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1// SPDX-License-Identifier: GPL-2.0-only
2/* Copyright (c) 2024 Meta, Inc */
3#include <linux/bpf.h>
4#include <linux/bpf_crypto.h>
5#include <linux/bpf_mem_alloc.h>
6#include <linux/btf.h>
7#include <linux/btf_ids.h>
8#include <linux/filter.h>
9#include <linux/scatterlist.h>
10#include <linux/skbuff.h>
11#include <crypto/skcipher.h>
12
13struct bpf_crypto_type_list {
14 const struct bpf_crypto_type *type;
15 struct list_head list;
16};
17
18/* BPF crypto initialization parameters struct */
19/**
20 * struct bpf_crypto_params - BPF crypto initialization parameters structure
21 * @type: The string of crypto operation type.
22 * @reserved: Reserved member, will be reused for more options in future
23 * Values:
24 * 0
25 * @algo: The string of algorithm to initialize.
26 * @key: The cipher key used to init crypto algorithm.
27 * @key_len: The length of cipher key.
28 * @authsize: The length of authentication tag used by algorithm.
29 */
30struct bpf_crypto_params {
31 char type[14];
32 u8 reserved[2];
33 char algo[128];
34 u8 key[256];
35 u32 key_len;
36 u32 authsize;
37};
38
39static LIST_HEAD(bpf_crypto_types);
40static DECLARE_RWSEM(bpf_crypto_types_sem);
41
42/**
43 * struct bpf_crypto_ctx - refcounted BPF crypto context structure
44 * @type: The pointer to bpf crypto type
45 * @tfm: The pointer to instance of crypto API struct.
46 * @siv_len: Size of IV and state storage for cipher
47 * @rcu: The RCU head used to free the crypto context with RCU safety.
48 * @usage: Object reference counter. When the refcount goes to 0, the
49 * memory is released back to the BPF allocator, which provides
50 * RCU safety.
51 */
52struct bpf_crypto_ctx {
53 const struct bpf_crypto_type *type;
54 void *tfm;
55 u32 siv_len;
56 struct rcu_head rcu;
57 refcount_t usage;
58};
59
60int bpf_crypto_register_type(const struct bpf_crypto_type *type)
61{
62 struct bpf_crypto_type_list *node;
63 int err = -EBUSY;
64
65 down_write(&bpf_crypto_types_sem);
66 list_for_each_entry(node, &bpf_crypto_types, list) {
67 if (!strcmp(node->type->name, type->name))
68 goto unlock;
69 }
70
71 node = kmalloc_obj(*node);
72 err = -ENOMEM;
73 if (!node)
74 goto unlock;
75
76 node->type = type;
77 list_add(&node->list, &bpf_crypto_types);
78 err = 0;
79
80unlock:
81 up_write(&bpf_crypto_types_sem);
82
83 return err;
84}
85EXPORT_SYMBOL_GPL(bpf_crypto_register_type);
86
87int bpf_crypto_unregister_type(const struct bpf_crypto_type *type)
88{
89 struct bpf_crypto_type_list *node;
90 int err = -ENOENT;
91
92 down_write(&bpf_crypto_types_sem);
93 list_for_each_entry(node, &bpf_crypto_types, list) {
94 if (strcmp(node->type->name, type->name))
95 continue;
96
97 list_del(&node->list);
98 kfree(node);
99 err = 0;
100 break;
101 }
102 up_write(&bpf_crypto_types_sem);
103
104 return err;
105}
106EXPORT_SYMBOL_GPL(bpf_crypto_unregister_type);
107
108static const struct bpf_crypto_type *bpf_crypto_get_type(const char *name)
109{
110 const struct bpf_crypto_type *type = ERR_PTR(-ENOENT);
111 struct bpf_crypto_type_list *node;
112
113 down_read(&bpf_crypto_types_sem);
114 list_for_each_entry(node, &bpf_crypto_types, list) {
115 if (strcmp(node->type->name, name))
116 continue;
117
118 if (try_module_get(node->type->owner))
119 type = node->type;
120 break;
121 }
122 up_read(&bpf_crypto_types_sem);
123
124 return type;
125}
126
127__bpf_kfunc_start_defs();
128
129/**
130 * bpf_crypto_ctx_create() - Create a mutable BPF crypto context.
