| Message ID | 20240403072131.54935-4-david@sigma-star.at (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | DCP as trusted keys backend | expand |
Hi David, > -----Original Message----- > From: David Gstir <david@sigma-star.at> > Sent: Wednesday, April 3, 2024 12:51 PM > To: Mimi Zohar <zohar@linux.ibm.com>; James Bottomley > <jejb@linux.ibm.com>; Jarkko Sakkinen <jarkko@kernel.org>; Herbert Xu > <herbert@gondor.apana.org.au>; David S. Miller <davem@davemloft.net> > Cc: David Gstir <david@sigma-star.at>; Shawn Guo <shawnguo@kernel.org>; > Jonathan Corbet <corbet@lwn.net>; Sascha Hauer > <s.hauer@pengutronix.de>; Pengutronix Kernel Team > <kernel@pengutronix.de>; Fabio Estevam <festevam@gmail.com>; dl-linux- > imx <linux-imx@nxp.com>; Ahmad Fatoum <a.fatoum@pengutronix.de>; > sigma star Kernel Team <upstream+dcp@sigma-star.at>; David Howells > <dhowells@redhat.com>; Li Yang <leoyang.li@nxp.com>; Paul Moore > <paul@paul-moore.com>; James Morris <jmorris@namei.org>; Serge E. > Hallyn <serge@hallyn.com>; Paul E. McKenney <paulmck@kernel.org>; > Randy Dunlap <rdunlap@infradead.org>; Catalin Marinas > <catalin.marinas@arm.com>; Rafael J. Wysocki > <rafael.j.wysocki@intel.com>; Tejun Heo <tj@kernel.org>; Steven Rostedt > (Google) <rostedt@goodmis.org>; linux-doc@vger.kernel.org; linux- > kernel@vger.kernel.org; linux-integrity@vger.kernel.org; > keyrings@vger.kernel.org; linux-crypto@vger.kernel.org; linux-arm- > kernel@lists.infradead.org; linuxppc-dev@lists.ozlabs.org; linux-security- > module@vger.kernel.org; Richard Weinberger <richard@nod.at>; David > Oberhollenzer <david.oberhollenzer@sigma-star.at> > Subject: [EXT] [PATCH v8 3/6] KEYS: trusted: Introduce NXP DCP-backed > trusted keys > > Caution: This is an external email. Please take care when clicking links or > opening attachments. When in doubt, report the message using the 'Report > this email' button > > > 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 similar to what CAAM offers. Unlike on CAAM, constructing and > parsing the blob has to happen in software (i.e. the kernel). > > The software-based blob format used by DCP trusted keys encrypts the > payload using AES-128-GCM with a freshly generated random key and > nonce. > The random key itself is AES-128-ECB encrypted using the DCP unique or > OTP key. > > The DCP trusted key blob format is: > /* > * 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; > > By default the unique key is used. It is also possible to use the OTP key. > While the unique key should be unique it is not documented how this key is > derived. Therefore selection the OTP key is supported as well via the > use_otp_key module parameter. > > Co-developed-by: Richard Weinberger <richard@nod.at> > Signed-off-by: Richard Weinberger <richard@nod.at> > Co-developed-by: David Oberhollenzer <david.oberhollenzer@sigma-star.at> > Signed-off-by: David Oberhollenzer <david.oberhollenzer@sigma-star.at> > Signed-off-by: David Gstir <david@sigma-star.at> > Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org> > --- > include/keys/trusted_dcp.h | 11 + > security/keys/trusted-keys/Kconfig | 8 + > security/keys/trusted-keys/Makefile | 2 + > security/keys/trusted-keys/trusted_core.c | 6 +- > security/keys/trusted-keys/trusted_dcp.c | 313 > ++++++++++++++++++++++ > 5 files changed, 339 insertions(+), 1 deletion(-) create mode 100644 > include/keys/trusted_dcp.h create mode 