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 = -EEXIST;
64
65 down_write(sem: &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(sizeof(*node), GFP_KERNEL);
72 err = -ENOMEM;
73 if (!node)
74 goto unlock;
75
76 node->type = type;
77 list_add(new: &node->list, head: &bpf_crypto_types);
78 err = 0;
79
80unlock:
81 up_write(sem: &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(sem: &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(entry: &node->list);
98 kfree(objp: node);
99 err = 0;
100 break;
101 }
102 up_write(sem: &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(error: -ENOENT);
111 struct bpf_crypto_type_list *node;
112
113 down_read(sem: &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(module: node->type->owner))
119 type = node->type;
120 break;
121 }
122 up_read(sem: &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 || params->reserved[0] || params->reserved[1] ||
153 params__sz != sizeof(struct bpf_crypto_params)) {
154 *err = -EINVAL;
155 return NULL;
156 }
157
158 type = bpf_crypto_get_type(name: params->type);
159 if (IS_ERR(ptr: type)) {
160 *err = PTR_ERR(ptr: type);
161 return NULL;
162 }
163
164 if (!type->has_algo(params->algo)) {
165 *err = -EOPNOTSUPP;
166 goto err_module_put;
167 }
168
169 if (!!params->authsize ^ !!type->setauthsize) {
170 *err = -EOPNOTSUPP;
171 goto err_module_put;
172 }
173
174 if (!params->key_len || params->key_len > sizeof(params->key)) {
175 *err = -EINVAL;
176 goto err_module_put;
177 }
178
179 ctx = kzalloc(sizeof(*ctx), GFP_KERNEL);
180 if (!ctx) {
181 *err = -ENOMEM;
182 goto err_module_put;
183 }
184
185 ctx->type = type;
186 ctx->tfm = type->alloc_tfm(params->algo);
187 if (IS_ERR(ptr: ctx->tfm)) {
188 *err = PTR_ERR(ptr: ctx->tfm);
189 goto err_free_ctx;
190 }
191
192 if (params->authsize) {
193 *err = type->setauthsize(ctx->tfm, params->authsize);
194 if (*err)
195 goto err_free_tfm;
196 }
197
198 *err = type->setkey(ctx->tfm, params->key, params->key_len);
199 if (*err)
200 goto err_free_tfm;
201
202 if (type->get_flags(ctx->tfm) & CRYPTO_TFM_NEED_KEY) {
203 *err = -EINVAL;
204 goto err_free_tfm;
205 }
206
207 ctx->siv_len = type->ivsize(ctx->tfm) + type->statesize(ctx->tfm);
208
209 refcount_set(r: &ctx->usage, n: 1);
210
211 return ctx;
212
213err_free_tfm:
214 type->free_tfm(ctx->tfm);
215err_free_ctx:
216 kfree(objp: ctx);
217err_module_put:
218 module_put(module: type->owner);
219
220 return NULL;
221}
222
223static void crypto_free_cb(struct rcu_head *head)
224{
225 struct bpf_crypto_ctx *ctx;
226
227 ctx = container_of(head, struct bpf_crypto_ctx, rcu);
228 ctx->type->free_tfm(ctx->tfm);
229 module_put(module: ctx->type->owner);
230 kfree(objp: ctx);
231}
232
233/**
234 * bpf_crypto_ctx_acquire() - Acquire a reference to a BPF crypto context.
235 * @ctx: The BPF crypto context being acquired. The ctx must be a trusted
236 * pointer.
237 *
238 * Acquires a reference to a BPF crypto context. The context returned by this function
239 * must either be embedded in a map as a kptr, or freed with
240 * bpf_crypto_ctx_release().
241 */
242__bpf_kfunc struct bpf_crypto_ctx *
243bpf_crypto_ctx_acquire(struct bpf_crypto_ctx *ctx)
244{
245 if (!refcount_inc_not_zero(r: &ctx->usage))
246 return NULL;
247 return ctx;
248}
249
250/**
251 * bpf_crypto_ctx_release() - Release a previously acquired BPF crypto context.
