gss_krb5_wrap.c revision 4ab4b0bedda7d41c63cef98cd5d6cabada460936
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 <linux/crypto.h> 8 9#ifdef RPC_DEBUG 10# define RPCDBG_FACILITY RPCDBG_AUTH 11#endif 12 13static inline int 14gss_krb5_padding(int blocksize, int length) 15{ 16 /* Most of the code is block-size independent but currently we 17 * use only 8: */ 18 BUG_ON(blocksize != 8); 19 return 8 - (length & 7); 20} 21 22static inline void 23gss_krb5_add_padding(struct xdr_buf *buf, int offset, int blocksize) 24{ 25 int padding = gss_krb5_padding(blocksize, buf->len - offset); 26 char *p; 27 struct kvec *iov; 28 29 if (buf->page_len || buf->tail[0].iov_len) 30 iov = &buf->tail[0]; 31 else 32 iov = &buf->head[0]; 33 p = iov->iov_base + iov->iov_len; 34 iov->iov_len += padding; 35 buf->len += padding; 36 memset(p, padding, padding); 37} 38 39static inline int 40gss_krb5_remove_padding(struct xdr_buf *buf, int blocksize) 41{ 42 u8 *ptr; 43 u8 pad; 44 size_t len = buf->len; 45 46 if (len <= buf->head[0].iov_len) { 47 pad = *(u8 *)(buf->head[0].iov_base + len - 1); 48 if (pad > buf->head[0].iov_len) 49 return -EINVAL; 50 buf->head[0].iov_len -= pad; 51 goto out; 52 } else 53 len -= buf->head[0].iov_len; 54 if (len <= buf->page_len) { 55 unsigned int last = (buf->page_base + len - 1) 56 >>PAGE_CACHE_SHIFT; 57 unsigned int offset = (buf->page_base + len - 1) 58 & (PAGE_CACHE_SIZE - 1); 59 ptr = kmap_atomic(buf->pages[last], KM_USER0); 60 pad = *(ptr + offset); 61 kunmap_atomic(ptr, KM_USER0); 62 goto out; 63 } else 64 len -= buf->page_len; 65 BUG_ON(len > buf->tail[0].iov_len); 66 pad = *(u8 *)(buf->tail[0].iov_base + len - 1); 67out: 68 /* XXX: NOTE: we do not adjust the page lengths--they represent 69 * a range of data in the real filesystem page cache, and we need 70 * to know that range so the xdr code can properly place read data. 71 * However adjusting the head length, as we do above, is harmless. 72 * In the case of a request that fits into a single page, the server 73 * also uses length and head length together to determine the original 74 * start of the request to copy the request for deferal; so it's 75 * easier on the server if we adjust head and tail length in tandem. 76 * It's not really a problem that we don't fool with the page and 77 * tail lengths, though--at worst badly formed xdr might lead the 78 * server to attempt to parse the padding. 79 * XXX: Document all these weird requirements for gss mechanism 80 * wrap/unwrap functions. */ 81 if (pad > blocksize) 82 return -EINVAL; 83 if (buf->len > pad) 84 buf->len -= pad; 85 else 86 return -EINVAL; 87 return 0; 88} 89 90static inline void 91make_confounder(char *p, int blocksize) 92{ 93 static u64 i = 0; 94 u64 *q = (u64 *)p; 95 96 /* rfc1964 claims this should be "random". But all that's really 97 * necessary is that it be unique. And not even that is necessary in 98 * our case since our "gssapi" implementation exists only to support 99 * rpcsec_gss, so we know that the only buffers we will ever encrypt 