On Mon Sep 18, 2023 at 5:18 PM EEST, David Gstir wrote: > DCP (Data Co-Processor) is the little brother of NXP's CAAM IP. > > Beside of accelerated crypto operations, it also offers support for > hardware-bound keys. Using this feature it is possible to implement a blob > mechanism just like CAAM offers. Unlike on CAAM, constructing and > parsing the blob has to happen in software. > > We chose the following format for the blob: Who is we? And there is no choosing anything if the below structure if hardware defined (not software defined): > /* > * 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 AES_BLOCK_SIZE is attached at the end of it. > * > * The total size of a DCP BLOB is sizeof(struct dcp_blob_fmt) + @payload_len + > * AES_BLOCK_SIZE. > */ > struct dcp_blob_fmt { > __u8 fmt_version; > __u8 blob_key[AES_KEYSIZE_128]; > __u8 nonce[AES_KEYSIZE_128]; > __le32 payload_len; > __u8 payload[]; > } __packed; > > @payload is the key provided by trusted_key_ops->seal(). > > By default the UNIQUE device key is used, it is also possible to use > the OTP key. While the UNIQUE device key should be unique it is not > entirely clear whether this is the case due to unclear documentation. > If someone wants to be sure they can burn their own unique key > into the OTP fuse and set the use_otp_key module parameter. > > Co-developed-by: Richard Weinberger <richard@xxxxxx> > Signed-off-by: Richard Weinberger <richard@xxxxxx> > Co-developed-by: David Oberhollenzer <david.oberhollenzer@xxxxxxxxxxxxx> > Signed-off-by: David Oberhollenzer <david.oberhollenzer@xxxxxxxxxxxxx> > Signed-off-by: David Gstir <david@xxxxxxxxxxxxx> > --- > .../admin-guide/kernel-parameters.txt | 13 + Separate commit for this. > MAINTAINERS | 9 + Ditto (i.e. total two additional patches). > include/keys/trusted_dcp.h | 11 + > security/keys/trusted-keys/Kconfig | 9 +- > security/keys/trusted-keys/Makefile | 2 + > security/keys/trusted-keys/trusted_core.c | 6 +- > security/keys/trusted-keys/trusted_dcp.c | 311 ++++++++++++++++++ > 7 files changed, 359 insertions(+), 2 deletions(-) > create mode 100644 include/keys/trusted_dcp.h > create mode 100644 security/keys/trusted-keys/trusted_dcp.c > > diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt > index 0a1731a0f0ef..c11eda8b38e0 100644 > --- a/Documentation/admin-guide/kernel-parameters.txt > +++ b/Documentation/admin-guide/kernel-parameters.txt > @@ -6566,6 +6566,7 @@ > - "tpm" > - "tee" > - "caam" > + - "dcp" > If not specified then it defaults to iterating through > the trust source list starting with TPM and assigns the > first trust source as a backend which is initialized > @@ -6581,6 +6582,18 @@ > If not specified, "default" is used. In this case, > the RNG's choice is left to each individual trust source. > > + trusted.dcp_use_otp_key > + This is intended to be used in combination with > + trusted.source=dcp and will select the DCP OTP key > + instead of the DCP UNIQUE key blob encryption. > + > + trusted.dcp_skip_zk_test > + This is intended to be used in combination with > + trusted.source=dcp and will disable the check if all > + the blob key is zero'ed. This is helpful for situations where > + having this key zero'ed is acceptable. E.g. in testing > + scenarios. > + > tsc= Disable clocksource stability checks for TSC. > Format: <string> > [x86] reliable: mark tsc clocksource as reliable, this > diff --git a/MAINTAINERS b/MAINTAINERS > index 90f13281d297..988d01226131 100644 > --- a/MAINTAINERS > +++ b/MAINTAINERS > @@ -11647,6 +11647,15 @@ S: Maintained > F: include/keys/trusted_caam.h > F: security/keys/trusted-keys/trusted_caam.c > > +KEYS-TRUSTED-DCP > +M: David Gstir <david@xxxxxxxxxxxxx> > +R: sigma star Kernel Team <upstream+dcp@xxxxxxxxxxxxx> > +L: linux-integrity@xxxxxxxxxxxxxxx > +L: keyrings@xxxxxxxxxxxxxxx > +S: Supported > +F: include/keys/trusted_dcp.h > +F: security/keys/trusted-keys/trusted_dcp.c > + > KEYS-TRUSTED-TEE > M: Sumit Garg <sumit.garg@xxxxxxxxxx> > L: linux-integrity@xxxxxxxxxxxxxxx > diff --git a/include/keys/trusted_dcp.h b/include/keys/trusted_dcp.h > new file mode 100644 > index 000000000000..9aaa42075b40 > --- /dev/null > +++ b/include/keys/trusted_dcp.h > @@ -0,0 +1,11 @@ > +/* SPDX-License-Identifier: GPL-2.0-only */ > +/* > + * Copyright (C) 2021 sigma star gmbh > + */ > + > +#ifndef TRUSTED_DCP_H > +#define TRUSTED_DCP_H > + > +extern struct trusted_key_ops dcp_trusted_key_ops; > + > +#endif > diff --git a/security/keys/trusted-keys/Kconfig b/security/keys/trusted-keys/Kconfig > index dbfdd8536468..c6b80b7e5c78 100644 > --- a/security/keys/trusted-keys/Kconfig > +++ b/security/keys/trusted-keys/Kconfig > @@ -33,6 +33,13 @@ config TRUSTED_KEYS_CAAM > Enable use of NXP's Cryptographic Accelerator and Assurance Module > (CAAM) as trusted key backend. > > -if !TRUSTED_KEYS_TPM && !TRUSTED_KEYS_TEE && !TRUSTED_KEYS_CAAM > +config TRUSTED_KEYS_DCP > + bool "DCP-based trusted keys" > + depends on CRYPTO_DEV_MXS_DCP >= TRUSTED_KEYS > + default y > + help > + Enable use of NXP's DCP (Data Co-Processor) as trusted key backend. > + > +if !TRUSTED_KEYS_TPM && !TRUSTED_KEYS_TEE && !TRUSTED_KEYS_CAAM && !TRUSTED_KEYS_DCP > comment "No trust source selected!" > endif > diff --git a/security/keys/trusted-keys/Makefile b/security/keys/trusted-keys/Makefile > index 735aa0bc08ef..f0f3b27f688b 100644 > --- a/security/keys/trusted-keys/Makefile > +++ b/security/keys/trusted-keys/Makefile > @@ -14,3 +14,5 @@ trusted-$(CONFIG_TRUSTED_KEYS_TPM) += tpm2key.asn1.o > trusted-$(CONFIG_TRUSTED_KEYS_TEE) += trusted_tee.o > > trusted-$(CONFIG_TRUSTED_KEYS_CAAM) += trusted_caam.o > + > +trusted-$(CONFIG_TRUSTED_KEYS_DCP) += trusted_dcp.o > diff --git a/security/keys/trusted-keys/trusted_core.c b/security/keys/trusted-keys/trusted_core.c > index c6fc50d67214..8af0988be850 100644 > --- a/security/keys/trusted-keys/trusted_core.c > +++ b/security/keys/trusted-keys/trusted_core.c > @@ -10,6 +10,7 @@ > #include <keys/trusted-type.h> > #include <keys/trusted_tee.h> > #include <keys/trusted_caam.h> > +#include <keys/trusted_dcp.h> > #include <keys/trusted_tpm.h> > #include <linux/capability.h> > #include <linux/err.h> > @@ -30,7 +31,7 @@ MODULE_PARM_DESC(rng, "Select trusted key RNG"); > > static char *trusted_key_source; > module_param_named(source, trusted_key_source, charp, 0); > -MODULE_PARM_DESC(source, "Select trusted keys source (tpm, tee or caam)"); > +MODULE_PARM_DESC(source, "Select trusted keys source (tpm, tee, caam or dcp)"); > > static const struct trusted_key_source trusted_key_sources[] = { > #if defined(CONFIG_TRUSTED_KEYS_TPM) > @@ -42,6 +43,9 @@ static const struct trusted_key_source trusted_key_sources[] = { > #if defined(CONFIG_TRUSTED_KEYS_CAAM) > { "caam", &trusted_key_caam_ops }, > #endif > +#if defined(CONFIG_TRUSTED_KEYS_DCP) > + { "dcp", &dcp_trusted_key_ops }, > +#endif > }; > > DEFINE_STATIC_CALL_NULL(trusted_key_init, *trusted_key_sources[0].ops->init); > diff --git a/security/keys/trusted-keys/trusted_dcp.c b/security/keys/trusted-keys/trusted_dcp.c > new file mode 100644 > index 000000000000..8d19b92fe976 > --- /dev/null > +++ b/security/keys/trusted-keys/trusted_dcp.c > @@ -0,0 +1,311 @@ > +// 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 is_encrypt) > +{ > + int res = 0; > + struct skcipher_request *req = NULL; > + DECLARE_CRYPTO_WAIT(wait); > + struct scatterlist src_sg, dst_sg; > + struct crypto_skcipher *tfm; > + u8 paes_key[DCP_PAES_KEYSIZE]; > + > + 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); > + pr_err("Unable to request DCP pAES-ECB cipher: %i\n", res); > + 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 (is_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 is_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); > + pr_err("Unable to request AES-GCM cipher: %i\n", ret); > + 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 (is_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 (is_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) > +{ > + 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_err("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_err("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, > +}; > -- > 2.35.3 BR, Jarkko