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57 #include <crypto/skcipher.h>
58 #include <linux/err.h>
59 #include <linux/types.h>
60 #include <linux/sunrpc/gss_krb5.h>
61 #include <linux/sunrpc/xdr.h>
62 #include <linux/lcm.h>
63 #include <crypto/hash.h>
64 #include <kunit/visibility.h>
66 #include "gss_krb5_internal.h"
68 #if IS_ENABLED(CONFIG_SUNRPC_DEBUG)
69 # define RPCDBG_FACILITY RPCDBG_AUTH
73 * krb5_nfold - n-fold function
74 * @inbits: number of bits in @in
75 * @in: buffer containing input to fold
76 * @outbits: number of bits in the output buffer
77 * @out: buffer to hold the result
79 * This is the n-fold function as described in rfc3961, sec 5.1
80 * Taken from MIT Kerberos and modified.
83 void krb5_nfold(u32 inbits, const u8 *in, u32 outbits, u8 *out)
88 /* the code below is more readable if I make these bytes
94 /* first compute lcm(n,k) */
95 ulcm = lcm(inbits, outbits);
97 /* now do the real work */
99 memset(out, 0, outbits);
102 /* this will end up cycling through k lcm(k,n)/k times, which
104 for (i = ulcm-1; i >= 0; i--) {
105 /* compute the msbit in k which gets added into this byte */
107 /* first, start with the msbit in the first,
110 /* then, for each byte, shift to the right
111 * for each repetition */
112 + (((inbits << 3) + 13) * (i/inbits))
113 /* last, pick out the correct byte within
114 * that shifted repetition */
115 + ((inbits - (i % inbits)) << 3)
118 /* pull out the byte value itself */
119 byte += (((in[((inbits - 1) - (msbit >> 3)) % inbits] << 8)|
120 (in[((inbits) - (msbit >> 3)) % inbits]))
121 >> ((msbit & 7) + 1)) & 0xff;
123 /* do the addition */
124 byte += out[i % outbits];
125 out[i % outbits] = byte & 0xff;
127 /* keep around the carry bit, if any */
132 /* if there's a carry bit left over, add it back in */
134 for (i = outbits - 1; i >= 0; i--) {
135 /* do the addition */
137 out[i] = byte & 0xff;
139 /* keep around the carry bit, if any */
144 EXPORT_SYMBOL_IF_KUNIT(krb5_nfold);
147 * This is the DK (derive_key) function as described in rfc3961, sec 5.1
148 * Taken from MIT Kerberos and modified.
150 static int krb5_DK(const struct gss_krb5_enctype *gk5e,
151 const struct xdr_netobj *inkey, u8 *rawkey,
152 const struct xdr_netobj *in_constant, gfp_t gfp_mask)
154 size_t blocksize, keybytes, keylength, n;
155 unsigned char *inblockdata, *outblockdata;
156 struct xdr_netobj inblock, outblock;
157 struct crypto_sync_skcipher *cipher;
160 keybytes = gk5e->keybytes;
161 keylength = gk5e->keylength;
163 if (inkey->len != keylength)
166 cipher = crypto_alloc_sync_skcipher(gk5e->encrypt_name, 0, 0);
169 blocksize = crypto_sync_skcipher_blocksize(cipher);
170 if (crypto_sync_skcipher_setkey(cipher, inkey->data, inkey->len))
174 inblockdata = kmalloc(blocksize, gfp_mask);
175 if (inblockdata == NULL)
176 goto err_free_cipher;
178 outblockdata = kmalloc(blocksize, gfp_mask);
179 if (outblockdata == NULL)
182 inblock.data = (char *) inblockdata;
183 inblock.len = blocksize;
185 outblock.data = (char *) outblockdata;
186 outblock.len = blocksize;
188 /* initialize the input block */
190 if (in_constant->len == inblock.len) {
191 memcpy(inblock.data, in_constant->data, inblock.len);
193 krb5_nfold(in_constant->len * 8, in_constant->data,
194 inblock.len * 8, inblock.data);
197 /* loop encrypting the blocks until enough key bytes are generated */
200 while (n < keybytes) {
201 krb5_encrypt(cipher, NULL, inblock.data, outblock.data,
204 if ((keybytes - n) <= outblock.len) {
205 memcpy(rawkey + n, outblock.data, (keybytes - n));
209 memcpy(rawkey + n, outblock.data, outblock.len);
210 memcpy(inblock.data, outblock.data, outblock.len);
216 kfree_sensitive(outblockdata);
218 kfree_sensitive(inblockdata);
220 crypto_free_sync_skcipher(cipher);
226 * This is the identity function, with some sanity checking.