100644 security/keys/trusted- > keys/trusted_dcp.c > > 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 553dc117f385..1fb8aa001995 100644 > --- a/security/keys/trusted-keys/Kconfig > +++ b/security/keys/trusted-keys/Kconfig > @@ -39,6 +39,14 @@ config TRUSTED_KEYS_CAAM > Enable use of NXP's Cryptographic Accelerator and Assurance Module > (CAAM) as trusted key backend. > > +config TRUSTED_KEYS_DCP > + bool "DCP-based trusted keys" > + depends on CRYPTO_DEV_MXS_DCP >= TRUSTED_KEYS > + default y > + select HAVE_TRUSTED_KEYS > + help > + Enable use of NXP's DCP (Data Co-Processor) as trusted key backend. > + > if !HAVE_TRUSTED_KEYS > 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 fee1ab2c734d..5113aeae5628 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_seal, *trusted_key_sources[0].ops- > >seal); > 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); We can use HWRNG instead of using kernel RNG. Please refer drivers/char/hw_random/imx-rngc.c > + > + 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, > +}; > -- > 2.35.3 > Regards, Kshitiz
Hello Kshitiz, On 09.04.24 12:54, Kshitiz Varshney wrote: > Hi David, >> + b->fmt_version = DCP_BLOB_VERSION; >> + get_random_bytes(b->nonce, AES_KEYSIZE_128); >> + get_random_bytes(b->blob_key, AES_KEYSIZE_128); > > We can use HWRNG instead of using kernel RNG. Please refer drivers/char/hw_random/imx-rngc.c imx-rngc can be enabled and used to seed the kernel entropy pool. Adding direct calls into imx-rngc here only introduces duplicated code at no extra benefit. Cheers, Ahmad
Hi Ahmad, > -----Original Message----- > From: Ahmad Fatoum <a.fatoum@pengutronix.de> > Sent: Tuesday, April 9, 2024 10:58 PM > To: Kshitiz Varshney <kshitiz.varshney@nxp.com>; David Gstir > <david@sigma-star.at>; Mimi Zohar <zohar@linux.ibm.com>; James > Bottomley <jejb@linux.ibm.com>; Jarkko Sakkinen <jarkko@kernel.org>; > Herbert Xu <herbert@gondor.apana.org.au>; David S. Miller > <davem@davemloft.net> > Cc: linux-doc@vger.kernel.org; Gaurav Jain <gaurav.jain@nxp.com>; Catalin > Marinas <catalin.marinas@arm.com>; David Howells > <dhowells@redhat.com>; keyrings@vger.kernel.org; Fabio Estevam > <festevam@gmail.com>; Paul Moore <paul@paul-moore.com>; Jonathan > Corbet <corbet@lwn.net>; Richard Weinberger <richard@nod.at>; Rafael J. > Wysocki <rafael.j.wysocki@intel.com>; James Morris <jmorris@namei.org>; > dl-linux-imx <linux-imx@nxp.com>; Serge E. Hallyn <serge@hallyn.com>; > Paul E. McKenney <paulmck@kernel.org>; Sascha Hauer > <s.hauer@pengutronix.de>; Pankaj Gupta <pankaj.gupta@nxp.com>; sigma > star Kernel Team <upstream+dcp@sigma-star.at>; Steven Rostedt (Google) > <rostedt@goodmis.org>; David Oberhollenzer <david.oberhollenzer@sigma- > star.at>; linux-arm-kernel@lists.infradead.org; linuxppc-dev@lists.ozlabs.org; > Randy Dunlap <rdunlap@infradead.org>; linux-kernel@vger.kernel.org; Li > Yang <leoyang.li@nxp.com>; linux-security-module@vger.kernel.org; linux- > crypto@vger.kernel.org; Pengutronix Kernel Team <kernel@pengutronix.de>; > Tejun Heo <tj@kernel.org>; linux-integrity@vger.kernel.org; Shawn Guo > <shawnguo@kernel.org>; Varun Sethi <V.Sethi@nxp.com> > Subject: Re: [EXT] [PATCH v8 3/6] KEYS: trusted: Introduce NXP DCP-backed > trusted keys > > Caution: This is an external email. Please take care when clicking links or > opening attachments. When in doubt, report the message using the 'Report > this email' button > > > Hello Kshitiz, > > On 09.04.24 12:54, Kshitiz Varshney wrote: > > Hi David, > >> + b->fmt_version = DCP_BLOB_VERSION; > >> + get_random_bytes(b->nonce, AES_KEYSIZE_128); > >> + get_random_bytes(b->blob_key, AES_KEYSIZE_128); > > > > We can use HWRNG instead of using kernel RNG. Please refer > > drivers/char/hw_random/imx-rngc.c > > imx-rngc can be enabled and used to seed the kernel entropy pool. Adding > direct calls into imx-rngc here only introduces duplicated code at no extra > benefit. > > Cheers, > Ahmad > > -- > Pengutronix e.K. | | > Steuerwalder Str. 21 | > https://eur01.safelinks.protection.outlook.com/?url=http%3A%2F%2Fwww. > pengutronix.de%2F&data=05%7C02%7Ckshitiz.varshney%40nxp.com%7Ce9 > 97f259d34548ad1a9808dc58ba63a8%7C686ea1d3bc2b4c6fa92cd99c5c30 > 1635%7C0%7C0%7C638482804763047266%7CUnknown%7CTWFpbGZsb3 > d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0 > %3D%7C0%7C%7C%7C&sdata=UZgE9MXqAqCwqVnWty67YLh8QnIwpuq%2 > F7%2BQeDLQhF8I%3D&reserved=0 | > 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | > Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 | Understood. Regards, Kshitiz
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 553dc117f385..1fb8aa001995 100644 --- a/security/keys/trusted-keys/Kconfig +++ b/security/keys/trusted-keys/Kconfig @@ -39,6 +39,14 @@ config TRUSTED_KEYS_CAAM Enable use of NXP's Cryptographic Accelerator and Assurance Module (CAAM) as trusted key backend. +config TRUSTED_KEYS_DCP + bool "DCP-based trusted keys" + depends on CRYPTO_DEV_MXS_DCP >= TRUSTED_KEYS + default y + select HAVE_TRUSTED_KEYS + help + Enable use of NXP's DCP (Data Co-Processor) as trusted key backend. + if !HAVE_TRUSTED_KEYS 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 fee1ab2c734d..5113aeae5628 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_seal, *trusted_key_sources[0].ops->seal); 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, +};
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 similar to what CAAM offers. Unlike on CAAM, constructing and parsing the blob has to happen in software (i.e. the kernel). The software-based blob format used by DCP trusted keys encrypts the payload using AES-128-GCM with a freshly generated random key and nonce. The random key itself is AES-128-ECB encrypted using the DCP unique or OTP key. The DCP trusted key blob format is: /* * 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; By default the unique key is used. It is also possible to use the OTP key. While the unique key should be unique it is not documented how this key is derived. Therefore selection the OTP key is supported as well via the use_otp_key module parameter. Co-developed-by: Richard Weinberger <richard@nod.at> Signed-off-by: Richard Weinberger <richard@nod.at> Co-developed-by: David Oberhollenzer <david.oberhollenzer@sigma-star.at> Signed-off-by: David Oberhollenzer <david.oberhollenzer@sigma-star.at> Signed-off-by: David Gstir <david@sigma-star.at> Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org> --- include/keys/trusted_dcp.h | 11 + security/keys/trusted-keys/Kconfig | 8 + security/keys/trusted-keys/Makefile | 2 + security/keys/trusted-keys/trusted_core.c | 6 +- security/keys/trusted-keys/trusted_dcp.c | 313 ++++++++++++++++++++++ 5 files changed, 339 insertions(+), 1 deletion(-) create mode 100644 include/keys/trusted_dcp.h create mode 100644 security/keys/trusted-keys/trusted_dcp.c