dsa.h

All headers

DSA contains functions for signing and verifying with the Digital Signature Algorithm.

This module is deprecated and retained for legacy reasons only. It is not considered a priority for performance or hardening work. Do not use it in new code. Use Ed25519, ECDSA with P-256, or RSA instead.

  1. Allocation and destruction
  2. DSA_new
  3. DSA_free
  4. DSA_up_ref
  5. Properties
  6. DSA_bits
  7. DSA_get0_pub_key
  8. DSA_get0_priv_key
  9. DSA_get0_p
  10. DSA_get0_q
  11. DSA_get0_g
  12. DSA_get0_key
  13. DSA_get0_pqg
  14. DSA_set0_key
  15. DSA_set0_pqg
  16. Parameter generation
  17. DSA_generate_parameters_ex
  18. DSAparams_dup
  19. Key generation
  20. DSA_generate_key
  21. Signatures
  22. DSA_SIG_st
  23. DSA_SIG_new
  24. DSA_SIG_free
  25. DSA_SIG_get0
  26. DSA_SIG_set0
  27. DSA_do_sign
  28. DSA_do_verify
  29. DSA_do_check_signature
  30. ASN.1 signatures
  31. DSA_sign
  32. DSA_verify
  33. DSA_check_signature
  34. DSA_size
  35. ASN.1 encoding
  36. DSA_SIG_parse
  37. DSA_SIG_marshal
  38. DSA_parse_public_key
  39. DSA_marshal_public_key
  40. DSA_parse_private_key
  41. DSA_marshal_private_key
  42. DSA_parse_parameters
  43. DSA_marshal_parameters
  44. Conversion
  45. DSA_dup_DH
  46. ex_data functions
  47. DSA_get_ex_new_index
  48. DSA_set_ex_data
  49. DSA_get_ex_data
  50. Deprecated functions
  51. d2i_DSA_SIG
  52. i2d_DSA_SIG
  53. d2i_DSAPublicKey
  54. i2d_DSAPublicKey
  55. d2i_DSAPrivateKey
  56. i2d_DSAPrivateKey
  57. d2i_DSAparams
  58. i2d_DSAparams
  59. DSA_generate_parameters

Allocation and destruction.

A DSA object represents a DSA key or group parameters. A given object may be used concurrently on multiple threads by non-mutating functions, provided no other thread is concurrently calling a mutating function. Unless otherwise documented, functions which take a const pointer are non-mutating and functions which take a non-const pointer are mutating.

DSA_new returns a new, empty DSA object or NULL on error.

OPENSSL_EXPORT DSA *DSA_new(void);

DSA_free decrements the reference count of dsa and frees it if the reference count drops to zero.

OPENSSL_EXPORT void DSA_free(DSA *dsa);

DSA_up_ref increments the reference count of dsa and returns one. It does not mutate dsa for thread-safety purposes and may be used concurrently.

OPENSSL_EXPORT int DSA_up_ref(DSA *dsa);

Properties.

DSA_bits returns the size of dsa's group modulus, in bits.

OPENSSL_EXPORT unsigned DSA_bits(const DSA *dsa);

DSA_get0_pub_key returns dsa's public key.

OPENSSL_EXPORT const BIGNUM *DSA_get0_pub_key(const DSA *dsa);

DSA_get0_priv_key returns dsa's private key, or NULL if dsa is a public key.

OPENSSL_EXPORT const BIGNUM *DSA_get0_priv_key(const DSA *dsa);

DSA_get0_p returns dsa's group modulus.

OPENSSL_EXPORT const BIGNUM *DSA_get0_p(const DSA *dsa);

DSA_get0_q returns the size of dsa's subgroup.

OPENSSL_EXPORT const BIGNUM *DSA_get0_q(const DSA *dsa);

DSA_get0_g returns dsa's group generator.

OPENSSL_EXPORT const BIGNUM *DSA_get0_g(const DSA *dsa);

DSA_get0_key sets *out_pub_key and *out_priv_key, if non-NULL, to dsa's public and private key, respectively. If dsa is a public key, the private key will be set to NULL.

