src/android/bcc.c - open-dice - Git at Google

 // Copyright 2021 Google LLC
 //
 // Licensed under the Apache License, Version 2.0 (the "License"); you may not
 // use this file except in compliance with the License. You may obtain a copy of
 // the License at
 //
 //     https://www.apache.org/licenses/LICENSE-2.0
 //
 // Unless required by applicable law or agreed to in writing, software
 // distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 // WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 // License for the specific language governing permissions and limitations under
 // the License.

 #include "dice/android/bcc.h"

 #include <string.h>

 #include "dice/cbor_reader.h"
 #include "dice/cbor_writer.h"
 #include "dice/ops/trait/cose.h"
 #include "dice/dice.h"
 #include "dice/ops.h"

 // Completely gratuitous bit twiddling.
 static size_t PopulationCount(uint32_t n) {
   n = n - ((n >> 1) & 0x55555555);
   n = (n & 0x33333333) + ((n >> 2) & 0x33333333);
   return (((n + (n >> 4)) & 0x0F0F0F0F) * 0x01010101) >> 24;
 }

 DiceResult BccFormatConfigDescriptor(const BccConfigValues* input_values,
                                      size_t buffer_size, uint8_t* buffer,
                                      size_t* actual_size) {
   static const int64_t kComponentNameLabel = -70002;
   static const int64_t kComponentVersionLabel = -70003;
   static const int64_t kResettableLabel = -70004;

   // BccConfigDescriptor = {
   //   ? -70002 : tstr,     ; Component name
   //   ? -70003 : int,      ; Component version
   //   ? -70004 : null,     ; Resettable
   // }
   struct CborOut out;
   CborOutInit(buffer, buffer_size, &out);
   CborWriteMap(PopulationCount(input_values->inputs), &out);
   if (input_values->inputs & BCC_INPUT_COMPONENT_NAME &&
       input_values->component_name) {
     CborWriteInt(kComponentNameLabel, &out);
     CborWriteTstr(input_values->component_name, &out);
   }
   if (input_values->inputs & BCC_INPUT_COMPONENT_VERSION) {
     CborWriteInt(kComponentVersionLabel, &out);
     CborWriteUint(input_values->component_version, &out);
   }
   if (input_values->inputs & BCC_INPUT_RESETTABLE) {
     CborWriteInt(kResettableLabel, &out);
     CborWriteNull(&out);
   }
   if (CborOutOverflowed(&out)) {
     return kDiceResultBufferTooSmall;
   }
   *actual_size = CborOutSize(&out);
   return kDiceResultOk;
 }

 DiceResult BccMainFlow(void* context,
                        const uint8_t current_cdi_attest[DICE_CDI_SIZE],
                        const uint8_t current_cdi_seal[DICE_CDI_SIZE],
                        const uint8_t* bcc, size_t bcc_size,
                        const DiceInputValues* input_values, size_t buffer_size,
                        uint8_t* buffer, size_t* actual_size,
                        uint8_t next_cdi_attest[DICE_CDI_SIZE],
                        uint8_t next_cdi_seal[DICE_CDI_SIZE]) {
   DiceResult result;
   enum CborReadResult res;
   struct CborIn in;
   size_t bcc_item_count;

   // The BCC has a more detailed internal structure, but those details aren't
   // relevant to the work of this function.
   //
   // Bcc = [
   //   COSE_Key,         ; Root public key
   //   + COSE_Sign1,     ; Bcc entries
   // ]
   CborInInit(bcc, bcc_size, &in);
   res = CborReadArray(&in, &bcc_item_count);
   if (res != CBOR_READ_RESULT_OK) {
     return kDiceResultInvalidInput;
   }

   if (bcc_item_count < 2 || bcc_item_count == SIZE_MAX) {
     // There should at least be the public key and one entry.
     return kDiceResultInvalidInput;
   }

