gss_krb5_wrap.c revision 14ae162c24d985593d5b19437d7f3d8fd0062b59 
1#include <linux/types.h>
2#include <linux/slab.h>
3#include <linux/jiffies.h>
4#include <linux/sunrpc/gss_krb5.h>
5#include <linux/random.h>
6#include <linux/pagemap.h>
7#include <asm/scatterlist.h>
8#include <linux/crypto.h>
9
10#ifdef RPC_DEBUG
11# define RPCDBG_FACILITY	RPCDBG_AUTH
12#endif
13
14static inline int
15gss_krb5_padding(int blocksize, int length)
16{
17	/* Most of the code is block-size independent but currently we
18	 * use only 8: */
19	BUG_ON(blocksize != 8);
20	return 8 - (length & 7);
21}
22
23static inline void
24gss_krb5_add_padding(struct xdr_buf *buf, int offset, int blocksize)
25{
26	int padding = gss_krb5_padding(blocksize, buf->len - offset);
27	char *p;
28	struct kvec *iov;
29
30	if (buf->page_len || buf->tail[0].iov_len)
31		iov = &buf->tail[0];
32	else
33		iov = &buf->head[0];
34	p = iov->iov_base + iov->iov_len;
35	iov->iov_len += padding;
36	buf->len += padding;
37	memset(p, padding, padding);
38}
39
40static inline int
41gss_krb5_remove_padding(struct xdr_buf *buf, int blocksize)
42{
43	u8 *ptr;
44	u8 pad;
45	int len = buf->len;
46
47	if (len <= buf->head[0].iov_len) {
48		pad = *(u8 *)(buf->head[0].iov_base + len - 1);
49		if (pad > buf->head[0].iov_len)
50			return -EINVAL;
51		buf->head[0].iov_len -= pad;
52		goto out;
53	} else
54		len -= buf->head[0].iov_len;
55	if (len <= buf->page_len) {
56		int last = (buf->page_base + len - 1)
57					>>PAGE_CACHE_SHIFT;
58		int offset = (buf->page_base + len - 1)
59					& (PAGE_CACHE_SIZE - 1);
60		ptr = kmap_atomic(buf->pages[last], KM_SKB_SUNRPC_DATA);
61		pad = *(ptr + offset);
62		kunmap_atomic(ptr, KM_SKB_SUNRPC_DATA);
63		goto out;
64	} else
65		len -= buf->page_len;
66	BUG_ON(len > buf->tail[0].iov_len);
67	pad = *(u8 *)(buf->tail[0].iov_base + len - 1);
68out:
69	/* XXX: NOTE: we do not adjust the page lengths--they represent
70	 * a range of data in the real filesystem page cache, and we need
71	 * to know that range so the xdr code can properly place read data.
72	 * However adjusting the head length, as we do above, is harmless.
73	 * In the case of a request that fits into a single page, the server
74	 * also uses length and head length together to determine the original
75	 * start of the request to copy the request for deferal; so it's
76	 * easier on the server if we adjust head and tail length in tandem.
77	 * It's not really a problem that we don't fool with the page and
78	 * tail lengths, though--at worst badly formed xdr might lead the
79	 * server to attempt to parse the padding.
80	 * XXX: Document all these weird requirements for gss mechanism
81	 * wrap/unwrap functions. */
82	if (pad > blocksize)
83		return -EINVAL;
84	if (buf->len > pad)
85		buf->len -= pad;
86	else
87		return -EINVAL;
88	return 0;
89}
90
91static inline void
92make_confounder(char *p, int blocksize)
93{
94	static u64 i = 0;
95	u64 *q = (u64 *)p;
96
97	/* rfc1964 claims this should be "random".  But all that's really
98	 * necessary is that it be unique.  And not even that is necessary in
99	 * our case since our "gssapi" implementation exists only to support
100	 * rpcsec_gss, so we know that the only buffers we will ever encrypt
101	 * already begin with a unique sequence number.  Just to hedge my bets
102	 * I'll make a half-hearted attempt at something unique, but ensuring
103	 * uniqueness would mean worrying about atomicity and rollover, and I
104	 * don't care enough. */
105
106	BUG_ON(blocksize != 8);
107	*q = i++;
108}
109
110/* Assumptions: the head and tail of inbuf are ours to play with.
