Messages in this thread | | On Wed, Jun 21, 2017 at 04:29:36PM +0200, Roberto Sassu wrote: > tpm2_pcr_read() now uses tpm_buf functions to build the TPM command > to read a PCR. Those functions are preferred to passing a tpm2_cmd > structure, as they provide protection against buffer overflow. > > Also, tpm2_pcr_read() code has been moved to tpm2_pcr_read_tpm_buf(). > Callers have to pass a tpm_buf structure, an algorithm supported by > the TPM and call tpm_buf_destroy(). The algorithm still cannot be > passed to the TPM driver interface. This parameter has been introduced > for determining the digest size of a given algorithm. > > Moving tpm2_pcr_read() code to tpm2_pcr_read_tpm_buf() is necessary > because callers of the new function obtain different information from > the output buffer: tpm2_pcr_read() gets the digest, tpm2_do_selftest() > will get the command return code and tpm2_get_pcr_allocation() will get > the digest size. > > Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
We want to migrate *everything* to use tpm_buf to the point that tpm_transmit takes tpm_buf as parameter.
> --- > drivers/char/tpm/tpm2-cmd.c | 54 +++++++++++++++++++++++++++------------------ > 1 file changed, 32 insertions(+), 22 deletions(-) > > diff --git a/drivers/char/tpm/tpm2-cmd.c b/drivers/char/tpm/tpm2-cmd.c > index 3a99643..afd1b63 100644 > --- a/drivers/char/tpm/tpm2-cmd.c > +++ b/drivers/char/tpm/tpm2-cmd.c > @@ -231,15 +231,37 @@ static const u8 tpm2_ordinal_duration[TPM2_CC_LAST - TPM2_CC_FIRST + 1] = { > (sizeof(struct tpm_input_header) + \ > sizeof(struct tpm2_pcr_read_in)) > > -#define TPM2_PCR_READ_RESP_BODY_SIZE \ > - sizeof(struct tpm2_pcr_read_out) > - > static const struct tpm_input_header tpm2_pcrread_header = { > .tag = cpu_to_be16(TPM2_ST_NO_SESSIONS), > .length = cpu_to_be32(TPM2_PCR_READ_IN_SIZE), > .ordinal = cpu_to_be32(TPM2_CC_PCR_READ) > };
Remove this and move tpm2_pcr_read_out declaration before tpm2_pcr_read. Its only a one shot helper structure for this function. You can take it of from the union and delete tpm2_pcr_read_in completely.
> +static int tpm2_pcr_read_tpm_buf(struct tpm_chip *chip, int pcr_idx, > + enum tpm2_algorithms algo, struct tpm_buf *buf, > + char *msg)
This wrapper is unnecessary especially since the fallback path is still in the responsiblity of the caller.
> +{ > + int rc; > + u8 pcr_select[TPM2_PCR_SELECT_MIN] = {0}; > + > + if (pcr_idx >= TPM2_PLATFORM_PCR) > + return -EINVAL; > + > + rc = tpm_buf_init(buf, TPM2_ST_NO_SESSIONS, TPM2_CC_PCR_READ); > + if (rc) > + return rc; > + > + pcr_select[pcr_idx >> 3] = 1 << (pcr_idx & 0x7); > + > + tpm_buf_append_u32(buf, 1); > + tpm_buf_append_u16(buf, algo); > + tpm_buf_append_u8(buf, TPM2_PCR_SELECT_MIN); > + tpm_buf_append(buf, (const unsigned char *)pcr_select, > + sizeof(pcr_select)); > + > + return tpm_transmit_cmd(chip, NULL, buf->data, PAGE_SIZE, 0, 0, msg); > +} > + > /** > * tpm2_pcr_read() - read a PCR value > * @chip: TPM chip to use. > @@ -251,29 +273,17 @@ static const struct tpm_input_header tpm2_pcrread_header = { > int tpm2_pcr_read(struct tpm_chip *chip, int pcr_idx, u8 *res_buf) > { > int rc; > - struct tpm2_cmd cmd; > - u8 *buf; > - > - if (pcr_idx >= TPM2_PLATFORM_PCR) > - return -EINVAL; > - > - cmd.header.in = tpm2_pcrread_header; > - cmd.params.pcrread_in.pcr_selects_cnt = cpu_to_be32(1); > - cmd.params.pcrread_in.hash_alg = cpu_to_be16(TPM2_ALG_SHA1); > - cmd.params.pcrread_in.pcr_select_size = TPM2_PCR_SELECT_MIN; > - > - memset(cmd.params.pcrread_in.pcr_select, 0, > - sizeof(cmd.params.pcrread_in.pcr_select)); > - cmd.params.pcrread_in.pcr_select[pcr_idx >> 3] = 1 << (pcr_idx & 0x7); > + struct tpm_buf buf; > + struct tpm2_pcr_read_out *out; > > - rc = tpm_transmit_cmd(chip, NULL, &cmd, sizeof(cmd), > - TPM2_PCR_READ_RESP_BODY_SIZE, > - 0, "attempting to read a pcr value"); > + rc = tpm2_pcr_read_tpm_buf(chip, pcr_idx, TPM2_ALG_SHA1, &buf, > + "attempting to read a pcr value"); > if (rc == 0) { > - buf = cmd.params.pcrread_out.digest; > - memcpy(res_buf, buf, TPM_DIGEST_SIZE); > + out = (struct tpm2_pcr_read_out *)&buf.data[TPM_HEADER_SIZE]; > + memcpy(res_buf, out->digest, TPM_DIGEST_SIZE);
I think that when changes are made that involve TPM_DIGEST_SIZE, it should be simply replaced with SHA1_DIGEST_SIZE. It's just a constant that makes reading the code harder.
> } > > + tpm_buf_destroy(&buf); > return rc; > }
With some adjustments this is a welcome change.
/Jarkko
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