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Class: OpenSSL::PKey::DH

Relationships & Source Files
Super Chains via Extension / Inclusion / Inheritance
Class Chain:
self, PKey
Instance Chain:
self, ::OpenSSL::Marshal, PKey
Inherits: OpenSSL::PKey::PKey
Defined in: ext/openssl/ossl_pkey_dh.c,
ext/openssl/lib/openssl/pkey.rb

Overview

An implementation of the Diffie-Hellman key exchange protocol based on discrete logarithms in finite fields, the same basis that DSA is built on.

Accessor methods for the Diffie-Hellman parameters

DH#p

The prime (an OpenSSL::BN) of the Diffie-Hellman parameters.

DH#g

The generator (an OpenSSL::BN) g of the Diffie-Hellman parameters.

DH#pub_key

The per-session public key (an OpenSSL::BN) matching the private key. This needs to be passed to DH#compute_key.

DH#priv_key

The per-session private key, an OpenSSL::BN.

Example of a key exchange

# you may send the parameters (der) and own public key (pub1) publicly
# to the participating party
dh1 = OpenSSL::PKey::DH.new(2048)
der = dh1.to_der
pub1 = dh1.pub_key

# the other party generates its per-session key pair
dhparams = OpenSSL::PKey::DH.new(der)
dh2 = OpenSSL::PKey.generate_key(dhparams)
pub2 = dh2.pub_key

symm_key1 = dh1.compute_key(pub2)
symm_key2 = dh2.compute_key(pub1)
puts symm_key1 == symm_key2 # => true

Class Method Summary

PKey - Inherited

.new

Because PKey is an abstract class, actually calling this method explicitly will raise a NotImplementedError.

Instance Attribute Summary

Instance Method Summary

::OpenSSL::Marshal - Included

#_dump

PKey - Inherited

#compare?

Used primarily to check if an X509::Certificate#public_key compares to its private key.
#decrypt

Performs a public key decryption operation using pkey.
#derive

Derives a shared secret from pkey and peer_pkey.
#encrypt

Performs a public key encryption operation using pkey.
#initialize_copy,
#inspect

Returns a string describing the PKey object.
#oid

Returns the short name of the OID associated with pkey.
#private_to_der

Serializes the private key to DER-encoded PKCS #8 format.
#private_to_pem

Serializes the private key to PEM-encoded PKCS #8 format.
#public_to_der

Serializes the public key to DER-encoded X.509 SubjectPublicKeyInfo format.
#public_to_pem

Serializes the public key to PEM-encoded X.509 SubjectPublicKeyInfo format.
#sign

Hashes and signs the data using a message digest algorithm digest and a private key pkey.
#sign_raw

Signs data using a private key pkey.
#to_text

Dumps key parameters, public key, and private key components contained in the key into a human-readable text.
#verify

Verifies the signature for the data using a message digest algorithm digest and a public key pkey.
#verify_raw

Verifies the signature for the data using a public key pkey.
#verify_recover

Recovers the signed data from signature using a public key pkey.

Constructor Details

.new ⇒ DH .new(string) ⇒ DH .new(size [, generator]) ⇒ DH

This method is for internal use only.

Creates a new instance of DH.

If called without arguments, an empty instance without any parameter or key components is created. Use #set_pqg to manually set the parameters afterwards (and optionally #set_key to set private and public key components).

If a String is given, tries to parse it as a DER- or PEM- encoded parameters. See also OpenSSL::PKey.read which can parse keys of any kinds.

The .new(size [, generator]) form is an alias of .generate.

string

A String that contains the DER or PEM encoded key.

size

See DH.generate.

generator

See DH.generate.

Examples:

# Creating an instance from scratch
# Note that this is deprecated and will not work on OpenSSL 3.0 or later.
dh = OpenSSL::PKey::DH.new
dh.set_pqg(bn_p, nil, bn_g)

# Generating a parameters and a key pair
dh = OpenSSL::PKey::DH.new(2048) # An alias of OpenSSL::PKey::DH.generate(2048)

# Reading DH parameters
dh_params = OpenSSL::PKey::DH.new(File.read('parameters.pem')) # loads parameters only
dh = OpenSSL::PKey.generate_key(dh_params) # generates a key pair
[ GitHub ] 

  


# File 'ext/openssl/ossl_pkey_dh.c', line 72



static VALUE
ossl_dh_initialize(int argc, VALUE *argv, VALUE self)
{
    EVP_PKEY *pkey;
    int type;
    DH *dh;
    BIO *in = NULL;
    VALUE arg;

