1 files changed, 313 insertions, 0 deletions
diff --git a/security/keys/trusted-keys/trusted_dcp.c b/security/keys/trusted-keys/trusted_dcp.c
new file mode 100644
index 000000000000..16c44aafeab3
--- /dev/null
+++ b/security/keys/trusted-keys/trusted_dcp.c
@@ -0,0 +1,313 @@
+// 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,
+};