Method. */
HAPTLV* flagsTLV; /**< kTLVType_Flags. */
} HAPPairingPairSetupM1TLVs;
/**
* Processes Pair Setup M1.
*
* @param server_ Accessory server.
* @param session_ The session over which the request has been received.
* @param tlvs TLVs.
*
* @return kHAPError_None If successful.
* @return kHAPError_InvalidState If a different request is expected in the current state.
* @return kHAPError_InvalidData If the controller sent a malformed request.
*/
HAP_RESULT_USE_CHECK
static HAPError HAPPairingPairSetupProcessM1(
HAPAccessoryServerRef* server_,
HAPSessionRef* session_,
const HAPPairingPairSetupM1TLVs* tlvs) {
HAPPrecondition(server_);
HAPAccessoryServer* server = (HAPAccessoryServer*) server_;
HAPPrecondition(session_);
HAPSession* session = (HAPSession*) session_;
HAPPrecondition(session->state.pairSetup.state == 1);
HAPPrecondition(!session->state.pairSetup.error);
HAPPrecondition(tlvs);
HAPPrecondition(tlvs->stateTLV);
HAPPrecondition(tlvs->stateTLV->type == kHAPPairingTLVType_State);
HAPPrecondition(tlvs->methodTLV);
HAPPrecondition(tlvs->methodTLV->type == kHAPPairingTLVType_Method);
HAPPrecondition(tlvs->flagsTLV);
HAPPrecondition(tlvs->flagsTLV->type == kHAPPairingTLVType_Flags);
// See HomeKit Accessory Protocol Specification R14
// Section 5.6.1 M1: iOS Device -> Accessory -- `SRP Start Request'
HAPLogDebug(&logObject, "Pair Setup M1: SRP Start Request.");
// Validate kTLVType_State.
if (!tlvs->stateTLV->value.bytes) {
HAPLog(&logObject, "Pair Setup M1: kTLVType_State missing.");
return kHAPError_InvalidData;
}
if (tlvs->stateTLV->value.numBytes != 1) {
HAPLog(&logObject, "Pair Setup M1: kTLVType_State has invalid length (%zu).", tlvs->stateTLV->value.numBytes);
return kHAPError_InvalidData;
}
uint8_t state = ((const uint8_t*) tlvs->stateTLV->value.bytes)[0];
if (state != 1) {
HAPLog(&logObject, "Pair Setup M1: kTLVType_State invalid: %u.", state);
return kHAPError_InvalidData;
}
// Validate kTLVType_Method.
if (!tlvs->methodTLV->value.bytes) {
HAPLog(&logObject, "Pair Setup M1: kTLVType_Method missing.");
return kHAPError_InvalidData;
}
if (tlvs->methodTLV->value.numBytes != 1) {
HAPLog(&logObject, "Pair Setup M1: kTLVType_Method has invalid length (%zu).", tlvs->methodTLV->value.numBytes);
return kHAPError_InvalidData;
}
uint8_t method = ((const uint8_t*) tlvs->methodTLV->value.bytes)[0];
if (method != kHAPPairingMethod_PairSetupWithAuth && method != kHAPPairingMethod_PairSetup) {
HAPLog(&logObject, "Pair Setup M1: kTLVType_Method invalid: %u.", method);
return kHAPError_InvalidData;
}
// Store method.
HAPLogDebug(&logObject, "Pair Setup M1: kTLVType_Method = %u.", method);
session->state.pairSetup.method = method;
// Validate and store kTLVType_Flags.
if (tlvs->flagsTLV->value.bytes) {
if (tlvs->flagsTLV->value.numBytes > sizeof(uint32_t)) {
HAPLog(&logObject,
"Pair Setup M1: kTLVType_Flags has invalid length (%zu).",
tlvs->flagsTLV->value.numBytes);
return kHAPError_InvalidData;
}
if (server->pairSetup.sessionThatIsCurrentlyPairing == session_) {
server->pairSetup.flagsPresent = true;
server->pairSetup.flags = HAPPairingReadFlags(tlvs->flagsTLV);
}
} else {
if (server->pairSetup.sessionThatIsCurrentlyPairing == session_) {
server->pairSetup.flagsPresent = false;
server->pairSetup.flags = 0;
}
}
return kHAPError_None;
}
/**
* Processes Pair Setup M2.
*
* @param server_ Accessory server.
* @param session_ The session over which the response will be sent.
* @param responseWriter TLV writer for serializing the response.
*
* @return kHAPError_None If successful.
* @return kHAPError_Unknown If persistent store access failed.
* @return kHAPError_InvalidState If a different request is expected in the current state.
* @return kHAPError_OutOfResources If response writer does not have enough capacity.
