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  • openssl/ossl_pkey.c

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OpenSSL::PKey::DSA

DSA, the Digital Signature Algorithm, is specified in NIST's FIPS 186-3. It is an asymmetric public key algorithm that may be used similar to e.g. RSA. Please note that for OpenSSL versions prior to 1.0.0 the digest algorithms OpenSSL::Digest::DSS (equivalent to SHA) or OpenSSL::Digest::DSS1 (equivalent to SHA-1) must be used for issuing signatures with a DSA key using OpenSSL::PKey#sign. Starting with OpenSSL 1.0.0, digest algorithms are no longer restricted, any Digest may be used for signing.

Public Class Methods

generate(size) → dsa click to toggle source

Creates a new DSA instance by generating a private/public key pair from scratch.

Parameters

  • size is an integer representing the desired key size.

 
               static VALUE
ossl_dsa_s_generate(VALUE klass, VALUE size)
{
    DSA *dsa = dsa_generate(NUM2INT(size)); /* err handled by dsa_instance */
    VALUE obj = dsa_instance(klass, dsa);

    if (obj == Qfalse) {
        DSA_free(dsa);
        ossl_raise(eDSAError, NULL);
    }

    return obj;
}
            
new([size | string [, pass]) → dsa click to toggle source

Creates a new DSA instance by reading an existing key from string.

Parameters

  • size is an integer representing the desired key size.

  • string contains a DER or PEM encoded key.

  • pass is a string that contains an optional password.

Examples

DSA.new -> dsa
DSA.new(1024) -> dsa
DSA.new(File.read('dsa.pem')) -> dsa
DSA.new(File.read('dsa.pem'), 'mypassword') -> dsa
 
               static VALUE
ossl_dsa_initialize(int argc, VALUE *argv, VALUE self)
{
    EVP_PKEY *pkey;
    DSA *dsa;
    BIO *in;
    char *passwd = NULL;
    VALUE arg, pass;

    GetPKey(self, pkey);
    if(rb_scan_args(argc, argv, "02", &arg, &pass) == 0) {
        dsa = DSA_new();
    }
    else if (FIXNUM_P(arg)) {
        if (!(dsa = dsa_generate(FIX2INT(arg)))) {
            ossl_raise(eDSAError, NULL);
        }
    }
    else {
        if (!NIL_P(pass)) passwd = StringValuePtr(pass);
        arg = ossl_to_der_if_possible(arg);
        in = ossl_obj2bio(arg);
        dsa = PEM_read_bio_DSAPrivateKey(in, NULL, ossl_pem_passwd_cb, passwd);
        if (!dsa) {
            OSSL_BIO_reset(in);
            dsa = PEM_read_bio_DSA_PUBKEY(in, NULL, NULL, NULL);
        }
        if (!dsa) {
            OSSL_BIO_reset(in);
            dsa = d2i_DSAPrivateKey_bio(in, NULL);
        }
        if (!dsa) {
            OSSL_BIO_reset(in);
            dsa = d2i_DSA_PUBKEY_bio(in, NULL);
        }
        if (!dsa) {
            OSSL_BIO_reset(in);
            dsa = PEM_read_bio_DSAPublicKey(in, NULL, NULL, NULL);
        }
        BIO_free(in);
        if (!dsa) {
            ERR_clear_error();
            ossl_raise(eDSAError, "Neither PUB key nor PRIV key");
        }
    }
    if (!EVP_PKEY_assign_DSA(pkey, dsa)) {
        DSA_free(dsa);
        ossl_raise(eDSAError, NULL);
    }

    return self;
}
            

Public Instance Methods

to_pem([cipher, password]) → aString click to toggle source

Encodes this DSA to its PEM encoding.

Parameters

  • cipher is an OpenSSL::Cipher.

  • password is a string containing your password.