100 * already begin with a unique sequence number. Just to hedge my bets 101 * I'll make a half-hearted attempt at something unique, but ensuring 102 * uniqueness would mean worrying about atomicity and rollover, and I 103 * don't care enough. */ 104 105 BUG_ON(blocksize != 8); 106 *q = i++; 107} 108 109/* Assumptions: the head and tail of inbuf are ours to play with. 110 * The pages, however, may be real pages in the page cache and we replace 111 * them with scratch pages from **pages before writing to them. */ 112/* XXX: obviously the above should be documentation of wrap interface, 113 * and shouldn't be in this kerberos-specific file. */ 114 115/* XXX factor out common code with seal/unseal. */ 116 117u32 118gss_wrap_kerberos(struct gss_ctx *ctx, int offset, 119 struct xdr_buf *buf, struct page **pages) 120{ 121 struct krb5_ctx *kctx = ctx->internal_ctx_id; 122 char cksumdata[16]; 123 struct xdr_netobj md5cksum = {.len = 0, .data = cksumdata}; 124 int blocksize = 0, plainlen; 125 unsigned char *ptr, *krb5_hdr, *msg_start; 126 s32 now; 127 int headlen; 128 struct page **tmp_pages; 129 u32 seq_send; 130 131 dprintk("RPC: gss_wrap_kerberos\n"); 132 133 now = get_seconds(); 134 135 blocksize = crypto_blkcipher_blocksize(kctx->enc); 136 gss_krb5_add_padding(buf, offset, blocksize); 137 BUG_ON((buf->len - offset) % blocksize); 138 plainlen = blocksize + buf->len - offset; 139 140 headlen = g_token_size(&kctx->mech_used, 24 + plainlen) - 141 (buf->len - offset); 142 143 ptr = buf->head[0].iov_base + offset; 144 /* shift data to make room for header. */ 145 /* XXX Would be cleverer to encrypt while copying. */ 146 /* XXX bounds checking, slack, etc. */ 147 memmove(ptr + headlen, ptr, buf->head[0].iov_len - offset); 148 buf->head[0].iov_len += headlen; 149 buf->len += headlen; 150 BUG_ON((buf->len - offset - headlen) % blocksize); 151 152 g_make_token_header(&kctx->mech_used, 24 + plainlen, &ptr); 153 154 155 *ptr++ = (unsigned char) ((KG_TOK_WRAP_MSG>>8)&0xff); 156 *ptr++ = (unsigned char) (KG_TOK_WRAP_MSG&0xff); 157 158 /* ptr now at byte 2 of header described in rfc 1964, section 1.2.1: */ 159 krb5_hdr = ptr - 2; 160 msg_start = krb5_hdr + 24; 161 162 *(__be16 *)(krb5_hdr + 2) = htons(SGN_ALG_DES_MAC_MD5); 163 memset(krb5_hdr + 4, 0xff, 4); 164 *(__be16 *)(krb5_hdr + 4) = htons(SEAL_ALG_DES); 165 166 make_confounder(msg_start, blocksize); 167 168 /* XXXJBF: UGH!: */ 169 tmp_pages = buf->pages; 170 buf->pages = pages; 171 if (make_checksum("md5", krb5_hdr, 8, buf, 172 offset + headlen - blocksize, &md5cksum)) 173 return GSS_S_FAILURE; 174 buf->pages = tmp_pages; 175 176 if (krb5_encrypt(kctx->seq, NULL, md5cksum.data, 177 md5cksum.data, md5cksum.len)) 178 return GSS_S_FAILURE; 179 memcpy(krb5_hdr + 16, md5cksum.data + md5cksum.len - 8, 8); 180 181 spin_lock(&krb5_seq_lock); 182 seq_send = kctx->seq_send++; 183 spin_unlock(&krb5_seq_lock); 184 185 /* XXX would probably be more efficient to compute checksum 186 * and encrypt at the same time: */ 187 if ((krb5_make_seq_num(kctx->seq, kctx->initiate ? 