gss_krb5_wrap.c revision e1f6c07b1160ef28e8754d12e6c03288dd9d5ca8 
1/*
2 * COPYRIGHT (c) 2008
3 * The Regents of the University of Michigan
4 * ALL RIGHTS RESERVED
5 *
6 * Permission is granted to use, copy, create derivative works
7 * and redistribute this software and such derivative works
8 * for any purpose, so long as the name of The University of
9 * Michigan is not used in any advertising or publicity
10 * pertaining to the use of distribution of this software
11 * without specific, written prior authorization.  If the
12 * above copyright notice or any other identification of the
13 * University of Michigan is included in any copy of any
14 * portion of this software, then the disclaimer below must
15 * also be included.
16 *
17 * THIS SOFTWARE IS PROVIDED AS IS, WITHOUT REPRESENTATION
18 * FROM THE UNIVERSITY OF MICHIGAN AS TO ITS FITNESS FOR ANY
19 * PURPOSE, AND WITHOUT WARRANTY BY THE UNIVERSITY OF
20 * MICHIGAN OF ANY KIND, EITHER EXPRESS OR IMPLIED, INCLUDING
21 * WITHOUT LIMITATION THE IMPLIED WARRANTIES OF
22 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE
23 * REGENTS OF THE UNIVERSITY OF MICHIGAN SHALL NOT BE LIABLE
24 * FOR ANY DAMAGES, INCLUDING SPECIAL, INDIRECT, INCIDENTAL, OR
25 * CONSEQUENTIAL DAMAGES, WITH RESPECT TO ANY CLAIM ARISING
26 * OUT OF OR IN CONNECTION WITH THE USE OF THE SOFTWARE, EVEN
27 * IF IT HAS BEEN OR IS HEREAFTER ADVISED OF THE POSSIBILITY OF
28 * SUCH DAMAGES.
29 */
30
31#include <linux/types.h>
32#include <linux/jiffies.h>
33#include <linux/sunrpc/gss_krb5.h>
34#include <linux/random.h>
35#include <linux/pagemap.h>
36#include <linux/crypto.h>
37
38#ifdef RPC_DEBUG
39# define RPCDBG_FACILITY	RPCDBG_AUTH
40#endif
41
42static inline int
43gss_krb5_padding(int blocksize, int length)
44{
45	return blocksize - (length % blocksize);
46}
47
48static inline void
49gss_krb5_add_padding(struct xdr_buf *buf, int offset, int blocksize)
50{
51	int padding = gss_krb5_padding(blocksize, buf->len - offset);
52	char *p;
53	struct kvec *iov;
54
55	if (buf->page_len || buf->tail[0].iov_len)
56		iov = &buf->tail[0];
57	else
58		iov = &buf->head[0];
59	p = iov->iov_base + iov->iov_len;
60	iov->iov_len += padding;
61	buf->len += padding;
62	memset(p, padding, padding);
63}
64
65static inline int
66gss_krb5_remove_padding(struct xdr_buf *buf, int blocksize)
67{
68	u8 *ptr;
69	u8 pad;
70	size_t len = buf->len;
71
72	if (len <= buf->head[0].iov_len) {
73		pad = *(u8 *)(buf->head[0].iov_base + len - 1);
74		if (pad > buf->head[0].iov_len)
75			return -EINVAL;
76		buf->head[0].iov_len -= pad;
77		goto out;
78	} else
79		len -= buf->head[0].iov_len;
80	if (len <= buf->page_len) {
81		unsigned int last = (buf->page_base + len - 1)
82					>>PAGE_CACHE_SHIFT;
83		unsigned int offset = (buf->page_base + len - 1)
84					& (PAGE_CACHE_SIZE - 1);
85		ptr = kmap_atomic(buf->pages[last], KM_USER0);
86		pad = *(ptr + offset);
87		kunmap_atomic(ptr, KM_USER0);
88		goto out;
89	} else
90		len -= buf->page_len;
91	BUG_ON(len > buf->tail[0].iov_len);
92	pad = *(u8 *)(buf->tail[0].iov_base + len - 1);
93out:
94	/* XXX: NOTE: we do not adjust the page lengths--they represent
95	 * a range of data in the real filesystem page cache, and we need
96	 * to know that range so the xdr code can properly place read data.
97	 * However adjusting the head length, as we do above, is harmless.
98	 * In the case of a request that fits into a single page, the server
99	 * also uses length and head length together to determine the original
100	 * start of the request to copy the request for deferal; so it's
101	 * easier on the server if we adjust head and tail length in tandem.
102	 * It's not really a problem that we don't fool with the page and
103	 * tail lengths, though--at worst badly formed xdr might lead the
104	 * server to attempt to parse the padding.