*/
HAP_RESULT_USE_CHECK
static HAPError HAPPairingPairSetupGetM2(
HAPAccessoryServerRef* server_,
HAPSessionRef* session_,
HAPTLVWriterRef* responseWriter) {
HAPPrecondition(server_);
HAPAccessoryServer* server = (HAPAccessoryServer*) server_;
HAPPrecondition(session_);
HAPSession* session = (HAPSession*) session_;
HAPPrecondition(session->state.pairSetup.state == 2);
HAPPrecondition(!session->state.pairSetup.error);
HAPPrecondition(responseWriter);
HAPError err;
// See HomeKit Accessory Protocol Specification R14
// Section 5.6.2 M2: Accessory -> iOS Device -- `SRP Start Response'
HAPLogDebug(&logObject, "Pair Setup M2: SRP Start Response.");
// Check if the accessory is already paired.
if (!server->pairSetup.sessionThatIsCurrentlyPairing || HAPAccessoryServerIsPaired(server_)) {
HAPLog(&logObject, "Pair Setup M2: Accessory is already paired.");
session->state.pairSetup.error = kHAPPairingError_Unavailable;
return kHAPError_None;
}
// Check if the accessory has received more than 100 unsuccessful authentication attempts.
bool found;
size_t numBytes;
uint8_t numAuthAttemptsBytes[sizeof(uint8_t)];
err = HAPPlatformKeyValueStoreGet(
server->platform.keyValueStore,
kHAPKeyValueStoreDomain_Configuration,
kHAPKeyValueStoreKey_Configuration_NumUnsuccessfulAuthAttempts,
numAuthAttemptsBytes,
sizeof numAuthAttemptsBytes,
&numBytes,
&found);
if (err) {
HAPAssert(err == kHAPError_Unknown);
return err;
}
if (!found) {
HAPRawBufferZero(numAuthAttemptsBytes, sizeof numAuthAttemptsBytes);
} else if (numBytes != sizeof numAuthAttemptsBytes) {
HAPLog(&logObject, "Invalid authentication attempts counter.");
return kHAPError_Unknown;
}
uint8_t numAuthAttempts = numAuthAttemptsBytes[0];
if (numAuthAttempts >= 100) {
HAPLog(&logObject, "Pair Setup M2: Accessory has received more than 100 unsuccessful authentication attempts.");
session->state.pairSetup.error = kHAPPairingError_MaxTries;
return kHAPError_None;
}
// Check if the accessory is currently performing a Pair Setup procedure with a different controller.
if (server->pairSetup.sessionThatIsCurrentlyPairing != session_) {
HAPLog(&logObject,
"Pair Setup M2: Accessory is performing a Pair Setup procedure with a different controller.");
session->state.pairSetup.error = kHAPPairingError_Busy;
return kHAPError_None;
}
// Get pairing flags.
uint32_t otherFlags = 0;
bool isTransient = false;
bool isSplit = false;
if (server->pairSetup.flagsPresent) {
uint32_t flags = server->pairSetup.flags;
if (flags & kHAPPairingFlag_Transient) {
if (session->state.pairSetup.method == kHAPPairingMethod_PairSetupWithAuth) {
HAPLog(&logObject,
"Pair Setup M2: Ignoring %s because Pair Setup with Auth was requested.",
"kPairingFlag_Transient");
} else {
HAPAssert(session->state.pairSetup.method == kHAPPairingMethod_PairSetup);
isTransient = true;
}
flags &= ~(uint32_t) kHAPPairingFlag_Transient;
}
if (flags & kHAPPairingFlag_Split) {
if (session->state.pairSetup.method == kHAPPairingMethod_PairSetupWithAuth) {
HAPLog(&logObject,
"Pair Setup M2: Ignoring %s because Pair Setup with Auth was requested.",
"kPairingFlag_Split");
} else {
HAPAssert(session->state.pairSetup.method == kHAPPairingMethod_PairSetup);
isSplit = true;
}
flags &= ~(uint32_t) kHAPPairingFlag_Split;
}
if (flags) {
HAPLog(&logObject, "Pair Setup M2: Ignoring unrecognized kTLVType_Flags: 0x%8lX.", (unsigned long) flags);
}
}
HAPLogDebug(
&logObject,
"Pair Setup M2: Processing using %s = %s / %s = %s.",
"kPairingFlag_Transient",
isTransient ? "true" : "false",
"kPairingFlag_Split",
isSplit ? "true" : "false");
// Recover setup info if requested.
HAPSetupInfo* _Nullable setupInfo =
HAPAccessorySetupInfoGetSetupInfo(server_, /* restorePrevious: */ !isTransient && isSplit);
if (!setupInfo) {
HAPLog(&logObject, "Pair Setup M2: kPairingFlag_Split requested but no previous setup info found.");
session->state.pairSetup.error = kHAPPairingError_Authentication;
return kHAPError_None;
}
HAPLogBufferDebug(&logObject, setupInfo->salt, sizeof setupInfo->salt, "Pair Setup M2: salt.");
HAPLogSensitiveBufferDebug(&logObject, setupInfo->verifier, sizeof setupInfo->verifier, "Pair Setup M2: verifier.");
// Generate private key b.
HAPPlatformRandomNumberFill(server->pairSetup.b, sizeof server->pairSetup.b);
HAPLogSensitiveBufferDebug(&logObject, server->pairSetup.b, sizeof server->pairSetup.b, "Pair Setup M2: b.");
// Derive public key B.
HAP_srp_public_key(server->pairSetup.B, server->pairSetup.b, setupInfo->verifier);
HAPLogBufferDebug(&logObject, server->pairSetup.B, sizeof server->pairSetup.B, "Pair Setup M2: B.");
// kTLVType_State.
err = HAPTLVWriterAppend(
responseWriter,
&(const HAPTLV) { .type = kHAPPairingTLVType_State,
.value = { .bytes = &session->state.pairSetup.state, .numBytes = 1 } });
if (err) {
HAPAssert(err == kHAPError_OutOfResources);
return err;
}
// kTLVType_PublicKey.
