From mboxrd@z Thu Jan 1 00:00:00 1970 From: Roberto Sassu Subject: Re: [PATCH v3 1/6] tpm: use tpm_buf functions to perform a PCR read Date: Thu, 22 Jun 2017 13:54:29 +0200 Message-ID: <7cea09d5-e213-8783-fabc-eb47fc601942@huawei.com> References: <20170621142941.32674-1-roberto.sassu@huawei.com> <20170621142941.32674-2-roberto.sassu@huawei.com> <20170622101404.blfpqcryrbe35ha4@linux.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20170622101404.blfpqcryrbe35ha4-VuQAYsv1563Yd54FQh9/CA@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: tpmdd-devel-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org To: Jarkko Sakkinen Cc: linux-ima-devel-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org, linux-security-module-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, tpmdd-devel-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org, keyrings-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: tpmdd-devel@lists.sourceforge.net On 6/22/2017 12:14 PM, Jarkko Sakkinen wrote: > 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 > > 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. This should be done in the next patch, because tpm2_pcrread_header and tpm2_pcr_read_in are still used by tpm2_do_selftest(). >> +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. Please have a look at patches 2/6 and 3/6. It will be more clear why this change is necessary. Alternatively, instead of tpm_buf, I can add the command return code and the digest size as parameters of this function. >> +{ >> + 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. Ok. Should I also replace TPM_DIGEST_SIZE in tpm2_pcr_read_out with SHA512_DIGEST_SIZE, given that the algorithm can be specified? Thanks Roberto >> } >> >> + tpm_buf_destroy(&buf); >> return rc; >> } > > With some adjustments this is a welcome change. > > /Jarkko > -- HUAWEI TECHNOLOGIES Duesseldorf GmbH, HRB 56063 Managing Director: Bo PENG, Qiuen PENG, Shengli WANG ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot