summaryrefslogtreecommitdiff
path: root/net/sunrpc/auth_gss/gss_krb5_wrap.c
blob: cc45c1605f80eb7bbc6f2382bb2c3952f0446ec9 (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
#include <linux/types.h>
#include <linux/slab.h>
#include <linux/jiffies.h>
#include <linux/sunrpc/gss_krb5.h>
#include <linux/random.h>
#include <linux/pagemap.h>
#include <asm/scatterlist.h>
#include <linux/crypto.h>

#ifdef RPC_DEBUG
# define RPCDBG_FACILITY	RPCDBG_AUTH
#endif

static inline int
gss_krb5_padding(int blocksize, int length)
{
	/* Most of the code is block-size independent but currently we
	 * use only 8: */
	BUG_ON(blocksize != 8);
	return 8 - (length & 7);
}

static inline void
gss_krb5_add_padding(struct xdr_buf *buf, int offset, int blocksize)
{
	int padding = gss_krb5_padding(blocksize, buf->len - offset);
	char *p;
	struct kvec *iov;

	if (buf->page_len || buf->tail[0].iov_len)
		iov = &buf->tail[0];
	else
		iov = &buf->head[0];
	p = iov->iov_base + iov->iov_len;
	iov->iov_len += padding;
	buf->len += padding;
	memset(p, padding, padding);
}

static inline int
gss_krb5_remove_padding(struct xdr_buf *buf, int blocksize)
{
	u8 *ptr;
	u8 pad;
	int len = buf->len;

	if (len <= buf->head[0].iov_len) {
		pad = *(u8 *)(buf->head[0].iov_base + len - 1);
		if (pad > buf->head[0].iov_len)
			return -EINVAL;
		buf->head[0].iov_len -= pad;
		goto out;
	} else
		len -= buf->head[0].iov_len;
	if (len <= buf->page_len) {
		int last = (buf->page_base + len - 1)
					>>PAGE_CACHE_SHIFT;
		int offset = (buf->page_base + len - 1)
					& (PAGE_CACHE_SIZE - 1);
		ptr = kmap_atomic(buf->pages[last], KM_SKB_SUNRPC_DATA);
		pad = *(ptr + offset);
		kunmap_atomic(ptr, KM_SKB_SUNRPC_DATA);
		goto out;
	} else
		len -= buf->page_len;
	BUG_ON(len > buf->tail[0].iov_len);
	pad = *(u8 *)(buf->tail[0].iov_base + len - 1);
out:
	/* XXX: NOTE: we do not adjust the page lengths--they represent
	 * a range of data in the real filesystem page cache, and we need
	 * to know that range so the xdr code can properly place read data.
	 * However adjusting the head length, as we do above, is harmless.
	 * In the case of a request that fits into a single page, the server
	 * also uses length and head length together to determine the original
	 * start of the request to copy the request for deferal; so it's
	 * easier on the server if we adjust head and tail length in tandem.
	 * It's not really a problem that we don't fool with the page and
	 * tail lengths, though--at worst badly formed xdr might lead the
	 * server to attempt to parse the padding.
	 * XXX: Document all these weird requirements for gss mechanism
	 * wrap/unwrap functions. */
	if (pad > blocksize)
		return -EINVAL;
	if (buf->len > pad)
		buf->len -= pad;
	else
		return -EINVAL;
	return 0;
}

static inline void
make_confounder(char *p, int blocksize)
{
	static u64 i = 0;
	u64 *q = (u64 *)p;

	/* rfc1964 claims this should be "random".  But all that's really
	 * necessary is that it be unique.  And not even that is necessary in
	 * our case since our "gssapi" implementation exists only to support
	 * rpcsec_gss, so we know that the only buffers we will ever encrypt
	 * already begin with a unique sequence number.  Just to hedge my bets
	 * I'll make a half-hearted attempt at something unique, but ensuring
	 * uniqueness would mean worrying about atomicity and rollover, and I
	 * don't care enough. */

	BUG_ON(blocksize != 8);
	*q = i++;
}

/* Assumptions: the head and tail of inbuf are ours to play with.
 * The pages, however, may be real pages in the page cache and we replace
 * them with scratch pages from **pages before writing to them. */
/* XXX: obviously the above should be documentation of wrap interface,
 * and shouldn't be in this kerberos-specific file. */

