// Copyright 2019 The BoringSSL Authors
//
// 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.

#ifndef OPENSSL_HEADER_CRYPTO_TRUST_TOKEN_INTERNAL_H
#define OPENSSL_HEADER_CRYPTO_TRUST_TOKEN_INTERNAL_H

#include <openssl/base.h>
#include <openssl/ec.h>
#include <openssl/ec_key.h>
#include <openssl/nid.h>

#include "../fipsmodule/ec/internal.h"

#include <openssl/trust_token.h>


BSSL_NAMESPACE_BEGIN

// For the following cryptographic schemes, we use P-384 instead of our usual
// choice of P-256. See Appendix I of
// https://eprint.iacr.org/2020/072/20200324:214215 which describes two attacks
// which may affect smaller curves. In particular, p-1 for P-256 is smooth,
// giving a low complexity for the p-1 attack. P-384's p-1 has a 281-bit prime
// factor,
// 3055465788140352002733946906144561090641249606160407884365391979704929268480326390471.
// This lower-bounds the p-1 attack at O(2^140). The p+1 attack is lower-bounded
// by O(p^(1/3)) or O(2^128), so we do not need to check the smoothness of p+1.


// TRUST_TOKEN_NONCE_SIZE is the size of nonces used as part of the Trust_Token
// protocol.
#define TRUST_TOKEN_NONCE_SIZE 64

typedef struct {
  // TODO(https://crbug.com/boringssl/334): These should store
  // `bssl::EC_PRECOMP` so that `TRUST_TOKEN_finish_issuance` can use
  // `ec_point_mul_scalar_precomp`.
  bssl::EC_AFFINE pub0;
  bssl::EC_AFFINE pub1;
  bssl::EC_AFFINE pubs;
} TRUST_TOKEN_CLIENT_KEY;

typedef struct {
  bssl::EC_SCALAR x0;
  bssl::EC_SCALAR y0;
  bssl::EC_SCALAR x1;
  bssl::EC_SCALAR y1;
  bssl::EC_SCALAR xs;
  bssl::EC_SCALAR ys;
  bssl::EC_AFFINE pub0;
  bssl::EC_PRECOMP pub0_precomp;
  bssl::EC_AFFINE pub1;
  bssl::EC_PRECOMP pub1_precomp;
  bssl::EC_AFFINE pubs;
  bssl::EC_PRECOMP pubs_precomp;
} TRUST_TOKEN_ISSUER_KEY;

// TRUST_TOKEN_PRETOKEN represents the intermediate state a client keeps during
// a Trust_Token issuance operation.
typedef struct pmb_pretoken_st {
  uint8_t salt[TRUST_TOKEN_NONCE_SIZE];
  uint8_t t[TRUST_TOKEN_NONCE_SIZE];
  bssl::EC_SCALAR r;
  bssl::EC_AFFINE Tp;
} TRUST_TOKEN_PRETOKEN;

// TRUST_TOKEN_PRETOKEN_free releases the memory associated with `token`.
OPENSSL_EXPORT void TRUST_TOKEN_PRETOKEN_free(TRUST_TOKEN_PRETOKEN *token);

DEFINE_NAMESPACED_STACK_OF(TRUST_TOKEN_PRETOKEN)


// PMBTokens.
//
// PMBTokens is described in https://eprint.iacr.org/2020/072/20200324:214215
// and provides anonymous tokens with private metadata. We implement the
// construction with validity verification, described in appendix H,
// construction 6.

