diff mbox series

[04/10] security: keys: trusted: Allow storage of PCR values in creation data

Message ID 20220504161439.4.I32591db064b6cdc91850d777f363c9d05c985b39@changeid (mailing list archive)
State New
Headers show
Series Encrypted Hibernation | expand

Commit Message

Evan Green May 4, 2022, 11:20 p.m. UTC 
From: Matthew Garrett <matthewgarrett@google.com>

When TPMs generate keys, they can also generate some information
describing the state of the PCRs at creation time. This data can then
later be certified by the TPM, allowing verification of the PCR values.
This allows us to determine the state of the system at the time a key
was generated. Add an additional argument to the trusted key creation
options, allowing the user to provide the set of PCRs that should have
their values incorporated into the creation data.

From: Matthew Garrett <mjg59@google.com>
Signed-off-by: Matthew Garrett <mjg59@google.com>

Signed-off-by: Evan Green <evgreen@chromium.org>
---
Matthew's original version of this patch is at:
https://patchwork.kernel.org/patch/12096503/

 .../security/keys/trusted-encrypted.rst       |  4 +++
 include/keys/trusted-type.h                   |  1 +
 security/keys/trusted-keys/trusted_tpm1.c     |  9 +++++++
 security/keys/trusted-keys/trusted_tpm2.c     | 25 +++++++++++++++++--
 4 files changed, 37 insertions(+), 2 deletions(-)

Comments

Eric Biggers Aug. 2, 2022, 11 p.m. UTC | #1 
On Wed, May 04, 2022 at 04:20:56PM -0700, Evan Green wrote:
> diff --git a/security/keys/trusted-keys/trusted_tpm1.c b/security/keys/trusted-keys/trusted_tpm1.c
> index aa108bea6739b3..2975827c01bec0 100644
> --- a/security/keys/trusted-keys/trusted_tpm1.c
> +++ b/security/keys/trusted-keys/trusted_tpm1.c
> @@ -713,6 +713,7 @@ enum {
>  	Opt_hash,
>  	Opt_policydigest,
>  	Opt_policyhandle,
> +	Opt_creationpcrs,
>  };
>  
>  static const match_table_t key_tokens = {
> @@ -725,6 +726,7 @@ static const match_table_t key_tokens = {
>  	{Opt_hash, "hash=%s"},
>  	{Opt_policydigest, "policydigest=%s"},
>  	{Opt_policyhandle, "policyhandle=%s"},
> +	{Opt_creationpcrs, "creationpcrs=%s"},
>  	{Opt_err, NULL}
>  };
>  
> @@ -858,6 +860,13 @@ static int getoptions(char *c, struct trusted_key_payload *pay,
>  				return -EINVAL;
>  			opt->policyhandle = handle;
>  			break;
> +		case Opt_creationpcrs:
> +			if (!tpm2)
> +				return -EINVAL;
> +			res = kstrtoint(args[0].from, 16, &opt->creation_pcrs);
> +			if (res < 0)
> +				return -EINVAL;
> +			break;

I thought that TPM1 is deprecated.  Are you sure you need more TPM1 features?

- Eric
Evan Green Aug. 3, 2022, 8:48 p.m. UTC | #2 
On Tue, Aug 2, 2022 at 4:00 PM Eric Biggers <ebiggers@kernel.org> wrote:
>
> On Wed, May 04, 2022 at 04:20:56PM -0700, Evan Green wrote:
> > diff --git a/security/keys/trusted-keys/trusted_tpm1.c b/security/keys/trusted-keys/trusted_tpm1.c
> > index aa108bea6739b3..2975827c01bec0 100644
> > --- a/security/keys/trusted-keys/trusted_tpm1.c
> > +++ b/security/keys/trusted-keys/trusted_tpm1.c
> > @@ -713,6 +713,7 @@ enum {
> >       Opt_hash,
> >       Opt_policydigest,
> >       Opt_policyhandle,
> > +     Opt_creationpcrs,
> >  };
> >
> >  static const match_table_t key_tokens = {
> > @@ -725,6 +726,7 @@ static const match_table_t key_tokens = {
> >       {Opt_hash, "hash=%s"},
> >       {Opt_policydigest, "policydigest=%s"},
> >       {Opt_policyhandle, "policyhandle=%s"},
> > +     {Opt_creationpcrs, "creationpcrs=%s"},
> >       {Opt_err, NULL}
> >  };
> >
> > @@ -858,6 +860,13 @@ static int getoptions(char *c, struct trusted_key_payload *pay,
> >                               return -EINVAL;
> >                       opt->policyhandle = handle;
> >                       break;
> > +             case Opt_creationpcrs:
> > +                     if (!tpm2)
> > +                             return -EINVAL;
> > +                     res = kstrtoint(args[0].from, 16, &opt->creation_pcrs);
> > +                     if (res < 0)
> > +                             return -EINVAL;
> > +                     break;
>
> I thought that TPM1 is deprecated.  Are you sure you need more TPM1 features?

