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 <crypto/skcipher.h>
32 #include <linux/types.h>
33 #include <linux/jiffies.h>
34 #include <linux/sunrpc/gss_krb5.h>
35 #include <linux/pagemap.h>
36 
37 #include "gss_krb5_internal.h"
38 
39 #if IS_ENABLED(CONFIG_SUNRPC_DEBUG)
40 # define RPCDBG_FACILITY	RPCDBG_AUTH
41 #endif
42 
43 /*
44  * We can shift data by up to LOCAL_BUF_LEN bytes in a pass.  If we need
45  * to do more than that, we shift repeatedly.  Kevin Coffman reports
46  * seeing 28 bytes as the value used by Microsoft clients and servers
47  * with AES, so this constant is chosen to allow handling 28 in one pass
48  * without using too much stack space.
49  *
50  * If that proves to a problem perhaps we could use a more clever
51  * algorithm.
52  */
53 #define LOCAL_BUF_LEN 32u
54 
55 static void rotate_buf_a_little(struct xdr_buf *buf, unsigned int shift)
56 {
57 	char head[LOCAL_BUF_LEN];
58 	char tmp[LOCAL_BUF_LEN];
59 	unsigned int this_len, i;
60 
61 	BUG_ON(shift > LOCAL_BUF_LEN);
62 
63 	read_bytes_from_xdr_buf(buf, 0, head, shift);
64 	for (i = 0; i + shift < buf->len; i += LOCAL_BUF_LEN) {
65 		this_len = min(LOCAL_BUF_LEN, buf->len - (i + shift));
66 		read_bytes_from_xdr_buf(buf, i+shift, tmp, this_len);
67 		write_bytes_to_xdr_buf(buf, i, tmp, this_len);
68 	}
69 	write_bytes_to_xdr_buf(buf, buf->len - shift, head, shift);
70 }
71 
72 static void _rotate_left(struct xdr_buf *buf, unsigned int shift)
73 {
74 	int shifted = 0;
75 	int this_shift;
76 
77 	shift %= buf->len;
78 	while (shifted < shift) {
79 		this_shift = min(shift - shifted, LOCAL_BUF_LEN);
80 		rotate_buf_a_little(buf, this_shift);
81 		shifted += this_shift;
82 	}
83 }
84 
85 static void rotate_left(u32 base, struct xdr_buf *buf, unsigned int shift)
86 {
87 	struct xdr_buf subbuf;
88 
89 	xdr_buf_subsegment(buf, &subbuf, base, buf->len - base);
90 	_rotate_left(&subbuf, shift);
91 }
92 
93 u32
94 gss_krb5_wrap_v2(struct krb5_ctx *kctx, int offset,
95 		 struct xdr_buf *buf, struct page **pages)
96 {
97 	u8		*ptr;
98 	time64_t	now;
99 	u8		flags = 0x00;
100 	__be16		*be16ptr;
101 	__be64		*be64ptr;
102 	u32		err;
103 
104 	dprintk("RPC:       %s\n", __func__);
105 
106 	/* make room for gss token header */
107 	if (xdr_extend_head(buf, offset, GSS_KRB5_TOK_HDR_LEN))
108 		return GSS_S_FAILURE;
109 
110 	/* construct gss token header */
111 	ptr = buf->head[0].iov_base + offset;
112 	*ptr++ = (unsigned char) ((KG2_TOK_WRAP>>8) & 0xff);
113 	*ptr++ = (unsigned char) (KG2_TOK_WRAP & 0xff);
114 
115 	if ((kctx->flags & KRB5_CTX_FLAG_INITIATOR) == 0)
116 		flags |= KG2_TOKEN_FLAG_SENTBYACCEPTOR;
117 	if ((kctx->flags & KRB5_CTX_FLAG_ACCEPTOR_SUBKEY) != 0)
118 		flags |= KG2_TOKEN_FLAG_ACCEPTORSUBKEY;
119 	/* We always do confidentiality in wrap tokens */
120 	flags |= KG2_TOKEN_FLAG_SEALED;
121 
122 	*ptr++ = flags;
123 	*ptr++ = 0xff;
124 	be16ptr = (__be16 *)ptr;
125 
126 	*be16ptr++ = 0;
127 	/* "inner" token header always uses 0 for RRC */
128 	*be16ptr++ = 0;
129 
130 	be64ptr = (__be64 *)be16ptr;
131 	*be64ptr = cpu_to_be64(atomic64_fetch_inc(&kctx->seq_send64));
132 
133 	err = (*kctx->gk5e->encrypt)(kctx, offset, buf, pages);
134 	if (err)
135 		return err;
136 
137 	now = ktime_get_real_seconds();
138 	return (kctx->endtime < now) ? GSS_S_CONTEXT_EXPIRED : GSS_S_COMPLETE;
