// SPDX-License-Identifier: GPL-2.0-only
/* Copyright (c) 2024 Meta, Inc */
#include <linux/bpf.h>
#include <linux/bpf_crypto.h>
#include <linux/bpf_mem_alloc.h>
#include <linux/btf.h>
#include <linux/btf_ids.h>
#include <linux/filter.h>
#include <linux/scatterlist.h>
#include <linux/skbuff.h>
#include <crypto/skcipher.h>
struct bpf_crypto_type_list {
const struct bpf_crypto_type *type;
struct list_head list;
};
/* BPF crypto initialization parameters struct */
/**
* struct bpf_crypto_params - BPF crypto initialization parameters structure
* @type: The string of crypto operation type.
* @reserved: Reserved member, will be reused for more options in future
* Values:
* 0
* @algo: The string of algorithm to initialize.
* @key: The cipher key used to init crypto algorithm.
* @key_len: The length of cipher key.
* @authsize: The length of authentication tag used by algorithm.
*/
struct bpf_crypto_params {
char type[14];
u8 reserved[2];
char algo[128];
u8 key[256];
u32 key_len;
u32 authsize;
};
static LIST_HEAD(bpf_crypto_types);
static DECLARE_RWSEM(bpf_crypto_types_sem);
/**
* struct bpf_crypto_ctx - refcounted BPF crypto context structure
* @type: The pointer to bpf crypto type
* @tfm: The pointer to instance of crypto API struct.
* @siv_len: Size of IV and state storage for cipher
* @rcu: The RCU head used to free the crypto context with RCU safety.
* @usage: Object reference counter. When the refcount goes to 0, the
* memory is released back to the BPF allocator, which provides
* RCU safety.
*/
struct bpf_crypto_ctx {
const struct bpf_crypto_type *type;
void *tfm;
u32 siv_len;
struct rcu_head rcu;
refcount_t usage;
};
int bpf_crypto_register_type(const struct bpf_crypto_type *type)
{
struct bpf_crypto_type_list *node;
int err = -EEXIST;
down_write(&bpf_crypto_types_sem);
list_for_each_entry(node, &bpf_crypto_types, list) {
if (!strcmp(node->type->name, type->name))
goto unlock;
}
node = kmalloc(sizeof(*node), GFP_KERNEL);
err = -ENOMEM;
if (!node)
goto unlock;
node->type = type;
list_add(&node->list, &bpf_crypto_types);
err = 0;
unlock:
up_write(&bpf_crypto_types_sem);
return err;
}
EXPORT_SYMBOL_GPL(bpf_crypto_register_type);
int bpf_crypto_unregister_type(const struct bpf_crypto_type *type)
{
struct bpf_crypto_type_list *node;
int err = -ENOENT;
down_write(&bpf_crypto_types_sem);
list_for_each_entry(node, &bpf_crypto_types, list) {
if (strcmp(node->type->name, type->name))
continue;
list_del(&node->list);
kfree(node);
err = 0;
break;
}
up_write(&bpf_crypto_types_sem);
return err;
}
EXPORT_SYMBOL_GPL(bpf_crypto_unregister_type);
static const struct bpf_crypto_type *bpf_crypto_get_type(const char *name)
{
const struct bpf_crypto_type *type = ERR_PTR(-ENOENT);
struct bpf_crypto_type_list *node;
down_read(&bpf_crypto_types_sem);
list_for_each_entry(node, &bpf_crypto_types, list) {
if (strcmp(node->type->name, name))
continue;
if (try_module_get(node->type->owner))
type = node->type;
break;
}
up_read(&bpf_crypto_types_sem);
return type;
}
__bpf_kfunc_start_defs();
/**
* bpf_crypto_ctx_create() - Create a mutable BPF crypto context.
*
* Allocates a crypto context that can be used, acquired, and released by
* a BPF program. The crypto context returned by this function must either
* be embedded in a map as a kptr, or freed with bpf_crypto_ctx_release().
* As crypto API functions use GFP_KERNEL allocations, this function can
* only be used in sleepable BPF programs.
*
* bpf_crypto_ctx_create() allocates memory for crypto context.
* It may return NULL if no memory is available.
* @params: pointer to struct bpf_crypto_params which contains all the
* details needed to initialise crypto context.
* @params__sz: size of steuct bpf_crypto_params usef by bpf program
* @err: integer to store error code when NULL is returned.