131 *
132 * Allocates a crypto context that can be used, acquired, and released by
133 * a BPF program. The crypto context returned by this function must either
134 * be embedded in a map as a kptr, or freed with bpf_crypto_ctx_release().
135 * As crypto API functions use GFP_KERNEL allocations, this function can
136 * only be used in sleepable BPF programs.
137 *
138 * bpf_crypto_ctx_create() allocates memory for crypto context.
139 * It may return NULL if no memory is available.
140 * @params: pointer to struct bpf_crypto_params which contains all the
141 * details needed to initialise crypto context.
142 * @params__sz: size of steuct bpf_crypto_params usef by bpf program
143 * @err: integer to store error code when NULL is returned.
144 */
145__bpf_kfunc struct bpf_crypto_ctx *
146bpf_crypto_ctx_create(const struct bpf_crypto_params *params, u32 params__sz,
147 int *err)
148{
149 const struct bpf_crypto_type *type;
150 struct bpf_crypto_ctx *ctx;
151
152 if (!params ||
153 params__sz != sizeof(struct bpf_crypto_params) ||
154 params->reserved[0] || params->reserved[1]) {
155 *err = -EINVAL;
156 return NULL;
157 }
158
159 type = bpf_crypto_get_type(params->type);
160 if (IS_ERR(type)) {
161 *err = PTR_ERR(type);
162 return NULL;
163 }
164
165 if (!type->has_algo(params->algo)) {
166 *err = -EOPNOTSUPP;
167 goto err_module_put;
168 }
169
170 if (!!params->authsize ^ !!type->setauthsize) {
171 *err = -EOPNOTSUPP;
172 goto err_module_put;
173 }
174
175 if (!params->key_len || params->key_len > sizeof(params->key)) {
176 *err = -EINVAL;
177 goto err_module_put;
178 }
179
180 ctx = kzalloc_obj(*ctx);
181 if (!ctx) {
182 *err = -ENOMEM;
183 goto err_module_put;
184 }
185
186 ctx->type = type;
187 ctx->tfm = type->alloc_tfm(params->algo);
188 if (IS_ERR(ctx->tfm)) {
189 *err = PTR_ERR(ctx->tfm);
190 goto err_free_ctx;
191 }
192
193 if (params->authsize) {
194 *err = type->setauthsize(ctx->tfm, params->authsize);
195 if (*err)
196 goto err_free_tfm;
197 }
198
199 *err = type->setkey(ctx->tfm, params->key, params->key_len);
200 if (*err)
201 goto err_free_tfm;
202
203 if (type->get_flags(ctx->tfm) & CRYPTO_TFM_NEED_KEY) {
204 *err = -EINVAL;
205 goto err_free_tfm;
206 }
207
208 ctx->siv_len = type->ivsize(ctx->tfm) + type->statesize(ctx->tfm);
209
210 refcount_set(&ctx->usage, 1);
211
212 return ctx;
213
214err_free_tfm:
215 type->free_tfm(ctx->tfm);
216err_free_ctx:
217 kfree(ctx);
218err_module_put:
219 module_put(type->owner);
220
221 return NULL;
222}
223
224static void crypto_free_cb(struct rcu_head *head)
225{
226 struct bpf_crypto_ctx *ctx;
227
228 ctx = container_of(head, struct bpf_crypto_ctx, rcu);
229 ctx->type->free_tfm(ctx->tfm);
230 module_put(ctx->type->owner);
231 kfree(ctx);
232}
233
234/**
235 * bpf_crypto_ctx_acquire() - Acquire a reference to a BPF crypto context.
236 * @ctx: The BPF crypto context being acquired. The ctx must be a trusted
237 * pointer.
