Class: OpenSSL::PKey::DH

Inherits:
PKey
  • Object
show all
Includes:
Marshal
Defined in:
ossl_pkey_dh.c,
lib/openssl/pkey.rb,
ossl_pkey_dh.c

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

dh1 = OpenSSL::PKey::DH.new(2048)
der = dh1.public_key.to_der #you may send this publicly to the participating party
dh2 = OpenSSL::PKey::DH.new(der)
dh2.generate_key! #generate the per-session key pair
symm_key1 = dh1.compute_key(dh2.pub_key)
symm_key2 = dh2.compute_key(dh1.pub_key)

puts symm_key1 == symm_key2 # => true

Class Method Summary collapse

Instance Method Summary collapse

Methods included from Marshal

#_dump, included

Methods inherited from PKey

#inspect, #oid, #private_to_der, #private_to_pem, #public_to_der, #public_to_pem, #sign, #verify

Constructor Details

#newObject #new(string) ⇒ Object #new(size[, generator]) ⇒ Object

Either generates a DH instance from scratch or by reading already existing DH parameters from string. Note that when reading a DH instance from data that was encoded from a DH instance by using DH#to_pem or DH#to_der the result will not contain a public/private key pair yet. This needs to be generated using DH#generate_key! first.

Parameters

  • size is an integer representing the desired key size. Keys smaller than 1024 bits should be considered insecure.

  • generator is a small number > 1, typically 2 or 5.

  • string contains the DER or PEM encoded key.

Examples

DH.new # -> dh
DH.new(1024) # -> dh
DH.new(1024, 5) # -> dh
#Reading DH parameters
dh = DH.new(File.read('parameters.pem')) # -> dh, but no public/private key yet
dh.generate_key! # -> dh with public and private key

202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
# File 'ossl_pkey_dh.c', line 202

static VALUE
ossl_dh_initialize(int argc, VALUE *argv, VALUE self)
{
    EVP_PKEY *pkey;
    DH *dh;
    int g = 2;
    BIO *in;
    VALUE arg, gen;

    GetPKey(self, pkey);
    if(rb_scan_args(argc, argv, "02", &arg, &gen) == 0) {
      dh = DH_new();
    }
    else if (RB_INTEGER_TYPE_P(arg)) {
	if (!NIL_P(gen)) {
	    g = NUM2INT(gen);
	}
	if (!(dh = dh_generate(NUM2INT(arg), g))) {
	    ossl_raise(eDHError, NULL);
	}
    }
    else {
	arg = ossl_to_der_if_possible(arg);
	in = ossl_obj2bio(&arg);
	dh = PEM_read_bio_DHparams(in, NULL, NULL, NULL);
	if (!dh){
	    OSSL_BIO_reset(in);
	    dh = d2i_DHparams_bio(in, NULL);
	}
	BIO_free(in);
	if (!dh) {
	    ossl_raise(eDHError, NULL);
	}
    }
    if (!EVP_PKEY_assign_DH(pkey, dh)) {
	DH_free(dh);
	ossl_raise(eDHError, NULL);
    }
    return self;
}

Class Method Details

.generate(size[, generator]) ⇒ Object

Creates a new DH instance from scratch by generating the private and public components alike.

Parameters

  • size is an integer representing the desired key size. Keys smaller than 1024 bits should be considered insecure.

  • generator is a small number > 1, typically 2 or 5.


157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
# File 'ossl_pkey_dh.c', line 157

static VALUE
ossl_dh_s_generate(int argc, VALUE *argv, VALUE klass)
{
    DH *dh ;
    int g = 2;
    VALUE size, gen, obj;

    if (rb_scan_args(argc, argv, "11", &size, &gen) == 2) {
	g = NUM2INT(gen);
    }
    dh = dh_generate(NUM2INT(size), g);
    obj = dh_instance(klass, dh);
    if (obj == Qfalse) {
	DH_free(dh);
	ossl_raise(eDHError, NULL);
    }

    return obj;
}

Instance Method Details

#compute_key(pub_bn) ⇒ aString

Returns a String containing a shared secret computed from the other party's public value. See DH_compute_key() for further information.

Parameters

  • pub_bn is a OpenSSL::BN, not the DH instance returned by

DH#public_key as that contains the DH parameters only.