OPENSSL_EXPORT void DSA_get0_key(const DSA *dsa, const BIGNUM **out_pub_key,
                                 const BIGNUM **out_priv_key);

DSA_get0_pqg sets *out_p, *out_q, and *out_g, if non-NULL, to dsa's p, q, and g parameters, respectively.

OPENSSL_EXPORT void DSA_get0_pqg(const DSA *dsa, const BIGNUM **out_p,
                                 const BIGNUM **out_q, const BIGNUM **out_g);

DSA_set0_key sets dsa's public and private key to pub_key and priv_key, respectively, if non-NULL. On success, it takes ownership of each argument and returns one. Otherwise, it returns zero.

priv_key may be NULL, but pub_key must either be non-NULL or already configured on dsa.

OPENSSL_EXPORT int DSA_set0_key(DSA *dsa, BIGNUM *pub_key, BIGNUM *priv_key);

DSA_set0_pqg sets dsa's parameters to p, q, and g, if non-NULL, and takes ownership of them. On success, it takes ownership of each argument and returns one. Otherwise, it returns zero.

Each argument must either be non-NULL or already configured on dsa.

OPENSSL_EXPORT int DSA_set0_pqg(DSA *dsa, BIGNUM *p, BIGNUM *q, BIGNUM *g);

Parameter generation.

DSA_generate_parameters_ex generates a set of DSA parameters by following the procedure given in FIPS 186-4, appendix A. (http://nvlpubs.nist.gov/nistpubs/FIPS/NIST.FIPS.186-4.pdf)

The larger prime will have a length of bits (e.g. 2048). The seed value allows others to generate and verify the same parameters and should be random input which is kept for reference. If out_counter or out_h are not NULL then the counter and h value used in the generation are written to them.

The cb argument is passed to BN_generate_prime_ex and is thus called during the generation process in order to indicate progress. See the comments for that function for details. In addition to the calls made by BN_generate_prime_ex, DSA_generate_parameters_ex will call it with event equal to 2 and 3 at different stages of the process.

It returns one on success and zero otherwise.

OPENSSL_EXPORT int DSA_generate_parameters_ex(DSA *dsa, unsigned bits,
                                              const uint8_t *seed,
                                              size_t seed_len, int *out_counter,
                                              unsigned long *out_h,
                                              BN_GENCB *cb);

DSAparams_dup returns a freshly allocated DSA that contains a copy of the parameters from dsa. It returns NULL on error.

OPENSSL_EXPORT DSA *DSAparams_dup(const DSA *dsa);

Key generation.

DSA_generate_key generates a public/private key pair in dsa, which must already have parameters setup. It returns one on success and zero on error.

OPENSSL_EXPORT int DSA_generate_key(DSA *dsa);

Signatures.

DSA_SIG_st (aka DSA_SIG) contains a DSA signature as a pair of integers.

struct DSA_SIG_st {
  BIGNUM *r, *s;
};

DSA_SIG_new returns a freshly allocated, DIG_SIG structure or NULL on error. Both r and s in the signature will be NULL.

OPENSSL_EXPORT DSA_SIG *DSA_SIG_new(void);

DSA_SIG_free frees the contents of sig and then frees sig itself.

OPENSSL_EXPORT void DSA_SIG_free(DSA_SIG *sig);

DSA_SIG_get0 sets *out_r and *out_s, if non-NULL, to the two components of sig.

OPENSSL_EXPORT void DSA_SIG_get0(const DSA_SIG *sig, const BIGNUM **out_r,
                                 const BIGNUM **out_s);

DSA_SIG_set0 sets sig's components to r and s, neither of which may be NULL. On success, it takes ownership of each argument and returns one. Otherwise, it returns zero.

OPENSSL_EXPORT int DSA_SIG_set0(DSA_SIG *sig, BIGNUM *r, BIGNUM *s);

DSA_do_sign returns a signature of the hash in digest by the key in dsa and returns an allocated, DSA_SIG structure, or NULL on error.

OPENSSL_EXPORT DSA_SIG *DSA_do_sign(const uint8_t *digest, size_t digest_len,
                                    const DSA *dsa);

DSA_do_verify verifies that sig is a valid signature, by the public key in dsa, of the hash in digest. It returns one if so, zero if invalid and -1 on error.

