aboutsummaryrefslogtreecommitdiffstats
path: root/src/scepclient/scep.c
blob: 29f6eab70ed623da60d94a71ea4cca6e12022e35 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
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
242
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
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
/**
 * @file scep.c
 * @brief SCEP specific functions
 *
 * Contains functions to build SCEP request's and to parse SCEP reply's.
 */

/*
 * Copyright (C) 2005 Jan Hutter, Martin Willi
 * Hochschule fuer Technik Rapperswil
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by the
 * Free Software Foundation; either version 2 of the License, or (at your
 * option) any later version.  See <http://www.fsf.org/copyleft/gpl.txt>.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
 * or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * for more details.
 */

#include <string.h>
#include <stdlib.h>

#include <freeswan.h>

#include <library.h>
#include <asn1/asn1.h>
#include <asn1/asn1_parser.h>
#include <asn1/oid.h>
#include <crypto/rngs/rng.h>
#include <crypto/hashers/hasher.h>

#include "../pluto/constants.h"
#include "../pluto/defs.h"
#include "../pluto/fetch.h"
#include "../pluto/log.h"

#include "scep.h"

static const chunk_t ASN1_messageType_oid = chunk_from_chars(
	0x06, 0x0A, 0x60, 0x86, 0x48, 0x01, 0x86, 0xF8, 0x45, 0x01, 0x09, 0x02
);
static const chunk_t ASN1_senderNonce_oid = chunk_from_chars(
	0x06, 0x0A, 0x60, 0x86, 0x48, 0x01, 0x86, 0xF8, 0x45, 0x01, 0x09, 0x05
);
static const chunk_t ASN1_transId_oid = chunk_from_chars(
	0x06, 0x0A, 0x60, 0x86, 0x48, 0x01, 0x86, 0xF8, 0x45, 0x01, 0x09, 0x07
);

static const char *pkiStatus_values[] = { "0", "2", "3" };

static const char *pkiStatus_names[] = {
	"SUCCESS",
	"FAILURE",
	"PENDING",
	"UNKNOWN"
};

static const char *msgType_values[] = { "3", "19", "20", "21", "22" };

static const char *msgType_names[] = {
	"CertRep",
	"PKCSReq",
	"GetCertInitial",
	"GetCert",
	"GetCRL",
	"Unknown"
};

static const char *failInfo_reasons[] = {
	"badAlg - unrecognized or unsupported algorithm identifier",
	"badMessageCheck - integrity check failed",
	"badRequest - transaction not permitted or supported",
	"badTime - Message time field was not sufficiently close to the system time",
	"badCertId - No certificate could be identified matching the provided criteria"
};

const scep_attributes_t empty_scep_attributes = {
	SCEP_Unknown_MSG   , /* msgType */
	SCEP_UNKNOWN       , /* pkiStatus */
	SCEP_unknown_REASON, /* failInfo */
	{ NULL, 0 }        , /* transID */
	{ NULL, 0 }        , /* senderNonce */
	{ NULL, 0 }        , /* recipientNonce */
};

/* ASN.1 definition of the X.501 atttribute type */

static const asn1Object_t attributesObjects[] = {
	{ 0, "attributes",    ASN1_SET,       ASN1_LOOP }, /* 0 */
	{ 1,   "attribute",   ASN1_SEQUENCE,  ASN1_NONE }, /* 1 */
	{ 2,     "type",      ASN1_OID,       ASN1_BODY }, /* 2 */
	{ 2,     "values",    ASN1_SET,       ASN1_LOOP }, /* 3 */
	{ 3,       "value",   ASN1_EOC,       ASN1_RAW  }, /* 4 */
	{ 2,     "end loop",  ASN1_EOC,       ASN1_END  }, /* 5 */
	{ 0, "end loop",      ASN1_EOC,       ASN1_END  }, /* 6 */
	{ 0, "exit",          ASN1_EOC,       ASN1_EXIT	}
};
#define ATTRIBUTE_OBJ_TYPE      2
#define ATTRIBUTE_OBJ_VALUE     4