105	 * XXX: Document all these weird requirements for gss mechanism
106	 * wrap/unwrap functions. */
107	if (pad > blocksize)
108		return -EINVAL;
109	if (buf->len > pad)
110		buf->len -= pad;
111	else
112		return -EINVAL;
113	return 0;
114}
115
116static void
117make_confounder(char *p, u32 conflen)
118{
119	static u64 i = 0;
120	u64 *q = (u64 *)p;
121
122	/* rfc1964 claims this should be "random".  But all that's really
123	 * necessary is that it be unique.  And not even that is necessary in
124	 * our case since our "gssapi" implementation exists only to support
125	 * rpcsec_gss, so we know that the only buffers we will ever encrypt
126	 * already begin with a unique sequence number.  Just to hedge my bets
127	 * I'll make a half-hearted attempt at something unique, but ensuring
128	 * uniqueness would mean worrying about atomicity and rollover, and I
129	 * don't care enough. */
130
131	/* initialize to random value */
132	if (i == 0) {
133		i = random32();
134		i = (i << 32) | random32();
135	}
136
137	switch (conflen) {
138	case 16:
139		*q++ = i++;
140		/* fall through */
141	case 8:
142		*q++ = i++;
143		break;
144	default:
145		BUG();
146	}
147}
148
149/* Assumptions: the head and tail of inbuf are ours to play with.
150 * The pages, however, may be real pages in the page cache and we replace
151 * them with scratch pages from **pages before writing to them. */
152/* XXX: obviously the above should be documentation of wrap interface,
153 * and shouldn't be in this kerberos-specific file. */
154
155/* XXX factor out common code with seal/unseal. */
156
157static u32
158gss_wrap_kerberos_v1(struct krb5_ctx *kctx, int offset,
159		struct xdr_buf *buf, struct page **pages)
160{
161	char			cksumdata[GSS_KRB5_MAX_CKSUM_LEN];
162	struct xdr_netobj	md5cksum = {.len = sizeof(cksumdata),
163					    .data = cksumdata};
164	int			blocksize = 0, plainlen;
165	unsigned char		*ptr, *msg_start;
166	s32			now;
167	int			headlen;
168	struct page		**tmp_pages;
169	u32			seq_send;
170	u8			*cksumkey;
171
172	dprintk("RPC:       %s\n", __func__);
173
174	now = get_seconds();
175
176	blocksize = crypto_blkcipher_blocksize(kctx->enc);
177	gss_krb5_add_padding(buf, offset, blocksize);
178	BUG_ON((buf->len - offset) % blocksize);
179	plainlen = blocksize + buf->len - offset;
180
181	headlen = g_token_size(&kctx->mech_used,
182		GSS_KRB5_TOK_HDR_LEN + kctx->gk5e->cksumlength + plainlen) -
183		(buf->len - offset);
184
185	ptr = buf->head[0].iov_base + offset;
186	/* shift data to make room for header. */
187	xdr_extend_head(buf, offset, headlen);
188
189	/* XXX Would be cleverer to encrypt while copying. */
190	BUG_ON((buf->len - offset - headlen) % blocksize);
191
192	g_make_token_header(&kctx->mech_used,
193				GSS_KRB5_TOK_HDR_LEN +
194				kctx->gk5e->cksumlength + plainlen, &ptr);
195
196
197	/* ptr now at header described in rfc 1964, section 1.2.1: */
198	ptr[0] = (unsigned char) ((KG_TOK_WRAP_MSG >> 8) & 0xff);
199	ptr[1] = (unsigned char) (KG_TOK_WRAP_MSG & 0xff);
200
201	msg_start = ptr + GSS_KRB5_TOK_HDR_LEN + kctx->gk5e->cksumlength;
202
203	*(__be16 *)(ptr + 2) = cpu_to_le16(kctx->gk5e->signalg);
204	memset(ptr + 4, 0xff, 4);
205	*(__be16 *)(ptr + 4) = cpu_to_le16(kctx->gk5e->sealalg);
206
207	make_confounder(msg_start, blocksize);
208
209	if (kctx->gk5e->keyed_cksum)
210		cksumkey = kctx->cksum;
211	else
212		cksumkey = NULL;
213
214	/* XXXJBF: UGH!: */
215	tmp_pages = buf->pages;
216	buf->pages = pages;
217	if (make_checksum(kctx, ptr, 8, buf, offset + headlen - blocksize,
218					cksumkey, &md5cksum))
219		return GSS_S_FAILURE;
220	buf->pages = tmp_pages;
221
222	memcpy(ptr + GSS_KRB5_TOK_HDR_LEN, md5cksum.data, md5cksum.len);
223
224	spin_lock(&krb5_seq_lock);
225	seq_send = kctx->seq_send++;
226	spin_unlock(&krb5_seq_lock);
227
228	/* XXX would probably be more efficient to compute checksum
229	 * and encrypt at the same time: */
230	if ((krb5_make_seq_num(kctx->seq, kctx->initiate ? 0 : 0xff,
231			       seq_send, ptr + GSS_KRB5_TOK_HDR_LEN, ptr + 8)))
