[v3,2/2] ima: support calculating the boot_aggregate based on different TPM banks
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Message ID 1580401363-5593-2-git-send-email-zohar@linux.ibm.com
State New
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Series
  • [v3,1/2] ima: support calculating the boot aggregate based on non-SHA1 algorithms
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Commit Message

Mimi Zohar Jan. 30, 2020, 4:22 p.m. UTC
Calculating the boot_aggregate attempts to read the TPM SHA1 bank,
assuming it is always enabled.  With TPM 2.0 hash agility, TPM chips
could support multiple TPM PCR banks, allowing firmware to configure and
enable different banks.

Instead of hard coding the TPM 2.0 bank hash algorithm used for calculating
the boot-aggregate, use the same hash algorithm for reading the TPM PCRs as
for calculating the boot aggregate digest.  Preference is given to the
configured IMA default hash algorithm.

For TPM 1.2 SHA1 is the only supported hash algorithm.

Reported-by: Jerry Snitselaar <jsnitsel@redhat.com>
Suggested-by: Roberto Sassu <roberto.sassu@huawei.com>
Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>
---
 security/integrity/ima/ima_crypto.c | 45 ++++++++++++++++++++++++++++++++++++-
 1 file changed, 44 insertions(+), 1 deletion(-)

Comments

Lakshmi Ramasubramanian Jan. 30, 2020, 4:53 p.m. UTC | #1
On 1/30/2020 8:22 AM, Mimi Zohar wrote:

> +static enum hash_algo get_hash_algo(const char *algname)
> +{
> +	int i;
> +
> +	for (i = 0; i < HASH_ALGO__LAST; i++) {
> +		if (strcmp(algname, hash_algo_name[i]) == 0)
> +			break;
> +	}
> +
> +	return i;
> +}
> +

ima_digest_data is passed to ima_calc_boot_aggregate(). This struct 
contains the hash_algo. Can that be passed to 
ima_calc_boot_aggregate_tfm() instead of using the above function to get 
the hash_algo?

  -lakshmi
Roberto Sassu Jan. 30, 2020, 4:54 p.m. UTC | #2
> -----Original Message-----
> From: linux-integrity-owner@vger.kernel.org [mailto:linux-integrity-
> owner@vger.kernel.org] On Behalf Of Mimi Zohar
> Sent: Thursday, January 30, 2020 5:23 PM
> To: linux-integrity@vger.kernel.org
> Cc: Jerry Snitselaar <jsnitsel@redhat.com>; James Bottomley
> <James.Bottomley@HansenPartnership.com>; linux-
> kernel@vger.kernel.org; Mimi Zohar <zohar@linux.ibm.com>
> Subject: [PATCH v3 2/2] ima: support calculating the boot_aggregate based
> on different TPM banks
> 
> Calculating the boot_aggregate attempts to read the TPM SHA1 bank,
> assuming it is always enabled.  With TPM 2.0 hash agility, TPM chips
> could support multiple TPM PCR banks, allowing firmware to configure and
> enable different banks.
> 
> Instead of hard coding the TPM 2.0 bank hash algorithm used for calculating
> the boot-aggregate, use the same hash algorithm for reading the TPM PCRs
> as
> for calculating the boot aggregate digest.  Preference is given to the
> configured IMA default hash algorithm.
> 
> For TPM 1.2 SHA1 is the only supported hash algorithm.
> 
> Reported-by: Jerry Snitselaar <jsnitsel@redhat.com>
> Suggested-by: Roberto Sassu <roberto.sassu@huawei.com>
> Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>
> ---
>  security/integrity/ima/ima_crypto.c | 45
> ++++++++++++++++++++++++++++++++++++-
>  1 file changed, 44 insertions(+), 1 deletion(-)
> 
> diff --git a/security/integrity/ima/ima_crypto.c
> b/security/integrity/ima/ima_crypto.c
> index 7967a6904851..a020aaefdea8 100644
> --- a/security/integrity/ima/ima_crypto.c
> +++ b/security/integrity/ima/ima_crypto.c
> @@ -656,13 +656,34 @@ static void __init ima_pcrread(u32 idx, struct
> tpm_digest *d)
>  		pr_err("Error Communicating to TPM chip\n");
>  }
> 
> +static enum hash_algo get_hash_algo(const char *algname)
> +{
> +	int i;
> +
> +	for (i = 0; i < HASH_ALGO__LAST; i++) {
> +		if (strcmp(algname, hash_algo_name[i]) == 0)
> +			break;
> +	}
> +
> +	return i;
> +}
> +
>  /*
> - * Calculate the boot aggregate hash
> + * The boot_aggregate is a cumulative hash over TPM registers 0 - 7.  With
> + * TPM 1.2 the boot_aggregate was based on reading the SHA1 PCRs, but
> with
> + * TPM 2.0 hash agility, TPM chips could support multiple TPM PCR banks,
> + * allowing firmware to configure and enable different banks.
> + *
> + * Knowing which TPM bank is read to calculate the boot_aggregate digest
> + * needs to be conveyed to a verifier.  For this reason, use the same
> + * hash algorithm for reading the TPM PCRs as for calculating the boot
> + * aggregate digest as stored in the measurement list.
>   */
>  static int __init ima_calc_boot_aggregate_tfm(char *digest,
>  					      struct crypto_shash *tfm)
>  {
>  	struct tpm_digest d = { .alg_id = TPM_ALG_SHA1, .digest = {0} };
> +	enum hash_algo crypto_id;
>  	int rc;
>  	u32 i;
>  	SHASH_DESC_ON_STACK(shash, tfm);
> @@ -673,6 +694,28 @@ static int __init ima_calc_boot_aggregate_tfm(char
> *digest,
>  	if (rc != 0)
>  		return rc;
> 
> +	crypto_id = get_hash_algo(crypto_shash_alg_name(tfm));