// Skip leading zeros.
size_t size = SRP_PUBLIC_KEY_BYTES;
uint8_t* B = server->pairSetup.B;
while (size && !(*B)) {
B++;
size--;
}
err = HAPTLVWriterAppend(
responseWriter,
&(const HAPTLV) { .type = kHAPPairingTLVType_PublicKey, .value = { .bytes = B, .numBytes = size } });
if (err) {
HAPAssert(err == kHAPError_OutOfResources);
return err;
}
// kTLVType_Salt.
err = HAPTLVWriterAppend(
responseWriter,
&(const HAPTLV) { .type = kHAPPairingTLVType_Salt,
.value = { .bytes = setupInfo->salt, .numBytes = sizeof setupInfo->salt } });
if (err) {
HAPAssert(err == kHAPError_OutOfResources);
return err;
}
// kTLVType_Flags.
uint32_t flags = otherFlags;
if (isTransient && isSplit) {
flags |= kHAPPairingFlag_Transient | kHAPPairingFlag_Split;
} else if (isSplit) {
flags |= kHAPPairingFlag_Split;
}
if (flags) {
uint8_t flagsBytes[] = { HAPExpandLittleUInt32(flags) };
err = HAPTLVWriterAppend(
responseWriter,
&(const HAPTLV) { .type = kHAPPairingTLVType_Flags,
.value = { .bytes = flagsBytes, .numBytes = HAPPairingGetNumBytes(flags) } });
if (err) {
HAPAssert(err == kHAPError_OutOfResources);
return err;
}
}
return kHAPError_None;
}
/**
* Pair Setup M3 TLVs.
*/
typedef struct {
HAPTLV* stateTLV; /**< kTLVType_State. */
HAPTLV* publicKeyTLV; /**< kTLVType_PublicKey. */
HAPTLV* proofTLV; /**< kTLVType_Proof. */
} HAPPairingPairSetupM3TLVs;
/**
* Processes Pair Setup M3.
*
* @param server_ Accessory server.
* @param session_ The session over which the request has been received.
* @param tlvs TLVs.
*
* @return kHAPError_None If successful.
* @return kHAPError_InvalidData If the controller sent a malformed request.
*/
HAP_RESULT_USE_CHECK
static HAPError HAPPairingPairSetupProcessM3(
HAPAccessoryServerRef* server_,
HAPSessionRef* session_,
const HAPPairingPairSetupM3TLVs* tlvs) {
HAPPrecondition(server_);
HAPAccessoryServer* server = (HAPAccessoryServer*) server_;
HAPPrecondition(server->pairSetup.sessionThatIsCurrentlyPairing == session_);
HAPPrecondition(session_);
HAPSession* session = (HAPSession*) session_;
HAPPrecondition(session->state.pairSetup.state == 3);
HAPPrecondition(!session->state.pairSetup.error);
HAPPrecondition(tlvs);
HAPPrecondition(tlvs->stateTLV);
HAPPrecondition(tlvs->stateTLV->type == kHAPPairingTLVType_State);
HAPPrecondition(tlvs->publicKeyTLV);
HAPPrecondition(tlvs->publicKeyTLV->type == kHAPPairingTLVType_PublicKey);
HAPPrecondition(tlvs->proofTLV);
HAPPrecondition(tlvs->proofTLV->type == kHAPPairingTLVType_Proof);
// See HomeKit Accessory Protocol Specification R14
// Section 5.6.3 M3: iOS Device -> Accessory -- `SRP Verify Request'
HAPLogDebug(&logObject, "Pair Setup M3: SRP Verify Request.");
// Validate kTLVType_State.
if (!tlvs->stateTLV->value.bytes) {
HAPLog(&logObject, "Pair Setup M3: kTLVType_State missing.");
return kHAPError_InvalidData;
}
if (tlvs->stateTLV->value.numBytes != 1) {
HAPLog(&logObject, "Pair Setup M3: kTLVType_State has invalid length (%zu).", tlvs->stateTLV->value.numBytes);
return kHAPError_InvalidData;
}
uint8_t state = ((const uint8_t*) tlvs->stateTLV->value.bytes)[0];
if (state != 3) {
HAPLog(&logObject, "Pair Setup M3: kTLVType_State invalid: %u.", state);
return kHAPError_InvalidData;
}
// Validate kTLVType_PublicKey.
if (!tlvs->publicKeyTLV->value.bytes) {
HAPLog(&logObject, "Pair Setup M3: kTLVType_PublicKey missing.");
return kHAPError_InvalidData;
}
if (tlvs->publicKeyTLV->value.numBytes > sizeof server->pairSetup.A) {
HAPLog(&logObject,
"Pair Setup M3: kTLVType_PublicKey has invalid length (%zu).",
tlvs->publicKeyTLV->value.numBytes);
return kHAPError_InvalidData;
}
// Validate kTLVType_Proof.
if (!tlvs->proofTLV->value.bytes) {
HAPLog(&logObject, "Pair Setup M3: kTLVType_Proof missing.");
return kHAPError_InvalidData;
}
if (tlvs->proofTLV->value.numBytes != sizeof server->pairSetup.M1) {
HAPLog(&logObject, "Pair Setup M3: kTLVType_Proof has invalid length (%zu).", tlvs->proofTLV->value.numBytes);
return kHAPError_InvalidData;
}
// Copy public key to A and zero-extend big-endian.
void* A = &server->pairSetup.A[sizeof server->pairSetup.A - tlvs->publicKeyTLV->value.numBytes];
HAPRawBufferZero(server->pairSetup.A, sizeof server->pairSetup.A - tlvs->publicKeyTLV->value.numBytes);
HAPRawBufferCopyBytes(A, HAPNonnullVoid(tlvs->publicKeyTLV->value.bytes), tlvs->publicKeyTLV->value.numBytes);
HAPLogBufferDebug(&logObject, server->pairSetup.A, sizeof server->pairSetup.A, "Pair Setup M3: A.");
// Copy proof.
