Re: [PATCH v10 0/6] tpm: retrieve digest size of unknown algorithms from TPM

[Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>]

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On Wed, Feb 06, 2019 at 03:25:48PM +0100, Roberto Sassu wrote:
> On 2/6/2019 2:54 PM, Jarkko Sakkinen wrote:
> > On Wed, Feb 06, 2019 at 02:07:04PM +0100, Roberto Sassu wrote:
> > > On 2/6/2019 1:57 PM, Jarkko Sakkinen wrote:
> > > > On Wed, Feb 06, 2019 at 11:57:18AM +0100, Roberto Sassu wrote:
> > > > > Update
> > > > > 
> > > > > This version of the patch set includes three additional patches (5-7/7)
> > > > > that allow users of the TPM driver to provide a digest for each PCR bank to
> > > > > tpm_pcr_extend(). The new patches have been included to facilitate the
> > > > > review of all the changes to support TPM 2.0 crypto agility for reading and
> > > > > extending PCRs.
> > > > > 
> > > > > 
> > > > > Original patch set description
> > > > > 
> > > > > The TPM driver currently relies on the crypto subsystem to determine the
> > > > > digest size of supported TPM algorithms. In the future, TPM vendors might
> > > > > implement new algorithms in their chips, and those algorithms might not
> > > > > be supported by the crypto subsystem.
> > > > > 
> > > > > Usually, vendors provide patches for the new hardware, and likely
> > > > > the crypto subsystem will be updated before the new algorithm is
> > > > > introduced. However, old kernels might be updated later, after patches
> > > > > are included in the mainline kernel. This would leave the opportunity
> > > > > for attackers to misuse PCRs, as PCR banks with an unknown algorithm
> > > > > are not extended.
> > > > > 
> > > > > This patch set provides a long term solution for this issue. If a TPM
> > > > > algorithm is not known by the crypto subsystem, the TPM driver retrieves
> > > > > the digest size from the TPM with a PCR read. All the PCR banks are
> > > > > extended, even if the algorithm is not yet supported by the crypto
> > > > > subsystem.
> > > > > 
> > > > > PCR bank information (TPM algorithm ID, digest size, crypto subsystem ID)
> > > > > is stored in the tpm_chip structure and available for users of the TPM
> > > > > driver.
> > > > > 
> > > > > Changelog
> > > > > 
> > > > > v9:
> > > > > - add comment for ima_load_kexec_buffer() in ima_init()
> > > > > - move 'digests' and ima_init_digests() to ima_queue.c
> > > > > - remove comment for TPM_RETRY
> > > > > 
> > > > > v8:
> > > > > - set digest array length in tpm_digest to new constant TPM_MAX_DIGEST_SIZE
> > > > > - replace enum tpm_const with #define
> > > > > - rename labels in init_trusted()
> > > > > - allocate tpm_digest array after retrieving random data in init_digests()
> > > > > 
> > > > > v7:
> > > > > - use memchr_inv() in tpm2_get_pcr_allocation()
> > > > > - add patch to move tpm_chip to include/linux/tpm.h
> > > > > - add patch to set the tpm_chip argument in trusted.c to a pointer from
> > > > >     tpm_default_chip()
> > > > > - remove definition of tpm_extend_digest
> > > > > - remove code in tpm2_pcr_extend() to extend unused PCR banks with the
> > > > >     first digest passed by the caller of tpm_pcr_extend()
> > > > > - remove count parameter from tpm_pcr_extend() and tpm2_pcr_extend()
> > > > > - remove padding of SHA1 digest in tpm_pcr_extend()
> > > > > - pre-allocate and initialize array of tpm_digest structures in
> > > > >     security/keys/trusted.c and security/integrity/ima/ima_init.c
> > > > > 
> > > > > v6:
> > > > > - squash patches 4-6
> > > > > - rename tpm_bank_list to tpm_extend_digest, extend_size and extend_data
> > > > >     members to size and data
> > > > > - add comment in tpm2_init_bank_info()
> > > > > 
> > > > > v5:
> > > > > - rename digest_struct variable to digest
> > > > > - add _head suffix to tcg_efi_specid_event and tcg_pcr_event2
> > > > > - rename digest_size member of tpm_bank_list to extend_size
> > > > > - change type of alg_id member of tpm_bank_list from u8 to u16