Returns:

  • (aString)

532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
# File 'ossl_pkey_dh.c', line 532

static VALUE
ossl_dh_compute_key(VALUE self, VALUE pub)
{
    DH *dh;
    const BIGNUM *pub_key, *dh_p;
    VALUE str;
    int len;

    GetDH(self, dh);
    DH_get0_pqg(dh, &dh_p, NULL, NULL);
    if (!dh_p)
	ossl_raise(eDHError, "incomplete DH");
    pub_key = GetBNPtr(pub);
    len = DH_size(dh);
    str = rb_str_new(0, len);
    if ((len = DH_compute_key((unsigned char *)RSTRING_PTR(str), pub_key, dh)) < 0) {
	ossl_raise(eDHError, NULL);
    }
    rb_str_set_len(str, len);

    return str;
}

#exportaString #to_pemaString #to_saString Also known as: to_pem, to_s

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.

Overloads:

  • #exportaString

    Returns:

    • (aString)
  • #to_pemaString

    Returns:

    • (aString)
  • #to_saString

    Returns:

    • (aString)

328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
# File 'ossl_pkey_dh.c', line 328

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;
}

#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 DH#public_key), then this method needs to be called first in order to generate the per-session keys before performing the actual key exchange.

Example

dh = OpenSSL::PKey::DH.new(2048)
public_key = dh.public_key #contains no private/public key yet
public_key.generate_key!
puts public_key.private? # => true

Returns:

  • (self)

510
511
512
513
514
515
516
517
518
519
# File 'ossl_pkey_dh.c', line 510

static VALUE
ossl_dh_generate_key(VALUE self)
{
    DH *dh;

    GetDH(self, dh);
    if (!DH_generate_key(dh))
	ossl_raise(eDHError, "Failed to generate key");
    return self;
}

#initialize_copy(other) ⇒ Object


243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
# File 'ossl_pkey_dh.c', line 243

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

    GetPKey(self, pkey);
    if (EVP_PKEY_base_id(pkey) != EVP_PKEY_NONE)
	ossl_raise(eDHError, "DH already initialized");
    GetDH(other, dh_other);

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

    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);
    }

    return self;
}

#paramsHash

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

Returns:

  • (Hash)

385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
# File 'ossl_pkey_dh.c', line 385

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;
}

#params_ok?Boolean

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.

Returns:

  • (Boolean)

480
481
482
483
484
485
486
487
488
489
490
491
492
# File 'ossl_pkey_dh.c', line 480

static VALUE
ossl_dh_check_params(VALUE self)
{
    DH *dh;
    int codes;

    GetDH(self, dh);
    if (!DH_check(dh, &codes)) {
	return Qfalse;
    }

    return codes == 0 ? Qtrue : Qfalse;
}

#private?Boolean

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

Returns:

  • (Boolean)

302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
# File 'ossl_pkey_dh.c', line 302

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

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

Returns:

  • (Boolean)

283
284
285
286
287
288
289
290
291
292
293
# File 'ossl_pkey_dh.c', line 283

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;
}

#public_keyObject

Returns a new DH instance that carries just the public information, i.e. the prime p and the generator g, but no public/private key yet. Such a pair may be generated using DH#generate_key!. The “public key” needed for a key exchange with DH#compute_key is considered as per-session information and may be retrieved with DH#pub_key once a key pair has been generated. If the current instance already contains private information (and thus a valid public/private key pair), this information will no longer be present in the new instance generated by DH#public_key. This feature is helpful for publishing the Diffie-Hellman parameters without leaking any of the private per-session information.

Example

dh = OpenSSL::PKey::DH.new(2048) # has public and private key set public_key = dh.public_key # contains only prime and generator parameters = public_key.to_der # it's safe to publish this


455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
# File 'ossl_pkey_dh.c', line 455

static VALUE
ossl_dh_to_public_key(VALUE self)
{
    DH *orig_dh, *dh;
    VALUE obj;

    GetDH(self, orig_dh);
    dh = DHparams_dup(orig_dh); /* err check perfomed by dh_instance */
    obj = dh_instance(rb_obj_class(self), dh);
    if (obj == Qfalse) {
	DH_free(dh);
	ossl_raise(eDHError, NULL);
    }

    return obj;
}

#set_key(pub_key, priv_key) ⇒ self

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

Returns:

  • (self)

#set_pqg(p, q, g) ⇒ self

Sets p, q, g to the DH instance.

Returns:

  • (self)

#to_deraString

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.

Returns:

  • (aString)

357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
# File 'ossl_pkey_dh.c', line 357

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;
}

#to_textaString

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

Returns:

  • (aString)

414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
# File 'ossl_pkey_dh.c', line 414

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

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

    return str;
}