gss_krb5_wrap.c revision d922a84a8bf1d627810906d033223d4fa629fdbf 
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_USER0);
61		pad = *(ptr + offset);
62		kunmap_atomic(ptr, KM_USER0);
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	char			cksumdata[16];
124	struct xdr_netobj	md5cksum = {.len = 0, .data = cksumdata};
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	u32			seq_send;
131
132	dprintk("RPC:     gss_wrap_kerberos\n");
133
134	now = get_seconds();
135
136	blocksize = crypto_blkcipher_blocksize(kctx->enc);
137	gss_krb5_add_padding(buf, offset, blocksize);
138	BUG_ON((buf->len - offset) % blocksize);
139	plainlen = blocksize + buf->len - offset;
140
141	headlen = g_token_size(&kctx->mech_used, 22 + plainlen) -
142						(buf->len - offset);
143
144	ptr = buf->head[0].iov_base + offset;
145	/* shift data to make room for header. */
146	/* XXX Would be cleverer to encrypt while copying. */
147	/* XXX bounds checking, slack, etc. */
148	memmove(ptr + headlen, ptr, buf->head[0].iov_len - offset);
149	buf->head[0].iov_len += headlen;
150	buf->len += headlen;
151	BUG_ON((buf->len - offset - headlen) % blocksize);
152
153	g_make_token_header(&kctx->mech_used, 22 + plainlen, &ptr);
154
155
156	*ptr++ = (unsigned char) ((KG_TOK_WRAP_MSG>>8)&0xff);
157	*ptr++ = (unsigned char) (KG_TOK_WRAP_MSG&0xff);
158
159	/* ptr now at byte 2 of header described in rfc 1964, section 1.2.1: */
160	krb5_hdr = ptr - 2;
161	msg_start = krb5_hdr + 24;
162	/* XXXJBF: */ BUG_ON(buf->head[0].iov_base + offset + headlen != msg_start + blocksize);
163
164	*(__be16 *)(krb5_hdr + 2) = htons(SGN_ALG_DES_MAC_MD5);
165	memset(krb5_hdr + 4, 0xff, 4);
166	*(__be16 *)(krb5_hdr + 4) = htons(SEAL_ALG_DES);
167
168	make_confounder(msg_start, blocksize);
169
170	/* XXXJBF: UGH!: */
171	tmp_pages = buf->pages;
172	buf->pages = pages;
173	if (make_checksum("md5", krb5_hdr, 8, buf,
174				offset + headlen - blocksize, &md5cksum))
175		return GSS_S_FAILURE;
176	buf->pages = tmp_pages;
177
178	if (krb5_encrypt(kctx->seq, NULL, md5cksum.data,
179			  md5cksum.data, md5cksum.len))
180		return GSS_S_FAILURE;
181	memcpy(krb5_hdr + 16,
182	       md5cksum.data + md5cksum.len - KRB5_CKSUM_LENGTH,
183	       KRB5_CKSUM_LENGTH);
184
185	spin_lock(&krb5_seq_lock);
186	seq_send = kctx->seq_send++;
187	spin_unlock(&krb5_seq_lock);
188
189	/* XXX would probably be more efficient to compute checksum
190	 * and encrypt at the same time: */
191	if ((krb5_make_seq_num(kctx->seq, kctx->initiate ? 0 : 0xff,
192			       seq_send, krb5_hdr + 16, krb5_hdr + 8)))
193		return GSS_S_FAILURE;
194
195	if (gss_encrypt_xdr_buf(kctx->enc, buf, offset + headlen - blocksize,
196									pages))
197		return GSS_S_FAILURE;
198
199	return ((kctx->endtime < now) ? GSS_S_CONTEXT_EXPIRED : GSS_S_COMPLETE);
200}
201
202u32
203gss_unwrap_kerberos(struct gss_ctx *ctx, int offset, struct xdr_buf *buf)
204{
205	struct krb5_ctx		*kctx = ctx->internal_ctx_id;
206	int			signalg;
207	int			sealalg;
208	char			cksumdata[16];
209	struct xdr_netobj	md5cksum = {.len = 0, .data = cksumdata};
210	s32			now;
211	int			direction;
212	s32			seqnum;
213	unsigned char		*ptr;
214	int			bodysize;
215	void			*data_start, *orig_start;
216	int			data_len;
217	int			blocksize;
218
219	dprintk("RPC:      gss_unwrap_kerberos\n");
220
221	ptr = (u8 *)buf->head[0].iov_base + offset;
222	if (g_verify_token_header(&kctx->mech_used, &bodysize, &ptr,
223					buf->len - offset))
224		return GSS_S_DEFECTIVE_TOKEN;
225
226	if ((*ptr++ != ((KG_TOK_WRAP_MSG>>8)&0xff)) ||
227	    (*ptr++ !=  (KG_TOK_WRAP_MSG    &0xff))   )
228		return GSS_S_DEFECTIVE_TOKEN;
229
230	/* XXX sanity-check bodysize?? */
231
232	/* get the sign and seal algorithms */
233
234	signalg = ptr[0] + (ptr[1] << 8);
235	sealalg = ptr[2] + (ptr[3] << 8);
236
237	/* Sanity checks */
238
239	if ((ptr[4] != 0xff) || (ptr[5] != 0xff))
240		return GSS_S_DEFECTIVE_TOKEN;
241
242	if (sealalg != SEAL_ALG_DES)
243		return GSS_S_DEFECTIVE_TOKEN;
244	if (signalg != SGN_ALG_DES_MAC_MD5)
245		return GSS_S_DEFECTIVE_TOKEN;
246
247	if (gss_decrypt_xdr_buf(kctx->enc, buf,
248			ptr + 22 - (unsigned char *)buf->head[0].iov_base))
249		return GSS_S_DEFECTIVE_TOKEN;
250
251	if (make_checksum("md5", ptr - 2, 8, buf,
252		 ptr + 22 - (unsigned char *)buf->head[0].iov_base, &md5cksum))
253		return GSS_S_FAILURE;
254
255	if (krb5_encrypt(kctx->seq, NULL, md5cksum.data,
256			   md5cksum.data, md5cksum.len))
257		return GSS_S_FAILURE;
258
259	if (memcmp(md5cksum.data + 8, ptr + 14, 8))
260		return GSS_S_BAD_SIG;
261
262	/* it got through unscathed.  Make sure the context is unexpired */
263
264	now = get_seconds();
265
266	if (now > kctx->endtime)
267		return GSS_S_CONTEXT_EXPIRED;
268
269	/* do sequencing checks */
270
271	if (krb5_get_seq_num(kctx->seq, ptr + 14, ptr + 6, &direction,
272				    &seqnum))
273		return GSS_S_BAD_SIG;
274
275	if ((kctx->initiate && direction != 0xff) ||
276	    (!kctx->initiate && direction != 0))
277		return GSS_S_BAD_SIG;
278
279	/* Copy the data back to the right position.  XXX: Would probably be
280	 * better to copy and encrypt at the same time. */
281
282	blocksize = crypto_blkcipher_blocksize(kctx->enc);
283	data_start = ptr + 22 + blocksize;
284	orig_start = buf->head[0].iov_base + offset;
285	data_len = (buf->head[0].iov_base + buf->head[0].iov_len) - data_start;
286	memmove(orig_start, data_start, data_len);
287	buf->head[0].iov_len -= (data_start - orig_start);
288	buf->len -= (data_start - orig_start);
289
290	if (gss_krb5_remove_padding(buf, blocksize))
291		return GSS_S_DEFECTIVE_TOKEN;
292
293	return GSS_S_COMPLETE;
294}
295