/**
 * Extract and store an attribute
 */
static bool extract_attribute(int oid, chunk_t object, u_int level,
							  scep_attributes_t *attrs)
{
	asn1_t type = ASN1_EOC;
	const char *name = "none";

	switch (oid)
	{
	case OID_PKCS9_CONTENT_TYPE:
		type = ASN1_OID;
		name = "contentType";
		break;
	case OID_PKCS9_SIGNING_TIME:
		type = ASN1_UTCTIME;
		name = "signingTime";
		break;
	case OID_PKCS9_MESSAGE_DIGEST:
		type = ASN1_OCTET_STRING;
		name = "messageDigest";
		break;
	case OID_PKI_MESSAGE_TYPE:
		type = ASN1_PRINTABLESTRING;
		name = "messageType";
		break;
	case OID_PKI_STATUS:
		type = ASN1_PRINTABLESTRING;
		name = "pkiStatus";
		break;
	case OID_PKI_FAIL_INFO:
		type = ASN1_PRINTABLESTRING;
		name = "failInfo";
		break;
	case OID_PKI_SENDER_NONCE:
		type = ASN1_OCTET_STRING;
		name = "senderNonce";
		 break;
	case OID_PKI_RECIPIENT_NONCE:
		type = ASN1_OCTET_STRING;
		name = "recipientNonce";
		break;
	case OID_PKI_TRANS_ID:
		type = ASN1_PRINTABLESTRING;
		name = "transID";
		break;
	default:
		break;
	}

	if (type == ASN1_EOC)
		return TRUE;

	if (!asn1_parse_simple_object(&object, type, level+1, name))
		return FALSE;

	switch (oid)
	{
	case OID_PKCS9_CONTENT_TYPE:
		break;
	case OID_PKCS9_SIGNING_TIME:
		break;
	case OID_PKCS9_MESSAGE_DIGEST:
		break;
	case OID_PKI_MESSAGE_TYPE:
		{
			scep_msg_t m;

			for (m = SCEP_CertRep_MSG; m < SCEP_Unknown_MSG; m++)
			{
				if (strncmp(msgType_values[m], object.ptr, object.len) == 0)
					attrs->msgType = m;
			}
			DBG(DBG_CONTROL,
				DBG_log("messageType:  %s", msgType_names[attrs->msgType])
			)
		}
		break;
	case OID_PKI_STATUS:
		{
			pkiStatus_t s;

			for (s = SCEP_SUCCESS; s < SCEP_UNKNOWN; s++)
			{
				if (strncmp(pkiStatus_values[s], object.ptr, object.len) == 0)
					attrs->pkiStatus = s;
			}
			DBG(DBG_CONTROL,
				DBG_log("pkiStatus:    %s", pkiStatus_names[attrs->pkiStatus])
			)
		}
		break;
	case OID_PKI_FAIL_INFO:
		if (object.len == 1
		&& *object.ptr >= '0' && *object.ptr <= '4')
		{
			attrs->failInfo = (failInfo_t)(*object.ptr - '0');
		}
		if (attrs->failInfo != SCEP_unknown_REASON)
			plog("failInfo:     %s", failInfo_reasons[attrs->failInfo]);
		break;
	case OID_PKI_SENDER_NONCE:
		attrs->senderNonce = object;
		break;
	case OID_PKI_RECIPIENT_NONCE:
		attrs->recipientNonce = object;
		break;
	case OID_PKI_TRANS_ID:
		attrs->transID = object;
	}
	return TRUE;
}

/**
 * Parse X.501 attributes
 */
bool parse_attributes(chunk_t blob, scep_attributes_t *attrs)
{
	asn1_parser_t *parser;
	chunk_t object;
	int oid = OID_UNKNOWN;
	int objectID;
	bool success = FALSE;

	parser = asn1_parser_create(attributesObjects, blob);
	DBG(DBG_CONTROL | DBG_PARSING,
		DBG_log("parsing attributes")
	)

	while (parser->iterate(parser, &objectID, &object))
	{
		switch (objectID)
		{
		case ATTRIBUTE_OBJ_TYPE:
			oid = asn1_known_oid(object);
			break;
		case ATTRIBUTE_OBJ_VALUE:
			if (!extract_attribute(oid, object, parser->get_level(parser), attrs))
			{
				goto end;
			}
		}
	}
	success = parser->success(parser);

end:
	parser->destroy(parser);
	return success;
}

/**
 * Generates a unique fingerprint of the pkcs10 request
 * by computing an MD5 hash over it
 */
chunk_t scep_generate_pkcs10_fingerprint(chunk_t pkcs10)
{
	chunk_t digest = chunk_alloca(HASH_SIZE_MD5);
	hasher_t *hasher;

