Messages in this thread | | | Date | Wed, 3 Jun 2015 15:23:31 +0300 | From | Jarkko Sakkinen <> | Subject | Re: [PATCH] tpm: introduce struct tpm_buf |
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On Tue, Jun 02, 2015 at 12:13:15PM -0600, Jason Gunthorpe wrote: > On Tue, Jun 02, 2015 at 04:04:22PM +0300, Jarkko Sakkinen wrote: > > +/* A string buffer type for constructing TPM commands. This is based on the > > + * code in security/keys/trusted.h. > > + */ > > + > > +#define TPM_BUF_SIZE 512 > > + > > +struct tpm_buf { > > + u8 data[TPM_BUF_SIZE]; > This should be u32 or u64 to guarentee correct alignment for the > casting.
Good catch. The functions where this might cause trouble are *_length() and *_tag().
In other places misalignment should not cause any regressions since data is not directly assigned to the buffer with pointer casting.
I would prefer to fix by changing *_length() and *_tag() to copy the value to a local variable and return that. It's a fail safe way and here the performance is not an issue.
> > +}; > > + > > +static inline void tpm_buf_init(struct tpm_buf *buf, u16 tag, u32 ordinal) > > +{ > > + struct tpm_input_header *head; > > + > > + head = (struct tpm_input_header *) buf->data; > > + > > + head->tag = cpu_to_be16(tag); > > + head->length = cpu_to_be32(sizeof(*head)); > > + head->ordinal = cpu_to_be32(ordinal); > > +} > > + > > +static inline u32 tpm_buf_length(struct tpm_buf *buf) > > +{ > > + struct tpm_input_header *head = (struct tpm_input_header *) buf->data; > > + > > + return be32_to_cpu(head->length); > > +} > > + > > +static inline u16 tpm_buf_tag(struct tpm_buf *buf) > > +{ > > + return be16_to_cpu(*(__be16 *) &buf->data[0]); > > be16_to_cpup ?
Thanks, I'll change this.
> Any thought on someday using this for tpm1 as well?
Yes, I think this could form the baseline so that the sealing code that currently resides is security/keys/trusted.c could be eventually moved to drivers/char/tpm.
I will be contributing API to include/linux/tpm.h that can be then called by trusted keys. I will also contribute the implementation for TPM 2.0 sealing but it is up to those who implemented TPM 1.x sealing code to do the migration. I put all the enablers in place so that doing that transition should be relatively painless.
I have PoC for TPM 2.0 trusted keys written in Python available here:
https://github.com/jsakkine/tpm2-scripts/blob/master/tpm2.py
(In kernel version the default hash algorithm should be probably SHA-256 as SHA-1 is not considered secure by NIST anymore)
Doing also all the TPM 1.x migration on top of this would make oversubscribed.
> Jason
/Jarkko
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