0 : 0xff, 188 seq_send, krb5_hdr + 16, krb5_hdr + 8))) 189 return GSS_S_FAILURE; 190 191 if (gss_encrypt_xdr_buf(kctx->enc, buf, offset + headlen - blocksize, 192 pages)) 193 return GSS_S_FAILURE; 194 195 return (kctx->endtime < now) ? GSS_S_CONTEXT_EXPIRED : GSS_S_COMPLETE; 196} 197 198u32 199gss_unwrap_kerberos(struct gss_ctx *ctx, int offset, struct xdr_buf *buf) 200{ 201 struct krb5_ctx *kctx = ctx->internal_ctx_id; 202 int signalg; 203 int sealalg; 204 char cksumdata[16]; 205 struct xdr_netobj md5cksum = {.len = 0, .data = cksumdata}; 206 s32 now; 207 int direction; 208 s32 seqnum; 209 unsigned char *ptr; 210 int bodysize; 211 void *data_start, *orig_start; 212 int data_len; 213 int blocksize; 214 215 dprintk("RPC: gss_unwrap_kerberos\n"); 216 217 ptr = (u8 *)buf->head[0].iov_base + offset; 218 if (g_verify_token_header(&kctx->mech_used, &bodysize, &ptr, 219 buf->len - offset)) 220 return GSS_S_DEFECTIVE_TOKEN; 221 222 if ((*ptr++ != ((KG_TOK_WRAP_MSG>>8)&0xff)) || 223 (*ptr++ != (KG_TOK_WRAP_MSG &0xff)) ) 224 return GSS_S_DEFECTIVE_TOKEN; 225 226 /* XXX sanity-check bodysize?? */ 227 228 /* get the sign and seal algorithms */ 229 230 signalg = ptr[0] + (ptr[1] << 8); 231 if (signalg != SGN_ALG_DES_MAC_MD5) 232 return GSS_S_DEFECTIVE_TOKEN; 233 234 sealalg = ptr[2] + (ptr[3] << 8); 235 if (sealalg != SEAL_ALG_DES) 236 return GSS_S_DEFECTIVE_TOKEN; 237 238 if ((ptr[4] != 0xff) || (ptr[5] != 0xff)) 239 return GSS_S_DEFECTIVE_TOKEN; 240 241 if (gss_decrypt_xdr_buf(kctx->enc, buf, 242 ptr + 22 - (unsigned char *)buf->head[0].iov_base)) 243 return GSS_S_DEFECTIVE_TOKEN; 244 245 if (make_checksum("md5", ptr - 2, 8, buf, 246 ptr + 22 - (unsigned char *)buf->head[0].iov_base, &md5cksum)) 247 return GSS_S_FAILURE; 248 249 if (krb5_encrypt(kctx->seq, NULL, md5cksum.data, 250 md5cksum.data, md5cksum.len)) 251 return GSS_S_FAILURE; 252 253 if (memcmp(md5cksum.data + 8, ptr + 14, 8)) 254 return GSS_S_BAD_SIG; 255 256 /* it got through unscathed. Make sure the context is unexpired */ 257 258 now = get_seconds(); 259 260 if (now > kctx->endtime) 261 return GSS_S_CONTEXT_EXPIRED; 262 263 /* do sequencing checks */ 264 265 if (krb5_get_seq_num(kctx->seq, ptr + 14, ptr + 6, &direction, 266 &seqnum)) 267 return GSS_S_BAD_SIG; 268 269 if ((kctx->initiate && direction != 0xff) || 270 (!kctx->initiate && direction != 0)) 271 return GSS_S_BAD_SIG; 272 273 /* Copy the data back to the right position. XXX: Would probably be 274 * better to copy and encrypt at the same time. */ 275 276 blocksize = crypto_blkcipher_blocksize(kctx->enc); 277 data_start = ptr + 22 + blocksize; 278 orig_start = buf->head[0].iov_base + offset; 279 data_len = (buf->head[0].iov_base + buf->head[0].iov_len) - data_start; 280 memmove(orig_start, data_start, data_len); 281 buf->head[0].iov_len -= (data_start - orig_start); 282 buf->len -= (data_start - orig_start); 283 284 if (gss_krb5_remove_padding(buf, blocksize)) 285 return GSS_S_DEFECTIVE_TOKEN; 286 287 return GSS_S_COMPLETE; 288} 289