   // Measure the existing BCC entries.
   size_t bcc_items_offset = CborInOffset(&in);
   for (size_t bcc_pos = 0; bcc_pos < bcc_item_count; ++bcc_pos) {
     res = CborReadSkip(&in);
     if (res != CBOR_READ_RESULT_OK) {
       return kDiceResultInvalidInput;
     }
   }
   size_t bcc_items_size = CborInOffset(&in) - bcc_items_offset;

   // Copy to the new buffer, with space in the BCC for one more entry.
   struct CborOut out;
   CborOutInit(buffer, buffer_size, &out);
   CborWriteArray(bcc_item_count + 1, &out);
   if (CborOutOverflowed(&out) ||
       bcc_items_size > buffer_size - CborOutSize(&out)) {
     return kDiceResultBufferTooSmall;
   }
   memcpy(buffer + CborOutSize(&out), bcc + bcc_items_offset, bcc_items_size);

   size_t certificate_size;
   result =
       DiceMainFlow(context, current_cdi_attest, current_cdi_seal, input_values,
                    buffer_size - (CborOutSize(&out) + bcc_items_size),
                    buffer + CborOutSize(&out) + bcc_items_size,
                    &certificate_size, next_cdi_attest, next_cdi_seal);
   if (result != kDiceResultOk) {
     return result;
   }

   *actual_size = CborOutSize(&out) + bcc_items_size + certificate_size;
   return kDiceResultOk;
 }

 static DiceResult BccMainFlowWithNewBcc(
     void* context, const uint8_t current_cdi_attest[DICE_CDI_SIZE],
     const uint8_t current_cdi_seal[DICE_CDI_SIZE],
     const DiceInputValues* input_values, size_t buffer_size, uint8_t* buffer,
     size_t* bcc_size, uint8_t next_cdi_attest[DICE_CDI_SIZE],
     uint8_t next_cdi_seal[DICE_CDI_SIZE]) {
   uint8_t current_cdi_private_key_seed[DICE_PRIVATE_KEY_SEED_SIZE];
   uint8_t attestation_public_key[DICE_PUBLIC_KEY_SIZE];
   uint8_t attestation_private_key[DICE_PRIVATE_KEY_SIZE];
   // Derive an asymmetric private key seed from the current attestation CDI
   // value.
   DiceResult result = DiceDeriveCdiPrivateKeySeed(context, current_cdi_attest,
                                                   current_cdi_private_key_seed);
   if (result != kDiceResultOk) {
     goto out;
   }
   // Derive attestation key pair.
   result = DiceKeypairFromSeed(context, current_cdi_private_key_seed,
                                attestation_public_key, attestation_private_key);
   if (result != kDiceResultOk) {
     goto out;
   }

   // Consruct the BCC from the attestation public key and the next CDI
   // certificate.
   struct CborOut out;
   CborOutInit(buffer, buffer_size, &out);
   CborWriteArray(2, &out);
   if (CborOutOverflowed(&out)) {
     result = kDiceResultBufferTooSmall;
     goto out;
   }
   size_t encoded_size_used = CborOutSize(&out);
   buffer += encoded_size_used;
   buffer_size -= encoded_size_used;

   size_t encoded_pub_key_size = 0;
   result = DiceCoseEncodePublicKey(context, attestation_public_key, buffer_size,
                                    buffer, &encoded_pub_key_size);
   if (result != kDiceResultOk) {
     goto out;
   }

   buffer += encoded_pub_key_size;
   buffer_size -= encoded_pub_key_size;

   result = DiceMainFlow(context, current_cdi_attest, current_cdi_seal,
                         input_values, buffer_size, buffer, bcc_size,
                         next_cdi_attest, next_cdi_seal);
   if (result != kDiceResultOk) {
     return result;
   }
   *bcc_size += encoded_size_used + encoded_pub_key_size;

 out:
   DiceClearMemory(context, sizeof(current_cdi_private_key_seed),
                   current_cdi_private_key_seed);
   DiceClearMemory(context, sizeof(attestation_private_key),
                   attestation_private_key);

   return result;
 }

 DiceResult BccHandoverMainFlow(void* context, const uint8_t* bcc_handover,
                                size_t bcc_handover_size,
                                const DiceInputValues* input_values,
                                size_t buffer_size, uint8_t* buffer,
                                size_t* actual_size) {
   static const int64_t kCdiAttestLabel = 1;
   static const int64_t kCdiSealLabel = 2;
   static const int64_t kBccLabel = 3;