> > > > > - add missing semi-colon in pcrlock()
> > > > > 
> > > > > v4:
> > > > > - rename active_banks to allocated_banks
> > > > > - replace kmalloc_array() with kcalloc()
> > > > > - increment nr_allocated_banks if at least one PCR in the bank is selected
> > > > > - pass multiple digests to tpm_pcr_extend()
> > > > > 
> > > > > v3:
> > > > > - remove end marker change
> > > > > - replace active_banks static array with pointer to dynamic array
> > > > > - remove TPM2_ACTIVE_PCR_BANKS
> > > > > 
> > > > > v2:
> > > > > - change the end marker of the active_banks array
> > > > > - check digest size from output of PCR read command
> > > > > - remove count parameter from tpm_pcr_read() and tpm2_pcr_read()
> > > > > 
> > > > > v1:
> > > > > - modify definition of tpm_pcr_read()
> > > > > - move hash algorithms and definition of tpm2_digest to include/linux/tpm.h
> > > > > 
> > > > > 
> > > > > Roberto Sassu (6):
> > > > >     tpm: dynamically allocate the allocated_banks array
> > > > >     tpm: rename and export tpm2_digest and tpm2_algorithms
> > > > >     tpm: retrieve digest size of unknown algorithms with PCR read
> > > > >     tpm: move tpm_chip definition to include/linux/tpm.h
> > > > >     KEYS: trusted: explicitly use tpm_chip structure from
> > > > >       tpm_default_chip()
> > > > >     tpm: pass an array of tpm_extend_digest structures to tpm_pcr_extend()
> > > > > 
> > > > >    drivers/char/tpm/tpm-chip.c         |   1 +
> > > > >    drivers/char/tpm/tpm-interface.c    |  38 ++++----
> > > > >    drivers/char/tpm/tpm.h              | 117 ++---------------------
> > > > >    drivers/char/tpm/tpm1-cmd.c         |  12 +++
> > > > >    drivers/char/tpm/tpm2-cmd.c         | 139 ++++++++++++++++++++--------
> > > > >    include/linux/tpm.h                 | 126 ++++++++++++++++++++++++-
> > > > >    include/linux/tpm_eventlog.h        |   9 +-
> > > > >    security/integrity/ima/ima.h        |   1 +
> > > > >    security/integrity/ima/ima_crypto.c |  10 +-
> > > > >    security/integrity/ima/ima_init.c   |   4 +
> > > > >    security/integrity/ima/ima_queue.c  |  27 +++++-
> > > > >    security/keys/trusted.c             |  73 +++++++++++----
> > > > >    12 files changed, 349 insertions(+), 208 deletions(-)
> > > > > 
> > > > > -- 
> > > > > 2.17.1
> > > > > 
> > > > 
> > > > Can you do two things:
> > > > 
> > > > 1. Check the v3: https://patchwork.kernel.org/patch/10797181/. Needs
> > > > to be applied first.
> > > > 2. Check that this does not cause merge conflicts with the current
> > > >      imaster? If it does, fix them, and use --subject-prefix="RESEND,PATCH v10".
> > > > 
> > > > Thanks.
> > > 
> > > I already applied the patch set on top of linux-tpmdd/next
> > > (41ac27d19b07) and your patch.
> > > 
> > > Also, there are no conflicts with the current master.
> > > 
> > > Roberto
> > 
> > Before getting your new version, I applied:
> > 
> > https://patchwork.kernel.org/project/linux-integrity/list/?series=76223
> > 
> > This causes some merge conflicts:
> > 
> > error: Failed to merge in the changes.
> > Patch failed at 0003 tpm: retrieve digest size of unknown algorithms with PCR read
> 
> I fixed it and patch 4/6. But, I think there is a problem in your patch
> 'tpm: move tpm_validate_commmand() to tpm2-space.c':
> 
> ---
> -int tpm2_prepare_space(struct tpm_chip *chip, struct tpm_space *space, u32
> cc,
> -                      u8 *cmd)
> +static int tpm_validate_command(struct tpm_chip *chip, struct tpm_space
> *space,
> +                               const void *cmd, size_t len)
> +{
> +       const struct tpm_header *header = (const void *)cmd;
> +       int i;
> +       u32 cc;
> +       u32 attrs;
> +       unsigned int nr_handles;
> +
> +       if (len < TPM_HEADER_SIZE)
> +               return -EINVAL;
> +
> +       if (chip->nr_commands) {
> 
> [...]
> 
> +       }
> +
> +       return cc;
> +
> ---
> 
> 'cc' may be not initialized before returning the value.

