include/openssl/ecdsa.h

/* ====================================================================
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 *
 * This product includes cryptographic software written by Eric Young
 * (eay@cryptsoft.com).  This product includes software written by Tim
 * Hudson (tjh@cryptsoft.com). */

#ifndef OPENSSL_HEADER_ECDSA_H
#define OPENSSL_HEADER_ECDSA_H

#include <openssl/base.h>

#include <openssl/ec_key.h>

#if defined(__cplusplus)
extern "C" {
#endif


// ECDSA contains functions for signing and verifying with the Digital Signature
// Algorithm over elliptic curves.


// Signing and verifying.

// ECDSA_sign signs |digest_len| bytes from |digest| with |key| and writes the
// resulting signature to |sig|, which must have |ECDSA_size(key)| bytes of
// space. On successful exit, |*sig_len| is set to the actual number of bytes
// written. The |type| argument should be zero. It returns one on success and
// zero otherwise.
OPENSSL_EXPORT int ECDSA_sign(int type, const uint8_t *digest,
                              size_t digest_len, uint8_t *sig,
                              unsigned int *sig_len, const EC_KEY *key);

// ECDSA_verify verifies that |sig_len| bytes from |sig| constitute a valid
// signature by |key| of |digest|. (The |type| argument should be zero.) It
// returns one on success or zero if the signature is invalid or an error
// occurred.
OPENSSL_EXPORT int ECDSA_verify(int type, const uint8_t *digest,
                                size_t digest_len, const uint8_t *sig,
                                size_t sig_len, const EC_KEY *key);

// ECDSA_size returns the maximum size of an ECDSA signature using |key|. It
// returns zero on error.
OPENSSL_EXPORT size_t ECDSA_size(const EC_KEY *key);


// Low-level signing and verification.
//
// Low-level functions handle signatures as |ECDSA_SIG| structures which allow
// the two values in an ECDSA signature to be handled separately.

struct ecdsa_sig_st {
  BIGNUM *r;
  BIGNUM *s;
};

// ECDSA_SIG_new returns a fresh |ECDSA_SIG| structure or NULL on error.
OPENSSL_EXPORT ECDSA_SIG *ECDSA_SIG_new(void);

// ECDSA_SIG_free frees |sig| its member |BIGNUM|s.
OPENSSL_EXPORT void ECDSA_SIG_free(ECDSA_SIG *sig);

// ECDSA_do_sign signs |digest_len| bytes from |digest| with |key| and returns
// the resulting signature structure, or NULL on error.
OPENSSL_EXPORT ECDSA_SIG *ECDSA_do_sign(const uint8_t *digest,
                                        size_t digest_len, const EC_KEY *key);

// ECDSA_do_verify verifies that |sig| constitutes a valid signature by |key|
// of |digest|. It returns one on success or zero if the signature is invalid
// or on error.
OPENSSL_EXPORT int ECDSA_do_verify(const uint8_t *digest, size_t digest_len,
                                   const ECDSA_SIG *sig, const EC_KEY *key);


// Signing with precomputation.
//
// Parts of the ECDSA signature can be independent of the message to be signed
// thus it's possible to precompute them and reduce the signing latency.
//
// TODO(fork): remove support for this as it cannot support safe-randomness.

// ECDSA_sign_setup precomputes parts of an ECDSA signing operation. It sets
// |*kinv| and |*rp| to the precomputed values and uses the |ctx| argument, if
// not NULL. It returns one on success and zero otherwise.
OPENSSL_EXPORT int ECDSA_sign_setup(const EC_KEY *eckey, BN_CTX *ctx,
                                    BIGNUM **kinv, BIGNUM **rp);

// ECDSA_do_sign_ex is the same as |ECDSA_do_sign| but takes precomputed values
// as generated by |ECDSA_sign_setup|.
OPENSSL_EXPORT ECDSA_SIG *ECDSA_do_sign_ex(const uint8_t *digest,
                                           size_t digest_len,
                                           const BIGNUM *kinv, const BIGNUM *rp,
                                           const EC_KEY *eckey);

// ECDSA_sign_ex is the same as |ECDSA_sign| but takes precomputed values as
// generated by |ECDSA_sign_setup|.
OPENSSL_EXPORT int ECDSA_sign_ex(int type, const uint8_t *digest,
                                 size_t digest_len, uint8_t *sig,
                                 unsigned int *sig_len, const BIGNUM *kinv,
                                 const BIGNUM *rp, const EC_KEY *eckey);


// ASN.1 functions.

