Hi Kshitiz, > On 09.04.2024, at 11:48, Kshitiz Varshney <kshitiz.varshney@xxxxxxx> wrote: > > Hi Jarkko, > > >> -----Original Message----- >> From: Jarkko Sakkinen <jarkko@xxxxxxxxxx> >> Sent: Wednesday, April 3, 2024 9:18 PM >> To: David Gstir <david@xxxxxxxxxxxxx>; Mimi Zohar <zohar@xxxxxxxxxxxxx>; >> James Bottomley <jejb@xxxxxxxxxxxxx>; Herbert Xu >> <herbert@xxxxxxxxxxxxxxxxxxx>; David S. Miller <davem@xxxxxxxxxxxxx> >> Cc: Shawn Guo <shawnguo@xxxxxxxxxx>; Jonathan Corbet >> <corbet@xxxxxxx>; Sascha Hauer <s.hauer@xxxxxxxxxxxxxx>; Pengutronix >> Kernel Team <kernel@xxxxxxxxxxxxxx>; Fabio Estevam >> <festevam@xxxxxxxxx>; dl-linux-imx <linux-imx@xxxxxxx>; Ahmad Fatoum >> <a.fatoum@xxxxxxxxxxxxxx>; sigma star Kernel Team >> <upstream+dcp@xxxxxxxxxxxxx>; David Howells <dhowells@xxxxxxxxxx>; Li >> Yang <leoyang.li@xxxxxxx>; Paul Moore <paul@xxxxxxxxxxxxxx>; James >> Morris <jmorris@xxxxxxxxx>; Serge E. Hallyn <serge@xxxxxxxxxx>; Paul E. >> McKenney <paulmck@xxxxxxxxxx>; Randy Dunlap <rdunlap@xxxxxxxxxxxxx>; >> Catalin Marinas <catalin.marinas@xxxxxxx>; Rafael J. Wysocki >> <rafael.j.wysocki@xxxxxxxxx>; Tejun Heo <tj@xxxxxxxxxx>; Steven Rostedt >> (Google) <rostedt@xxxxxxxxxxx>; linux-doc@xxxxxxxxxxxxxxx; linux- >> kernel@xxxxxxxxxxxxxxx; linux-integrity@xxxxxxxxxxxxxxx; >> keyrings@xxxxxxxxxxxxxxx; linux-crypto@xxxxxxxxxxxxxxx; linux-arm- >> kernel@xxxxxxxxxxxxxxxxxxx; linuxppc-dev@xxxxxxxxxxxxxxxx; linux-security- >> module@xxxxxxxxxxxxxxx; Richard Weinberger <richard@xxxxxx>; David >> Oberhollenzer <david.oberhollenzer@xxxxxxxxxxxxx> >> Subject: [EXT] Re: [PATCH v8 6/6] docs: trusted-encrypted: add DCP as new >> trust source >> >> 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 >> >> >> On Wed Apr 3, 2024 at 10:21 AM EEST, David Gstir wrote: >>> Update the documentation for trusted and encrypted KEYS with DCP as >>> new trust source: >>> >>> - Describe security properties of DCP trust source >>> - Describe key usage >>> - Document blob format >>> >>> 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> >>> --- >>> .../security/keys/trusted-encrypted.rst | 53 +++++++++++++++++++ >>> security/keys/trusted-keys/trusted_dcp.c | 19 +++++++ >>> 2 files changed, 72 insertions(+) >>> >>> diff --git a/Documentation/security/keys/trusted-encrypted.rst >>> b/Documentation/security/keys/trusted-encrypted.rst >>> index e989b9802f92..f4d7e162d5e4 100644 >>> --- a/Documentation/security/keys/trusted-encrypted.rst >>> +++ b/Documentation/security/keys/trusted-encrypted.rst >>> @@ -42,6 +42,14 @@ safe. >>> randomly generated and fused into each SoC at manufacturing time. >>> Otherwise, a common fixed test key is used instead. >>> >>> + (4) DCP (Data Co-Processor: crypto accelerator of various i.MX >>> + SoCs) >>> + >>> + Rooted to a one-time programmable key (OTP) that is generally >> burnt >>> + in the on-chip fuses and is accessible to the DCP encryption engine >> only. >>> + DCP provides two keys that can be used as root of trust: the OTP >> key >>> + and the UNIQUE key. Default is to use the UNIQUE key, but selecting >>> + the OTP key can be done via a module parameter >> (dcp_use_otp_key). >>> + >>> * Execution isolation >>> >>> (1) TPM >>> @@ -57,6 +65,12 @@ safe. >>> >>> Fixed set of operations running in isolated execution environment. >>> >>> + (4) DCP >>> + >>> + Fixed set of cryptographic operations running in isolated execution >>> + environment. Only basic blob key encryption is executed there. >>> + The actual key sealing/unsealing is done on main processor/kernel >> space. >>> + >>> * Optional binding to platform integrity state >>> >>> (1) TPM >>> @@ -79,6 +93,11 @@ safe. >>> Relies on the High Assurance Boot (HAB) mechanism of NXP SoCs >>> for platform integrity. >>> >>> + (4) DCP >>> + >>> + Relies on Secure/Trusted boot process (called HAB by vendor) for >>> + platform integrity. >>> + >>> * Interfaces and APIs >>> >>> (1) TPM >>> @@ -94,6 +113,11 @@ safe. >>> >>> Interface is specific to silicon vendor. >>> >>> + (4) DCP >>> + >>> + Vendor-specific API that is implemented as part of the DCP crypto >> driver in >>> + ``drivers/crypto/mxs-dcp.c``. >>> + >>> * Threat model >>> >>> The strength and appropriateness of a particular trust source >>> for a given @@ -129,6 +153,13 @@ selected trust source: >>> CAAM HWRNG, enable CRYPTO_DEV_FSL_CAAM_RNG_API and ensure >> the device >>> is probed. >>> >>> + * DCP (Data Co-Processor: crypto accelerator of various i.MX SoCs) >>> + >>> + The DCP hardware device itself does not provide a dedicated RNG >> interface, >>> + so the kernel default RNG is used. SoCs with DCP like the i.MX6ULL do >> have >>> + a dedicated hardware RNG that is independent from DCP which can be >> enabled >>> + to back the kernel RNG. >>> + >>> Users may override this by specifying ``trusted.rng=kernel`` on the >>> kernel command-line to override the used RNG with the kernel's random >> number pool. >>> >>> @@ -231,6 +262,19 @@ Usage:: >>> CAAM-specific format. The key length for new keys is always in bytes. >>> Trusted Keys can be 32 - 128 bytes (256 - 1024 bits). >>> >>> +Trusted Keys usage: DCP >>> +----------------------- >>> + >>> +Usage:: >>> + >>> + keyctl add trusted name "new keylen" ring >>> + keyctl add trusted name "load hex_blob" ring >>> + keyctl print keyid >>> + >>> +"keyctl print" returns an ASCII hex copy of the sealed key, which is >>> +in format specific to this DCP key-blob implementation. The key >>> +length for new keys is always in bytes. Trusted Keys can be 32 - 128 bytes >> (256 - 1024 bits). >>> + >>> Encrypted Keys usage >>> -------------------- >>> >>> @@ -426,3 +470,12 @@ string length. >>> privkey is the binary representation of TPM2B_PUBLIC excluding the >>> initial TPM2B header which can be reconstructed from the ASN.1 octed >>> string length. >>> + >>> +DCP Blob Format >>> +--------------- >>> + >>> +.. kernel-doc:: security/keys/trusted-keys/trusted_dcp.c >>> + :doc: dcp blob format >>> + >>> +.. kernel-doc:: security/keys/trusted-keys/trusted_dcp.c >>> + :identifiers: struct dcp_blob_fmt >>> diff --git a/security/keys/trusted-keys/trusted_dcp.c >>> b/security/keys/trusted-keys/trusted_dcp.c >>> index 16c44aafeab3..b5f81a05be36 100644 >>> --- a/security/keys/trusted-keys/trusted_dcp.c >>> +++ b/security/keys/trusted-keys/trusted_dcp.c >>> @@ -19,6 +19,25 @@ >>> #define DCP_BLOB_VERSION 1 >>> #define DCP_BLOB_AUTHLEN 16 >>> >>> +/** >>> + * DOC: dcp blob format >>> + * >>> + * The Data Co-Processor (DCP) provides hardware-bound AES keys using >>> +its >>> + * AES encryption engine only. It does not provide direct key >> sealing/unsealing. >>> + * To make DCP hardware encryption keys usable as trust source, we >>> +define >>> + * our own custom format that uses a hardware-bound key to secure the >>> +sealing >>> + * key stored in the key blob. >>> + * >>> + * Whenever a new trusted key using DCP is generated, we generate a >>> +random 128-bit >>> + * blob encryption key (BEK) and 128-bit nonce. The BEK and nonce are >>> +used to >>> + * encrypt the trusted key payload using AES-128-GCM. >>> + * >>> + * The BEK itself is encrypted using the hardware-bound key using the >>> +DCP's AES >>> + * encryption engine with AES-128-ECB. The encrypted BEK, generated >>> +nonce, >>> + * BEK-encrypted payload and authentication tag make up the blob >>> +format together >>> + * with a version number, payload length and authentication tag. >>> + */ >>> + >>> /** >>> * struct dcp_blob_fmt - DCP BLOB format. >>> * >> >> Reviewed-by: Jarkko Sakkinen <jarkko@xxxxxxxxxx> >> >> I can only test that this does not break a machine without the hardware >> feature. >> >> Is there anyone who could possibly peer test these patches? > I am already working on testing this patchset on i.MX6 platform. Did you get around to testing this? I’d greatly appreciate a Tested-by for this. :-) Thanks! BR, David