WARNING: do not use. This function returns -1 for error, 0 for invalid and 1 for valid. However, this is dangerously different to the usual OpenSSL convention and could be a disaster if a user did |if (DSA_do_verify(...))|. Because of this, DSA_check_signature is a safer version of this.

TODO(fork): deprecate.

OPENSSL_EXPORT int DSA_do_verify(const uint8_t *digest, size_t digest_len,
                                 const DSA_SIG *sig, const DSA *dsa);

DSA_do_check_signature sets *out_valid to zero. Then it verifies that sig is a valid signature, by the public key in dsa of the hash in digest and, if so, it sets *out_valid to one.

It returns one if it was able to verify the signature as valid or invalid, and zero on error.

OPENSSL_EXPORT int DSA_do_check_signature(int *out_valid, const uint8_t *digest,
                                          size_t digest_len, const DSA_SIG *sig,
                                          const DSA *dsa);

ASN.1 signatures.

These functions also perform DSA signature operations, but deal with ASN.1 encoded signatures as opposed to raw BIGNUMs. If you don't know what encoding a DSA signature is in, it's probably ASN.1.

DSA_sign signs digest with the key in dsa and writes the resulting signature, in ASN.1 form, to out_sig and the length of the signature to *out_siglen. There must be, at least, DSA_size(dsa) bytes of space in out_sig. It returns one on success and zero otherwise.

(The type argument is ignored.)

OPENSSL_EXPORT int DSA_sign(int type, const uint8_t *digest, size_t digest_len,
                            uint8_t *out_sig, unsigned int *out_siglen,
                            const DSA *dsa);

DSA_verify verifies that sig is a valid, ASN.1 signature, by the public key in dsa, of the hash in digest. It returns one if so, zero if invalid and -1 on error.

(The type argument is ignored.)

WARNING: do not use. This function returns -1 for error, 0 for invalid and 1 for valid. However, this is dangerously different to the usual OpenSSL convention and could be a disaster if a user did |if (DSA_do_verify(...))|. Because of this, DSA_check_signature is a safer version of this.

TODO(fork): deprecate.

OPENSSL_EXPORT int DSA_verify(int type, const uint8_t *digest,
                              size_t digest_len, const uint8_t *sig,
                              size_t sig_len, const DSA *dsa);

DSA_check_signature sets *out_valid to zero. Then it verifies that sig is a valid, ASN.1 signature, by the public key in dsa, of the hash in digest. If so, it sets *out_valid to one.

It returns one if it was able to verify the signature as valid or invalid, and zero on error.

OPENSSL_EXPORT int DSA_check_signature(int *out_valid, const uint8_t *digest,
                                       size_t digest_len, const uint8_t *sig,
                                       size_t sig_len, const DSA *dsa);

DSA_size returns the size, in bytes, of an ASN.1 encoded, DSA signature generated by dsa. Parameters must already have been setup in dsa.

OPENSSL_EXPORT int DSA_size(const DSA *dsa);

ASN.1 encoding.

DSA_SIG_parse parses a DER-encoded DSA-Sig-Value structure from cbs and advances cbs. It returns a newly-allocated DSA_SIG or NULL on error.

OPENSSL_EXPORT DSA_SIG *DSA_SIG_parse(CBS *cbs);

DSA_SIG_marshal marshals sig as a DER-encoded DSA-Sig-Value and appends the result to cbb. It returns one on success and zero on error.

OPENSSL_EXPORT int DSA_SIG_marshal(CBB *cbb, const DSA_SIG *sig);

DSA_parse_public_key parses a DER-encoded DSA public key from cbs and advances cbs. It returns a newly-allocated DSA or NULL on error.

OPENSSL_EXPORT DSA *DSA_parse_public_key(CBS *cbs);

DSA_marshal_public_key marshals dsa as a DER-encoded DSA public key and appends the result to cbb. It returns one on success and zero on failure.

OPENSSL_EXPORT int DSA_marshal_public_key(CBB *cbb, const DSA *dsa);

DSA_parse_private_key parses a DER-encoded DSA private key from cbs and advances cbs. It returns a newly-allocated DSA or NULL on error.

OPENSSL_EXPORT DSA *DSA_parse_private_key(CBS *cbs);

DSA_marshal_private_key marshals dsa as a DER-encoded DSA private key and appends the result to cbb. It returns one on success and zero on failure.