   DiceResult result;
   const uint8_t* current_cdi_attest;
   const uint8_t* current_cdi_seal;
   const uint8_t* bcc;

   // Extract details from the handover data.
   //
   // BccHandover = {
   //   1 : bstr .size 32,     ; CDI_Attest
   //   2 : bstr .size 32,     ; CDI_Seal
   //   ? 3 : Bcc,             ; Certificate chain
   // }
   struct CborIn in;
   int64_t label;
   size_t item_size;
   CborInInit(bcc_handover, bcc_handover_size, &in);
   if (CborReadMap(&in, &item_size) != CBOR_READ_RESULT_OK || item_size < 2 ||
       // Read the attestation CDI.
       CborReadInt(&in, &label) != CBOR_READ_RESULT_OK ||
       label != kCdiAttestLabel ||
       CborReadBstr(&in, &item_size, &current_cdi_attest) !=
           CBOR_READ_RESULT_OK ||
       item_size != DICE_CDI_SIZE ||
       // Read the sealing CDI.
       CborReadInt(&in, &label) != CBOR_READ_RESULT_OK ||
       label != kCdiSealLabel ||
       CborReadBstr(&in, &item_size, &current_cdi_seal) != CBOR_READ_RESULT_OK ||
       item_size != DICE_CDI_SIZE) {
     return kDiceResultInvalidInput;
   }

   size_t bcc_size = 0;
   // Calculate the BCC size, if the BCC is present in the BccHandover.
   if (CborReadInt(&in, &label) == CBOR_READ_RESULT_OK) {
     if (label != kBccLabel) {
       return kDiceResultInvalidInput;
     }
     size_t bcc_start = CborInOffset(&in);
     bcc = bcc_handover + bcc_start;
     if (CborReadSkip(&in) != CBOR_READ_RESULT_OK) {
       return kDiceResultInvalidInput;
     }
     bcc_size = CborInOffset(&in) - bcc_start;
   }

   // Write the new handover data.
   struct CborOut out;
   CborOutInit(buffer, buffer_size, &out);
   CborWriteMap(/*num_pairs=*/3, &out);
   CborWriteInt(kCdiAttestLabel, &out);
   uint8_t* next_cdi_attest = CborAllocBstr(DICE_CDI_SIZE, &out);
   CborWriteInt(kCdiSealLabel, &out);
   uint8_t* next_cdi_seal = CborAllocBstr(DICE_CDI_SIZE, &out);
   CborWriteInt(kBccLabel, &out);

   if (CborOutOverflowed(&out) || !next_cdi_attest || !next_cdi_seal) {
     return kDiceResultBufferTooSmall;
   }

   if (bcc_size != 0) {
     // If BCC is present in the bcc_handover, append the next certificate to the
     // existing BCC.
     result = BccMainFlow(context, current_cdi_attest, current_cdi_seal, bcc,
                          bcc_size, input_values, buffer_size - CborOutSize(&out),
                          buffer + CborOutSize(&out), &bcc_size, next_cdi_attest,
                          next_cdi_seal);
   } else {
     // If BCC is not present in the bcc_handover, construct BCC from the public key
     // derived from the current CDI attest and the next CDI certificate.
     result = BccMainFlowWithNewBcc(
         context, current_cdi_attest, current_cdi_seal, input_values,
         buffer_size - CborOutSize(&out), buffer + CborOutSize(&out), &bcc_size,
         next_cdi_attest, next_cdi_seal);
   }
   if (result != kDiceResultOk) {
       return result;
   }
   *actual_size = CborOutSize(&out) + bcc_size;
   return kDiceResultOk;
 }
	// Copyright 2021 Google LLC
	//
	// Licensed under the Apache License, Version 2.0 (the "License"); you may not
	// use this file except in compliance with the License. You may obtain a copy of
	// the License at
	//
	// https://www.apache.org/licenses/LICENSE-2.0
	//
	// Unless required by applicable law or agreed to in writing, software
	// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
	// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
	// License for the specific language governing permissions and limitations under
	// the License.