HAPRawBufferCopyBytes(
server->pairSetup.M1, HAPNonnullVoid(tlvs->proofTLV->value.bytes), tlvs->proofTLV->value.numBytes);
HAPLogBufferDebug(&logObject, server->pairSetup.M1, sizeof server->pairSetup.M1, "Pair Setup M3: M1.");
return kHAPError_None;
}
/**
* Processes Pair Setup M4.
*
* @param server_ Accessory server.
* @param session_ The session over which the response will be sent.
* @param responseWriter TLV writer for serializing the response.
*
* @return kHAPError_None If successful.
* @return kHAPError_Unknown If communication with Apple Auth Coprocessor or persistent store access failed.
* @return kHAPError_InvalidState If a different request is expected in the current state.
* @return kHAPError_OutOfResources If response writer does not have enough capacity.
*/
HAP_RESULT_USE_CHECK
static HAPError HAPPairingPairSetupGetM4(
HAPAccessoryServerRef* server_,
HAPSessionRef* session_,
HAPTLVWriterRef* responseWriter) {
HAPPrecondition(server_);
HAPAccessoryServer* server = (HAPAccessoryServer*) server_;
HAPPrecondition(server->pairSetup.sessionThatIsCurrentlyPairing == session_);
HAPPrecondition(session_);
HAPSession* session = (HAPSession*) session_;
HAPPrecondition(session->state.pairSetup.state == 4);
HAPPrecondition(!session->state.pairSetup.error);
HAPPrecondition(responseWriter);
HAPError err;
// See HomeKit Accessory Protocol Specification R14
// Section 5.6.4 M4: Accessory -> iOS Device -- `SRP Verify Response'
HAPLogDebug(&logObject, "Pair Setup M4: SRP Verify Response.");
// Compute SRP shared secret key.
{
void* bytes;
size_t maxBytes;
HAPTLVWriterGetScratchBytes(responseWriter, &bytes, &maxBytes);
void* u = HAPTLVScratchBufferAlloc(&bytes, &maxBytes, SRP_SCRAMBLING_PARAMETER_BYTES);
void* S = HAPTLVScratchBufferAlloc(&bytes, &maxBytes, SRP_PREMASTER_SECRET_BYTES);
void* M1 = HAPTLVScratchBufferAlloc(&bytes, &maxBytes, SRP_PROOF_BYTES);
if (!u || !S || !M1) {
HAPLog(&logObject, "Pair Setup M4: Not enough memory to allocate u / S / M1.");
return kHAPError_OutOfResources;
}
HAP_srp_scrambling_parameter(u, server->pairSetup.A, server->pairSetup.B);
HAPLogSensitiveBufferDebug(&logObject, u, SRP_SCRAMBLING_PARAMETER_BYTES, "Pair Setup M4: u.");
bool restorePrevious = false;
if (server->pairSetup.flagsPresent) {
restorePrevious = !(server->pairSetup.flags & kHAPPairingFlag_Transient) &&
server->pairSetup.flags & kHAPPairingFlag_Split;
}
HAPSetupInfo* _Nullable setupInfo = HAPAccessorySetupInfoGetSetupInfo(server_, restorePrevious);
HAPAssert(setupInfo);
int e = HAP_srp_premaster_secret(S, server->pairSetup.A, server->pairSetup.b, u, setupInfo->verifier);
if (e) {
HAPAssert(e == 1);
// Illegal key A.
HAPLog(&logObject, "Pair Setup M4: Illegal key A.");
session->state.pairSetup.error = kHAPPairingError_Authentication;
return kHAPError_None;
}
HAPLogSensitiveBufferDebug(&logObject, S, SRP_PREMASTER_SECRET_BYTES, "Pair Setup M4: S.");
HAP_srp_session_key(server->pairSetup.K, S);
HAPLogSensitiveBufferDebug(&logObject, server->pairSetup.K, sizeof server->pairSetup.K, "Pair Setup M4: K.");
static const uint8_t userName[] = "Pair-Setup";
HAP_srp_proof_m1(
M1,
userName,
sizeof userName - 1,
setupInfo->salt,
server->pairSetup.A,
server->pairSetup.B,
server->pairSetup.K);
HAPLogSensitiveBufferDebug(&logObject, M1, SRP_PROOF_BYTES, "Pair Setup M4: M1");
// Verify the controller's SRP proof.