111 * The pages, however, may be real pages in the page cache and we replace
112 * them with scratch pages from **pages before writing to them. */
113/* XXX: obviously the above should be documentation of wrap interface,
114 * and shouldn't be in this kerberos-specific file. */
115
116/* XXX factor out common code with seal/unseal. */
117
118u32
119gss_wrap_kerberos(struct gss_ctx *ctx, u32 qop, int offset,
120		struct xdr_buf *buf, struct page **pages)
121{
122	struct krb5_ctx		*kctx = ctx->internal_ctx_id;
123	s32			checksum_type;
124	struct xdr_netobj	md5cksum = {.len = 0, .data = NULL};
125	int			blocksize = 0, plainlen;
126	unsigned char		*ptr, *krb5_hdr, *msg_start;
127	s32			now;
128	int			headlen;
129	struct page		**tmp_pages;
130
131	dprintk("RPC:     gss_wrap_kerberos\n");
132
133	now = get_seconds();
134
135	if (qop != 0)
136		goto out_err;
137
138	switch (kctx->signalg) {
139		case SGN_ALG_DES_MAC_MD5:
140			checksum_type = CKSUMTYPE_RSA_MD5;
141			break;
142		default:
143			dprintk("RPC:      gss_krb5_seal: kctx->signalg %d not"
144				" supported\n", kctx->signalg);
145			goto out_err;
146	}
147	if (kctx->sealalg != SEAL_ALG_NONE && kctx->sealalg != SEAL_ALG_DES) {
148		dprintk("RPC:      gss_krb5_seal: kctx->sealalg %d not supported\n",
149			kctx->sealalg);
150		goto out_err;
151	}
152
153	blocksize = crypto_tfm_alg_blocksize(kctx->enc);
154	gss_krb5_add_padding(buf, offset, blocksize);
155	BUG_ON((buf->len - offset) % blocksize);
156	plainlen = blocksize + buf->len - offset;
157
158	headlen = g_token_size(&kctx->mech_used, 22 + plainlen) -
159						(buf->len - offset);
160
161	ptr = buf->head[0].iov_base + offset;
162	/* shift data to make room for header. */
163	/* XXX Would be cleverer to encrypt while copying. */
164	/* XXX bounds checking, slack, etc. */
165	memmove(ptr + headlen, ptr, buf->head[0].iov_len - offset);
166	buf->head[0].iov_len += headlen;
167	buf->len += headlen;
168	BUG_ON((buf->len - offset - headlen) % blocksize);
169
170	g_make_token_header(&kctx->mech_used, 22 + plainlen, &ptr);
171
172
173	*ptr++ = (unsigned char) ((KG_TOK_WRAP_MSG>>8)&0xff);
174	*ptr++ = (unsigned char) (KG_TOK_WRAP_MSG&0xff);
175
176	/* ptr now at byte 2 of header described in rfc 1964, section 1.2.1: */
177	krb5_hdr = ptr - 2;
178	msg_start = krb5_hdr + 24;
179	/* XXXJBF: */ BUG_ON(buf->head[0].iov_base + offset + headlen != msg_start + blocksize);
180
181	*(u16 *)(krb5_hdr + 2) = htons(kctx->signalg);
182	memset(krb5_hdr + 4, 0xff, 4);
183	*(u16 *)(krb5_hdr + 4) = htons(kctx->sealalg);
184
185	make_confounder(msg_start, blocksize);
186
187	/* XXXJBF: UGH!: */
188	tmp_pages = buf->pages;
189	buf->pages = pages;
190	if (make_checksum(checksum_type, krb5_hdr, 8, buf,
191				offset + headlen - blocksize, &md5cksum))
192		goto out_err;
193	buf->pages = tmp_pages;
194
195	switch (kctx->signalg) {
196	case SGN_ALG_DES_MAC_MD5:
197		if (krb5_encrypt(kctx->seq, NULL, md5cksum.data,
198				  md5cksum.data, md5cksum.len))
199			goto out_err;
200		memcpy(krb5_hdr + 16,
201		       md5cksum.data + md5cksum.len - KRB5_CKSUM_LENGTH,
202		       KRB5_CKSUM_LENGTH);
203
204		dprintk("RPC:      make_seal_token: cksum data: \n");
205		print_hexl((u32 *) (krb5_hdr + 16), KRB5_CKSUM_LENGTH, 0);
206		break;
207	default:
208		BUG();
209	}
210
211	kfree(md5cksum.data);
212
213	/* XXX would probably be more efficient to compute checksum
214	 * and encrypt at the same time: */
215	if ((krb5_make_seq_num(kctx->seq, kctx->initiate ? 0 : 0xff,
216			       kctx->seq_send, krb5_hdr + 16, krb5_hdr + 8)))
217		goto out_err;
218
219	if (gss_encrypt_xdr_buf(kctx->enc, buf, offset + headlen - blocksize,
220									pages))
221		goto out_err;
222
223	kctx->seq_send++;
224
225	return ((kctx->endtime < now) ? GSS_S_CONTEXT_EXPIRED : GSS_S_COMPLETE);
226out_err:
227	if (md5cksum.data) kfree(md5cksum.data);