228 static int krb5_random_to_key_v2(const struct gss_krb5_enctype *gk5e,
229 struct xdr_netobj *randombits,
230 struct xdr_netobj *key)
234 if (key->len != 16 && key->len != 32) {
235 dprintk("%s: key->len is %d\n", __func__, key->len);
238 if (randombits->len != 16 && randombits->len != 32) {
239 dprintk("%s: randombits->len is %d\n",
240 __func__, randombits->len);
243 if (randombits->len != key->len) {
244 dprintk("%s: randombits->len is %d, key->len is %d\n",
245 __func__, randombits->len, key->len);
248 memcpy(key->data, randombits->data, key->len);
255 * krb5_derive_key_v2 - Derive a subkey for an RFC 3962 enctype
256 * @gk5e: Kerberos 5 enctype profile
257 * @inkey: base protocol key
258 * @outkey: OUT: derived key
259 * @label: subkey usage label
260 * @gfp_mask: memory allocation control flags
262 * Caller sets @outkey->len to the desired length of the derived key.
264 * On success, returns 0 and fills in @outkey. A negative errno value
265 * is returned on failure.
267 int krb5_derive_key_v2(const struct gss_krb5_enctype *gk5e,
268 const struct xdr_netobj *inkey,
269 struct xdr_netobj *outkey,
270 const struct xdr_netobj *label,
273 struct xdr_netobj inblock;
276 inblock.len = gk5e->keybytes;
277 inblock.data = kmalloc(inblock.len, gfp_mask);
281 ret = krb5_DK(gk5e, inkey, inblock.data, label, gfp_mask);
283 ret = krb5_random_to_key_v2(gk5e, &inblock, outkey);
285 kfree_sensitive(inblock.data);
290 * K(i) = CMAC(key, K(i-1) | i | constant | 0x00 | k)
292 * i: A block counter is used with a length of 4 bytes, represented
293 * in big-endian order.
295 * constant: The label input to the KDF is the usage constant supplied
296 * to the key derivation function
298 * k: The length of the output key in bits, represented as a 4-byte
299 * string in big-endian order.
301 * Caller fills in K(i-1) in @step, and receives the result K(i)
302 * in the same buffer.
305 krb5_cmac_Ki(struct crypto_shash *tfm, const struct xdr_netobj *constant,
306 u32 outlen, u32 count, struct xdr_netobj *step)
308 __be32 k = cpu_to_be32(outlen * 8);
309 SHASH_DESC_ON_STACK(desc, tfm);
310 __be32 i = cpu_to_be32(count);
315 ret = crypto_shash_init(desc);
319 ret = crypto_shash_update(desc, step->data, step->len);
322 ret = crypto_shash_update(desc, (u8 *)&i, sizeof(i));
325 ret = crypto_shash_update(desc, constant->data, constant->len);
328 ret = crypto_shash_update(desc, &zero, sizeof(zero));
331 ret = crypto_shash_update(desc, (u8 *)&k, sizeof(k));
334 ret = crypto_shash_final(desc, step->data);
339 shash_desc_zero(desc);
344 * krb5_kdf_feedback_cmac - Derive a subkey for a Camellia/CMAC-based enctype
345 * @gk5e: Kerberos 5 enctype parameters
346 * @inkey: base protocol key
347 * @outkey: OUT: derived key
348 * @constant: subkey usage label
349 * @gfp_mask: memory allocation control flags
351 * RFC 6803 Section 3:
353 * "We use a key derivation function from the family specified in
354 * [SP800-108], Section 5.2, 'KDF in Feedback Mode'."
356 * n = ceiling(k / 128)
358 * K(i) = CMAC(key, K(i-1) | i | constant | 0x00 | k)
359 * DR(key, constant) = k-truncate(K(1) | K(2) | ... | K(n))
360 * KDF-FEEDBACK-CMAC(key, constant) = random-to-key(DR(key, constant))
362 * Caller sets @outkey->len to the desired length of the derived key (k).
364 * On success, returns 0 and fills in @outkey. A negative errno value
365 * is returned on failure.
