--- /dev/null
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2021 sigma star gmbh
+ */
+
+#include <crypto/aead.h>
+#include <crypto/aes.h>
+#include <crypto/algapi.h>
+#include <crypto/gcm.h>
+#include <crypto/skcipher.h>
+#include <keys/trusted-type.h>
+#include <linux/key-type.h>
+#include <linux/module.h>
+#include <linux/printk.h>
+#include <linux/random.h>
+#include <linux/scatterlist.h>
+#include <soc/fsl/dcp.h>
+
+#define DCP_BLOB_VERSION 1
+#define DCP_BLOB_AUTHLEN 16
+
+/**
+ * struct dcp_blob_fmt - DCP BLOB format.
+ *
+ * @fmt_version: Format version, currently being %1.
+ * @blob_key: Random AES 128 key which is used to encrypt @payload,
+ * @blob_key itself is encrypted with OTP or UNIQUE device key in
+ * AES-128-ECB mode by DCP.
+ * @nonce: Random nonce used for @payload encryption.
+ * @payload_len: Length of the plain text @payload.
+ * @payload: The payload itself, encrypted using AES-128-GCM and @blob_key,
+ * GCM auth tag of size DCP_BLOB_AUTHLEN is attached at the end of it.
+ *
+ * The total size of a DCP BLOB is sizeof(struct dcp_blob_fmt) + @payload_len +
+ * DCP_BLOB_AUTHLEN.
+ */
+struct dcp_blob_fmt {
+ __u8 fmt_version;
+ __u8 blob_key[AES_KEYSIZE_128];
+ __u8 nonce[AES_KEYSIZE_128];
+ __le32 payload_len;
+ __u8 payload[];
+} __packed;
+
+static bool use_otp_key;
+module_param_named(dcp_use_otp_key, use_otp_key, bool, 0);
+MODULE_PARM_DESC(dcp_use_otp_key, "Use OTP instead of UNIQUE key for sealing");
+
+static bool skip_zk_test;
+module_param_named(dcp_skip_zk_test, skip_zk_test, bool, 0);
+MODULE_PARM_DESC(dcp_skip_zk_test, "Don't test whether device keys are zero'ed");
+
+static unsigned int calc_blob_len(unsigned int payload_len)
+{
+ return sizeof(struct dcp_blob_fmt) + payload_len + DCP_BLOB_AUTHLEN;
+}
+
+static int do_dcp_crypto(u8 *in, u8 *out, bool do_encrypt)
+{
+ struct skcipher_request *req = NULL;
+ struct scatterlist src_sg, dst_sg;
+ struct crypto_skcipher *tfm;
+ u8 paes_key[DCP_PAES_KEYSIZE];
+ DECLARE_CRYPTO_WAIT(wait);
+ int res = 0;
+
+ if (use_otp_key)
+ paes_key[0] = DCP_PAES_KEY_OTP;
+ else
+ paes_key[0] = DCP_PAES_KEY_UNIQUE;
+
+ tfm = crypto_alloc_skcipher("ecb-paes-dcp", CRYPTO_ALG_INTERNAL,
+ CRYPTO_ALG_INTERNAL);
+ if (IS_ERR(tfm)) {
+ res = PTR_ERR(tfm);
+ tfm = NULL;
+ goto out;
+ }
+
+ req = skcipher_request_alloc(tfm, GFP_NOFS);
+ if (!req) {
+ res = -ENOMEM;
+ goto out;
+ }
+
+ skcipher_request_set_callback(req, CRYPTO_TFM_REQ_MAY_BACKLOG |
+ CRYPTO_TFM_REQ_MAY_SLEEP,
+ crypto_req_done, &wait);
+ res = crypto_skcipher_setkey(tfm, paes_key, sizeof(paes_key));
+ if (res < 0)
+ goto out;
+
+ sg_init_one(&src_sg, in, AES_KEYSIZE_128);
+ sg_init_one(&dst_sg, out, AES_KEYSIZE_128);
+ skcipher_request_set_crypt(req, &src_sg, &dst_sg, AES_KEYSIZE_128,
+ NULL);
+
+ if (do_encrypt)
+ res = crypto_wait_req(crypto_skcipher_encrypt(req), &wait);
+ else
+ res = crypto_wait_req(crypto_skcipher_decrypt(req), &wait);
+
+out:
+ skcipher_request_free(req);
+ crypto_free_skcipher(tfm);
+
+ return res;
+}
+
+static int do_aead_crypto(u8 *in, u8 *out, size_t len, u8 *key, u8 *nonce,
+ bool do_encrypt)
+{
+ struct aead_request *aead_req = NULL;
+ struct scatterlist src_sg, dst_sg;
+ struct crypto_aead *aead;
+ int ret;
+
+ aead = crypto_alloc_aead("gcm(aes)", 0, CRYPTO_ALG_ASYNC);
+ if (IS_ERR(aead)) {
+ ret = PTR_ERR(aead);
+ goto out;
+ }
+
+ ret = crypto_aead_setauthsize(aead, DCP_BLOB_AUTHLEN);
+ if (ret < 0) {
+ pr_err("Can't set crypto auth tag len: %d\n", ret);
+ goto free_aead;
+ }
+
+ aead_req = aead_request_alloc(aead, GFP_KERNEL);
+ if (!aead_req) {
+ ret = -ENOMEM;
+ goto free_aead;
+ }
+
+ sg_init_one(&src_sg, in, len);
+ if (do_encrypt) {
+ /*
+ * If we encrypt our buffer has extra space for the auth tag.
