gss_krb5_wrap.c revision 00fd6e14255fe7a249315746386d640bc4e9e758 
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, 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	switch (kctx->signalg) {
136		case SGN_ALG_DES_MAC_MD5:
137			checksum_type = CKSUMTYPE_RSA_MD5;
138			break;
139		default:
140			dprintk("RPC:      gss_krb5_seal: kctx->signalg %d not"
141				" supported\n", kctx->signalg);
142			goto out_err;
143	}
144	if (kctx->sealalg != SEAL_ALG_NONE && kctx->sealalg != SEAL_ALG_DES) {
145		dprintk("RPC:      gss_krb5_seal: kctx->sealalg %d not supported\n",
146			kctx->sealalg);
147		goto out_err;
148	}
149
150	blocksize = crypto_tfm_alg_blocksize(kctx->enc);
151	gss_krb5_add_padding(buf, offset, blocksize);
152	BUG_ON((buf->len - offset) % blocksize);
153	plainlen = blocksize + buf->len - offset;
154
155	headlen = g_token_size(&kctx->mech_used, 22 + plainlen) -
156						(buf->len - offset);
157
158	ptr = buf->head[0].iov_base + offset;
159	/* shift data to make room for header. */
160	/* XXX Would be cleverer to encrypt while copying. */
161	/* XXX bounds checking, slack, etc. */
162	memmove(ptr + headlen, ptr, buf->head[0].iov_len - offset);
163	buf->head[0].iov_len += headlen;
164	buf->len += headlen;
165	BUG_ON((buf->len - offset - headlen) % blocksize);
166
167	g_make_token_header(&kctx->mech_used, 22 + plainlen, &ptr);
168
169
170	*ptr++ = (unsigned char) ((KG_TOK_WRAP_MSG>>8)&0xff);
171	*ptr++ = (unsigned char) (KG_TOK_WRAP_MSG&0xff);
172
173	/* ptr now at byte 2 of header described in rfc 1964, section 1.2.1: */
174	krb5_hdr = ptr - 2;
175	msg_start = krb5_hdr + 24;
176	/* XXXJBF: */ BUG_ON(buf->head[0].iov_base + offset + headlen != msg_start + blocksize);
177
178	*(u16 *)(krb5_hdr + 2) = htons(kctx->signalg);
179	memset(krb5_hdr + 4, 0xff, 4);
180	*(u16 *)(krb5_hdr + 4) = htons(kctx->sealalg);
181
182	make_confounder(msg_start, blocksize);
183
184	/* XXXJBF: UGH!: */
185	tmp_pages = buf->pages;
186	buf->pages = pages;
187	if (make_checksum(checksum_type, krb5_hdr, 8, buf,
188				offset + headlen - blocksize, &md5cksum))
189		goto out_err;
190	buf->pages = tmp_pages;
191
192	switch (kctx->signalg) {
193	case SGN_ALG_DES_MAC_MD5:
194		if (krb5_encrypt(kctx->seq, NULL, md5cksum.data,
195				  md5cksum.data, md5cksum.len))
196			goto out_err;
197		memcpy(krb5_hdr + 16,
198		       md5cksum.data + md5cksum.len - KRB5_CKSUM_LENGTH,
199		       KRB5_CKSUM_LENGTH);
200
201		dprintk("RPC:      make_seal_token: cksum data: \n");
202		print_hexl((u32 *) (krb5_hdr + 16), KRB5_CKSUM_LENGTH, 0);
203		break;
204	default:
205		BUG();
206	}
207
208	kfree(md5cksum.data);
209
210	/* XXX would probably be more efficient to compute checksum
211	 * and encrypt at the same time: */
212	if ((krb5_make_seq_num(kctx->seq, kctx->initiate ? 0 : 0xff,
213			       kctx->seq_send, krb5_hdr + 16, krb5_hdr + 8)))
214		goto out_err;
215
216	if (gss_encrypt_xdr_buf(kctx->enc, buf, offset + headlen - blocksize,
217									pages))
218		goto out_err;
219
220	kctx->seq_send++;
221
222	return ((kctx->endtime < now) ? GSS_S_CONTEXT_EXPIRED : GSS_S_COMPLETE);
223out_err:
224	if (md5cksum.data) kfree(md5cksum.data);
225	return GSS_S_FAILURE;
226}
227
228u32
229gss_unwrap_kerberos(struct gss_ctx *ctx, int offset, struct xdr_buf *buf)
230{
231	struct krb5_ctx		*kctx = ctx->internal_ctx_id;
232	int			signalg;
233	int			sealalg;
234	s32			checksum_type;
235	struct xdr_netobj	md5cksum = {.len = 0, .data = NULL};
236	s32			now;