252 * @ctx: The crypto context being released.
253 *
254 * Releases a previously acquired reference to a BPF crypto context. When the final
255 * reference of the BPF crypto context has been released, its memory
256 * will be released.
257 */
258__bpf_kfunc void bpf_crypto_ctx_release(struct bpf_crypto_ctx *ctx)
259{
260 if (refcount_dec_and_test(r: &ctx->usage))
261 call_rcu(head: &ctx->rcu, func: crypto_free_cb);
262}
263
264static int bpf_crypto_crypt(const struct bpf_crypto_ctx *ctx,
265 const struct bpf_dynptr_kern *src,
266 const struct bpf_dynptr_kern *dst,
267 const struct bpf_dynptr_kern *siv,
268 bool decrypt)
269{
270 u32 src_len, dst_len, siv_len;
271 const u8 *psrc;
272 u8 *pdst, *piv;
273 int err;
274
275 if (__bpf_dynptr_is_rdonly(ptr: dst))
276 return -EINVAL;
277
278 siv_len = siv ? __bpf_dynptr_size(ptr: siv) : 0;
279 src_len = __bpf_dynptr_size(ptr: src);
280 dst_len = __bpf_dynptr_size(ptr: dst);
281 if (!src_len || !dst_len || src_len > dst_len)
282 return -EINVAL;
283
284 if (siv_len != ctx->siv_len)
285 return -EINVAL;
286
287 psrc = __bpf_dynptr_data(ptr: src, len: src_len);
288 if (!psrc)
289 return -EINVAL;
290 pdst = __bpf_dynptr_data_rw(ptr: dst, len: dst_len);
291 if (!pdst)
292 return -EINVAL;
293
294 piv = siv_len ? __bpf_dynptr_data_rw(ptr: siv, len: siv_len) : NULL;
295 if (siv_len && !piv)
296 return -EINVAL;
297
298 err = decrypt ? ctx->type->decrypt(ctx->tfm, psrc, pdst, src_len, piv)
299 : ctx->type->encrypt(ctx->tfm, psrc, pdst, src_len, piv);
300
301 return err;
302}
303
304/**
305 * bpf_crypto_decrypt() - Decrypt buffer using configured context and IV provided.
306 * @ctx: The crypto context being used. The ctx must be a trusted pointer.
307 * @src: bpf_dynptr to the encrypted data. Must be a trusted pointer.
308 * @dst: bpf_dynptr to the buffer where to store the result. Must be a trusted pointer.
309 * @siv__nullable: bpf_dynptr to IV data and state data to be used by decryptor. May be NULL.
310 *
311 * Decrypts provided buffer using IV data and the crypto context. Crypto context must be configured.
312 */
313__bpf_kfunc int bpf_crypto_decrypt(struct bpf_crypto_ctx *ctx,
314 const struct bpf_dynptr *src,
315 const struct bpf_dynptr *dst,
316 const struct bpf_dynptr *siv__nullable)
317{
318 const struct bpf_dynptr_kern *src_kern = (struct bpf_dynptr_kern *)src;
319 const struct bpf_dynptr_kern *dst_kern = (struct bpf_dynptr_kern *)dst;
320 const struct bpf_dynptr_kern *siv_kern = (struct bpf_dynptr_kern *)siv__nullable;
321
322 return bpf_crypto_crypt(ctx, src: src_kern, dst: dst_kern, siv: siv_kern, decrypt: true);
323}
324
325/**
326 * bpf_crypto_encrypt() - Encrypt buffer using configured context and IV provided.
327 * @ctx: The crypto context being used. The ctx must be a trusted pointer.
328 * @src: bpf_dynptr to the plain data. Must be a trusted pointer.