	#include "dice/android/bcc.h"

	#include <string.h>

	#include "dice/cbor_reader.h"
	#include "dice/cbor_writer.h"
	#include "dice/ops/trait/cose.h"
	#include "dice/dice.h"
	#include "dice/ops.h"

	// Completely gratuitous bit twiddling.
	static size_t PopulationCount(uint32_t n) {
	n = n - ((n >> 1) & 0x55555555);
	n = (n & 0x33333333) + ((n >> 2) & 0x33333333);
	return (((n + (n >> 4)) & 0x0F0F0F0F) * 0x01010101) >> 24;
	}

	DiceResult BccFormatConfigDescriptor(const BccConfigValues* input_values,
	size_t buffer_size, uint8_t* buffer,
	size_t* actual_size) {
	static const int64_t kComponentNameLabel = -70002;
	static const int64_t kComponentVersionLabel = -70003;
	static const int64_t kResettableLabel = -70004;

	// BccConfigDescriptor = {
	// ? -70002 : tstr, ; Component name
	// ? -70003 : int, ; Component version
	// ? -70004 : null, ; Resettable
	// }
	struct CborOut out;
	CborOutInit(buffer, buffer_size, &out);
	CborWriteMap(PopulationCount(input_values->inputs), &out);
	if (input_values->inputs & BCC_INPUT_COMPONENT_NAME &&
	input_values->component_name) {
	CborWriteInt(kComponentNameLabel, &out);
	CborWriteTstr(input_values->component_name, &out);
	}
	if (input_values->inputs & BCC_INPUT_COMPONENT_VERSION) {
	CborWriteInt(kComponentVersionLabel, &out);
	CborWriteUint(input_values->component_version, &out);
	}
	if (input_values->inputs & BCC_INPUT_RESETTABLE) {
	CborWriteInt(kResettableLabel, &out);
	CborWriteNull(&out);
	}
	if (CborOutOverflowed(&out)) {
	return kDiceResultBufferTooSmall;
	}
	*actual_size = CborOutSize(&out);
	return kDiceResultOk;
	}

	DiceResult BccMainFlow(void* context,
	const uint8_t current_cdi_attest[DICE_CDI_SIZE],
	const uint8_t current_cdi_seal[DICE_CDI_SIZE],
	const uint8_t* bcc, size_t bcc_size,
	const DiceInputValues* input_values, size_t buffer_size,
	uint8_t* buffer, size_t* actual_size,
	uint8_t next_cdi_attest[DICE_CDI_SIZE],
	uint8_t next_cdi_seal[DICE_CDI_SIZE]) {
	DiceResult result;
	enum CborReadResult res;
	struct CborIn in;
	size_t bcc_item_count;

	// The BCC has a more detailed internal structure, but those details aren't
	// relevant to the work of this function.
	//
	// Bcc = [
	// COSE_Key, ; Root public key
	// + COSE_Sign1, ; Bcc entries
	// ]
	CborInInit(bcc, bcc_size, &in);
	res = CborReadArray(&in, &bcc_item_count);
	if (res != CBOR_READ_RESULT_OK) {
	return kDiceResultInvalidInput;
	}

	if (bcc_item_count < 2 \|\| bcc_item_count == SIZE_MAX) {
	// There should at least be the public key and one entry.
	return kDiceResultInvalidInput;
	}