*/
__bpf_kfunc struct bpf_crypto_ctx *
bpf_crypto_ctx_create(const struct bpf_crypto_params *params, u32 params__sz,
int *err)
{
const struct bpf_crypto_type *type;
struct bpf_crypto_ctx *ctx;
if (!params || params->reserved[0] || params->reserved[1] ||
params__sz != sizeof(struct bpf_crypto_params)) {
*err = -EINVAL;
return NULL;
}
type = bpf_crypto_get_type(params->type);
if (IS_ERR(type)) {
*err = PTR_ERR(type);
return NULL;
}
if (!type->has_algo(params->algo)) {
*err = -EOPNOTSUPP;
goto err_module_put;
}
if (!!params->authsize ^ !!type->setauthsize) {
*err = -EOPNOTSUPP;
goto err_module_put;
}
if (!params->key_len || params->key_len > sizeof(params->key)) {
*err = -EINVAL;
goto err_module_put;
}
ctx = kzalloc(sizeof(*ctx), GFP_KERNEL);
if (!ctx) {
*err = -ENOMEM;
goto err_module_put;
}
ctx->type = type;
ctx->tfm = type->alloc_tfm(params->algo);
if (IS_ERR(ctx->tfm)) {
*err = PTR_ERR(ctx->tfm);
goto err_free_ctx;
}
if (params->authsize) {
*err = type->setauthsize(ctx->tfm, params->authsize);
if (*err)
goto err_free_tfm;
}
*err = type->setkey(ctx->tfm, params->key, params->key_len);
if (*err)
goto err_free_tfm;
if (type->get_flags(ctx->tfm) & CRYPTO_TFM_NEED_KEY) {
*err = -EINVAL;
goto err_free_tfm;
}
ctx->siv_len = type->ivsize(ctx->tfm) + type->statesize(ctx->tfm);
refcount_set(&ctx->usage, 1);
return ctx;
err_free_tfm:
type->free_tfm(ctx->tfm);
err_free_ctx:
kfree(ctx);
err_module_put:
module_put(type->owner);
return NULL;
}
static void crypto_free_cb(struct rcu_head *head)
{
struct bpf_crypto_ctx *ctx;
ctx = container_of(head, struct bpf_crypto_ctx, rcu);
ctx->type->free_tfm(ctx->tfm);
module_put(ctx->type->owner);
kfree(ctx);
}
/**
* bpf_crypto_ctx_acquire() - Acquire a reference to a BPF crypto context.
* @ctx: The BPF crypto context being acquired. The ctx must be a trusted
* pointer.
*
* Acquires a reference to a BPF crypto context. The context returned by this function
* must either be embedded in a map as a kptr, or freed with
* bpf_crypto_ctx_release().
*/
__bpf_kfunc struct bpf_crypto_ctx *
bpf_crypto_ctx_acquire(struct bpf_crypto_ctx *ctx)
{
if (!refcount_inc_not_zero(&ctx->usage))
return NULL;
return ctx;
}
/**
* bpf_crypto_ctx_release() - Release a previously acquired BPF crypto context.
* @ctx: The crypto context being released.
*
* Releases a previously acquired reference to a BPF crypto context. When the final
* reference of the BPF crypto context has been released, its memory
* will be released.
*/
__bpf_kfunc void bpf_crypto_ctx_release(struct bpf_crypto_ctx *ctx)
{
if (refcount_dec_and_test(&ctx->usage))
call_rcu(&ctx->rcu, crypto_free_cb);
}
static int bpf_crypto_crypt(const struct bpf_crypto_ctx *ctx,
const struct bpf_dynptr_kern *src,
const struct bpf_dynptr_kern *dst,
const struct bpf_dynptr_kern *siv,
bool decrypt)
{
u32 src_len, dst_len, siv_len;
const u8 *psrc;
u8 *pdst, *piv;
int err;
if (__bpf_dynptr_is_rdonly(dst))
return -EINVAL;
siv_len = siv ? __bpf_dynptr_size(siv) : 0;
src_len = __bpf_dynptr_size(src);
dst_len = __bpf_dynptr_size(dst);
if (!src_len || !dst_len)
return -EINVAL;
if (siv_len != ctx->siv_len)
return -EINVAL;
psrc = __bpf_dynptr_data(src, src_len);
if (!psrc)
return -EINVAL;
pdst = __bpf_dynptr_data_rw(dst, dst_len);
if (!pdst)
return -EINVAL;
piv = siv_len ? __bpf_dynptr_data_rw(siv, siv_len) : NULL;
if (siv_len && !piv)
return -EINVAL;
err = decrypt ? ctx->type->decrypt(ctx->tfm, psrc, pdst, src_len, piv)
: ctx->type->encrypt(ctx->tfm, psrc, pdst, src_len, piv);
return err;
}
/**
* bpf_crypto_decrypt() - Decrypt buffer using configured context and IV provided.