238 *
239 * Acquires a reference to a BPF crypto context. The context returned by this function
240 * must either be embedded in a map as a kptr, or freed with
241 * bpf_crypto_ctx_release().
242 */
243__bpf_kfunc struct bpf_crypto_ctx *
244bpf_crypto_ctx_acquire(struct bpf_crypto_ctx *ctx)
245{
246 if (!refcount_inc_not_zero(&ctx->usage))
247 return NULL;
248 return ctx;
249}
250
251/**
252 * bpf_crypto_ctx_release() - Release a previously acquired BPF crypto context.
253 * @ctx: The crypto context being released.
254 *
255 * Releases a previously acquired reference to a BPF crypto context. When the final
256 * reference of the BPF crypto context has been released, its memory
257 * will be released.
258 */
259__bpf_kfunc void bpf_crypto_ctx_release(struct bpf_crypto_ctx *ctx)
260{
261 if (refcount_dec_and_test(&ctx->usage))
262 call_rcu(&ctx->rcu, crypto_free_cb);
263}
264
265__bpf_kfunc void bpf_crypto_ctx_release_dtor(void *ctx)
266{
267 bpf_crypto_ctx_release(ctx);
268}
269CFI_NOSEAL(bpf_crypto_ctx_release_dtor);
270
271static int bpf_crypto_crypt(const struct bpf_crypto_ctx *ctx,
272 const struct bpf_dynptr_kern *src,
273 const struct bpf_dynptr_kern *dst,
274 const struct bpf_dynptr_kern *siv,
275 bool decrypt)
276{
277 u32 src_len, dst_len, siv_len;
278 const u8 *psrc;
279 u8 *pdst, *piv;
280 int err;
281
282 if (__bpf_dynptr_is_rdonly(dst))
283 return -EINVAL;
284
285 siv_len = siv ? __bpf_dynptr_size(siv) : 0;
286 src_len = __bpf_dynptr_size(src);
287 dst_len = __bpf_dynptr_size(dst);
288 if (!src_len || !dst_len || src_len > dst_len)
289 return -EINVAL;
290
291 if (siv_len != ctx->siv_len)
292 return -EINVAL;
293
294 psrc = __bpf_dynptr_data(src, src_len);
295 if (!psrc)
296 return -EINVAL;
297 pdst = __bpf_dynptr_data_rw(dst, dst_len);
298 if (!pdst)
299 return -EINVAL;
300
301 piv = siv_len ? __bpf_dynptr_data_rw(siv, siv_len) : NULL;
302 if (siv_len && !piv)
303 return -EINVAL;
304
305 err = decrypt ? ctx->type->decrypt(ctx->tfm, psrc, pdst, src_len, piv)
306 : ctx->type->encrypt(ctx->tfm, psrc, pdst, src_len, piv);
307
308 return err;
309}
310
311/**
312 * bpf_crypto_decrypt() - Decrypt buffer using configured context and IV provided.
313 * @ctx: The crypto context being used. The ctx must be a trusted pointer.
314 * @src: bpf_dynptr to the encrypted data. Must be a trusted pointer.
315 * @dst: bpf_dynptr to the buffer where to store the result. Must be a trusted pointer.
316 * @siv__nullable: bpf_dynptr to IV data and state data to be used by decryptor. May be NULL.
317 *
318 * Decrypts provided buffer using IV data and the crypto context. Crypto context must be configured.
319 */
320__bpf_kfunc int bpf_crypto_decrypt(struct bpf_crypto_ctx *ctx,
321 const struct bpf_dynptr *src,
322 const struct bpf_dynptr *dst,
323 const struct bpf_dynptr *siv__nullable)
324{
325 const struct bpf_dynptr_kern *src_kern = (struct bpf_dynptr_kern *)src;
326 const struct bpf_dynptr_kern *dst_kern = (struct bpf_dynptr_kern *)dst;
327 const struct bpf_dynptr_kern *siv_kern = (struct bpf_dynptr_kern *)siv__nullable;
328
329 return bpf_crypto_crypt(ctx, src_kern, dst_kern, siv_kern, true);
330}
331
332/**
333 * bpf_crypto_encrypt() - Encrypt buffer using configured context and IV provided.