OPENSSL_EXPORT int DSA_marshal_private_key(CBB *cbb, const DSA *dsa);

DSA_parse_parameters parses a DER-encoded Dss-Parms structure (RFC 3279) from cbs and advances cbs. It returns a newly-allocated DSA or NULL on error.

OPENSSL_EXPORT DSA *DSA_parse_parameters(CBS *cbs);

DSA_marshal_parameters marshals dsa as a DER-encoded Dss-Parms structure (RFC 3279) and appends the result to cbb. It returns one on success and zero on failure.

OPENSSL_EXPORT int DSA_marshal_parameters(CBB *cbb, const DSA *dsa);

Conversion.

DSA_dup_DH returns a DH constructed from the parameters of dsa. This is sometimes needed when Diffie-Hellman parameters are stored in the form of DSA parameters. It returns an allocated DH on success or NULL on error.

OPENSSL_EXPORT DH *DSA_dup_DH(const DSA *dsa);

ex_data functions.

See ex_data.h for details.

OPENSSL_EXPORT int DSA_get_ex_new_index(long argl, void *argp,
                                        CRYPTO_EX_unused *unused,
                                        CRYPTO_EX_dup *dup_unused,
                                        CRYPTO_EX_free *free_func);
OPENSSL_EXPORT int DSA_set_ex_data(DSA *dsa, int idx, void *arg);
OPENSSL_EXPORT void *DSA_get_ex_data(const DSA *dsa, int idx);

Deprecated functions.

d2i_DSA_SIG parses a DER-encoded DSA-Sig-Value structure from len bytes at *inp, as described in d2i_SAMPLE.

Use DSA_SIG_parse instead.

OPENSSL_EXPORT DSA_SIG *d2i_DSA_SIG(DSA_SIG **out_sig, const uint8_t **inp,
                                    long len);

i2d_DSA_SIG marshals in to a DER-encoded DSA-Sig-Value structure, as described in i2d_SAMPLE.

Use DSA_SIG_marshal instead.

OPENSSL_EXPORT int i2d_DSA_SIG(const DSA_SIG *in, uint8_t **outp);

d2i_DSAPublicKey parses a DER-encoded DSA public key from len bytes at *inp, as described in d2i_SAMPLE.

Use DSA_parse_public_key instead.

OPENSSL_EXPORT DSA *d2i_DSAPublicKey(DSA **out, const uint8_t **inp, long len);

i2d_DSAPublicKey marshals in as a DER-encoded DSA public key, as described in i2d_SAMPLE.

Use DSA_marshal_public_key instead.

OPENSSL_EXPORT int i2d_DSAPublicKey(const DSA *in, uint8_t **outp);

d2i_DSAPrivateKey parses a DER-encoded DSA private key from len bytes at *inp, as described in d2i_SAMPLE.

Use DSA_parse_private_key instead.

OPENSSL_EXPORT DSA *d2i_DSAPrivateKey(DSA **out, const uint8_t **inp, long len);

i2d_DSAPrivateKey marshals in as a DER-encoded DSA private key, as described in i2d_SAMPLE.

Use DSA_marshal_private_key instead.

OPENSSL_EXPORT int i2d_DSAPrivateKey(const DSA *in, uint8_t **outp);

d2i_DSAparams parses a DER-encoded Dss-Parms structure (RFC 3279) from len bytes at *inp, as described in d2i_SAMPLE.

Use DSA_parse_parameters instead.

OPENSSL_EXPORT DSA *d2i_DSAparams(DSA **out, const uint8_t **inp, long len);

i2d_DSAparams marshals in's parameters as a DER-encoded Dss-Parms structure (RFC 3279), as described in i2d_SAMPLE.

Use DSA_marshal_parameters instead.

OPENSSL_EXPORT int i2d_DSAparams(const DSA *in, uint8_t **outp);

DSA_generate_parameters is a deprecated version of DSA_generate_parameters_ex that creates and returns a DSA*. Don't use it.

OPENSSL_EXPORT DSA *DSA_generate_parameters(int bits, unsigned char *seed,
                                            int seed_len, int *counter_ret,
                                            unsigned long *h_ret,
                                            void (*callback)(int, int, void *),
                                            void *cb_arg);