+ */
+ sg_init_one(&dst_sg, out, len + DCP_BLOB_AUTHLEN);
+ } else {
+ sg_init_one(&dst_sg, out, len);
+ }
+
+ aead_request_set_crypt(aead_req, &src_sg, &dst_sg, len, nonce);
+ aead_request_set_callback(aead_req, CRYPTO_TFM_REQ_MAY_SLEEP, NULL,
+ NULL);
+ aead_request_set_ad(aead_req, 0);
+
+ if (crypto_aead_setkey(aead, key, AES_KEYSIZE_128)) {
+ pr_err("Can't set crypto AEAD key\n");
+ ret = -EINVAL;
+ goto free_req;
+ }
+
+ if (do_encrypt)
+ ret = crypto_aead_encrypt(aead_req);
+ else
+ ret = crypto_aead_decrypt(aead_req);
+
+free_req:
+ aead_request_free(aead_req);
+free_aead:
+ crypto_free_aead(aead);
+out:
+ return ret;
+}
+
+static int decrypt_blob_key(u8 *key)
+{
+ return do_dcp_crypto(key, key, false);
+}
+
+static int encrypt_blob_key(u8 *key)
+{
+ return do_dcp_crypto(key, key, true);
+}
+
+static int trusted_dcp_seal(struct trusted_key_payload *p, char *datablob)
+{
+ struct dcp_blob_fmt *b = (struct dcp_blob_fmt *)p->blob;
+ int blen, ret;
+
+ blen = calc_blob_len(p->key_len);
+ if (blen > MAX_BLOB_SIZE)
+ return -E2BIG;
+
+ b->fmt_version = DCP_BLOB_VERSION;
+ get_random_bytes(b->nonce, AES_KEYSIZE_128);
+ get_random_bytes(b->blob_key, AES_KEYSIZE_128);
+
+ ret = do_aead_crypto(p->key, b->payload, p->key_len, b->blob_key,
+ b->nonce, true);
+ if (ret) {
+ pr_err("Unable to encrypt blob payload: %i\n", ret);
+ return ret;
+ }
+
+ ret = encrypt_blob_key(b->blob_key);
+ if (ret) {
+ pr_err("Unable to encrypt blob key: %i\n", ret);
+ return ret;
+ }
+
+ b->payload_len = get_unaligned_le32(&p->key_len);
+ p->blob_len = blen;
+ return 0;
+}
+
+static int trusted_dcp_unseal(struct trusted_key_payload *p, char *datablob)
+{
+ struct dcp_blob_fmt *b = (struct dcp_blob_fmt *)p->blob;
+ int blen, ret;
+
+ if (b->fmt_version != DCP_BLOB_VERSION) {
+ pr_err("DCP blob has bad version: %i, expected %i\n",
+ b->fmt_version, DCP_BLOB_VERSION);
+ ret = -EINVAL;
+ goto out;
+ }
+
+ p->key_len = le32_to_cpu(b->payload_len);
+ blen = calc_blob_len(p->key_len);
+ if (blen != p->blob_len) {
+ pr_err("DCP blob has bad length: %i != %i\n", blen,
+ p->blob_len);
+ ret = -EINVAL;
+ goto out;
+ }
+
+ ret = decrypt_blob_key(b->blob_key);
+ if (ret) {
+ pr_err("Unable to decrypt blob key: %i\n", ret);
+ goto out;
+ }
+
+ ret = do_aead_crypto(b->payload, p->key, p->key_len + DCP_BLOB_AUTHLEN,
+ b->blob_key, b->nonce, false);
+ if (ret) {
+ pr_err("Unwrap of DCP payload failed: %i\n", ret);
+ goto out;
+ }
+
+ ret = 0;
+out:
+ return ret;
+}
+
+static int test_for_zero_key(void)
+{
+ /*
+ * Encrypting a plaintext of all 0x55 bytes will yield
+ * this ciphertext in case the DCP test key is used.
+ */
+ static const u8 bad[] = {0x9a, 0xda, 0xe0, 0x54, 0xf6, 0x3d, 0xfa, 0xff,
+ 0x5e, 0xa1, 0x8e, 0x45, 0xed, 0xf6, 0xea, 0x6f};
+ void *buf = NULL;
+ int ret = 0;
+
+ if (skip_zk_test)
+ goto out;
+
+ buf = kmalloc(AES_BLOCK_SIZE, GFP_KERNEL);
+ if (!buf) {
+ ret = -ENOMEM;
+ goto out;
+ }
+
+ memset(buf, 0x55, AES_BLOCK_SIZE);
+
+ ret = do_dcp_crypto(buf, buf, true);
+ if (ret)
+ goto out;
+
+ if (memcmp(buf, bad, AES_BLOCK_SIZE) == 0) {
+ pr_warn("Device neither in secure nor trusted mode!\n");
+ ret = -EINVAL;
+ }
+out:
+ kfree(buf);
+ return ret;
+}
+
+static int trusted_dcp_init(void)
+{
+ int ret;
+
+ if (use_otp_key)
+ pr_info("Using DCP OTP key\n");
+
+ ret = test_for_zero_key();
+ if (ret) {
+ pr_warn("Test for zero'ed keys failed: %i\n", ret);
+
+ return -EINVAL;
+ }
+
+ return register_key_type(&key_type_trusted);
+}
+
+static void trusted_dcp_exit(void)
+{
+ unregister_key_type(&key_type_trusted);
+}
+
+struct trusted_key_ops dcp_trusted_key_ops = {
+ .exit = trusted_dcp_exit,
+ .init = trusted_dcp_init,
+ .seal = trusted_dcp_seal,
+ .unseal = trusted_dcp_unseal,
+ .migratable = 0,
+};
projects / thirdparty / kernel / linux.git / blobdiff