Ah. Thank you for catching that one. Can you quickly check the attached
commit? I'll squash it to the corresponding commit.

/Jarkko

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From 6aa9a3a16a9f4e93d67859c634742b00d743ecb5 Mon Sep 17 00:00:00 2001
From: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Date: Wed, 6 Feb 2019 17:26:55 +0200
Subject: [PATCH] tpm: fail tpm_validate_command() if chip->nr_commands is zero

Now that tpm_validate_command() is only on TPM2 space code path, it
should return -EINVAL in the case nr_command is zero, as it should never
be. Not doing this could cause cc to be uninitialized. This commit fixes
the issue.

Fixes: a4bfd02c6b00 ("tpm: move tpm_validate_commmand() to tpm2-space.c")
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
---
 drivers/char/tpm/tpm2-space.c | 35 +++++++++++++++++------------------
 1 file changed, 17 insertions(+), 18 deletions(-)

diff --git a/drivers/char/tpm/tpm2-space.c b/drivers/char/tpm/tpm2-space.c
index a9ced49546ad..4a2773c3374f 100644
--- a/drivers/char/tpm/tpm2-space.c
+++ b/drivers/char/tpm/tpm2-space.c
@@ -263,8 +263,9 @@ static int tpm2_map_command(struct tpm_chip *chip, u32 cc, u8 *cmd)
 	return 0;
 }
 
-static int tpm_validate_command(struct tpm_chip *chip, struct tpm_space *space,
-				const void *cmd, size_t len)
+static int tpm_find_and_validate_cc(struct tpm_chip *chip,
+				    struct tpm_space *space,
+				    const void *cmd, size_t len)
 {
 	const struct tpm_header *header = (const void *)cmd;
 	int i;
@@ -272,26 +273,24 @@ static int tpm_validate_command(struct tpm_chip *chip, struct tpm_space *space,
 	u32 attrs;
 	unsigned int nr_handles;
 
-	if (len < TPM_HEADER_SIZE)
+	if (len < TPM_HEADER_SIZE || !chip->nr_commands)
 		return -EINVAL;
 
-	if (chip->nr_commands) {
-		cc = be32_to_cpu(header->ordinal);
+	cc = be32_to_cpu(header->ordinal);
 
-		i = tpm2_find_cc(chip, cc);
-		if (i < 0) {
-			dev_dbg(&chip->dev, "0x%04X is an invalid command\n",
-				cc);
-			return -EOPNOTSUPP;
-		}
-
-		attrs = chip->cc_attrs_tbl[i];
-		nr_handles =
-			4 * ((attrs >> TPM2_CC_ATTR_CHANDLES) & GENMASK(2, 0));
-		if (len < TPM_HEADER_SIZE + 4 * nr_handles)
-			goto err_len;
+	i = tpm2_find_cc(chip, cc);
+	if (i < 0) {
+		dev_dbg(&chip->dev, "0x%04X is an invalid command\n",
+			cc);
+		return -EOPNOTSUPP;
 	}
 
+	attrs = chip->cc_attrs_tbl[i];
+	nr_handles =
+		4 * ((attrs >> TPM2_CC_ATTR_CHANDLES) & GENMASK(2, 0));
+	if (len < TPM_HEADER_SIZE + 4 * nr_handles)
+		goto err_len;
+
 	return cc;
 err_len:
 	dev_dbg(&chip->dev, "%s: insufficient command length %zu", __func__,
@@ -308,7 +307,7 @@ int tpm2_prepare_space(struct tpm_chip *chip, struct tpm_space *space, u8 *cmd,
 	if (!space)
 		return 0;
 
-	cc = tpm_validate_command(chip, space, cmd, cmdsiz);
+	cc = tpm_find_and_validate_cc(chip, space, cmd, cmdsiz);
 	if (cc < 0)
 		return cc;
 
-- 
2.19.1