Re: [PATCH bpf-next v9 1/4] bpf: make common crypto API for TC/XDP programs

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On 4/16/24 1:40 PM, Vadim Fedorenko wrote:
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 5034c1b4ded7..acc479c13f52 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -1265,6 +1265,7 @@ int bpf_dynptr_check_size(u32 size);
  u32 __bpf_dynptr_size(const struct bpf_dynptr_kern *ptr);
  const void *__bpf_dynptr_data(const struct bpf_dynptr_kern *ptr, u32 len);
  void *__bpf_dynptr_data_rw(const struct bpf_dynptr_kern *ptr, u32 len);
+bool __bpf_dynptr_is_rdonly(const struct bpf_dynptr_kern *ptr);
#ifdef CONFIG_BPF_JIT
  int bpf_trampoline_link_prog(struct bpf_tramp_link *link, struct bpf_trampoline *tr);
diff --git a/include/linux/bpf_crypto.h b/include/linux/bpf_crypto.h
new file mode 100644
index 000000000000..a41e71d4e2d9
--- /dev/null
+++ b/include/linux/bpf_crypto.h
@@ -0,0 +1,24 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/* Copyright (c) 2024 Meta Platforms, Inc. and affiliates. */
+#ifndef _BPF_CRYPTO_H
+#define _BPF_CRYPTO_H
+
+struct bpf_crypto_type {
+	void *(*alloc_tfm)(const char *algo);
+	void (*free_tfm)(void *tfm);
+	int (*has_algo)(const char *algo);
+	int (*setkey)(void *tfm, const u8 *key, unsigned int keylen);
+	int (*setauthsize)(void *tfm, unsigned int authsize);
+	int (*encrypt)(void *tfm, const u8 *src, u8 *dst, unsigned int len, u8 *iv);
+	int (*decrypt)(void *tfm, const u8 *src, u8 *dst, unsigned int len, u8 *iv);
+	unsigned int (*ivsize)(void *tfm);
+	unsigned int (*statesize)(void *tfm);
+	u32 (*get_flags)(void *tfm);
+	struct module *owner;
+	char name[14];
+};
+
+int bpf_crypto_register_type(const struct bpf_crypto_type *type);
+int bpf_crypto_unregister_type(const struct bpf_crypto_type *type);
+
+#endif /* _BPF_CRYPTO_H */
diff --git a/kernel/bpf/Makefile b/kernel/bpf/Makefile
index 368c5d86b5b7..736bd22e5ce0 100644
--- a/kernel/bpf/Makefile
+++ b/kernel/bpf/Makefile
@@ -44,6 +44,9 @@ obj-$(CONFIG_BPF_SYSCALL) += bpf_struct_ops.o
  obj-$(CONFIG_BPF_SYSCALL) += cpumask.o
  obj-${CONFIG_BPF_LSM} += bpf_lsm.o
  endif
+ifeq ($(CONFIG_CRYPTO),y)
+obj-$(CONFIG_BPF_SYSCALL) += crypto.o
+endif
  obj-$(CONFIG_BPF_PRELOAD) += preload/
obj-$(CONFIG_BPF_SYSCALL) += relo_core.o
diff --git a/kernel/bpf/crypto.c b/kernel/bpf/crypto.c
new file mode 100644
index 000000000000..a76d80f37f55
--- /dev/null
+++ b/kernel/bpf/crypto.c
@@ -0,0 +1,377 @@
+// 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.
+ * @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];
+	char algo[128];
+	__u8 key[256];

It should have a two byte hole here. Add
	__u8 reserved[2];

and check for 0 in bpf_crypto_ctx_create() in case it could be reused later. The bpf_crypto_ctx_create() should not be called very often.

+	__u32 key_len;
+	__u32 authsize;

I don't think there is tail padding of this struct, so should be fine.

+} __attribute__((aligned(8)));

Does it need aligned(8) here?

+
+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.
+ * @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.
+ * @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, int *err)

Add a "u32 params__sz" arg in case that the params struct will have addition.
Take a look at how opts__sz is checked in nf_conntrack_bpf.c.

+{
+	const struct bpf_crypto_type *type;
+	struct bpf_crypto_ctx *ctx;
+
+	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->authsize && !type->setauthsize) {

nit. Together with the previous "if" test, replace them with one test like:

	if (!!params->authsize ^ !!type->setauthsize) {


+		*err = -EOPNOTSUPP;
+		goto err_module_put;
+	}
+
+	if (!params->key_len) {

Also checks "|| 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_skcipher_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, it is subsequently freed in
+ * an RCU callback in the BPF memory allocator.
+ */
+__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,
+			    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 = __bpf_dynptr_size(siv);
+	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;

It has been a while. I don't remember if it has already been brought up before.

The "const struct bpf_dynptr_kern *siv" here is essentially an optional pointer. Allowing NULL is a more intuitive usage instead of passing a 0-len dynptr. The verifier needs some changes to take __nullable suffix for "struct bpf_dynptr_kern *siv__nullable". This could be a follow up to relax the restriction to allow NULL and not necessary in this set.

+	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;
+}






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