/* XXX factor out common code with seal/unseal. */

u32
gss_wrap_kerberos(struct gss_ctx *ctx, int offset,
		struct xdr_buf *buf, struct page **pages)
{
	struct krb5_ctx		*kctx = ctx->internal_ctx_id;
	s32			checksum_type;
	char			cksumdata[16];
	struct xdr_netobj	md5cksum = {.len = 0, .data = cksumdata};
	int			blocksize = 0, plainlen;
	unsigned char		*ptr, *krb5_hdr, *msg_start;
	s32			now;
	int			headlen;
	struct page		**tmp_pages;
	u32			seq_send;

	dprintk("RPC:     gss_wrap_kerberos\n");

	now = get_seconds();

	switch (kctx->signalg) {
		case SGN_ALG_DES_MAC_MD5:
			checksum_type = CKSUMTYPE_RSA_MD5;
			break;
		default:
			dprintk("RPC:      gss_krb5_seal: kctx->signalg %d not"
				" supported\n", kctx->signalg);
			goto out_err;
	}
	if (kctx->sealalg != SEAL_ALG_NONE && kctx->sealalg != SEAL_ALG_DES) {
		dprintk("RPC:      gss_krb5_seal: kctx->sealalg %d not supported\n",
			kctx->sealalg);
		goto out_err;
	}

	blocksize = crypto_blkcipher_blocksize(kctx->enc);
	gss_krb5_add_padding(buf, offset, blocksize);
	BUG_ON((buf->len - offset) % blocksize);
	plainlen = blocksize + buf->len - offset;

	headlen = g_token_size(&kctx->mech_used, 22 + plainlen) -
						(buf->len - offset);

	ptr = buf->head[0].iov_base + offset;
	/* shift data to make room for header. */
	/* XXX Would be cleverer to encrypt while copying. */
	/* XXX bounds checking, slack, etc. */
	memmove(ptr + headlen, ptr, buf->head[0].iov_len - offset);
	buf->head[0].iov_len += headlen;
	buf->len += headlen;
	BUG_ON((buf->len - offset - headlen) % blocksize);

	g_make_token_header(&kctx->mech_used, 22 + plainlen, &ptr);


	*ptr++ = (unsigned char) ((KG_TOK_WRAP_MSG>>8)&0xff);
	*ptr++ = (unsigned char) (KG_TOK_WRAP_MSG&0xff);

	/* ptr now at byte 2 of header described in rfc 1964, section 1.2.1: */
	krb5_hdr = ptr - 2;
	msg_start = krb5_hdr + 24;
	/* XXXJBF: */ BUG_ON(buf->head[0].iov_base + offset + headlen != msg_start + blocksize);

	*(__be16 *)(krb5_hdr + 2) = htons(kctx->signalg);
	memset(krb5_hdr + 4, 0xff, 4);
	*(__be16 *)(krb5_hdr + 4) = htons(kctx->sealalg);

	make_confounder(msg_start, blocksize);

	/* XXXJBF: UGH!: */
	tmp_pages = buf->pages;
	buf->pages = pages;
	if (make_checksum(checksum_type, krb5_hdr, 8, buf,
				offset + headlen - blocksize, &md5cksum))
		goto out_err;
	buf->pages = tmp_pages;

	switch (kctx->signalg) {
	case SGN_ALG_DES_MAC_MD5:
		if (krb5_encrypt(kctx->seq, NULL, md5cksum.data,
				  md5cksum.data, md5cksum.len))
			goto out_err;
		memcpy(krb5_hdr + 16,
		       md5cksum.data + md5cksum.len - KRB5_CKSUM_LENGTH,
		       KRB5_CKSUM_LENGTH);

		dprintk("RPC:      make_seal_token: cksum data: \n");
		print_hexl((u32 *) (krb5_hdr + 16), KRB5_CKSUM_LENGTH, 0);
		break;
	default:
		BUG();
	}

	spin_lock(&krb5_seq_lock);
	seq_send = kctx->seq_send++;
	spin_unlock(&krb5_seq_lock);

	/* XXX would probably be more efficient to compute checksum
	 * and encrypt at the same time: */
	if ((krb5_make_seq_num(kctx->seq, kctx->initiate ? 0 : 0xff,
			       seq_send, krb5_hdr + 16, krb5_hdr + 8)))
		goto out_err;

	if (gss_encrypt_xdr_buf(kctx->enc, buf, offset + headlen - blocksize,
									pages))
		goto out_err;

	return ((kctx->endtime < now) ? GSS_S_CONTEXT_EXPIRED : GSS_S_COMPLETE);
out_err:
	return GSS_S_FAILURE;
}