It seems that trusted_tpm1.c is not just TPM1 functions, but also
common functions that call TPM2 primitives. A few of these functions
(like this getoptions()) seem to even error out if !tpm_is_tpm2(chip).

-Evan
diff mbox series

Patch

diff --git a/Documentation/security/keys/trusted-encrypted.rst b/Documentation/security/keys/trusted-encrypted.rst
index f614dad7de12f9..7215b067bf128f 100644
--- a/Documentation/security/keys/trusted-encrypted.rst
+++ b/Documentation/security/keys/trusted-encrypted.rst
@@ -170,6 +170,10 @@  Usage::
        policyhandle= handle to an authorization policy session that defines the
                      same policy and with the same hash algorithm as was used to
                      seal the key.
+       creationpcrs= hex integer representing the set of PCR values to be
+                     included in the PCR creation data. The bit corresponding
+		     to each PCR should be 1 to be included, 0 to be ignored.
+		     TPM2 only.
 
 "keyctl print" returns an ascii hex copy of the sealed key, which is in standard
 TPM_STORED_DATA format.  The key length for new keys are always in bytes.
diff --git a/include/keys/trusted-type.h b/include/keys/trusted-type.h
index 8a793ae1ad9f70..b3ac4afe8ba987 100644
--- a/include/keys/trusted-type.h
+++ b/include/keys/trusted-type.h
@@ -54,6 +54,7 @@  struct trusted_key_options {
 	uint32_t policydigest_len;
 	unsigned char policydigest[MAX_DIGEST_SIZE];
 	uint32_t policyhandle;
+	uint32_t creation_pcrs;
 };
 
 struct trusted_key_ops {
diff --git a/security/keys/trusted-keys/trusted_tpm1.c b/security/keys/trusted-keys/trusted_tpm1.c
index aa108bea6739b3..2975827c01bec0 100644
--- a/security/keys/trusted-keys/trusted_tpm1.c
+++ b/security/keys/trusted-keys/trusted_tpm1.c
@@ -713,6 +713,7 @@  enum {
 	Opt_hash,
 	Opt_policydigest,
 	Opt_policyhandle,
+	Opt_creationpcrs,
 };
 
 static const match_table_t key_tokens = {
@@ -725,6 +726,7 @@  static const match_table_t key_tokens = {
 	{Opt_hash, "hash=%s"},
 	{Opt_policydigest, "policydigest=%s"},
 	{Opt_policyhandle, "policyhandle=%s"},
+	{Opt_creationpcrs, "creationpcrs=%s"},
 	{Opt_err, NULL}
 };
 
@@ -858,6 +860,13 @@  static int getoptions(char *c, struct trusted_key_payload *pay,
 				return -EINVAL;
 			opt->policyhandle = handle;
 			break;
+		case Opt_creationpcrs:
+			if (!tpm2)
+				return -EINVAL;
+			res = kstrtoint(args[0].from, 16, &opt->creation_pcrs);
+			if (res < 0)
+				return -EINVAL;
+			break;
 		default:
 			return -EINVAL;
 		}
diff --git a/security/keys/trusted-keys/trusted_tpm2.c b/security/keys/trusted-keys/trusted_tpm2.c
index 296a00f872ba40..b7ddb78e644d17 100644
--- a/security/keys/trusted-keys/trusted_tpm2.c
+++ b/security/keys/trusted-keys/trusted_tpm2.c
@@ -290,7 +290,7 @@  int tpm2_seal_trusted(struct tpm_chip *chip,
 	struct tpm_buf buf;
 	u32 hash;
 	u32 flags;
-	int i;
+	int i, j;
 	int rc;
 
 	for (i = 0; i < ARRAY_SIZE(tpm2_hash_map); i++) {
@@ -359,7 +359,28 @@  int tpm2_seal_trusted(struct tpm_chip *chip,
 	tpm_buf_append_u16(&buf, 0);
 
 	/* creation PCR */
-	tpm_buf_append_u32(&buf, 0);
+	if (options->creation_pcrs) {
+		/* One bank */
+		tpm_buf_append_u32(&buf, 1);
+		/* Which bank to use */
+		tpm_buf_append_u16(&buf, hash);
+		/* Length of the PCR bitmask */
+		tpm_buf_append_u8(&buf, 3);
+		/* PCR bitmask */
+		for (i = 0; i < 3; i++) {
+			char tmp = 0;
+
+			for (j = 0; j < 8; j++) {
+				char bit = (i * 8) + j;
+
+				if (options->creation_pcrs & (1 << bit))
+					tmp |= (1 << j);
+			}
+			tpm_buf_append_u8(&buf, tmp);
+		}
+	} else {
+		tpm_buf_append_u32(&buf, 0);
+	}
 
 	if (buf.flags & TPM_BUF_OVERFLOW) {
 		rc = -E2BIG;