Examples

DSA.to_pem -> aString
DSA.to_pem(cipher, 'mypassword') -> aString
 
               static VALUE
ossl_dsa_export(int argc, VALUE *argv, VALUE self)
{
    EVP_PKEY *pkey;
    BIO *out;
    const EVP_CIPHER *ciph = NULL;
    char *passwd = NULL;
    VALUE cipher, pass, str;

    GetPKeyDSA(self, pkey);
    rb_scan_args(argc, argv, "02", &cipher, &pass);
    if (!NIL_P(cipher)) {
        ciph = GetCipherPtr(cipher);
        if (!NIL_P(pass)) {
            StringValue(pass);
            if (RSTRING_LENINT(pass) < OSSL_MIN_PWD_LEN)
                ossl_raise(eOSSLError, "OpenSSL requires passwords to be at least four characters long");
            passwd = RSTRING_PTR(pass);
        }
    }
    if (!(out = BIO_new(BIO_s_mem()))) {
        ossl_raise(eDSAError, NULL);
    }
    if (DSA_HAS_PRIVATE(pkey->pkey.dsa)) {
        if (!PEM_write_bio_DSAPrivateKey(out, pkey->pkey.dsa, ciph,
                                         NULL, 0, ossl_pem_passwd_cb, passwd)){
            BIO_free(out);
            ossl_raise(eDSAError, NULL);
        }
    } else {
        if (!PEM_write_bio_DSA_PUBKEY(out, pkey->pkey.dsa)) {
            BIO_free(out);
            ossl_raise(eDSAError, NULL);
        }
    }
    str = ossl_membio2str(out);

    return str;
}
            
Also aliased as: to_pem, to_s
params → hash click to toggle source

Stores all parameters of key to the hash INSECURE: PRIVATE INFORMATIONS CAN LEAK OUT!!! Don’t use :-)) (I’s up to you)

 
               static VALUE
ossl_dsa_get_params(VALUE self)
{
    EVP_PKEY *pkey;
    VALUE hash;

    GetPKeyDSA(self, pkey);

    hash = rb_hash_new();

    rb_hash_aset(hash, rb_str_new2("p"), ossl_bn_new(pkey->pkey.dsa->p));
    rb_hash_aset(hash, rb_str_new2("q"), ossl_bn_new(pkey->pkey.dsa->q));
    rb_hash_aset(hash, rb_str_new2("g"), ossl_bn_new(pkey->pkey.dsa->g));
    rb_hash_aset(hash, rb_str_new2("pub_key"), ossl_bn_new(pkey->pkey.dsa->pub_key));
    rb_hash_aset(hash, rb_str_new2("priv_key"), ossl_bn_new(pkey->pkey.dsa->priv_key));

    return hash;
}
            
private? → true | false click to toggle source

Indicates whether this DSA instance has a private key associated with it or not. The private key may be retrieved with DSA#private_key.

 
               static VALUE
ossl_dsa_is_private(VALUE self)
{
    EVP_PKEY *pkey;

    GetPKeyDSA(self, pkey);

    return (DSA_PRIVATE(self, pkey->pkey.dsa)) ? Qtrue : Qfalse;
}
            
public? → true | false click to toggle source

Indicates whether this DSA instance has a public key associated with it or not. The public key may be retrieved with #public_key.

 
               static VALUE
ossl_dsa_is_public(VALUE self)
{
    EVP_PKEY *pkey;

    GetPKeyDSA(self, pkey);

    return (pkey->pkey.dsa->pub_key) ? Qtrue : Qfalse;
}
            
public_key → aDSA click to toggle source

Returns a new DSA instance that carries just the public key information. If the current instance has also private key information, this will no longer be present in the new instance. This feature is helpful for publishing the public key information without leaking any of the private information.

Example

dsa = OpenSSL::PKey::DSA.new(2048) # has public and private information
pub_key = dsa.public_key # has only the public part available
pub_key_der = pub_key.to_der # it's safe to publish this
 
               static VALUE
ossl_dsa_to_public_key(VALUE self)
{
    EVP_PKEY *pkey;
    DSA *dsa;
    VALUE obj;

    GetPKeyDSA(self, pkey);
    /* err check performed by dsa_instance */
    dsa = DSAPublicKey_dup(pkey->pkey.dsa);
    obj = dsa_instance(CLASS_OF(self), dsa);
    if (obj == Qfalse) {
        DSA_free(dsa);
        ossl_raise(eDSAError, NULL);
    }
    return obj;
}
            
syssign(string) → aString click to toggle source

Computes and returns the DSA signature of string, where string is expected to be an already-computed message digest of the original input data. The signature is issued using the private key of this DSA instance.

