Method: OpenSSL::PKey::RSA#sign_pss

Defined in:
ossl_pkey_rsa.c

#sign_pss(digest, data, salt_length: , mgf1_hash: ) ⇒ String

Signs data using the Probabilistic Signature Scheme (RSA-PSS) and returns the calculated signature.

RSAError will be raised if an error occurs.

See #verify_pss for the verification operation.

Parameters

digest

A String containing the message digest algorithm name.

data

A String. The data to be signed.

salt_length

The length in octets of the salt. Two special values are reserved: :digest means the digest length, and :max means the maximum possible length for the combination of the private key and the selected message digest algorithm.

mgf1_hash

The hash algorithm used in MGF1 (the currently supported mask generation function (MGF)).

Example

data = "Sign me!"
pkey = OpenSSL::PKey::RSA.new(2048)
signature = pkey.sign_pss("SHA256", data, salt_length: :max, mgf1_hash: "SHA256")
pub_key = pkey.public_key
puts pub_key.verify_pss("SHA256", signature, data,
                        salt_length: :auto, mgf1_hash: "SHA256") # => true

Returns:

  • (String)
[View source]

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# File 'ossl_pkey_rsa.c', line 580

static VALUE
ossl_rsa_sign_pss(int argc, VALUE *argv, VALUE self)
{
    VALUE digest, data, options, kwargs[2], signature;
    static ID kwargs_ids[2];
    EVP_PKEY *pkey;
    EVP_PKEY_CTX *pkey_ctx;
    const EVP_MD *md, *mgf1md;
    EVP_MD_CTX *md_ctx;
    size_t buf_len;
    int salt_len;

    if (!kwargs_ids[0]) {
	kwargs_ids[0] = rb_intern_const("salt_length");
	kwargs_ids[1] = rb_intern_const("mgf1_hash");
    }
    rb_scan_args(argc, argv, "2:", &digest, &data, &options);
    rb_get_kwargs(options, kwargs_ids, 2, 0, kwargs);
    if (kwargs[0] == ID2SYM(rb_intern("max")))
	salt_len = -2; /* RSA_PSS_SALTLEN_MAX_SIGN */
    else if (kwargs[0] == ID2SYM(rb_intern("digest")))
	salt_len = -1; /* RSA_PSS_SALTLEN_DIGEST */
    else
	salt_len = NUM2INT(kwargs[0]);
    mgf1md = ossl_evp_get_digestbyname(kwargs[1]);

    pkey = GetPrivPKeyPtr(self);
    buf_len = EVP_PKEY_size(pkey);
    md = ossl_evp_get_digestbyname(digest);
    StringValue(data);
    signature = rb_str_new(NULL, (long)buf_len);

    md_ctx = EVP_MD_CTX_new();
    if (!md_ctx)
	goto err;

    if (EVP_DigestSignInit(md_ctx, &pkey_ctx, md, NULL, pkey) != 1)
	goto err;

    if (EVP_PKEY_CTX_set_rsa_padding(pkey_ctx, RSA_PKCS1_PSS_PADDING) != 1)
	goto err;

    if (EVP_PKEY_CTX_set_rsa_pss_saltlen(pkey_ctx, salt_len) != 1)
	goto err;

    if (EVP_PKEY_CTX_set_rsa_mgf1_md(pkey_ctx, mgf1md) != 1)
	goto err;

    if (EVP_DigestSignUpdate(md_ctx, RSTRING_PTR(data), RSTRING_LEN(data)) != 1)
	goto err;

    if (EVP_DigestSignFinal(md_ctx, (unsigned char *)RSTRING_PTR(signature), &buf_len) != 1)
	goto err;

    rb_str_set_len(signature, (long)buf_len);

    EVP_MD_CTX_free(md_ctx);
    return signature;

  err:
    EVP_MD_CTX_free(md_ctx);
    ossl_raise(eRSAError, NULL);
}