if (!HAPRawBufferAreEqual(M1, server->pairSetup.M1, SRP_PROOF_BYTES)) {
bool found;
size_t numBytes;
uint8_t numAuthAttemptsBytes[sizeof(uint8_t)];
err = HAPPlatformKeyValueStoreGet(
server->platform.keyValueStore,
kHAPKeyValueStoreDomain_Configuration,
kHAPKeyValueStoreKey_Configuration_NumUnsuccessfulAuthAttempts,
numAuthAttemptsBytes,
sizeof numAuthAttemptsBytes,
&numBytes,
&found);
if (err) {
HAPAssert(err == kHAPError_Unknown);
return err;
}
if (!found) {
HAPRawBufferZero(numAuthAttemptsBytes, sizeof numAuthAttemptsBytes);
} else if (numBytes != sizeof numAuthAttemptsBytes) {
HAPLog(&logObject, "Invalid authentication attempts counter.");
return kHAPError_Unknown;
}
uint8_t numAuthAttempts = numAuthAttemptsBytes[0];
HAPAssert(numAuthAttempts < UINT8_MAX);
numAuthAttempts++;
numAuthAttemptsBytes[0] = numAuthAttempts;
err = HAPPlatformKeyValueStoreSet(
server->platform.keyValueStore,
kHAPKeyValueStoreDomain_Configuration,
kHAPKeyValueStoreKey_Configuration_NumUnsuccessfulAuthAttempts,
numAuthAttemptsBytes,
sizeof numAuthAttemptsBytes);
if (err) {
HAPAssert(err == kHAPError_Unknown);
return err;
}
HAPLog(&logObject,
"Pair Setup M4: Incorrect setup code. Unsuccessful authentication attempts = %u / 100.",
numAuthAttempts);
session->state.pairSetup.error = kHAPPairingError_Authentication;
return kHAPError_None;
}
// Reset authentication attempts counter.
err = HAPPlatformKeyValueStoreRemove(
server->platform.keyValueStore,
kHAPKeyValueStoreDomain_Configuration,
kHAPKeyValueStoreKey_Configuration_NumUnsuccessfulAuthAttempts);
if (err) {
HAPAssert(err == kHAPError_Unknown);
return err;
}
// Generate accessory-side SRP proof.
HAP_srp_proof_m2(server->pairSetup.M2, server->pairSetup.A, M1, server->pairSetup.K);
HAPLogBufferDebug(&logObject, server->pairSetup.M2, sizeof server->pairSetup.M2, "Pair Setup M4: M2.");
// Derive the symmetric session encryption key.
static const uint8_t salt[] = "Pair-Setup-Encrypt-Salt";
static const uint8_t info[] = "Pair-Setup-Encrypt-Info";
HAP_hkdf_sha512(
server->pairSetup.SessionKey,
sizeof server->pairSetup.SessionKey,
server->pairSetup.K,
sizeof server->pairSetup.K,
salt,
sizeof salt - 1,
info,
sizeof info - 1);
HAPLogSensitiveBufferDebug(
&logObject,
server->pairSetup.SessionKey,
sizeof server->pairSetup.SessionKey,
"Pair Setup M4: SessionKey");
}
// kTLVType_State.
err = HAPTLVWriterAppend(
responseWriter,
&(const HAPTLV) { .type = kHAPPairingTLVType_State,
.value = { .bytes = &session->state.pairSetup.state, .numBytes = 1 } });
if (err) {
HAPAssert(err == kHAPError_OutOfResources);
return err;
}
// kTLVType_Proof.
err = HAPTLVWriterAppend(
responseWriter,
&(const HAPTLV) { .type = kHAPPairingTLVType_Proof,
.value = { .bytes = server->pairSetup.M2, .numBytes = sizeof server->pairSetup.M2 } });
if (err) {
HAPAssert(err == kHAPError_OutOfResources);
return err;
}
// kTLVType_EncryptedData.
if (session->state.pairSetup.method == kHAPPairingMethod_PairSetupWithAuth) {
// Construct sub-TLV writer.
HAPTLVWriterRef subWriter;
{
void* bytes;
size_t maxBytes;
HAPTLVWriterGetScratchBytes(responseWriter, &bytes, &maxBytes);
if (maxBytes < CHACHA20_POLY1305_TAG_BYTES) {
HAPLog(&logObject, "Pair Setup M4: Not enough memory for kTLVType_EncryptedData auth tag.");
return kHAPError_OutOfResources;
}
maxBytes -= CHACHA20_POLY1305_TAG_BYTES;
HAPTLVWriterCreate(&subWriter, bytes, maxBytes);
}
if (session->state.pairSetup.method == kHAPPairingMethod_PairSetupWithAuth) {
HAPMFiAuth mfiAuth;
{
if (!server->platform.authentication.mfiHWAuth || !HAPAccessoryServerSupportsMFiHWAuth(server_)) {
HAPLog(&logObject, "Pair Setup M4: Apple Authentication Coprocessor is not available.");
return kHAPError_InvalidState;
}
HAPLogInfo(&logObject, "Using Apple Authentication Coprocessor.");
mfiAuth.copyCertificate = HAPMFiHWAuthCopyCertificate;
mfiAuth.createSignature = HAPMFiHWAuthCreateSignature;
}
// kTLVType_Signature.