    TypedData_Get_Struct(self, EVP_PKEY, &ossl_evp_pkey_type, pkey);
    if (pkey)
        rb_raise(rb_eTypeError, "pkey already initialized");

    /* The DH.new(size, generator) form is handled by lib/openssl/pkey.rb */
    if (rb_scan_args(argc, argv, "01", &arg) == 0) {
        dh = DH_new();
        if (!dh)
            ossl_raise(eDHError, "DH_new");
        goto legacy;
    }

    arg = ossl_to_der_if_possible(arg);
    in = ossl_obj2bio(&arg);

    /*
     * On OpenSSL <= 1.1.1 and current versions of LibreSSL, the generic
     * routine does not support DER-encoded parameters
     */
    dh = d2i_DHparams_bio(in, NULL);
    if (dh)
        goto legacy;
    OSSL_BIO_reset(in);

    pkey = ossl_pkey_read_generic(in, Qnil);
    BIO_free(in);
    if (!pkey)
        ossl_raise(eDHError, "could not parse pkey");

    type = EVP_PKEY_base_id(pkey);
    if (type != EVP_PKEY_DH) {
        EVP_PKEY_free(pkey);
        rb_raise(eDHError, "incorrect pkey type: %s", OBJ_nid2sn(type));
    }
    RTYPEDDATA_DATA(self) = pkey;
    return self;

  legacy:
    BIO_free(in);
    pkey = EVP_PKEY_new();
    if (!pkey || EVP_PKEY_assign_DH(pkey, dh) != 1) {
        EVP_PKEY_free(pkey);
        DH_free(dh);
        ossl_raise(eDHError, "EVP_PKEY_assign_DH");
    }
    RTYPEDDATA_DATA(self) = pkey;
    return self;
}


  







Class Method Details



  

    .generate(size, generator = 2)  ⇒ DH   



  

    

Creates a new DH instance from scratch by generating random parameters and a key pair.



See also OpenSSL::PKey.generate_parameters and OpenSSL::PKey.generate_key.


size



The desired key size in bits.


generator



The generator.




  



  [ GitHub ]


  

  


# File 'ext/openssl/lib/openssl/pkey.rb', line 118



def generate(size, generator = 2, &blk)
  dhparams = OpenSSL::PKey.generate_parameters("DH", {
    "dh_paramgen_prime_len" => size,
    "dh_paramgen_generator" => generator,
  }, &blk)
  OpenSSL::PKey.generate_key(dhparams)
end


  







Instance Attribute Details



  

    #params_ok?  ⇒ Boolean  (readonly)  



  

    

Validates the Diffie-Hellman parameters associated with this instance. It checks whether a safe prime and a suitable generator are used. If this is not the case, false is returned.



See also the man page EVP_PKEY_param_check(3).


  



  [ GitHub ]


  

  


# File 'ext/openssl/ossl_pkey_dh.c', line 311



static VALUE
ossl_dh_check_params(VALUE self)
{
    int ret;
#ifdef HAVE_EVP_PKEY_CHECK
    EVP_PKEY *pkey;
    EVP_PKEY_CTX *pctx;

    GetPKey(self, pkey);
    pctx = EVP_PKEY_CTX_new(pkey, /* engine */NULL);
    if (!pctx)
        ossl_raise(eDHError, "EVP_PKEY_CTX_new");
    ret = EVP_PKEY_param_check(pctx);
    EVP_PKEY_CTX_free(pctx);
#else
    DH *dh;
    int codes;

    GetDH(self, dh);
    ret = DH_check(dh, &codes) == 1 && codes == 0;
#endif

    if (ret == 1)
        return Qtrue;
    else {
        /* DH_check_ex() will put error entry on failure */
        ossl_clear_error();
        return Qfalse;
    }
}


  








  

    #private?  ⇒ Boolean  (readonly)  



  

    

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


  



  [ GitHub ]


  

  


# File 'ext/openssl/ossl_pkey_dh.c', line 197



static VALUE
ossl_dh_is_private(VALUE self)
{
    DH *dh;
    const BIGNUM *bn;

    GetDH(self, dh);
    DH_get0_key(dh, NULL, &bn);

#if !defined(OPENSSL_NO_ENGINE)
    return (bn || DH_get0_engine(dh)) ? Qtrue : Qfalse;
#else
    return bn ? Qtrue : Qfalse;
#endif
}


  








  

    #public?  ⇒ Boolean  (readonly)  



  

    

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


  



  [ GitHub ]


  

  


# File 'ext/openssl/ossl_pkey_dh.c', line 178



static VALUE
ossl_dh_is_public(VALUE self)
{
    DH *dh;
    const BIGNUM *bn;

    GetDH(self, dh);
    DH_get0_key(dh, &bn, NULL);

    return bn ? Qtrue : Qfalse;
}


  







Instance Method Details



  

    #compute_key(pub_bn)  ⇒ String   



  

    

Returns a String containing a shared secret computed from the other party’s public value.