u32
gss_unwrap_kerberos(struct gss_ctx *ctx, int offset, struct xdr_buf *buf)
{
	struct krb5_ctx		*kctx = ctx->internal_ctx_id;
	int			signalg;
	int			sealalg;
	s32			checksum_type;
	char			cksumdata[16];
	struct xdr_netobj	md5cksum = {.len = 0, .data = cksumdata};
	s32			now;
	int			direction;
	s32			seqnum;
	unsigned char		*ptr;
	int			bodysize;
	u32			ret = GSS_S_DEFECTIVE_TOKEN;
	void			*data_start, *orig_start;
	int			data_len;
	int			blocksize;

	dprintk("RPC:      gss_unwrap_kerberos\n");

	ptr = (u8 *)buf->head[0].iov_base + offset;
	if (g_verify_token_header(&kctx->mech_used, &bodysize, &ptr,
					buf->len - offset))
		goto out;

	if ((*ptr++ != ((KG_TOK_WRAP_MSG>>8)&0xff)) ||
	    (*ptr++ !=  (KG_TOK_WRAP_MSG    &0xff))   )
		goto out;

	/* XXX sanity-check bodysize?? */

	/* get the sign and seal algorithms */

	signalg = ptr[0] + (ptr[1] << 8);
	sealalg = ptr[2] + (ptr[3] << 8);

	/* Sanity checks */

	if ((ptr[4] != 0xff) || (ptr[5] != 0xff))
		goto out;

	if (sealalg == 0xffff)
		goto out;

	/* in the current spec, there is only one valid seal algorithm per
	   key type, so a simple comparison is ok */

	if (sealalg != kctx->sealalg)
		goto out;

	/* there are several mappings of seal algorithms to sign algorithms,
	   but few enough that we can try them all. */

	if ((kctx->sealalg == SEAL_ALG_NONE && signalg > 1) ||
	    (kctx->sealalg == SEAL_ALG_1 && signalg != SGN_ALG_3) ||
	    (kctx->sealalg == SEAL_ALG_DES3KD &&
	     signalg != SGN_ALG_HMAC_SHA1_DES3_KD))
		goto out;

	if (gss_decrypt_xdr_buf(kctx->enc, buf,
			ptr + 22 - (unsigned char *)buf->head[0].iov_base))
		goto out;

	/* compute the checksum of the message */

	/* initialize the the cksum */
	switch (signalg) {
	case SGN_ALG_DES_MAC_MD5:
		checksum_type = CKSUMTYPE_RSA_MD5;
		break;
	default:
		ret = GSS_S_DEFECTIVE_TOKEN;
		goto out;
	}

	switch (signalg) {
	case SGN_ALG_DES_MAC_MD5:
		ret = make_checksum(checksum_type, ptr - 2, 8, buf,
			 ptr + 22 - (unsigned char *)buf->head[0].iov_base, &md5cksum);
		if (ret)
			goto out;

		ret = krb5_encrypt(kctx->seq, NULL, md5cksum.data,
				   md5cksum.data, md5cksum.len);
		if (ret)
			goto out;

		if (memcmp(md5cksum.data + 8, ptr + 14, 8)) {
			ret = GSS_S_BAD_SIG;
			goto out;
		}
		break;
	default:
		ret = GSS_S_DEFECTIVE_TOKEN;
		goto out;
	}

	/* it got through unscathed.  Make sure the context is unexpired */

	now = get_seconds();

	ret = GSS_S_CONTEXT_EXPIRED;
	if (now > kctx->endtime)
		goto out;

	/* do sequencing checks */

	ret = GSS_S_BAD_SIG;
	if ((ret = krb5_get_seq_num(kctx->seq, ptr + 14, ptr + 6, &direction,
				    &seqnum)))
		goto out;

	if ((kctx->initiate && direction != 0xff) ||
	    (!kctx->initiate && direction != 0))
		goto out;

	/* Copy the data back to the right position.  XXX: Would probably be
	 * better to copy and encrypt at the same time. */

	blocksize = crypto_blkcipher_blocksize(kctx->enc);
	data_start = ptr + 22 + blocksize;
	orig_start = buf->head[0].iov_base + offset;
	data_len = (buf->head[0].iov_base + buf->head[0].iov_len) - data_start;
	memmove(orig_start, data_start, data_len);
	buf->head[0].iov_len -= (data_start - orig_start);
	buf->len -= (data_start - orig_start);

	ret = GSS_S_DEFECTIVE_TOKEN;
	if (gss_krb5_remove_padding(buf, blocksize))
		goto out;

	ret = GSS_S_COMPLETE;
out:
	return ret;
}