334 * @ctx: The crypto context being used. The ctx must be a trusted pointer.
335 * @src: bpf_dynptr to the plain data. Must be a trusted pointer.
336 * @dst: bpf_dynptr to the buffer where to store the result. Must be a trusted pointer.
337 * @siv__nullable: bpf_dynptr to IV data and state data to be used by decryptor. May be NULL.
338 *
339 * Encrypts provided buffer using IV data and the crypto context. Crypto context must be configured.
340 */
341__bpf_kfunc int bpf_crypto_encrypt(struct bpf_crypto_ctx *ctx,
342 const struct bpf_dynptr *src,
343 const struct bpf_dynptr *dst,
344 const struct bpf_dynptr *siv__nullable)
345{
346 const struct bpf_dynptr_kern *src_kern = (struct bpf_dynptr_kern *)src;
347 const struct bpf_dynptr_kern *dst_kern = (struct bpf_dynptr_kern *)dst;
348 const struct bpf_dynptr_kern *siv_kern = (struct bpf_dynptr_kern *)siv__nullable;
349
350 return bpf_crypto_crypt(ctx, src_kern, dst_kern, siv_kern, false);
351}
352
353__bpf_kfunc_end_defs();
354
355BTF_KFUNCS_START(crypt_init_kfunc_btf_ids)
356BTF_ID_FLAGS(func, bpf_crypto_ctx_create, KF_ACQUIRE | KF_RET_NULL | KF_SLEEPABLE)
357BTF_ID_FLAGS(func, bpf_crypto_ctx_release, KF_RELEASE)
358BTF_ID_FLAGS(func, bpf_crypto_ctx_acquire, KF_ACQUIRE | KF_RCU | KF_RET_NULL)
359BTF_KFUNCS_END(crypt_init_kfunc_btf_ids)
360
361static const struct btf_kfunc_id_set crypt_init_kfunc_set = {
362 .owner = THIS_MODULE,
363 .set = &crypt_init_kfunc_btf_ids,
364};
365
366BTF_KFUNCS_START(crypt_kfunc_btf_ids)
367BTF_ID_FLAGS(func, bpf_crypto_decrypt, KF_RCU)
368BTF_ID_FLAGS(func, bpf_crypto_encrypt, KF_RCU)
369BTF_KFUNCS_END(crypt_kfunc_btf_ids)
370
371static const struct btf_kfunc_id_set crypt_kfunc_set = {
372 .owner = THIS_MODULE,
373 .set = &crypt_kfunc_btf_ids,
374};
375
376BTF_ID_LIST(bpf_crypto_dtor_ids)
377BTF_ID(struct, bpf_crypto_ctx)
378BTF_ID(func, bpf_crypto_ctx_release_dtor)
379
380static int __init crypto_kfunc_init(void)
381{
382 int ret;
383 const struct btf_id_dtor_kfunc bpf_crypto_dtors[] = {
384 {
385 .btf_id = bpf_crypto_dtor_ids[0],
386 .kfunc_btf_id = bpf_crypto_dtor_ids[1]
387 },
388 };
389
390 ret = register_btf_kfunc_id_set(BPF_PROG_TYPE_SCHED_CLS, &crypt_kfunc_set);
391 ret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_SCHED_ACT, &crypt_kfunc_set);
392 ret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_XDP, &crypt_kfunc_set);
393 ret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_SYSCALL,
394 &crypt_init_kfunc_set);
395 return ret ?: register_btf_id_dtor_kfuncs(bpf_crypto_dtors,
396 ARRAY_SIZE(bpf_crypto_dtors),
397 THIS_MODULE);
398}
399
400late_initcall(crypto_kfunc_init);