	// Measure the existing BCC entries.
	size_t bcc_items_offset = CborInOffset(&in);
	for (size_t bcc_pos = 0; bcc_pos < bcc_item_count; ++bcc_pos) {
	res = CborReadSkip(&in);
	if (res != CBOR_READ_RESULT_OK) {
	return kDiceResultInvalidInput;
	}
	}
	size_t bcc_items_size = CborInOffset(&in) - bcc_items_offset;

	// Copy to the new buffer, with space in the BCC for one more entry.
	struct CborOut out;
	CborOutInit(buffer, buffer_size, &out);
	CborWriteArray(bcc_item_count + 1, &out);
	if (CborOutOverflowed(&out) \|\|
	bcc_items_size > buffer_size - CborOutSize(&out)) {
	return kDiceResultBufferTooSmall;
	}
	memcpy(buffer + CborOutSize(&out), bcc + bcc_items_offset, bcc_items_size);

	size_t certificate_size;
	result =
	DiceMainFlow(context, current_cdi_attest, current_cdi_seal, input_values,
	buffer_size - (CborOutSize(&out) + bcc_items_size),
	buffer + CborOutSize(&out) + bcc_items_size,
	&certificate_size, next_cdi_attest, next_cdi_seal);
	if (result != kDiceResultOk) {
	return result;
	}

	*actual_size = CborOutSize(&out) + bcc_items_size + certificate_size;
	return kDiceResultOk;
	}

	static DiceResult BccMainFlowWithNewBcc(
	void* context, const uint8_t current_cdi_attest[DICE_CDI_SIZE],
	const uint8_t current_cdi_seal[DICE_CDI_SIZE],
	const DiceInputValues* input_values, size_t buffer_size, uint8_t* buffer,
	size_t* bcc_size, uint8_t next_cdi_attest[DICE_CDI_SIZE],
	uint8_t next_cdi_seal[DICE_CDI_SIZE]) {
	uint8_t current_cdi_private_key_seed[DICE_PRIVATE_KEY_SEED_SIZE];
	uint8_t attestation_public_key[DICE_PUBLIC_KEY_SIZE];
	uint8_t attestation_private_key[DICE_PRIVATE_KEY_SIZE];
	// Derive an asymmetric private key seed from the current attestation CDI
	// value.
	DiceResult result = DiceDeriveCdiPrivateKeySeed(context, current_cdi_attest,
	current_cdi_private_key_seed);
	if (result != kDiceResultOk) {
	goto out;
	}
	// Derive attestation key pair.
	result = DiceKeypairFromSeed(context, current_cdi_private_key_seed,
	attestation_public_key, attestation_private_key);
	if (result != kDiceResultOk) {
	goto out;
	}

	// Consruct the BCC from the attestation public key and the next CDI
	// certificate.
	struct CborOut out;
	CborOutInit(buffer, buffer_size, &out);
	CborWriteArray(2, &out);
	if (CborOutOverflowed(&out)) {
	result = kDiceResultBufferTooSmall;
	goto out;
	}
	size_t encoded_size_used = CborOutSize(&out);
	buffer += encoded_size_used;
	buffer_size -= encoded_size_used;

	size_t encoded_pub_key_size = 0;
	result = DiceCoseEncodePublicKey(context, attestation_public_key, buffer_size,
	buffer, &encoded_pub_key_size);
	if (result != kDiceResultOk) {
	goto out;
	}

	buffer += encoded_pub_key_size;
	buffer_size -= encoded_pub_key_size;

	result = DiceMainFlow(context, current_cdi_attest, current_cdi_seal,
	input_values, buffer_size, buffer, bcc_size,
	next_cdi_attest, next_cdi_seal);
	if (result != kDiceResultOk) {
	return result;
	}
	*bcc_size += encoded_size_used + encoded_pub_key_size;

	out:
	DiceClearMemory(context, sizeof(current_cdi_private_key_seed),
	current_cdi_private_key_seed);
	DiceClearMemory(context, sizeof(attestation_private_key),
	attestation_private_key);

	return result;
	}

	DiceResult BccHandoverMainFlow(void* context, const uint8_t* bcc_handover,
	size_t bcc_handover_size,
	const DiceInputValues* input_values,
	size_t buffer_size, uint8_t* buffer,
	size_t* actual_size) {
	static const int64_t kCdiAttestLabel = 1;
	static const int64_t kCdiSealLabel = 2;
	static const int64_t kBccLabel = 3;