// The following functions implement the corresponding `TRUST_TOKENS_METHOD`
// functions for `TRUST_TOKENS_experiment_v1`'s PMBTokens construction which
// uses P-384.
int pmbtoken_exp1_generate_key(CBB *out_private, CBB *out_public);
int pmbtoken_exp1_derive_key_from_secret(CBB *out_private, CBB *out_public,
                                         const uint8_t *secret,
                                         size_t secret_len);
int pmbtoken_exp1_client_key_from_bytes(TRUST_TOKEN_CLIENT_KEY *key,
                                        const uint8_t *in, size_t len);
int pmbtoken_exp1_issuer_key_from_bytes(TRUST_TOKEN_ISSUER_KEY *key,
                                        const uint8_t *in, size_t len);
STACK_OF(TRUST_TOKEN_PRETOKEN) *pmbtoken_exp1_blind(CBB *cbb, size_t count,
                                                    int include_message,
                                                    const uint8_t *msg,
                                                    size_t msg_len);
int pmbtoken_exp1_sign(const TRUST_TOKEN_ISSUER_KEY *key, CBB *cbb, CBS *cbs,
                       size_t num_requested, size_t num_to_issue,
                       uint8_t private_metadata);
STACK_OF(TRUST_TOKEN) *pmbtoken_exp1_unblind(
    const TRUST_TOKEN_CLIENT_KEY *key,
    const STACK_OF(TRUST_TOKEN_PRETOKEN) *pretokens, CBS *cbs, size_t count,
    uint32_t key_id);
int pmbtoken_exp1_read(const TRUST_TOKEN_ISSUER_KEY *key,
                       uint8_t out_nonce[TRUST_TOKEN_NONCE_SIZE],
                       uint8_t *out_private_metadata, const uint8_t *token,
                       size_t token_len, int include_message,
                       const uint8_t *msg, size_t msg_len);

// pmbtoken_exp1_get_h_for_testing returns H in uncompressed coordinates. This
// function is used to confirm H was computed as expected.
OPENSSL_EXPORT int pmbtoken_exp1_get_h_for_testing(uint8_t out[97]);

// The following functions implement the corresponding `TRUST_TOKENS_METHOD`
// functions for `TRUST_TOKENS_experiment_v2`'s PMBTokens construction which
// uses P-384.
int pmbtoken_exp2_generate_key(CBB *out_private, CBB *out_public);
int pmbtoken_exp2_derive_key_from_secret(CBB *out_private, CBB *out_public,
                                         const uint8_t *secret,
                                         size_t secret_len);
int pmbtoken_exp2_client_key_from_bytes(TRUST_TOKEN_CLIENT_KEY *key,
                                        const uint8_t *in, size_t len);
int pmbtoken_exp2_issuer_key_from_bytes(TRUST_TOKEN_ISSUER_KEY *key,
                                        const uint8_t *in, size_t len);
STACK_OF(TRUST_TOKEN_PRETOKEN) *pmbtoken_exp2_blind(CBB *cbb, size_t count,
                                                    int include_message,
                                                    const uint8_t *msg,
                                                    size_t msg_len);
int pmbtoken_exp2_sign(const TRUST_TOKEN_ISSUER_KEY *key, CBB *cbb, CBS *cbs,
                       size_t num_requested, size_t num_to_issue,
                       uint8_t private_metadata);
STACK_OF(TRUST_TOKEN) *pmbtoken_exp2_unblind(
    const TRUST_TOKEN_CLIENT_KEY *key,
    const STACK_OF(TRUST_TOKEN_PRETOKEN) *pretokens, CBS *cbs, size_t count,
    uint32_t key_id);
int pmbtoken_exp2_read(const TRUST_TOKEN_ISSUER_KEY *key,
                       uint8_t out_nonce[TRUST_TOKEN_NONCE_SIZE],
                       uint8_t *out_private_metadata, const uint8_t *token,
                       size_t token_len, int include_message,
                       const uint8_t *msg, size_t msg_len);

// pmbtoken_exp2_get_h_for_testing returns H in uncompressed coordinates. This
// function is used to confirm H was computed as expected.
OPENSSL_EXPORT int pmbtoken_exp2_get_h_for_testing(uint8_t out[97]);

