| Message ID | 1560421833-27414-7-git-send-email-sumit.garg@linaro.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Introduce TEE based Trusted Keys support | expand |
On Thu, Jun 13, 2019 at 04:00:32PM +0530, Sumit Garg wrote: > Provide documentation for usage of TEE based Trusted Keys via existing > user-space "keyctl" utility. Also, document various use-cases. > > Signed-off-by: Sumit Garg <sumit.garg@linaro.org> Sorry missed this patch. Anyway, I don't think we want multiple trusted keys subsystems. You have to fix the existing one if you care to get these changes in. There is no really other way around this. /Jarkko
On Thu, 13 Jun 2019 at 21:04, Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com> wrote: > > On Thu, Jun 13, 2019 at 04:00:32PM +0530, Sumit Garg wrote: > > Provide documentation for usage of TEE based Trusted Keys via existing > > user-space "keyctl" utility. Also, document various use-cases. > > > > Signed-off-by: Sumit Garg <sumit.garg@linaro.org> > > Sorry missed this patch. Anyway, I don't think we want multiple trusted > keys subsystems. You have to fix the existing one if you care to get > these changes in. There is no really other way around this. > I understand your point. When I initially looked at trusted key implementation, it seemed to be tightly coupled to use TPM device. So I implemented a parallel implementation to get initial feedback (functionality-wise) on this new approach. I will work on abstraction of trusted key apis to use either approach. But is it fine with you if I send if I send a separate RFC patch for abstraction and later once reviewed I will incorporate that patch in this patch-set. It will be really helpful if you could help to test that abstraction patch with a real TPM device as I doesn't posses one to test. -Sumit > /Jarkko
On Fri, Jun 14, 2019 at 11:07:23AM +0530, Sumit Garg wrote: > On Thu, 13 Jun 2019 at 21:04, Jarkko Sakkinen > <jarkko.sakkinen@linux.intel.com> wrote: > > > > On Thu, Jun 13, 2019 at 04:00:32PM +0530, Sumit Garg wrote: > > > Provide documentation for usage of TEE based Trusted Keys via existing > > > user-space "keyctl" utility. Also, document various use-cases. > > > > > > Signed-off-by: Sumit Garg <sumit.garg@linaro.org> > > > > Sorry missed this patch. Anyway, I don't think we want multiple trusted > > keys subsystems. You have to fix the existing one if you care to get > > these changes in. There is no really other way around this. > > > > I understand your point. > > When I initially looked at trusted key implementation, it seemed to be > tightly coupled to use TPM device. So I implemented a parallel > implementation to get initial feedback (functionality-wise) on this > new approach. Yeah, I completely get this. My feedback this is: we can definitely consider TEE based trusted keys, and I know that trusted.ko is a mess, but still that is the only right long-term path. Think about the positive side: if you as a side-effect can make it cleaner and more versatile, your patch set will improve the quality of the kernel as a whole i.e. you benefit larger audience than just TEE user base :-) > I will work on abstraction of trusted key apis to use either approach. > But is it fine with you if I send if I send a separate RFC patch for > abstraction and later once reviewed I will incorporate that patch in > this patch-set. > > It will be really helpful if you could help to test that abstraction > patch with a real TPM device as I doesn't posses one to test. I can, yes. /Jarkko
diff --git a/Documentation/security/keys/tee-trusted.rst b/Documentation/security/keys/tee-trusted.rst new file mode 100644 index 0000000..ef03745 --- /dev/null +++ b/Documentation/security/keys/tee-trusted.rst @@ -0,0 +1,93 @@ +====================== +TEE based Trusted Keys +====================== + +TEE based Trusted Keys provides an alternative approach for providing Trusted +Keys in case TPM chip isn't present. + +Trusted Keys use a TEE service/device both to generate and to seal the keys. +Keys are sealed under a hardware unique key in the TEE, and only unsealed by +the TEE. + +For more information about TEE, refer to ``Documentation/tee.txt``. + +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 TEE device implementation. The key length for new keys are always +in bytes. Trusted Keys can be 32 - 128 bytes (256 - 1024 bits). + +Examples of trusted key and its usage as 'master' key for encrypted key usage: + +More details about encrypted keys can be found here: +``Documentation/security/keys/trusted-encrypted.rst`` + +Create and save a trusted key named "kmk" of length 32 bytes:: + + $ keyctl add trusted kmk "new 32" @u + 754414669 + + $ keyctl show + Session Keyring + 827385718 --alswrv 0 65534 keyring: _uid_ses.0 + 274124851 --alswrv 0 65534 \_ keyring: _uid.0 + 754414669 --als-rv 0 0 \_ trusted: kmk + + $ keyctl print 754414669 + 15676790697861b422175596ae001c2f505cea2c6f3ebbc5fb08eeb1f343a07e + + $ keyctl pipe 754414669 > kmk.blob + +Load a trusted key from the saved blob:: + + $ keyctl add trusted kmk "load `cat kmk.blob`" @u + 491638700 + + $ keyctl print 491638700 + 15676790697861b422175596ae001c2f505cea2c6f3ebbc5fb08eeb1f343a07e + +The initial consumer of trusted keys is EVM, which at boot time needs a high +quality symmetric key for HMAC protection of file metadata. The use of a +TEE based trusted key provides security that the EVM key has not been +compromised by a user level problem and tied to particular hardware. + +Create and save an encrypted key "evm" using the above trusted key "kmk": + +option 1: omitting 'format':: + + $ keyctl add encrypted evm "new trusted:kmk 32" @u + 608915065 + +option 2: explicitly defining 'format' as 'default':: + + $ keyctl add encrypted evm "new default trusted:kmk 32" @u + 608915065 + + $ keyctl print 608915065 + default trusted:kmk 32 f380ac588a925f488d5be007cf23e4c900b8b652ab62241c8 + ed54906189b6659d139d619d4b51752a2645537b11fd44673f13154a65b3f595d5fb2131 + 2fe45529ea0407c644ea4026f2a1a75661f2c9b66 + + $ keyctl pipe 608915065 > evm.blob + +Load an encrypted key "evm" from saved blob:: + + $ keyctl add encrypted evm "load `cat evm.blob`" @u + 831684262 + + $ keyctl print 831684262 + default trusted:kmk 32 f380ac588a925f488d5be007cf23e4c900b8b652ab62241c8 + ed54906189b6659d139d619d4b51752a2645537b11fd44673f13154a65b3f595d5fb2131 + 2fe45529ea0407c644ea4026f2a1a75661f2c9b66 + +Other uses for trusted and encrypted keys, such as for disk and file encryption +are anticipated. In particular the 'ecryptfs' encrypted keys format can be used +to mount an eCryptfs filesystem. More details about the usage can be found in +the file ``Documentation/security/keys/ecryptfs.rst``. + +Another format 'enc32' can be used to support encrypted keys with payload size +of 32 bytes.
Provide documentation for usage of TEE based Trusted Keys via existing user-space "keyctl" utility. Also, document various use-cases. Signed-off-by: Sumit Garg <sumit.garg@linaro.org> --- Documentation/security/keys/tee-trusted.rst | 93 +++++++++++++++++++++++++++++ 1 file changed, 93 insertions(+) create mode 100644 Documentation/security/keys/tee-trusted.rst