[v8,6/6] docs: trusted-encrypted: add DCP as new trust source

Commit Message

David Gstir April 3, 2024, 7:21 a.m. UTC

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 <[e-mail]>
Signed-off-by: Richard Weinberger <[e-mail]>
Co-developed-by: David Oberhollenzer <[e-mail]>
Signed-off-by: David Oberhollenzer <[e-mail]>
Signed-off-by: David Gstir <[e-mail]>
---
 .../security/keys/trusted-encrypted.rst       | 53 +++++++++++++++++++
 security/keys/trusted-keys/trusted_dcp.c      | 19 +++++++
 2 files changed, 72 insertions(+)

Comments

Bagas Sanjaya April 3, 2024, 1:24 p.m. UTC | #1

On Wed, Apr 03, 2024 at 09:21:22AM +0200, David Gstir wrote:
> 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.
>   *

The doc LGTM, thanks!

Reviewed-by: Bagas Sanjaya <[e-mail]>

Jarkko Sakkinen April 3, 2024, 3:47 p.m. UTC | #2

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 <[e-mail]>
> Signed-off-by: Richard Weinberger <[e-mail]>
> Co-developed-by: David Oberhollenzer <[e-mail]>
> Signed-off-by: David Oberhollenzer <[e-mail]>
> Signed-off-by: David Gstir <[e-mail]>
> ---
>  .../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 <[e-mail]>

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?

BR, Jarkko

Kshitiz Varshney April 9, 2024, 9:48 a.m. UTC | #3

Hi Jarkko,


> -----Original Message-----
> From: Jarkko Sakkinen <[e-mail]>
> Sent: Wednesday, April 3, 2024 9:18 PM
> To: David Gstir <[e-mail]>; Mimi Zohar <[e-mail]>;
> James Bottomley <[e-mail]>; Herbert Xu
> <[e-mail]>; David S. Miller <[e-mail]>
> Cc: Shawn Guo <[e-mail]>; Jonathan Corbet
> <[e-mail]>; Sascha Hauer <[e-mail]>; Pengutronix
> Kernel Team <[e-mail]>; Fabio Estevam
> <[e-mail]>; dl-linux-imx <[e-mail]>; Ahmad Fatoum
> <[e-mail]>; sigma star Kernel Team
> <[e-mail]>; David Howells <[e-mail]>; Li
> Yang <[e-mail]>; Paul Moore <[e-mail]>; James
> Morris <[e-mail]>; Serge E. Hallyn <[e-mail]>; Paul E.
> McKenney <[e-mail]>; Randy Dunlap <[e-mail]>;
> Catalin Marinas <[e-mail]>; Rafael J. Wysocki
> <[e-mail]>; Tejun Heo <[e-mail]>; Steven Rostedt
> (Google) <[e-mail]>; [e-mail]; linux-
> [e-mail]; [e-mail];
> [e-mail]; [e-mail]; linux-arm-
> [e-mail]; [e-mail]; linux-security-
> [e-mail]; Richard Weinberger <[e-mail]>; David
> Oberhollenzer <[e-mail]>
> 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 <[e-mail]>
> > Signed-off-by: Richard Weinberger <[e-mail]>
> > Co-developed-by: David Oberhollenzer
> > <[e-mail]>
> > Signed-off-by: David Oberhollenzer <[e-mail]>
> > Signed-off-by: David Gstir <[e-mail]>
> > ---
> >  .../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 <[e-mail]>
> 
> 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

Herbert Xu April 12, 2024, 6:26 a.m. UTC | #4

On Wed, Apr 03, 2024 at 06:47:51PM +0300, Jarkko Sakkinen wrote:
>
> Reviewed-by: Jarkko Sakkinen <[e-mail]>
> 
> I can only test that this does not break a machine without the
> hardware feature.

Please feel free to take this through your tree.