329 * @dst: bpf_dynptr to the buffer where to store the result. Must be a trusted pointer.
330 * @siv__nullable: bpf_dynptr to IV data and state data to be used by decryptor. May be NULL.
331 *
332 * Encrypts provided buffer using IV data and the crypto context. Crypto context must be configured.
333 */
334__bpf_kfunc int bpf_crypto_encrypt(struct bpf_crypto_ctx *ctx,
335 const struct bpf_dynptr *src,
336 const struct bpf_dynptr *dst,
337 const struct bpf_dynptr *siv__nullable)
338{
339 const struct bpf_dynptr_kern *src_kern = (struct bpf_dynptr_kern *)src;
340 const struct bpf_dynptr_kern *dst_kern = (struct bpf_dynptr_kern *)dst;
341 const struct bpf_dynptr_kern *siv_kern = (struct bpf_dynptr_kern *)siv__nullable;
342
343 return bpf_crypto_crypt(ctx, src: src_kern, dst: dst_kern, siv: siv_kern, decrypt: false);
344}
345
346__bpf_kfunc_end_defs();
347
348BTF_KFUNCS_START(crypt_init_kfunc_btf_ids)
349BTF_ID_FLAGS(func, bpf_crypto_ctx_create, KF_ACQUIRE | KF_RET_NULL | KF_SLEEPABLE)
350BTF_ID_FLAGS(func, bpf_crypto_ctx_release, KF_RELEASE)
351BTF_ID_FLAGS(func, bpf_crypto_ctx_acquire, KF_ACQUIRE | KF_RCU | KF_RET_NULL)
352BTF_KFUNCS_END(crypt_init_kfunc_btf_ids)
353
354static const struct btf_kfunc_id_set crypt_init_kfunc_set = {
355 .owner = THIS_MODULE,
356 .set = &crypt_init_kfunc_btf_ids,
357};
358
359BTF_KFUNCS_START(crypt_kfunc_btf_ids)
360BTF_ID_FLAGS(func, bpf_crypto_decrypt, KF_RCU)
361BTF_ID_FLAGS(func, bpf_crypto_encrypt, KF_RCU)
362BTF_KFUNCS_END(crypt_kfunc_btf_ids)
363
364static const struct btf_kfunc_id_set crypt_kfunc_set = {
365 .owner = THIS_MODULE,
366 .set = &crypt_kfunc_btf_ids,
367};
368
369BTF_ID_LIST(bpf_crypto_dtor_ids)
370BTF_ID(struct, bpf_crypto_ctx)
371BTF_ID(func, bpf_crypto_ctx_release)
372
373static int __init crypto_kfunc_init(void)
374{
375 int ret;
376 const struct btf_id_dtor_kfunc bpf_crypto_dtors[] = {
377 {
378 .btf_id = bpf_crypto_dtor_ids[0],
379 .kfunc_btf_id = bpf_crypto_dtor_ids[1]
380 },
381 };
382
383 ret = register_btf_kfunc_id_set(prog_type: BPF_PROG_TYPE_SCHED_CLS, s: &crypt_kfunc_set);
384 ret = ret ?: register_btf_kfunc_id_set(prog_type: BPF_PROG_TYPE_SCHED_ACT, s: &crypt_kfunc_set);
385 ret = ret ?: register_btf_kfunc_id_set(prog_type: BPF_PROG_TYPE_XDP, s: &crypt_kfunc_set);
386 ret = ret ?: register_btf_kfunc_id_set(prog_type: BPF_PROG_TYPE_SYSCALL,
387 s: &crypt_init_kfunc_set);
388 return ret ?: register_btf_id_dtor_kfuncs(dtors: bpf_crypto_dtors,
389 ARRAY_SIZE(bpf_crypto_dtors),
390 THIS_MODULE);
391}
392
393late_initcall(crypto_kfunc_init);
394

source code of linux/kernel/bpf/crypto.c