139 }
140 
141 u32
142 gss_krb5_unwrap_v2(struct krb5_ctx *kctx, int offset, int len,
143 		   struct xdr_buf *buf, unsigned int *slack,
144 		   unsigned int *align)
145 {
146 	time64_t	now;
147 	u8		*ptr;
148 	u8		flags = 0x00;
149 	u16		ec, rrc;
150 	int		err;
151 	u32		headskip, tailskip;
152 	u8		decrypted_hdr[GSS_KRB5_TOK_HDR_LEN];
153 	unsigned int	movelen;
154 
155 
156 	dprintk("RPC:       %s\n", __func__);
157 
158 	ptr = buf->head[0].iov_base + offset;
159 
160 	if (be16_to_cpu(*((__be16 *)ptr)) != KG2_TOK_WRAP)
161 		return GSS_S_DEFECTIVE_TOKEN;
162 
163 	flags = ptr[2];
164 	if ((!kctx->initiate && (flags & KG2_TOKEN_FLAG_SENTBYACCEPTOR)) ||
165 	    (kctx->initiate && !(flags & KG2_TOKEN_FLAG_SENTBYACCEPTOR)))
166 		return GSS_S_BAD_SIG;
167 
168 	if ((flags & KG2_TOKEN_FLAG_SEALED) == 0) {
169 		dprintk("%s: token missing expected sealed flag\n", __func__);
170 		return GSS_S_DEFECTIVE_TOKEN;
171 	}
172 
173 	if (ptr[3] != 0xff)
174 		return GSS_S_DEFECTIVE_TOKEN;
175 
176 	ec = be16_to_cpup((__be16 *)(ptr + 4));
177 	rrc = be16_to_cpup((__be16 *)(ptr + 6));
178 
179 	/*
180 	 * NOTE: the sequence number at ptr + 8 is skipped, rpcsec_gss
181 	 * doesn't want it checked; see page 6 of rfc 2203.
182 	 */
183 
184 	if (rrc != 0)
185 		rotate_left(offset + 16, buf, rrc);
186 
187 	err = (*kctx->gk5e->decrypt)(kctx, offset, len, buf,
188 				     &headskip, &tailskip);
189 	if (err)
190 		return GSS_S_FAILURE;
191 
192 	/*
193 	 * Retrieve the decrypted gss token header and verify
194 	 * it against the original
195 	 */
196 	err = read_bytes_from_xdr_buf(buf,
197 				len - GSS_KRB5_TOK_HDR_LEN - tailskip,
198 				decrypted_hdr, GSS_KRB5_TOK_HDR_LEN);
199 	if (err) {
200 		dprintk("%s: error %u getting decrypted_hdr\n", __func__, err);
201 		return GSS_S_FAILURE;
202 	}
203 	if (memcmp(ptr, decrypted_hdr, 6)
204 				|| memcmp(ptr + 8, decrypted_hdr + 8, 8)) {
205 		dprintk("%s: token hdr, plaintext hdr mismatch!\n", __func__);
206 		return GSS_S_FAILURE;
207 	}
208 
209 	/* do sequencing checks */
210 
211 	/* it got through unscathed.  Make sure the context is unexpired */
212 	now = ktime_get_real_seconds();
213 	if (now > kctx->endtime)
214 		return GSS_S_CONTEXT_EXPIRED;
215 
216 	/*
217 	 * Move the head data back to the right position in xdr_buf.
218 	 * We ignore any "ec" data since it might be in the head or
219 	 * the tail, and we really don't need to deal with it.
220 	 * Note that buf->head[0].iov_len may indicate the available
221 	 * head buffer space rather than that actually occupied.
222 	 */
223 	movelen = min_t(unsigned int, buf->head[0].iov_len, len);
224 	movelen -= offset + GSS_KRB5_TOK_HDR_LEN + headskip;
225 	BUG_ON(offset + GSS_KRB5_TOK_HDR_LEN + headskip + movelen >
226 							buf->head[0].iov_len);
227 	memmove(ptr, ptr + GSS_KRB5_TOK_HDR_LEN + headskip, movelen);
228 	buf->head[0].iov_len -= GSS_KRB5_TOK_HDR_LEN + headskip;
229 	buf->len = len - (GSS_KRB5_TOK_HDR_LEN + headskip);
230 
231 	/* Trim off the trailing "extra count" and checksum blob */
232 	xdr_buf_trim(buf, ec + GSS_KRB5_TOK_HDR_LEN + tailskip);
233 
234 	*align = XDR_QUADLEN(GSS_KRB5_TOK_HDR_LEN + headskip);
235 	*slack = *align + XDR_QUADLEN(ec + GSS_KRB5_TOK_HDR_LEN + tailskip);
236 	return GSS_S_COMPLETE;
237 }
238