{
void* bytes;
size_t maxBytes;
HAPTLVWriterGetScratchBytes(&subWriter, &bytes, &maxBytes);
const size_t numChallengeBytes = 32;
void* challengeBytes = HAPTLVScratchBufferAlloc(&bytes, &maxBytes, numChallengeBytes);
const size_t maxMFiProofBytes = maxBytes;
void* mfiProofBytes = HAPTLVScratchBufferAllocUnaligned(&bytes, &maxBytes, maxMFiProofBytes);
if (!challengeBytes || !mfiProofBytes) {
HAPLog(&logObject, "Pair Setup M4: Not enough memory to allocate MFiChallenge / MFi Proof.");
return kHAPError_OutOfResources;
}
// Generate MFi challenge.
static const uint8_t salt[] = "MFi-Pair-Setup-Salt";
static const uint8_t info[] = "MFi-Pair-Setup-Info";
HAP_hkdf_sha512(
challengeBytes,
numChallengeBytes,
server->pairSetup.K,
sizeof server->pairSetup.K,
salt,
sizeof salt - 1,
info,
sizeof info - 1);
HAPLogSensitiveBufferDebug(
&logObject, challengeBytes, numChallengeBytes, "Pair Setup M4: MFiChallenge.");
// Generate the MFi proof.
size_t numMFiProofBytes;
err = mfiAuth.createSignature(
server_, challengeBytes, numChallengeBytes, mfiProofBytes, maxMFiProofBytes, &numMFiProofBytes);
if (err) {
HAPAssert(err == kHAPError_Unknown);
return err;
}
HAPLogSensitiveBufferDebug(
&logObject, mfiProofBytes, numMFiProofBytes, "Pair Setup M4: kTLVType_Signature.");
// kTLVType_Signature.
err = HAPTLVWriterAppend(
&subWriter,
&(const HAPTLV) { .type = kHAPPairingTLVType_Signature,
.value = { .bytes = mfiProofBytes, .numBytes = numMFiProofBytes } });
if (err) {
HAPAssert(err == kHAPError_OutOfResources);
return err;
}
}
// kTLVType_Certificate.
{
void* bytes;
size_t maxBytes;
HAPTLVWriterGetScratchBytes(&subWriter, &bytes, &maxBytes);
const size_t maxCertificateBytes = maxBytes;
void* certificateBytes = HAPTLVScratchBufferAllocUnaligned(&bytes, &maxBytes, maxCertificateBytes);
if (!certificateBytes) {
HAPLog(&logObject, "Pair Setup M4: Not enough memory to allocate Accessory Certificate.");
return kHAPError_OutOfResources;
}
// Read the Accessory Certificate.
size_t numCertificateBytes;
err = mfiAuth.copyCertificate(server_, certificateBytes, maxCertificateBytes, &numCertificateBytes);
if (err) {
HAPAssert(err == kHAPError_Unknown);
return err;
}
HAPLogSensitiveBufferDebug(
&logObject, certificateBytes, numCertificateBytes, "Pair Setup M4: kTLVType_Certificate.");
// kTLVType_Certificate.
err = HAPTLVWriterAppend(
&subWriter,
&(const HAPTLV) { .type = kHAPPairingTLVType_Certificate,
.value = { .bytes = certificateBytes, .numBytes = numCertificateBytes } });
if (err) {
HAPAssert(err == kHAPError_OutOfResources);
return err;
}
}
}
// Encrypt the sub-TLV.
void* bytes;
size_t numBytes;
HAPTLVWriterGetBuffer(&subWriter, &bytes, &numBytes);
static const uint8_t nonce[] = "PS-Msg04";
HAP_chacha20_poly1305_encrypt(
&((uint8_t*) bytes)[numBytes],
bytes,
bytes,
numBytes,
nonce,
sizeof nonce - 1,
server->pairSetup.SessionKey);
numBytes += CHACHA20_POLY1305_TAG_BYTES;
HAPLogBufferDebug(&logObject, bytes, numBytes, "Pair Setup M4: kTLVType_EncryptedData.");
// kTLVType_EncryptedData.
err = HAPTLVWriterAppend(
responseWriter,
&(const HAPTLV) { .type = kHAPPairingTLVType_EncryptedData,
.value = { .bytes = bytes, .numBytes = numBytes } });
if (err) {
HAPAssert(err == kHAPError_OutOfResources);
return err;
}
}
if (session->state.pairSetup.method == kHAPPairingMethod_PairSetup && server->pairSetup.flagsPresent &&
server->pairSetup.flags & kHAPPairingFlag_Transient) {
// Initialize HAP session.
HAPRawBufferZero(&session->hap, sizeof session->hap);
// Derive encryption keys.
static const uint8_t salt[] = "SplitSetupSalt";
{
static const uint8_t info[] = "AccessoryEncrypt-Control";
HAP_hkdf_sha512(
session->hap.accessoryToController.controlChannel.key.bytes,
sizeof session->hap.accessoryToController.controlChannel.key.bytes,
server->pairSetup.K,
sizeof server->pairSetup.K,
salt,
sizeof salt - 1,
info,
sizeof info - 1);
HAPLogSensitiveBufferDebug(
&logObject,
session->hap.accessoryToController.controlChannel.key.bytes,
sizeof session->hap.accessoryToController.controlChannel.key.bytes,
"Transient Pair Setup Start Session: AccessoryEncryptKey");
}
{
static const uint8_t info[] = "ControllerEncrypt-Control";
HAP_hkdf_sha512(
session->hap.controllerToAccessory.controlChannel.key.bytes,
sizeof session->hap.controllerToAccessory.controlChannel.key.bytes,
server->pairSetup.K,
sizeof server->pairSetup.K,
salt,
sizeof salt - 1,
info,
sizeof info - 1);
HAPLogSensitiveBufferDebug(
&logObject,
session->hap.controllerToAccessory.controlChannel.key.bytes,
sizeof session->hap.controllerToAccessory.controlChannel.key.bytes,
"Transient Pair Setup Start Session: ControllerEncryptKey");
}
session->hap.accessoryToController.controlChannel.nonce = 0;
session->hap.controllerToAccessory.controlChannel.nonce = 0;
// Activate session.