// The following functions implement the corresponding `TRUST_TOKENS_METHOD`
// functions for `TRUST_TOKENS_pst_v1`'s PMBTokens construction which uses
// P-384.
int pmbtoken_pst1_generate_key(CBB *out_private, CBB *out_public);
int pmbtoken_pst1_derive_key_from_secret(CBB *out_private, CBB *out_public,
                                         const uint8_t *secret,
                                         size_t secret_len);
int pmbtoken_pst1_client_key_from_bytes(TRUST_TOKEN_CLIENT_KEY *key,
                                        const uint8_t *in, size_t len);
int pmbtoken_pst1_issuer_key_from_bytes(TRUST_TOKEN_ISSUER_KEY *key,
                                        const uint8_t *in, size_t len);
STACK_OF(TRUST_TOKEN_PRETOKEN) *pmbtoken_pst1_blind(CBB *cbb, size_t count,
                                                    int include_message,
                                                    const uint8_t *msg,
                                                    size_t msg_len);
int pmbtoken_pst1_sign(const TRUST_TOKEN_ISSUER_KEY *key, CBB *cbb, CBS *cbs,
                       size_t num_requested, size_t num_to_issue,
                       uint8_t private_metadata);
STACK_OF(TRUST_TOKEN) *pmbtoken_pst1_unblind(
    const TRUST_TOKEN_CLIENT_KEY *key,
    const STACK_OF(TRUST_TOKEN_PRETOKEN) *pretokens, CBS *cbs, size_t count,
    uint32_t key_id);
int pmbtoken_pst1_read(const TRUST_TOKEN_ISSUER_KEY *key,
                       uint8_t out_nonce[TRUST_TOKEN_NONCE_SIZE],
                       uint8_t *out_private_metadata, const uint8_t *token,
                       size_t token_len, int include_message,
                       const uint8_t *msg, size_t msg_len);

// pmbtoken_pst1_get_h_for_testing returns H in uncompressed coordinates. This
// function is used to confirm H was computed as expected.
OPENSSL_EXPORT int pmbtoken_pst1_get_h_for_testing(uint8_t out[97]);


// VOPRF.
//
// VOPRFs are described in https://tools.ietf.org/html/draft-irtf-cfrg-voprf-04
// and provide anonymous tokens. This implementation uses TrustToken DSTs and
// the DLEQ batching primitive from
// https://eprint.iacr.org/2020/072/20200324:214215.
// VOPRF only uses the `pub`' field of the TRUST_TOKEN_CLIENT_KEY and
// `xs`/`pubs` fields of the TRUST_TOKEN_ISSUER_KEY.

// The following functions implement the corresponding `TRUST_TOKENS_METHOD`
// functions for `TRUST_TOKENS_experiment_v2`'s VOPRF construction which uses
// P-384.
int voprf_exp2_generate_key(CBB *out_private, CBB *out_public);
int voprf_exp2_derive_key_from_secret(CBB *out_private, CBB *out_public,
                                      const uint8_t *secret, size_t secret_len);
int voprf_exp2_client_key_from_bytes(TRUST_TOKEN_CLIENT_KEY *key,
                                     const uint8_t *in, size_t len);
int voprf_exp2_issuer_key_from_bytes(TRUST_TOKEN_ISSUER_KEY *key,
                                     const uint8_t *in, size_t len);
STACK_OF(TRUST_TOKEN_PRETOKEN) *voprf_exp2_blind(CBB *cbb, size_t count,
                                                 int include_message,
                                                 const uint8_t *msg,
                                                 size_t msg_len);
int voprf_exp2_sign(const TRUST_TOKEN_ISSUER_KEY *key, CBB *cbb, CBS *cbs,
                    size_t num_requested, size_t num_to_issue,
                    uint8_t private_metadata);
STACK_OF(TRUST_TOKEN) *voprf_exp2_unblind(
    const TRUST_TOKEN_CLIENT_KEY *key,
    const STACK_OF(TRUST_TOKEN_PRETOKEN) *pretokens, CBS *cbs, size_t count,
    uint32_t key_id);
int voprf_exp2_read(const TRUST_TOKEN_ISSUER_KEY *key,
                    uint8_t out_nonce[TRUST_TOKEN_NONCE_SIZE],
                    uint8_t *out_private_metadata, const uint8_t *token,
                    size_t token_len, int include_message, const uint8_t *msg,
                    size_t msg_len);