Thanks,

Jarkko Sakkinen April 13, 2024, 9:24 p.m. UTC | #5

On Tue Apr 9, 2024 at 12:48 PM EEST, Kshitiz Varshney wrote:
> Hi Jarkko,
>
>
> > -----Original Message-----
> > From: Jarkko Sakkinen <[e-mail]>
> > Sent: Wednesday, April 3, 2024 9:18 PM
> > To: David Gstir <[e-mail]>; Mimi Zohar <[e-mail]>;
> > James Bottomley <[e-mail]>; Herbert Xu
> > <[e-mail]>; David S. Miller <[e-mail]>
> > Cc: Shawn Guo <[e-mail]>; Jonathan Corbet
> > <[e-mail]>; Sascha Hauer <[e-mail]>; Pengutronix
> > Kernel Team <[e-mail]>; Fabio Estevam
> > <[e-mail]>; dl-linux-imx <[e-mail]>; Ahmad Fatoum
> > <[e-mail]>; sigma star Kernel Team
> > <[e-mail]>; David Howells <[e-mail]>; Li
> > Yang <[e-mail]>; Paul Moore <[e-mail]>; James
> > Morris <[e-mail]>; Serge E. Hallyn <[e-mail]>; Paul E.
> > McKenney <[e-mail]>; Randy Dunlap <[e-mail]>;
> > Catalin Marinas <[e-mail]>; Rafael J. Wysocki
> > <[e-mail]>; Tejun Heo <[e-mail]>; Steven Rostedt
> > (Google) <[e-mail]>; [e-mail]; linux-
> > [e-mail]; [e-mail];
> > [e-mail]; [e-mail]; linux-arm-
> > [e-mail]; [e-mail]; linux-security-
> > [e-mail]; Richard Weinberger <[e-mail]>; David
> > Oberhollenzer <[e-mail]>
> > 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 <[e-mail]>
> > > Signed-off-by: Richard Weinberger <[e-mail]>
> > > Co-developed-by: David Oberhollenzer
> > > <[e-mail]>
> > > Signed-off-by: David Oberhollenzer <[e-mail]>
> > > Signed-off-by: David Gstir <[e-mail]>
> > > ---
> > >  .../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 <[e-mail]>
> > 
> > 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

OK great.

BR, Jarkko

Jarkko Sakkinen April 13, 2024, 9:44 p.m. UTC | #6

On Fri Apr 12, 2024 at 9:26 AM EEST, Herbert Xu wrote:
> On Wed, Apr 03, 2024 at 06:47:51PM +0300, Jarkko Sakkinen wrote:
> >
> > Reviewed-by: Jarkko Sakkinen <[e-mail]>
> > 
> > I can only test that this does not break a machine without the
> > hardware feature.
>
> Please feel free to take this through your tree.
>
> Thanks,

OK, thanks!

BR, Jarkko

David Gstir April 29, 2024, 11:35 a.m. UTC | #7

Hi Kshitiz,

> On 09.04.2024, at 11:48, Kshitiz Varshney <[e-mail]> wrote:
> 
> Hi Jarkko,
> 
> 
>> -----Original Message-----
>> From: Jarkko Sakkinen <[e-mail]>
>> Sent: Wednesday, April 3, 2024 9:18 PM
>> To: David Gstir <[e-mail]>; Mimi Zohar <[e-mail]>;
>> James Bottomley <[e-mail]>; Herbert Xu
>> <[e-mail]>; David S. Miller <[e-mail]>
>> Cc: Shawn Guo <[e-mail]>; Jonathan Corbet
>> <[e-mail]>; Sascha Hauer <[e-mail]>; Pengutronix
>> Kernel Team <[e-mail]>; Fabio Estevam
>> <[e-mail]>; dl-linux-imx <[e-mail]>; Ahmad Fatoum
>> <[e-mail]>; sigma star Kernel Team
>> <[e-mail]>; David Howells <[e-mail]>; Li
>> Yang <[e-mail]>; Paul Moore <[e-mail]>; James
>> Morris <[e-mail]>; Serge E. Hallyn <[e-mail]>; Paul E.
>> McKenney <[e-mail]>; Randy Dunlap <[e-mail]>;
>> Catalin Marinas <[e-mail]>; Rafael J. Wysocki
>> <[e-mail]>; Tejun Heo <[e-mail]>; Steven Rostedt
>> (Google) <[e-mail]>; [e-mail]; linux-
>> [e-mail]; [e-mail];
>> [e-mail]; [e-mail]; linux-arm-
>> [e-mail]; [e-mail]; linux-security-
>> [e-mail]; Richard Weinberger <[e-mail]>; David
>> Oberhollenzer <[e-mail]>
>> 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 <[e-mail]>
>>> Signed-off-by: Richard Weinberger <[e-mail]>
>>> Co-developed-by: David Oberhollenzer
>>> <[e-mail]>
>>> Signed-off-by: David Oberhollenzer <[e-mail]>
>>> Signed-off-by: David Gstir <[e-mail]>
>>> ---
>>> .../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 <[e-mail]>
>> 
>> 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

Patch

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.
  *