session->hap.isTransient = true;
session->hap.active = true;
// Persist setup info for next Pair Setup procedure if requested.
if (server->pairSetup.flags & kHAPPairingFlag_Split) {
server->pairSetup.keepSetupInfo = true;
} else {
HAPLog(&logObject, "Transient Pair Setup procedure requested without kHAPPairingFlag_Split.");
}
// Reset Pair Setup procedure.
HAPPairingPairSetupResetForSession(server_, session_);
HAPLogInfo(&logObject, "Transient Pair Setup procedure completed.");
// Inform application.
if (server->callbacks.handleSessionAccept) {
server->callbacks.handleSessionAccept(server_, session_, server->context);
}
if (server->transports.ble) {
HAPNonnull(server->transports.ble)->peripheralManager.handleSessionAccept(server_, session_);
}
}
return kHAPError_None;
}
/**
* Pair Setup M5 TLVs.
*/
typedef struct {
HAPTLV* stateTLV; /**< kTLVType_State. */
HAPTLV* encryptedDataTLV; /**< kTLVType_EncryptedData. */
} HAPPairingPairSetupM5TLVs;
/**
* Processes Pair Setup M5.
*
* @param server_ Accessory server.
* @param session_ The session over which the request has been received.
* @param scratchBytes Free memory.
* @param numScratchBytes Length of free memory buffer.
* @param tlvs TLVs.
*
* @return kHAPError_None If successful.
* @return kHAPError_InvalidState If a different request is expected in the current state.
* @return kHAPError_InvalidData If the controller sent a malformed request.
* @return kHAPError_OutOfResources If the free memory buffer does not have enough capacity.
*/
HAP_RESULT_USE_CHECK
static HAPError HAPPairingPairSetupProcessM5(
HAPAccessoryServerRef* server_,
HAPSessionRef* session_,
void* scratchBytes,
size_t numScratchBytes,
const HAPPairingPairSetupM5TLVs* tlvs) {
HAPPrecondition(server_);
HAPAccessoryServer* server = (HAPAccessoryServer*) server_;
HAPPrecondition(server->pairSetup.sessionThatIsCurrentlyPairing == session_);
HAPPrecondition(session_);
HAPSession* session = (HAPSession*) session_;
HAPPrecondition(session->state.pairSetup.state == 5);
HAPPrecondition(!session->state.pairSetup.error);
HAPPrecondition(tlvs);
HAPPrecondition(tlvs->stateTLV);
HAPPrecondition(tlvs->stateTLV->type == kHAPPairingTLVType_State);
HAPPrecondition(tlvs->encryptedDataTLV);
HAPPrecondition(tlvs->encryptedDataTLV->type == kHAPPairingTLVType_EncryptedData);
HAPError err;
// See HomeKit Accessory Protocol Specification R14
// Section 5.6.5 M5: iOS Device -> Accessory -- `Exchange Request'
HAPLogDebug(&logObject, "Pair Setup M5: Exchange Request.");
// Validate kTLVType_State.
if (!tlvs->stateTLV->value.bytes) {
HAPLog(&logObject, "Pair Setup M5: kTLVType_State missing.");
return kHAPError_InvalidData;
}
if (tlvs->stateTLV->value.numBytes != 1) {
HAPLog(&logObject, "Pair Setup M5: kTLVType_State has invalid length (%zu).", tlvs->stateTLV->value.numBytes);
return kHAPError_InvalidData;
}
uint8_t state = ((const uint8_t*) tlvs->stateTLV->value.bytes)[0];
if (state != 5) {
HAPLog(&logObject, "Pair Setup M5: kTLVType_State invalid: %u.", state);
return kHAPError_InvalidData;
}
// Validate kTLVType_EncryptedData.
if (!tlvs->encryptedDataTLV->value.bytes) {
HAPLog(&logObject, "Pair Setup M5: kTLVType_EncryptedData missing.");
return kHAPError_InvalidData;
}
if (tlvs->encryptedDataTLV->value.numBytes < CHACHA20_POLY1305_TAG_BYTES) {
HAPLog(&logObject,
"Pair Setup M5: kTLVType_EncryptedData has invalid length (%zu).",
tlvs->encryptedDataTLV->value.numBytes);
return kHAPError_InvalidData;
}
// Verify auth tag and decrypt.
