Re: [RFC 0/2] add integrity and security to TPM2 transactions
On 3/5/2018 9:04 AM, Jason Gunthorpe wrote: On Fri, Mar 02, 2018 at 10:04:54PM -0800, James Bottomley wrote: By now, everybody knows we have a problem with the TPM2_RS_PW easy button on TPM2 in that transactions on the TPM bus can be intercepted and altered. The way to fix this is to use real sessions for HMAC capabilities to ensure integrity and to use parameter and response encryption to ensure confidentiality of the data flowing over the TPM bus. We have the same issue for TPM1 then right? TPM 1.2 did not have the concept of plaintext password sessions. If authorization was used, it was always with an HMAC.
Re: [RFC 0/2] add integrity and security to TPM2 transactions
On Mon, 2018-03-05 at 07:04 -0700, Jason Gunthorpe wrote: > On Fri, Mar 02, 2018 at 10:04:54PM -0800, James Bottomley wrote: > > > > By now, everybody knows we have a problem with the TPM2_RS_PW easy > > button on TPM2 in that transactions on the TPM bus can be > > intercepted and altered. The way to fix this is to use real > > sessions for HMAC capabilities to ensure integrity and to use > > parameter and response encryption to ensure confidentiality of the > > data flowing over the TPM bus. > > We have the same issue for TPM1 then right? Sort of. HMAC authentication isn't optional in TPM1 like it is in TPM2, so we do already use it (in the trusted keys code, for instance), so we have less of a problem becasuse it doesn't have the insecure TPM_RS_PW option. However, TPM1 also has a specific weakness here in that if you don't have authority in the object (i.e. no shared secret), the HMAC provides no protection against an intelligent attacker. The only way to get the same security as we have with TPM2 in this situation is to use transport encryption. Given that sha1 is already compromised, TPM1 has a strictly limited shelf life, especially as all laptops are being shipped with TPM2 now, so I don't think it's unreasonable to say if you're worried about this compromise you should use TPM2. James
Re: [RFC 0/2] add integrity and security to TPM2 transactions
On Fri, Mar 02, 2018 at 10:04:54PM -0800, James Bottomley wrote: > By now, everybody knows we have a problem with the TPM2_RS_PW easy > button on TPM2 in that transactions on the TPM bus can be intercepted > and altered. The way to fix this is to use real sessions for HMAC > capabilities to ensure integrity and to use parameter and response > encryption to ensure confidentiality of the data flowing over the TPM > bus. We have the same issue for TPM1 then right? Jason
[RFC 0/2] add integrity and security to TPM2 transactions
By now, everybody knows we have a problem with the TPM2_RS_PW easy button on TPM2 in that transactions on the TPM bus can be intercepted and altered. The way to fix this is to use real sessions for HMAC capabilities to ensure integrity and to use parameter and response encryption to ensure confidentiality of the data flowing over the TPM bus. This RFC is about adding a simple API which can ensure the above properties as a layered addition to the existing TPM handling code. Eventually we can add this to the random number generator, the PCR extensions and the trusted key handling, but this all depends on the conversion to tpm_buf which is not yet upstream, so I've constructed a second patch which demonstrates the new API in a test module for those who wish to play with it. This series is also dependent on additions to the crypto subsystem to fix problems in the elliptic curve key handling and add the Cipher FeedBack encryption scheme: https://marc.info/?l=linux-crypto-vger=151994371015475 --- James Bottomley (2): tpm2-sessions: Add full HMAC and encrypt/decrypt session handling tpm2-sessions: NOT FOR COMMITTING add sessions testing drivers/char/tpm/Kconfig | 3 + drivers/char/tpm/Makefile | 3 +- drivers/char/tpm/tpm-chip.c | 1 + drivers/char/tpm/tpm.h| 22 + drivers/char/tpm/tpm2-cmd.c | 22 +- drivers/char/tpm/tpm2-sessions-test.c | 178 +++ drivers/char/tpm/tpm2-sessions.c | 907 ++ drivers/char/tpm/tpm2-sessions.h | 55 +++ drivers/char/tpm/tpm2b.h | 82 +++ 9 files changed, 1260 insertions(+), 13 deletions(-) create mode 100644 drivers/char/tpm/tpm2-sessions-test.c create mode 100644 drivers/char/tpm/tpm2-sessions.c create mode 100644 drivers/char/tpm/tpm2-sessions.h create mode 100644 drivers/char/tpm/tpm2b.h -- 2.12.3