237	int			direction;
238	s32			seqnum;
239	unsigned char		*ptr;
240	int			bodysize;
241	u32			ret = GSS_S_DEFECTIVE_TOKEN;
242	void			*data_start, *orig_start;
243	int			data_len;
244	int			blocksize;
245
246	dprintk("RPC:      gss_unwrap_kerberos\n");
247
248	ptr = (u8 *)buf->head[0].iov_base + offset;
249	if (g_verify_token_header(&kctx->mech_used, &bodysize, &ptr,
250					buf->len - offset))
251		goto out;
252
253	if ((*ptr++ != ((KG_TOK_WRAP_MSG>>8)&0xff)) ||
254	    (*ptr++ !=  (KG_TOK_WRAP_MSG    &0xff))   )
255		goto out;
256
257	/* XXX sanity-check bodysize?? */
258
259	/* get the sign and seal algorithms */
260
261	signalg = ptr[0] + (ptr[1] << 8);
262	sealalg = ptr[2] + (ptr[3] << 8);
263
264	/* Sanity checks */
265
266	if ((ptr[4] != 0xff) || (ptr[5] != 0xff))
267		goto out;
268
269	if (sealalg == 0xffff)
270		goto out;
271
272	/* in the current spec, there is only one valid seal algorithm per
273	   key type, so a simple comparison is ok */
274
275	if (sealalg != kctx->sealalg)
276		goto out;
277
278	/* there are several mappings of seal algorithms to sign algorithms,
279	   but few enough that we can try them all. */
280
281	if ((kctx->sealalg == SEAL_ALG_NONE && signalg > 1) ||
282	    (kctx->sealalg == SEAL_ALG_1 && signalg != SGN_ALG_3) ||
283	    (kctx->sealalg == SEAL_ALG_DES3KD &&
284	     signalg != SGN_ALG_HMAC_SHA1_DES3_KD))
285		goto out;
286
287	if (gss_decrypt_xdr_buf(kctx->enc, buf,
288			ptr + 22 - (unsigned char *)buf->head[0].iov_base))
289		goto out;
290
291	/* compute the checksum of the message */
292
293	/* initialize the the cksum */
294	switch (signalg) {
295	case SGN_ALG_DES_MAC_MD5:
296		checksum_type = CKSUMTYPE_RSA_MD5;
297		break;
298	default:
299		ret = GSS_S_DEFECTIVE_TOKEN;
300		goto out;
301	}
302
303	switch (signalg) {
304	case SGN_ALG_DES_MAC_MD5:
305		ret = make_checksum(checksum_type, ptr - 2, 8, buf,
306			 ptr + 22 - (unsigned char *)buf->head[0].iov_base, &md5cksum);
307		if (ret)
308			goto out;
309
310		ret = krb5_encrypt(kctx->seq, NULL, md5cksum.data,
311				   md5cksum.data, md5cksum.len);
312		if (ret)
313			goto out;
314
315		if (memcmp(md5cksum.data + 8, ptr + 14, 8)) {
316			ret = GSS_S_BAD_SIG;
317			goto out;
318		}
319		break;
320	default:
321		ret = GSS_S_DEFECTIVE_TOKEN;
322		goto out;
323	}
324
325	/* it got through unscathed.  Make sure the context is unexpired */
326
327	now = get_seconds();
328
329	ret = GSS_S_CONTEXT_EXPIRED;
330	if (now > kctx->endtime)
331		goto out;
332
333	/* do sequencing checks */
334
335	ret = GSS_S_BAD_SIG;
336	if ((ret = krb5_get_seq_num(kctx->seq, ptr + 14, ptr + 6, &direction,
337				    &seqnum)))
338		goto out;
339
340	if ((kctx->initiate && direction != 0xff) ||
341	    (!kctx->initiate && direction != 0))
342		goto out;
343
344	/* Copy the data back to the right position.  XXX: Would probably be
345	 * better to copy and encrypt at the same time. */
346
347	blocksize = crypto_tfm_alg_blocksize(kctx->enc);
348	data_start = ptr + 22 + blocksize;
349	orig_start = buf->head[0].iov_base + offset;
350	data_len = (buf->head[0].iov_base + buf->head[0].iov_len) - data_start;
351	memmove(orig_start, data_start, data_len);
352	buf->head[0].iov_len -= (data_start - orig_start);
353	buf->len -= (data_start - orig_start);
354
355	ret = GSS_S_DEFECTIVE_TOKEN;
356	if (gss_krb5_remove_padding(buf, blocksize))
357		goto out;
358
359	ret = GSS_S_COMPLETE;
360out:
361	if (md5cksum.data) kfree(md5cksum.data);
362	return ret;
363}
364