* @ctx: The crypto context being used. The ctx must be a trusted pointer.
* @src: bpf_dynptr to the encrypted data. Must be a trusted pointer.
* @dst: bpf_dynptr to the buffer where to store the result. Must be a trusted pointer.
* @siv__nullable: bpf_dynptr to IV data and state data to be used by decryptor. May be NULL.
*
* Decrypts provided buffer using IV data and the crypto context. Crypto context must be configured.
*/
__bpf_kfunc int bpf_crypto_decrypt(struct bpf_crypto_ctx *ctx,
const struct bpf_dynptr *src,
const struct bpf_dynptr *dst,
const struct bpf_dynptr *siv__nullable)
{
const struct bpf_dynptr_kern *src_kern = (struct bpf_dynptr_kern *)src;
const struct bpf_dynptr_kern *dst_kern = (struct bpf_dynptr_kern *)dst;
const struct bpf_dynptr_kern *siv_kern = (struct bpf_dynptr_kern *)siv__nullable;
return bpf_crypto_crypt(ctx, src_kern, dst_kern, siv_kern, true);
}
/**
* bpf_crypto_encrypt() - Encrypt buffer using configured context and IV provided.
* @ctx: The crypto context being used. The ctx must be a trusted pointer.
* @src: bpf_dynptr to the plain data. Must be a trusted pointer.
* @dst: bpf_dynptr to the buffer where to store the result. Must be a trusted pointer.
* @siv__nullable: bpf_dynptr to IV data and state data to be used by decryptor. May be NULL.
*
* Encrypts provided buffer using IV data and the crypto context. Crypto context must be configured.
*/
__bpf_kfunc int bpf_crypto_encrypt(struct bpf_crypto_ctx *ctx,
const struct bpf_dynptr *src,
const struct bpf_dynptr *dst,
const struct bpf_dynptr *siv__nullable)
{
const struct bpf_dynptr_kern *src_kern = (struct bpf_dynptr_kern *)src;
const struct bpf_dynptr_kern *dst_kern = (struct bpf_dynptr_kern *)dst;
const struct bpf_dynptr_kern *siv_kern = (struct bpf_dynptr_kern *)siv__nullable;
return bpf_crypto_crypt(ctx, src_kern, dst_kern, siv_kern, false);
}
__bpf_kfunc_end_defs();
BTF_KFUNCS_START(crypt_init_kfunc_btf_ids)
BTF_ID_FLAGS(func, bpf_crypto_ctx_create, KF_ACQUIRE | KF_RET_NULL | KF_SLEEPABLE)
BTF_ID_FLAGS(func, bpf_crypto_ctx_release, KF_RELEASE)
BTF_ID_FLAGS(func, bpf_crypto_ctx_acquire, KF_ACQUIRE | KF_RCU | KF_RET_NULL)
BTF_KFUNCS_END(crypt_init_kfunc_btf_ids)
static const struct btf_kfunc_id_set crypt_init_kfunc_set = {
.owner = THIS_MODULE,
.set = &crypt_init_kfunc_btf_ids,
};
BTF_KFUNCS_START(crypt_kfunc_btf_ids)
BTF_ID_FLAGS(func, bpf_crypto_decrypt, KF_RCU)
BTF_ID_FLAGS(func, bpf_crypto_encrypt, KF_RCU)
BTF_KFUNCS_END(crypt_kfunc_btf_ids)
static const struct btf_kfunc_id_set crypt_kfunc_set = {
.owner = THIS_MODULE,
.set = &crypt_kfunc_btf_ids,
};
BTF_ID_LIST(bpf_crypto_dtor_ids)
BTF_ID(struct, bpf_crypto_ctx)
BTF_ID(func, bpf_crypto_ctx_release)
static int __init crypto_kfunc_init(void)
{
int ret;
const struct btf_id_dtor_kfunc bpf_crypto_dtors[] = {
{
.btf_id = bpf_crypto_dtor_ids[0],
.kfunc_btf_id = bpf_crypto_dtor_ids[1]
},
};
ret = register_btf_kfunc_id_set(BPF_PROG_TYPE_SCHED_CLS, &crypt_kfunc_set);
ret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_SCHED_ACT, &crypt_kfunc_set);
ret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_XDP, &crypt_kfunc_set);
ret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_SYSCALL,
&crypt_init_kfunc_set);
return ret ?: register_btf_id_dtor_kfuncs(bpf_crypto_dtors,
ARRAY_SIZE(bpf_crypto_dtors),
THIS_MODULE);
}
late_initcall(crypto_kfunc_init);
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