	DiceResult result;
	const uint8_t* current_cdi_attest;
	const uint8_t* current_cdi_seal;
	const uint8_t* bcc;

	// Extract details from the handover data.
	//
	// BccHandover = {
	// 1 : bstr .size 32, ; CDI_Attest
	// 2 : bstr .size 32, ; CDI_Seal
	// ? 3 : Bcc, ; Certificate chain
	// }
	struct CborIn in;
	int64_t label;
	size_t item_size;
	CborInInit(bcc_handover, bcc_handover_size, &in);
	if (CborReadMap(&in, &item_size) != CBOR_READ_RESULT_OK \|\| item_size < 2 \|\|
	// Read the attestation CDI.
	CborReadInt(&in, &label) != CBOR_READ_RESULT_OK \|\|
	label != kCdiAttestLabel \|\|
	CborReadBstr(&in, &item_size, &current_cdi_attest) !=
	CBOR_READ_RESULT_OK \|\|
	item_size != DICE_CDI_SIZE \|\|
	// Read the sealing CDI.
	CborReadInt(&in, &label) != CBOR_READ_RESULT_OK \|\|
	label != kCdiSealLabel \|\|
	CborReadBstr(&in, &item_size, &current_cdi_seal) != CBOR_READ_RESULT_OK \|\|
	item_size != DICE_CDI_SIZE) {
	return kDiceResultInvalidInput;
	}

	size_t bcc_size = 0;
	// Calculate the BCC size, if the BCC is present in the BccHandover.
	if (CborReadInt(&in, &label) == CBOR_READ_RESULT_OK) {
	if (label != kBccLabel) {
	return kDiceResultInvalidInput;
	}
	size_t bcc_start = CborInOffset(&in);
	bcc = bcc_handover + bcc_start;
	if (CborReadSkip(&in) != CBOR_READ_RESULT_OK) {
	return kDiceResultInvalidInput;
	}
	bcc_size = CborInOffset(&in) - bcc_start;
	}

	// Write the new handover data.
	struct CborOut out;
	CborOutInit(buffer, buffer_size, &out);
	CborWriteMap(/num_pairs=/3, &out);
	CborWriteInt(kCdiAttestLabel, &out);
	uint8_t* next_cdi_attest = CborAllocBstr(DICE_CDI_SIZE, &out);
	CborWriteInt(kCdiSealLabel, &out);
	uint8_t* next_cdi_seal = CborAllocBstr(DICE_CDI_SIZE, &out);
	CborWriteInt(kBccLabel, &out);

	if (CborOutOverflowed(&out) \|\| !next_cdi_attest \|\| !next_cdi_seal) {
	return kDiceResultBufferTooSmall;
	}

	if (bcc_size != 0) {
	// If BCC is present in the bcc_handover, append the next certificate to the
	// existing BCC.
	result = BccMainFlow(context, current_cdi_attest, current_cdi_seal, bcc,
	bcc_size, input_values, buffer_size - CborOutSize(&out),
	buffer + CborOutSize(&out), &bcc_size, next_cdi_attest,
	next_cdi_seal);
	} else {
	// If BCC is not present in the bcc_handover, construct BCC from the public key
	// derived from the current CDI attest and the next CDI certificate.
	result = BccMainFlowWithNewBcc(
	context, current_cdi_attest, current_cdi_seal, input_values,
	buffer_size - CborOutSize(&out), buffer + CborOutSize(&out), &bcc_size,
	next_cdi_attest, next_cdi_seal);
	}
	if (result != kDiceResultOk) {
	return result;
	}
	*actual_size = CborOutSize(&out) + bcc_size;
	return kDiceResultOk;
	}