228	return GSS_S_FAILURE;
229}
230
231u32
232gss_unwrap_kerberos(struct gss_ctx *ctx, u32 *qop, int offset,
233			struct xdr_buf *buf)
234{
235	struct krb5_ctx		*kctx = ctx->internal_ctx_id;
236	int			signalg;
237	int			sealalg;
238	s32			checksum_type;
239	struct xdr_netobj	md5cksum = {.len = 0, .data = NULL};
240	s32			now;
241	int			direction;
242	s32			seqnum;
243	unsigned char		*ptr;
244	int			bodysize;
245	u32			ret = GSS_S_DEFECTIVE_TOKEN;
246	void			*data_start, *orig_start;
247	int			data_len;
248	int			blocksize;
249
250	dprintk("RPC:      gss_unwrap_kerberos\n");
251
252	ptr = (u8 *)buf->head[0].iov_base + offset;
253	if (g_verify_token_header(&kctx->mech_used, &bodysize, &ptr,
254					buf->len - offset))
255		goto out;
256
257	if ((*ptr++ != ((KG_TOK_WRAP_MSG>>8)&0xff)) ||
258	    (*ptr++ !=  (KG_TOK_WRAP_MSG    &0xff))   )
259		goto out;
260
261	/* XXX sanity-check bodysize?? */
262
263	/* get the sign and seal algorithms */
264
265	signalg = ptr[0] + (ptr[1] << 8);
266	sealalg = ptr[2] + (ptr[3] << 8);
267
268	/* Sanity checks */
269
270	if ((ptr[4] != 0xff) || (ptr[5] != 0xff))
271		goto out;
272
273	if (sealalg == 0xffff)
274		goto out;
275
276	/* in the current spec, there is only one valid seal algorithm per
277	   key type, so a simple comparison is ok */
278
279	if (sealalg != kctx->sealalg)
280		goto out;
281
282	/* there are several mappings of seal algorithms to sign algorithms,
283	   but few enough that we can try them all. */
284
285	if ((kctx->sealalg == SEAL_ALG_NONE && signalg > 1) ||
286	    (kctx->sealalg == SEAL_ALG_1 && signalg != SGN_ALG_3) ||
287	    (kctx->sealalg == SEAL_ALG_DES3KD &&
288	     signalg != SGN_ALG_HMAC_SHA1_DES3_KD))
289		goto out;
290
291	if (gss_decrypt_xdr_buf(kctx->enc, buf,
292			ptr + 22 - (unsigned char *)buf->head[0].iov_base))
293		goto out;
294
295	/* compute the checksum of the message */
296
297	/* initialize the the cksum */
298	switch (signalg) {
299	case SGN_ALG_DES_MAC_MD5:
300		checksum_type = CKSUMTYPE_RSA_MD5;
301		break;
302	default:
303		ret = GSS_S_DEFECTIVE_TOKEN;
304		goto out;
305	}
306
307	switch (signalg) {
308	case SGN_ALG_DES_MAC_MD5:
309		ret = make_checksum(checksum_type, ptr - 2, 8, buf,
310			 ptr + 22 - (unsigned char *)buf->head[0].iov_base, &md5cksum);
311		if (ret)
312			goto out;
313
314		ret = krb5_encrypt(kctx->seq, NULL, md5cksum.data,
315				   md5cksum.data, md5cksum.len);
316		if (ret)
317			goto out;
318
319		if (memcmp(md5cksum.data + 8, ptr + 14, 8)) {
320			ret = GSS_S_BAD_SIG;
321			goto out;
322		}
323		break;
324	default:
325		ret = GSS_S_DEFECTIVE_TOKEN;
326		goto out;
327	}
328
329	/* it got through unscathed.  Make sure the context is unexpired */
330
331	if (qop)
332		*qop = GSS_C_QOP_DEFAULT;
333
334	now = get_seconds();
335
336	ret = GSS_S_CONTEXT_EXPIRED;
337	if (now > kctx->endtime)
338		goto out;
339
340	/* do sequencing checks */
341
342	ret = GSS_S_BAD_SIG;
343	if ((ret = krb5_get_seq_num(kctx->seq, ptr + 14, ptr + 6, &direction,
344				    &seqnum)))
345		goto out;
346
347	if ((kctx->initiate && direction != 0xff) ||
348	    (!kctx->initiate && direction != 0))
349		goto out;
350
351	/* Copy the data back to the right position.  XXX: Would probably be
352	 * better to copy and encrypt at the same time. */
353
354	blocksize = crypto_tfm_alg_blocksize(kctx->enc);
355	data_start = ptr + 22 + blocksize;
356	orig_start = buf->head[0].iov_base + offset;
357	data_len = (buf->head[0].iov_base + buf->head[0].iov_len) - data_start;
358	memmove(orig_start, data_start, data_len);
359	buf->head[0].iov_len -= (data_start - orig_start);
360	buf->len -= (data_start - orig_start);
361
362	ret = GSS_S_DEFECTIVE_TOKEN;
363	if (gss_krb5_remove_padding(buf, blocksize))
364		goto out;
365
366	ret = GSS_S_COMPLETE;
367out:
368	if (md5cksum.data) kfree(md5cksum.data);
369	return ret;
370}
371