	hasher = lib->crypto->create_hasher(lib->crypto, HASH_MD5);
	hasher->get_hash(hasher, pkcs10, digest.ptr);
	hasher->destroy(hasher);

	return chunk_to_hex(digest, NULL, FALSE);
}

/**
 * Generate a transaction id as the MD5 hash of an public key
 * the transaction id is also used as a unique serial number
 */
void scep_generate_transaction_id(public_key_t *key, chunk_t *transID,
								  chunk_t *serialNumber)
{
	chunk_t digest = chunk_alloca(HASH_SIZE_MD5);
	chunk_t keyEncoding = chunk_empty, keyInfo;
	hasher_t *hasher;
	bool msb_set;
	u_char *pos;

	key->get_encoding(key, PUBKEY_ASN1_DER, &keyEncoding);

	keyInfo = asn1_wrap(ASN1_SEQUENCE, "mm",
						asn1_algorithmIdentifier(OID_RSA_ENCRYPTION),
						asn1_bitstring("m", keyEncoding));

	hasher = lib->crypto->create_hasher(lib->crypto, HASH_MD5);
	hasher->get_hash(hasher, keyInfo, digest.ptr);
	hasher->destroy(hasher);
	free(keyInfo.ptr);

	/* is the most significant bit of the digest set? */
	msb_set = (*digest.ptr & 0x80) == 0x80;

	/* allocate space for the serialNumber */
	serialNumber->len = msb_set + digest.len;
	serialNumber->ptr = malloc(serialNumber->len);

	/* the serial number as the two's complement of the digest */
	pos = serialNumber->ptr;
	if (msb_set)
	{
		*pos++ = 0x00;
	}
	memcpy(pos, digest.ptr, digest.len);

	/* the transaction id is the serial number in hex format */
	transID->len = 2*digest.len;
	transID->ptr = malloc(transID->len + 1);
	datatot(digest.ptr, digest.len, 16, transID->ptr, transID->len + 1);
}

/**
 * Builds a transId attribute
 */
chunk_t scep_transId_attribute(chunk_t transID)
{
	return asn1_wrap(ASN1_SEQUENCE, "cm"
				, ASN1_transId_oid
				, asn1_wrap(ASN1_SET, "m"
					, asn1_simple_object(ASN1_PRINTABLESTRING, transID)
				  )
			  );
}

/**
 * Builds a messageType attribute
 */
chunk_t scep_messageType_attribute(scep_msg_t m)
{
	chunk_t msgType = {
		(u_char*)msgType_values[m],
		strlen(msgType_values[m])
	};

	return asn1_wrap(ASN1_SEQUENCE, "cm"
				, ASN1_messageType_oid
				, asn1_wrap(ASN1_SET, "m"
					, asn1_simple_object(ASN1_PRINTABLESTRING, msgType)
				  )
			  );
}

/**
 * Builds a senderNonce attribute
 */
chunk_t scep_senderNonce_attribute(void)
{
	const size_t nonce_len = 16;
	u_char nonce_buf[nonce_len];
	chunk_t senderNonce = { nonce_buf, nonce_len };
	rng_t *rng;

	rng = lib->crypto->create_rng(lib->crypto, RNG_WEAK);
	rng->get_bytes(rng, nonce_len, nonce_buf);
	rng->destroy(rng);

	return asn1_wrap(ASN1_SEQUENCE, "cm"
				, ASN1_senderNonce_oid
				, asn1_wrap(ASN1_SET, "m"
					, asn1_simple_object(ASN1_OCTET_STRING, senderNonce)
				  )
			  );
}

/**
 * Builds a pkcs7 enveloped and signed scep request
 */
chunk_t scep_build_request(chunk_t data, chunk_t transID, scep_msg_t msg,
						   certificate_t *enc_cert, int enc_alg,
						   certificate_t *signer_cert, int digest_alg,
						   private_key_t *private_key)
{
	chunk_t envelopedData, attributes, request;

	envelopedData = pkcs7_build_envelopedData(data, enc_cert, enc_alg);

	attributes = asn1_wrap(ASN1_SET, "mmmmm"
					, pkcs7_contentType_attribute()
					, pkcs7_messageDigest_attribute(envelopedData
						, digest_alg)
					, scep_transId_attribute(transID)
					, scep_messageType_attribute(msg)
					, scep_senderNonce_attribute());

	request = pkcs7_build_signedData(envelopedData, attributes
					, signer_cert, digest_alg, private_key);
	free(envelopedData.ptr);
	free(attributes.ptr);
	return request;
}

