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. Regards, Kshitiz > BR, Jarkko