Parameters

  • string is a message digest of the original input data to be signed

Example

dsa = OpenSSL::PKey::DSA.new(2048)
doc = "Sign me"
digest = OpenSSL::Digest::SHA1.digest(doc)
sig = dsa.syssign(digest)
 
               static VALUE
ossl_dsa_sign(VALUE self, VALUE data)
{
    EVP_PKEY *pkey;
    unsigned int buf_len;
    VALUE str;

    GetPKeyDSA(self, pkey);
    StringValue(data);
    if (!DSA_PRIVATE(self, pkey->pkey.dsa)) {
        ossl_raise(eDSAError, "Private DSA key needed!");
    }
    str = rb_str_new(0, ossl_dsa_buf_size(pkey));
    if (!DSA_sign(0, (unsigned char *)RSTRING_PTR(data), RSTRING_LENINT(data),
                  (unsigned char *)RSTRING_PTR(str),
                  &buf_len, pkey->pkey.dsa)) { /* type is ignored (0) */
        ossl_raise(eDSAError, NULL);
    }
    rb_str_set_len(str, buf_len);

    return str;
}
            
sysverify(digest, sig) → true | false click to toggle source

Verifies whether the signature is valid given the message digest input. It does so by validating sig using the public key of this DSA instance.

Parameters

  • digest is a message digest of the original input data to be signed

  • sig is a DSA signature value

Example

dsa = OpenSSL::PKey::DSA.new(2048)
doc = "Sign me"
digest = OpenSSL::Digest::SHA1.digest(doc)
sig = dsa.syssign(digest)
puts dsa.sysverify(digest, sig) # => true
 
               static VALUE
ossl_dsa_verify(VALUE self, VALUE digest, VALUE sig)
{
    EVP_PKEY *pkey;
    int ret;

    GetPKeyDSA(self, pkey);
    StringValue(digest);
    StringValue(sig);
    /* type is ignored (0) */
    ret = DSA_verify(0, (unsigned char *)RSTRING_PTR(digest), RSTRING_LENINT(digest),
                     (unsigned char *)RSTRING_PTR(sig), RSTRING_LENINT(sig), pkey->pkey.dsa);
    if (ret < 0) {
        ossl_raise(eDSAError, NULL);
    }
    else if (ret == 1) {
        return Qtrue;
    }

    return Qfalse;
}
            
to_der → aString click to toggle source

Encodes this DSA to its DER encoding.

 
               static VALUE
ossl_dsa_to_der(VALUE self)
{
    EVP_PKEY *pkey;
    int (*i2d_func)_((DSA*, unsigned char**));
    unsigned char *p;
    long len;
    VALUE str;

    GetPKeyDSA(self, pkey);
    if(DSA_HAS_PRIVATE(pkey->pkey.dsa))
        i2d_func = (int(*)_((DSA*,unsigned char**)))i2d_DSAPrivateKey;
    else
        i2d_func = i2d_DSA_PUBKEY;
    if((len = i2d_func(pkey->pkey.dsa, NULL)) <= 0)
        ossl_raise(eDSAError, NULL);
    str = rb_str_new(0, len);
    p = (unsigned char *)RSTRING_PTR(str);
    if(i2d_func(pkey->pkey.dsa, &p) < 0)
        ossl_raise(eDSAError, NULL);
    ossl_str_adjust(str, p);

    return str;
}
            
to_pem(p1 = v1, p2 = v2) click to toggle source
Alias for: export
to_s(p1 = v1, p2 = v2) click to toggle source
Alias for: export
to_text → aString click to toggle source

Prints all parameters of key to buffer INSECURE: PRIVATE INFORMATIONS CAN LEAK OUT!!! Don’t use :-)) (I’s up to you)

 
               static VALUE
ossl_dsa_to_text(VALUE self)
{
    EVP_PKEY *pkey;
    BIO *out;
    VALUE str;

    GetPKeyDSA(self, pkey);
    if (!(out = BIO_new(BIO_s_mem()))) {
        ossl_raise(eDSAError, NULL);
    }
    if (!DSA_print(out, pkey->pkey.dsa, 0)) { /* offset = 0 */
        BIO_free(out);
        ossl_raise(eDSAError, NULL);
    }
    str = ossl_membio2str(out);

    return str;
}
            

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