HAPLogBufferDebug(
&logObject,
tlvs->encryptedDataTLV->value.bytes,
tlvs->encryptedDataTLV->value.numBytes,
"Pair Setup M5: kTLVType_EncryptedData.");
void* bytes = (void*) (uintptr_t) tlvs->encryptedDataTLV->value.bytes;
size_t numBytes = tlvs->encryptedDataTLV->value.numBytes - CHACHA20_POLY1305_TAG_BYTES;
static const uint8_t nonce[] = "PS-Msg05";
int e = HAP_chacha20_poly1305_decrypt(
&((uint8_t*) bytes)[numBytes],
bytes,
bytes,
numBytes,
nonce,
sizeof nonce - 1,
server->pairSetup.SessionKey);
if (e) {
HAPAssert(e == -1);
HAPLog(&logObject, "Pair Setup M5: Failed to decrypt kTLVType_EncryptedData.");
session->state.pairSetup.error = kHAPPairingError_Authentication;
return kHAPError_None;
}
HAPLogSensitiveBufferDebug(&logObject, bytes, numBytes, "Pair Setup M5: kTLVType_EncryptedData (decrypted).");
// Parse sub-TLV.
HAPTLV identifierTLV, publicKeyTLV, signatureTLV;
identifierTLV.type = kHAPPairingTLVType_Identifier;
publicKeyTLV.type = kHAPPairingTLVType_PublicKey;
signatureTLV.type = kHAPPairingTLVType_Signature;
{
HAPTLVReaderRef subReader;
HAPTLVReaderCreate(&subReader, bytes, numBytes);
err = HAPTLVReaderGetAll(&subReader, (HAPTLV* const[]) { &identifierTLV, &publicKeyTLV, &signatureTLV, NULL });
if (err) {
HAPAssert(err == kHAPError_InvalidData);
return err;
}
// Validate kTLVType_Identifier.
if (!identifierTLV.value.bytes) {
HAPLog(&logObject, "Pair Setup M5: kTLVType_Identifier missing.");
return kHAPError_InvalidData;
}
if (identifierTLV.value.numBytes > sizeof(HAPPairingID)) {
HAPLog(&logObject,
"Pair Setup M5: kTLVType_Identifier has invalid length (%zu).",
identifierTLV.value.numBytes);
return kHAPError_InvalidData;
}
// Validate kTLVType_PublicKey.
if (!publicKeyTLV.value.bytes) {
HAPLog(&logObject, "Pair Setup M5: kTLVType_PublicKey missing.");
return kHAPError_InvalidData;
}
if (publicKeyTLV.value.numBytes != sizeof(HAPPairingPublicKey)) {
HAPLog(&logObject,
"Pair Setup M5: kTLVType_PublicKey has invalid length (%zu).",
publicKeyTLV.value.numBytes);
return kHAPError_InvalidData;
}
// Validate kTLVType_Signature.
if (!signatureTLV.value.bytes) {
HAPLog(&logObject, "Pair Setup M5: kTLVType_Signature missing.");
return kHAPError_InvalidData;
}
if (signatureTLV.value.numBytes != ED25519_BYTES) {
HAPLog(&logObject,
"Pair Setup M5: kTLVType_Signature has invalid length (%zu).",
signatureTLV.value.numBytes);
return kHAPError_InvalidData;
}
}
const size_t XLength = 32;
void* X = HAPTLVScratchBufferAlloc(&scratchBytes, &numScratchBytes, XLength);
void* pairingID = HAPTLVScratchBufferAllocUnaligned(&scratchBytes, &numScratchBytes, identifierTLV.value.numBytes);
void* ltpk = HAPTLVScratchBufferAllocUnaligned(&scratchBytes, &numScratchBytes, ED25519_PUBLIC_KEY_BYTES);
if (!X || !pairingID || !ltpk) {
HAPLog(&logObject,
"Pair Setup M5: Not enough memory to allocate iOSDeviceX / iOSDevicePairingID / iOSDeviceLTPK.");
return kHAPError_OutOfResources;
}
// Derive iOSDeviceX from the SRP shared secret.
static const uint8_t salt[] = "Pair-Setup-Controller-Sign-Salt";
static const uint8_t info[] = "Pair-Setup-Controller-Sign-Info";
HAP_hkdf_sha512(
X, XLength, server->pairSetup.K, sizeof server->pairSetup.K, salt, sizeof salt - 1, info, sizeof info - 1);
// Construct iOSDeviceInfo: iOSDeviceX, iOSDevicePairingID, iOSDeviceLTPK.
HAPRawBufferCopyBytes(pairingID, HAPNonnullVoid(identifierTLV.value.bytes), identifierTLV.value.numBytes);
HAPRawBufferCopyBytes(ltpk, HAPNonnullVoid(publicKeyTLV.value.bytes), publicKeyTLV.value.numBytes);
// Finalize info.
void* infoBytes = X;
size_t numInfoBytes = XLength + identifierTLV.value.numBytes + ED25519_PUBLIC_KEY_BYTES;
HAPLogSensitiveBufferDebug(&logObject, infoBytes, numInfoBytes, "Pair Setup M5: iOSDeviceInfo.");
// Verify signature.
HAPLogSensitiveBufferDebug(
&logObject, signatureTLV.value.bytes, signatureTLV.value.numBytes, "Pair Setup M5: kTLVType_Signature.");
e = HAP_ed25519_verify(signatureTLV.value.bytes, infoBytes, numInfoBytes, ltpk);
if (e) {
HAPAssert(e == -1);
HAPLog(&logObject, "Pair Setup M5: iOSDeviceInfo signature is incorrect.");
session->state.pairSetup.error = kHAPPairingError_Authentication;
return kHAPError_None;
}
// Persistently save the iOSDevicePairingID and iOSDeviceLTPK as a pairing.
HAPPairing pairing;