// The following functions implement the corresponding `TRUST_TOKENS_METHOD`
// functions for `TRUST_TOKENS_pst_v1`'s VOPRF construction which uses P-384.
int voprf_pst1_generate_key(CBB *out_private, CBB *out_public);
int voprf_pst1_derive_key_from_secret(CBB *out_private, CBB *out_public,
                                      const uint8_t *secret, size_t secret_len);
int voprf_pst1_client_key_from_bytes(TRUST_TOKEN_CLIENT_KEY *key,
                                     const uint8_t *in, size_t len);
int voprf_pst1_issuer_key_from_bytes(TRUST_TOKEN_ISSUER_KEY *key,
                                     const uint8_t *in, size_t len);
STACK_OF(TRUST_TOKEN_PRETOKEN) *voprf_pst1_blind(CBB *cbb, size_t count,
                                                 int include_message,
                                                 const uint8_t *msg,
                                                 size_t msg_len);
int voprf_pst1_sign(const TRUST_TOKEN_ISSUER_KEY *key, CBB *cbb, CBS *cbs,
                    size_t num_requested, size_t num_to_issue,
                    uint8_t private_metadata);
OPENSSL_EXPORT int voprf_pst1_sign_with_proof_scalar_for_testing(
    const TRUST_TOKEN_ISSUER_KEY *key, CBB *cbb, CBS *cbs, size_t num_requested,
    size_t num_to_issue, uint8_t private_metadata,
    const uint8_t *proof_scalar_buf, size_t proof_scalar_len);
STACK_OF(TRUST_TOKEN) *voprf_pst1_unblind(
    const TRUST_TOKEN_CLIENT_KEY *key,
    const STACK_OF(TRUST_TOKEN_PRETOKEN) *pretokens, CBS *cbs, size_t count,
    uint32_t key_id);
int voprf_pst1_read(const TRUST_TOKEN_ISSUER_KEY *key,
                    uint8_t out_nonce[TRUST_TOKEN_NONCE_SIZE],
                    uint8_t *out_private_metadata, const uint8_t *token,
                    size_t token_len, int include_message, const uint8_t *msg,
                    size_t msg_len);

using StackOfTrustTokenPretoken = STACK_OF(TRUST_TOKEN_PRETOKEN);

BSSL_NAMESPACE_END

// Trust Tokens internals.

struct trust_token_method_st {
  // generate_key generates a fresh keypair and writes their serialized
  // forms into `out_private` and `out_public`. It returns one on success and
  // zero on failure.
  int (*generate_key)(CBB *out_private, CBB *out_public);

  // derive_key_from_secret deterministically derives a keypair based on
  // `secret` and writes their serialized forms into `out_private` and
  // `out_public`. It returns one on success and zero on failure.
  int (*derive_key_from_secret)(CBB *out_private, CBB *out_public,
                                const uint8_t *secret, size_t secret_len);

  // client_key_from_bytes decodes a client key from `in` and sets `key`
  // to the resulting key. It returns one on success and zero
  // on failure.
  int (*client_key_from_bytes)(bssl::TRUST_TOKEN_CLIENT_KEY *key,
                               const uint8_t *in, size_t len);

  // issuer_key_from_bytes decodes a issuer key from `in` and sets `key`
  // to the resulting key. It returns one on success and zero
  // on failure.
  int (*issuer_key_from_bytes)(bssl::TRUST_TOKEN_ISSUER_KEY *key,
                               const uint8_t *in, size_t len);

  // blind generates a new issuance request for `count` tokens. If
  // `include_message` is set, then `msg` is used to derive the token nonces. On
  // success, it returns a newly-allocated `STACK_OF(TRUST_TOKEN_PRETOKEN)` and
  // writes a request to the issuer to `cbb`. On failure, it returns NULL. The
  // `STACK_OF(TRUST_TOKEN_PRETOKEN)`s should be passed to `pmbtoken_unblind`
  // when the server responds.
  //
  // This function implements the AT.Usr0 operation.
  bssl::StackOfTrustTokenPretoken *(*blind)(CBB *cbb, size_t count,
                                            int include_message,
                                            const uint8_t *msg, size_t msg_len);