232		return GSS_S_FAILURE;
233
234	if (gss_encrypt_xdr_buf(kctx->enc, buf, offset + headlen - blocksize,
235									pages))
236		return GSS_S_FAILURE;
237
238	return (kctx->endtime < now) ? GSS_S_CONTEXT_EXPIRED : GSS_S_COMPLETE;
239}
240
241static u32
242gss_unwrap_kerberos_v1(struct krb5_ctx *kctx, int offset, struct xdr_buf *buf)
243{
244	int			signalg;
245	int			sealalg;
246	char			cksumdata[GSS_KRB5_MAX_CKSUM_LEN];
247	struct xdr_netobj	md5cksum = {.len = sizeof(cksumdata),
248					    .data = cksumdata};
249	s32			now;
250	int			direction;
251	s32			seqnum;
252	unsigned char		*ptr;
253	int			bodysize;
254	void			*data_start, *orig_start;
255	int			data_len;
256	int			blocksize;
257	int			crypt_offset;
258	u8			*cksumkey;
259
260	dprintk("RPC:       gss_unwrap_kerberos\n");
261
262	ptr = (u8 *)buf->head[0].iov_base + offset;
263	if (g_verify_token_header(&kctx->mech_used, &bodysize, &ptr,
264					buf->len - offset))
265		return GSS_S_DEFECTIVE_TOKEN;
266
267	if ((ptr[0] != ((KG_TOK_WRAP_MSG >> 8) & 0xff)) ||
268	    (ptr[1] !=  (KG_TOK_WRAP_MSG & 0xff)))
269		return GSS_S_DEFECTIVE_TOKEN;
270
271	/* XXX sanity-check bodysize?? */
272
273	/* get the sign and seal algorithms */
274
275	signalg = ptr[2] + (ptr[3] << 8);
276	if (signalg != kctx->gk5e->signalg)
277		return GSS_S_DEFECTIVE_TOKEN;
278
279	sealalg = ptr[4] + (ptr[5] << 8);
280	if (sealalg != kctx->gk5e->sealalg)
281		return GSS_S_DEFECTIVE_TOKEN;
282
283	if ((ptr[6] != 0xff) || (ptr[7] != 0xff))
284		return GSS_S_DEFECTIVE_TOKEN;
285
286	/*
287	 * Data starts after token header and checksum.  ptr points
288	 * to the beginning of the token header
289	 */
290	crypt_offset = ptr + (GSS_KRB5_TOK_HDR_LEN + kctx->gk5e->cksumlength) -
291					(unsigned char *)buf->head[0].iov_base;
292	if (gss_decrypt_xdr_buf(kctx->enc, buf, crypt_offset))
293		return GSS_S_DEFECTIVE_TOKEN;
294
295	if (kctx->gk5e->keyed_cksum)
296		cksumkey = kctx->cksum;
297	else
298		cksumkey = NULL;
299
300	if (make_checksum(kctx, ptr, 8, buf, crypt_offset,
301						cksumkey, &md5cksum))
302		return GSS_S_FAILURE;
303
304	if (memcmp(md5cksum.data, ptr + GSS_KRB5_TOK_HDR_LEN,
305						kctx->gk5e->cksumlength))
306		return GSS_S_BAD_SIG;
307
308	/* it got through unscathed.  Make sure the context is unexpired */
309
310	now = get_seconds();
311
312	if (now > kctx->endtime)
313		return GSS_S_CONTEXT_EXPIRED;
314
315	/* do sequencing checks */
316
317	if (krb5_get_seq_num(kctx->seq, ptr + GSS_KRB5_TOK_HDR_LEN, ptr + 8,
318				    &direction, &seqnum))
319		return GSS_S_BAD_SIG;
320
321	if ((kctx->initiate && direction != 0xff) ||
322	    (!kctx->initiate && direction != 0))
323		return GSS_S_BAD_SIG;
324
325	/* Copy the data back to the right position.  XXX: Would probably be
326	 * better to copy and encrypt at the same time. */
327
328	blocksize = crypto_blkcipher_blocksize(kctx->enc);
329	data_start = ptr + (GSS_KRB5_TOK_HDR_LEN + kctx->gk5e->cksumlength) +
330					blocksize;
331	orig_start = buf->head[0].iov_base + offset;
332	data_len = (buf->head[0].iov_base + buf->head[0].iov_len) - data_start;
333	memmove(orig_start, data_start, data_len);
334	buf->head[0].iov_len -= (data_start - orig_start);
335	buf->len -= (data_start - orig_start);
336
337	if (gss_krb5_remove_padding(buf, blocksize))
338		return GSS_S_DEFECTIVE_TOKEN;
339
340	return GSS_S_COMPLETE;
341}
342
343u32
344gss_wrap_kerberos(struct gss_ctx *gctx, int offset,
345		  struct xdr_buf *buf, struct page **pages)
346{
347	struct krb5_ctx	*kctx = gctx->internal_ctx_id;
348
349	switch (kctx->enctype) {
350	default:
351		BUG();
352	case ENCTYPE_DES_CBC_RAW:
353		return gss_wrap_kerberos_v1(kctx, offset, buf, pages);
354	}
355}
356
357u32
358gss_unwrap_kerberos(struct gss_ctx *gctx, int offset, struct xdr_buf *buf)
359{
360	struct krb5_ctx	*kctx = gctx->internal_ctx_id;
361
362	switch (kctx->enctype) {
363	default:
364		BUG();
365	case ENCTYPE_DES_CBC_RAW:
366		return gss_unwrap_kerberos_v1(kctx, offset, buf);
367	}
368}
369
370