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SubjectRe: [PATCH RFC] tpm: migrate pubek_show to struct tpm_buf
On Thu, May 25, 2017 at 03:16:13PM -0600, Jason Gunthorpe wrote:
> On Thu, May 25, 2017 at 02:11:04PM -0700, Jarkko Sakkinen wrote:
> > struct tpm_chip *chip = to_tpm_chip(dev);
> > + char anti_replay[20];
> >
> > - tpm_cmd.header.in = tpm_readpubek_header;
> > - err = tpm_transmit_cmd(chip, NULL, &tpm_cmd, READ_PUBEK_RESULT_SIZE,
> > + rc = tpm_buf_init(&tpm_buf, TPM_TAG_RQU_COMMAND, TPM_ORD_READPUBEK);
> > + if (rc)
> > + return rc;
> > +
> > + /* The checksum is ignored so it doesn't matter what the contents are.
> > + */
> > + tpm_buf_append(&tpm_buf, anti_replay, sizeof(anti_replay));
>
> It does matter, we do not want to leak random kernel memory incase it
> has something sensitive. Zero anti_replay.

If there was a leak it has existed before this change as tpm_cmd was
also allocated from stack. And there is not leak because the checksum is
not printed.

> > +
> > - /*
> > - ignore header 10 bytes
> > - algorithm 32 bits (1 == RSA )
> > - encscheme 16 bits
> > - sigscheme 16 bits
> > - parameters (RSA 12->bytes: keybit, #primes, expbit)
> > - keylenbytes 32 bits
> > - 256 byte modulus
> > - ignore checksum 20 bytes
> > - */
>
> Not sure we should delete the comment, tpm buf does not make the parse
> any clearer.

I think better idea would be to move struct tpm_readpubek_params_out
declaration here and use it to refer different fields. Previously this
has been a complete mess. The structure has been declared but it has not
been used for anything. I wonder what is the history here...

/Jarkko

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