  // sign parses a request for `num_requested` tokens from `cbs` and
  // issues `num_to_issue` tokens with `key` and a private metadata value of
  // `private_metadata`. It then writes the response to `cbb`. It returns one on
  // success and zero on failure.
  //
  // This function implements the AT.Sig operation.
  int (*sign)(const bssl::TRUST_TOKEN_ISSUER_KEY *key, CBB *cbb, CBS *cbs,
              size_t num_requested, size_t num_to_issue,
              uint8_t private_metadata);

  // unblind processes an issuance response for `count` tokens from `cbs`
  // and unblinds the signed tokens. `pretokens` are the pre-tokens returned
  // from the corresponding `blind` call. On success, the function returns a
  // newly-allocated `STACK_OF(TRUST_TOKEN)` containing the resulting tokens.
  // Each token's serialization will have `key_id` prepended. Otherwise, it
  // returns NULL.
  //
  // This function implements the AT.Usr1 operation.
  STACK_OF(TRUST_TOKEN) *(*unblind)(
      const bssl::TRUST_TOKEN_CLIENT_KEY *key,
      const bssl::StackOfTrustTokenPretoken *pretokens, CBS *cbs, size_t count,
      uint32_t key_id);

  // read parses a token from `token` and verifies it using `key`. If
  // `include_message` is set, then the nonce is derived from `msg` and the salt
  // in the token. On success, it returns one and stores the nonce and private
  // metadata bit in `out_nonce` and `*out_private_metadata`. Otherwise, it
  // returns zero. Note that, unlike the output of `unblind`, `token` does not
  // have a four-byte key ID prepended.
  int (*read)(const bssl::TRUST_TOKEN_ISSUER_KEY *key,
              uint8_t out_nonce[TRUST_TOKEN_NONCE_SIZE],
              uint8_t *out_private_metadata, const uint8_t *token,
              size_t token_len, int include_message, const uint8_t *msg,
              size_t msg_len);

  // whether the construction supports private metadata.
  int has_private_metadata;

  // max keys that can be configured.
  size_t max_keys;

  // whether the SRR is part of the protocol.
  int has_srr;
};

BSSL_NAMESPACE_BEGIN

// Structure representing a single Trust Token public key with the specified ID.
struct trust_token_client_key_st {
  uint32_t id;
  TRUST_TOKEN_CLIENT_KEY key;
};

// Structure representing a single Trust Token private key with the specified
// ID.
struct trust_token_issuer_key_st {
  uint32_t id;
  TRUST_TOKEN_ISSUER_KEY key;
};

BSSL_NAMESPACE_END

struct trust_token_client_st {
  const TRUST_TOKEN_METHOD *method;

  // max_batchsize is the maximum supported batchsize.
  uint16_t max_batchsize;

  // keys is the set of public keys that are supported by the client for
  // issuance/redemptions.
  // TODO(crbug.com/42290036): Replace this and `num_keys` with an
  // InplaceVector.
  struct bssl::trust_token_client_key_st keys[6];

  // num_keys is the number of keys currently configured.
  size_t num_keys;

  // pretokens is the intermediate state during an active issuance.
  bssl::StackOfTrustTokenPretoken *pretokens;

  // srr_key is the public key used to verify the signature of the SRR.
  EVP_PKEY *srr_key;
};


struct trust_token_issuer_st {
  const TRUST_TOKEN_METHOD *method;

  // max_batchsize is the maximum supported batchsize.
  uint16_t max_batchsize;

  // keys is the set of private keys that are supported by the issuer for
  // issuance/redemptions. The public metadata is an index into this list of
  // keys.
  struct bssl::trust_token_issuer_key_st keys[6];

  // num_keys is the number of keys currently configured.
  size_t num_keys;

  // srr_key is the private key used to sign the SRR.
  EVP_PKEY *srr_key;
};

BSSL_NAMESPACE_BEGIN

BORINGSSL_MAKE_DELETER(TRUST_TOKEN_PRETOKEN, TRUST_TOKEN_PRETOKEN_free)

BSSL_NAMESPACE_END

#endif  // OPENSSL_HEADER_CRYPTO_TRUST_TOKEN_INTERNAL_H