368 krb5_kdf_feedback_cmac(const struct gss_krb5_enctype *gk5e,
369 const struct xdr_netobj *inkey,
370 struct xdr_netobj *outkey,
371 const struct xdr_netobj *constant,
374 struct xdr_netobj step = { .data = NULL };
375 struct xdr_netobj DR = { .data = NULL };
376 unsigned int blocksize, offset;
377 struct crypto_shash *tfm;
381 * This implementation assumes the CMAC used for an enctype's
382 * key derivation is the same as the CMAC used for its
383 * checksumming. This happens to be true for enctypes that
384 * are currently supported by this implementation.
386 tfm = crypto_alloc_shash(gk5e->cksum_name, 0, 0);
391 ret = crypto_shash_setkey(tfm, inkey->data, inkey->len);
395 blocksize = crypto_shash_digestsize(tfm);
396 n = (outkey->len + blocksize - 1) / blocksize;
398 /* K(0) is all zeroes */
400 step.len = blocksize;
401 step.data = kzalloc(step.len, gfp_mask);
405 DR.len = blocksize * n;
406 DR.data = kmalloc(DR.len, gfp_mask);
410 /* XXX: Does not handle partial-block key sizes */
411 for (offset = 0, count = 1; count <= n; count++) {
412 ret = krb5_cmac_Ki(tfm, constant, outkey->len, count, &step);
416 memcpy(DR.data + offset, step.data, blocksize);
420 /* k-truncate and random-to-key */
421 memcpy(outkey->data, DR.data, outkey->len);
425 crypto_free_shash(tfm);
427 kfree_sensitive(step.data);
428 kfree_sensitive(DR.data);
433 * K1 = HMAC-SHA(key, 0x00000001 | label | 0x00 | k)
435 * key: The source of entropy from which subsequent keys are derived.
437 * label: An octet string describing the intended usage of the
440 * k: Length in bits of the key to be outputted, expressed in
441 * big-endian binary representation in 4 bytes.
444 krb5_hmac_K1(struct crypto_shash *tfm, const struct xdr_netobj *label,
445 u32 outlen, struct xdr_netobj *K1)
447 __be32 k = cpu_to_be32(outlen * 8);
448 SHASH_DESC_ON_STACK(desc, tfm);
449 __be32 one = cpu_to_be32(1);
454 ret = crypto_shash_init(desc);
457 ret = crypto_shash_update(desc, (u8 *)&one, sizeof(one));
460 ret = crypto_shash_update(desc, label->data, label->len);
463 ret = crypto_shash_update(desc, &zero, sizeof(zero));
466 ret = crypto_shash_update(desc, (u8 *)&k, sizeof(k));
469 ret = crypto_shash_final(desc, K1->data);
474 shash_desc_zero(desc);
479 * krb5_kdf_hmac_sha2 - Derive a subkey for an AES/SHA2-based enctype
480 * @gk5e: Kerberos 5 enctype policy parameters
481 * @inkey: base protocol key
482 * @outkey: OUT: derived key
483 * @label: subkey usage label
484 * @gfp_mask: memory allocation control flags
486 * RFC 8009 Section 3:
488 * "We use a key derivation function from Section 5.1 of [SP800-108],
489 * which uses the HMAC algorithm as the PRF."
491 * function KDF-HMAC-SHA2(key, label, [context,] k):
494 * Caller sets @outkey->len to the desired length of the derived key.
496 * On success, returns 0 and fills in @outkey. A negative errno value
497 * is returned on failure.
500 krb5_kdf_hmac_sha2(const struct gss_krb5_enctype *gk5e,
501 const struct xdr_netobj *inkey,
502 struct xdr_netobj *outkey,
503 const struct xdr_netobj *label,
506 struct crypto_shash *tfm;
507 struct xdr_netobj K1 = {
513 * This implementation assumes the HMAC used for an enctype's
514 * key derivation is the same as the HMAC used for its
515 * checksumming. This happens to be true for enctypes that
516 * are currently supported by this implementation.
518 tfm = crypto_alloc_shash(gk5e->cksum_name, 0, 0);
523 ret = crypto_shash_setkey(tfm, inkey->data, inkey->len);
527 K1.len = crypto_shash_digestsize(tfm);
528 K1.data = kmalloc(K1.len, gfp_mask);
534 ret = krb5_hmac_K1(tfm, label, outkey->len, &K1);
538 /* k-truncate and random-to-key */
539 memcpy(outkey->data, K1.data, outkey->len);
542 kfree_sensitive(K1.data);
543 crypto_free_shash(tfm);