// ECDSA_SIG_parse parses a DER-encoded ECDSA-Sig-Value structure from |cbs| and
// advances |cbs|. It returns a newly-allocated |ECDSA_SIG| or NULL on error.
OPENSSL_EXPORT ECDSA_SIG *ECDSA_SIG_parse(CBS *cbs);

// ECDSA_SIG_from_bytes parses |in| as a DER-encoded ECDSA-Sig-Value structure.
// It returns a newly-allocated |ECDSA_SIG| structure or NULL on error.
OPENSSL_EXPORT ECDSA_SIG *ECDSA_SIG_from_bytes(const uint8_t *in,
                                               size_t in_len);

// ECDSA_SIG_marshal marshals |sig| as a DER-encoded ECDSA-Sig-Value and appends
// the result to |cbb|. It returns one on success and zero on error.
OPENSSL_EXPORT int ECDSA_SIG_marshal(CBB *cbb, const ECDSA_SIG *sig);

// ECDSA_SIG_to_bytes marshals |sig| as a DER-encoded ECDSA-Sig-Value and, on
// success, sets |*out_bytes| to a newly allocated buffer containing the result
// and returns one. Otherwise, it returns zero. The result should be freed with
// |OPENSSL_free|.
OPENSSL_EXPORT int ECDSA_SIG_to_bytes(uint8_t **out_bytes, size_t *out_len,
                                      const ECDSA_SIG *sig);

// ECDSA_SIG_max_len returns the maximum length of a DER-encoded ECDSA-Sig-Value
// structure for a group whose order is represented in |order_len| bytes, or
// zero on overflow.
OPENSSL_EXPORT size_t ECDSA_SIG_max_len(size_t order_len);


// Deprecated functions.

// d2i_ECDSA_SIG parses an ASN.1, DER-encoded, signature from |len| bytes at
// |*inp|. If |out| is not NULL then, on exit, a pointer to the result is in
// |*out|. Note that, even if |*out| is already non-NULL on entry, it will not
// be written to. Rather, a fresh |ECDSA_SIG| is allocated and the previous one
// is freed. On successful exit, |*inp| is advanced past the DER structure. It
// returns the result or NULL on error.
OPENSSL_EXPORT ECDSA_SIG *d2i_ECDSA_SIG(ECDSA_SIG **out, const uint8_t **inp,
                                        long len);

// i2d_ECDSA_SIG marshals a signature from |sig| to an ASN.1, DER
// structure. If |outp| is not NULL then the result is written to |*outp| and
// |*outp| is advanced just past the output. It returns the number of bytes in
// the result, whether written or not, or a negative value on error.
OPENSSL_EXPORT int i2d_ECDSA_SIG(const ECDSA_SIG *sig, uint8_t **outp);


#if defined(__cplusplus)
}  // extern C

extern "C++" {

namespace bssl {

BORINGSSL_MAKE_DELETER(ECDSA_SIG, ECDSA_SIG_free)

}  // namespace bssl

}  // extern C++

#endif

#define ECDSA_R_BAD_SIGNATURE 100
#define ECDSA_R_MISSING_PARAMETERS 101
#define ECDSA_R_NEED_NEW_SETUP_VALUES 102
#define ECDSA_R_NOT_IMPLEMENTED 103
#define ECDSA_R_RANDOM_NUMBER_GENERATION_FAILED 104
#define ECDSA_R_ENCODE_ERROR 105

#endif  // OPENSSL_HEADER_ECDSA_H