/**
 * Converts a binary request to base64 with 64 characters per line
 * newline and '+' characters are escaped by %0A and %2B, respectively
 */
static char* escape_http_request(chunk_t req)
{
	char *escaped_req = NULL;
	char *p1, *p2;
	int lines = 0;
	int plus  = 0;
	int n     = 0;

	/* compute and allocate the size of the base64-encoded request */
	int len = 1 + 4*((req.len + 2)/3);
	char *encoded_req = malloc(len);

	/* do the base64 conversion */
	len = datatot(req.ptr, req.len, 64, encoded_req, len);

	/* compute newline characters to be inserted every 64 characters */
	lines = (len - 2) / 64;

	/* count number of + characters to be escaped */
	p1 = encoded_req;
	while (*p1 != '\0')
	{
		if (*p1++ == '+')
			plus++;
	}

	escaped_req = malloc(len + 3*(lines + plus));

	/* escape special characters in the request */
	p1 = encoded_req;
	p2 = escaped_req;
	while (*p1 != '\0')
	{
		if (n == 64)
		{
			memcpy(p2, "%0A", 3);
			p2 += 3;
			n = 0;
		}
		if (*p1 == '+')
		{
			memcpy(p2, "%2B", 3);
			p2 += 3;
		}
		else
		{
			*p2++ = *p1;
		}
		p1++;
		n++;
	}
	*p2 = '\0';
	free(encoded_req);
	return escaped_req;
}

/**
 * Send a SCEP request via HTTP and wait for a response
 */
bool scep_http_request(const char *url, chunk_t pkcs7, scep_op_t op,
					   bool http_get_request, chunk_t *response)
{
	int len;
	status_t status;
	char *complete_url = NULL;

	/* initialize response */
	*response = chunk_empty;

	DBG(DBG_CONTROL,
		DBG_log("sending scep request to '%s'", url)
	)

	if (op == SCEP_PKI_OPERATION)
	{
		const char operation[] = "PKIOperation";

		if (http_get_request)
		{
			char *escaped_req = escape_http_request(pkcs7);

			/* form complete url */
			len = strlen(url) + 20 + strlen(operation) + strlen(escaped_req) + 1;
			complete_url = malloc(len);
			snprintf(complete_url, len, "%s?operation=%s&message=%s"
					, url, operation, escaped_req);
			free(escaped_req);

			status = lib->fetcher->fetch(lib->fetcher, complete_url, response,
										 FETCH_HTTP_VERSION_1_0,
										 FETCH_REQUEST_HEADER, "Pragma:",
										 FETCH_REQUEST_HEADER, "Host:",
										 FETCH_REQUEST_HEADER, "Accept:",
										 FETCH_END);
		}
		else /* HTTP_POST */
		{
			/* form complete url */
			len = strlen(url) + 11 + strlen(operation) + 1;
			complete_url = malloc(len);
			snprintf(complete_url, len, "%s?operation=%s", url, operation);

			status = lib->fetcher->fetch(lib->fetcher, complete_url, response,
										 FETCH_REQUEST_DATA, pkcs7,
										 FETCH_REQUEST_TYPE, "",
										 FETCH_REQUEST_HEADER, "Expect:",
										 FETCH_END);
		}
	}
	else  /* SCEP_GET_CA_CERT */
	{
		const char operation[] = "GetCACert";

		/* form complete url */
		len = strlen(url) + 32 + strlen(operation) + 1;
		complete_url = malloc(len);
		snprintf(complete_url, len, "%s?operation=%s&message=CAIdentifier"
				, url, operation);

		status = lib->fetcher->fetch(lib->fetcher, complete_url, response,
									 FETCH_END);
	}

	free(complete_url);
	return (status == SUCCESS);
}

err_t scep_parse_response(chunk_t response, chunk_t transID, contentInfo_t *data,
						  scep_attributes_t *attrs, certificate_t *signer_cert)
{
	chunk_t attributes;

	if (!pkcs7_parse_signedData(response, data, NULL, &attributes, signer_cert))
	{
		return "error parsing the scep response";
	}
	if (!parse_attributes(attributes, attrs))
	{
		return "error parsing the scep response attributes";
	}
	if (!chunk_equals(transID, attrs->transID))
	{
		return "transaction ID of scep response does not match";
	}
	return NULL;
}