This method is provided for backwards compatibility, and calls #derive internally.



Parameters


  • 

    pub_bn is a ::OpenSSL::BN, not the DH instance returned by DH#public_key as that contains the DH parameters only.
    



  



  [ GitHub ]


  

  


# File 'ext/openssl/lib/openssl/pkey.rb', line 49



def compute_key(pub_bn)
  # FIXME: This is constructing an X.509 SubjectPublicKeyInfo and is very
  # inefficient
  obj = OpenSSL::ASN1.Sequence([
    OpenSSL::ASN1.Sequence([
      OpenSSL::ASN1.ObjectId("dhKeyAgreement"),
      OpenSSL::ASN1.Sequence([
        OpenSSL::ASN1.Integer(p),
        OpenSSL::ASN1.Integer(g),
      ]),
    ]),
    OpenSSL::ASN1.BitString(OpenSSL::ASN1.Integer(pub_bn).to_der),
  ])
  derive(OpenSSL::PKey.read(obj.to_der))
end


  








  

    

      #export  ⇒ String 
      #to_pem  ⇒ String 
      #to_s  ⇒ String 
    

  



  

    

Alias for #to_s.


  





  








  

    #generate_key!  ⇒ self   



  

    

Generates a private and public key unless a private key already exists. If this DH instance was generated from public DH parameters (e.g. by encoding the result of #public_key), then this method needs to be called first in order to generate the per-session keys before performing the actual key exchange.



Deprecated in version 3.0. This method is incompatible with ::OpenSSL 3.0.0 or later.



See also OpenSSL::PKey.generate_key.



Example:



# DEPRECATED USAGE: This will not work on OpenSSL 3.0 or later
dh0 = OpenSSL::PKey::DH.new(2048)
dh = dh0.public_key # #public_key only copies the DH parameters (contrary to the name)
dh.generate_key!
puts dh.private? # => true
puts dh0.pub_key == dh.pub_key #=> false

# With OpenSSL::PKey.generate_key
dh0 = OpenSSL::PKey::DH.new(2048)
dh = OpenSSL::PKey.generate_key(dh0)
puts dh0.pub_key == dh.pub_key #=> false


  



  [ GitHub ]


  

  


# File 'ext/openssl/lib/openssl/pkey.rb', line 91



def generate_key!
  if OpenSSL::OPENSSL_VERSION_NUMBER >= 0x30000000
    raise DHError, "OpenSSL::PKey::DH is immutable on OpenSSL 3.0; " \
    "use OpenSSL::PKey.generate_key instead"
  end

  unless priv_key
    tmp = OpenSSL::PKey.generate_key(self)
    set_key(tmp.pub_key, tmp.priv_key)
  end
  self
end


  








  

    #initialize_copy(other)  
  

  [ GitHub ]


  

  


# File 'ext/openssl/ossl_pkey_dh.c', line 131



static VALUE
ossl_dh_initialize_copy(VALUE self, VALUE other)
{
    EVP_PKEY *pkey;
    DH *dh, *dh_other;
    const BIGNUM *pub, *priv;

    TypedData_Get_Struct(self, EVP_PKEY, &ossl_evp_pkey_type, pkey);
    if (pkey)
        rb_raise(rb_eTypeError, "pkey already initialized");
    GetDH(other, dh_other);

    dh = DHparams_dup(dh_other);
    if (!dh)
	ossl_raise(eDHError, "DHparams_dup");

    DH_get0_key(dh_other, &pub, &priv);
    if (pub) {
	BIGNUM *pub2 = BN_dup(pub);
	BIGNUM *priv2 = BN_dup(priv);

        if (!pub2 || (priv && !priv2)) {
	    BN_clear_free(pub2);
	    BN_clear_free(priv2);
	    ossl_raise(eDHError, "BN_dup");
	}
	DH_set0_key(dh, pub2, priv2);
    }

    pkey = EVP_PKEY_new();
    if (!pkey || EVP_PKEY_assign_DH(pkey, dh) != 1) {
        EVP_PKEY_free(pkey);
        DH_free(dh);
        ossl_raise(eDHError, "EVP_PKEY_assign_DH");
    }
    RTYPEDDATA_DATA(self) = pkey;
    return self;
}


  








  

    #params  ⇒ Hash   



  

    

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


  



  [ GitHub ]


  

  


# File 'ext/openssl/ossl_pkey_dh.c', line 280



static VALUE
ossl_dh_get_params(VALUE self)
{
    DH *dh;
    VALUE hash;
    const BIGNUM *p, *q, *g, *pub_key, *priv_key;

    GetDH(self, dh);
    DH_get0_pqg(dh, &p, &q, &g);
    DH_get0_key(dh, &pub_key, &priv_key);

    hash = rb_hash_new();
    rb_hash_aset(hash, rb_str_new2("p"), ossl_bn_new(p));
    rb_hash_aset(hash, rb_str_new2("q"), ossl_bn_new(q));
    rb_hash_aset(hash, rb_str_new2("g"), ossl_bn_new(g));
    rb_hash_aset(hash, rb_str_new2("pub_key"), ossl_bn_new(pub_key));
    rb_hash_aset(hash, rb_str_new2("priv_key"), ossl_bn_new(priv_key));

    return hash;
}


  








  

    #public_key  ⇒ DH   



  

    

Returns a new DH instance that carries just the DH parameters.



Contrary to the method name, the returned DH object contains only parameters and not the public key.



This method is provided for backwards compatibility. In most cases, there is no need to call this method.



For the purpose of re-generating the key pair while keeping the parameters, check OpenSSL::PKey.generate_key.



Example:



# OpenSSL::PKey::DH.generate by default generates a random key pair
dh1 = OpenSSL::PKey::DH.generate(2048)
p dh1.priv_key #=> #<OpenSSL::BN 1288347...>
dhcopy = dh1.public_key
p dhcopy.priv_key #=> nil


  



  [ GitHub ]


  

  


# File 'ext/openssl/lib/openssl/pkey.rb', line 33



def public_key
  DH.new(to_der)
end


  








  

    #set_key(pub_key, priv_key)  ⇒ self   



  

    

Sets pub_key and priv_key for the DH instance. priv_key may be nil.


  



  [ GitHub ]






  

    #set_pqg(p, q, g)  ⇒ self   



  

    

Sets p, q, g to the DH instance.


  



  [ GitHub ]






  

    #to_der  ⇒ String   



  

    

Encodes this DH to its DER encoding. Note that any existing per-session public/private keys will not get encoded, just the Diffie-Hellman parameters will be encoded.


  



  [ GitHub ]


  

  


# File 'ext/openssl/ossl_pkey_dh.c', line 252



static VALUE
ossl_dh_to_der(VALUE self)
{
    DH *dh;
    unsigned char *p;
    long len;
    VALUE str;

    GetDH(self, dh);
    if((len = i2d_DHparams(dh, NULL)) <= 0)
	ossl_raise(eDHError, NULL);
    str = rb_str_new(0, len);
    p = (unsigned char *)RSTRING_PTR(str);
    if(i2d_DHparams(dh, &p) < 0)
	ossl_raise(eDHError, NULL);
    ossl_str_adjust(str, p);

    return str;
}


  








  

    

      #export  ⇒ String 
      #to_pem  ⇒ String 
      #to_s  ⇒ String 
    

  



  

    

Alias for #to_s.


  









  

    

      #export  ⇒ String 
      #to_pem  ⇒ String 
      #to_s  ⇒ String 
    

    Also known as: #export, #to_pem
  



  

    

Encodes this DH to its PEM encoding. Note that any existing per-session public/private keys will not get encoded, just the Diffie-Hellman parameters will be encoded.


  



  [ GitHub ]


  

  


# File 'ext/openssl/ossl_pkey_dh.c', line 223



static VALUE
ossl_dh_export(VALUE self)
{
    DH *dh;
    BIO *out;
    VALUE str;

    GetDH(self, dh);
    if (!(out = BIO_new(BIO_s_mem()))) {
	ossl_raise(eDHError, NULL);
    }
    if (!PEM_write_bio_DHparams(out, dh)) {
	BIO_free(out);
	ossl_raise(eDHError, NULL);
    }
    str = ossl_membio2str(out);

    return str;
}