Wouldn't be better to determine the index of ima_tpm_chip->allocated_banks
in patch 1/2 and pass that index here, to avoid another search?

Roberto

HUAWEI TECHNOLOGIES Duesseldorf GmbH, HRB 56063
Managing Director: Li Peng, Li Jian, Shi Yanli
Mimi Zohar Jan. 30, 2020, 5:32 p.m. UTC | #3
On Thu, 2020-01-30 at 16:54 +0000, Roberto Sassu wrote:
> > -----Original Message-----
> > From: linux-integrity-owner@vger.kernel.org [mailto:linux-integrity-
> > owner@vger.kernel.org] On Behalf Of Mimi Zohar
> > Sent: Thursday, January 30, 2020 5:23 PM
> > To: linux-integrity@vger.kernel.org
> > Cc: Jerry Snitselaar <jsnitsel@redhat.com>; James Bottomley
> > <James.Bottomley@HansenPartnership.com>; linux-
> > kernel@vger.kernel.org; Mimi Zohar <zohar@linux.ibm.com>
> > Subject: [PATCH v3 2/2] ima: support calculating the boot_aggregate based
> > on different TPM banks
> > 
> > Calculating the boot_aggregate attempts to read the TPM SHA1 bank,
> > assuming it is always enabled.  With TPM 2.0 hash agility, TPM chips
> > could support multiple TPM PCR banks, allowing firmware to configure and
> > enable different banks.
> > 
> > Instead of hard coding the TPM 2.0 bank hash algorithm used for calculating
> > the boot-aggregate, use the same hash algorithm for reading the TPM PCRs
> > as
> > for calculating the boot aggregate digest.  Preference is given to the
> > configured IMA default hash algorithm.
> > 
> > For TPM 1.2 SHA1 is the only supported hash algorithm.
> > 
> > Reported-by: Jerry Snitselaar <jsnitsel@redhat.com>
> > Suggested-by: Roberto Sassu <roberto.sassu@huawei.com>
> > Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>
> > ---
> >  security/integrity/ima/ima_crypto.c | 45
> > ++++++++++++++++++++++++++++++++++++-
> >  1 file changed, 44 insertions(+), 1 deletion(-)
> > 
> > diff --git a/security/integrity/ima/ima_crypto.c
> > b/security/integrity/ima/ima_crypto.c
> > index 7967a6904851..a020aaefdea8 100644
> > --- a/security/integrity/ima/ima_crypto.c
> > +++ b/security/integrity/ima/ima_crypto.c
> > @@ -656,13 +656,34 @@ static void __init ima_pcrread(u32 idx, struct
> > tpm_digest *d)
> >  		pr_err("Error Communicating to TPM chip\n");
> >  }
> > 
> > +static enum hash_algo get_hash_algo(const char *algname)
> > +{
> > +	int i;
> > +
> > +	for (i = 0; i < HASH_ALGO__LAST; i++) {
> > +		if (strcmp(algname, hash_algo_name[i]) == 0)
> > +			break;
> > +	}
> > +
> > +	return i;
> > +}
> > +
> >  /*
> > - * Calculate the boot aggregate hash
> > + * The boot_aggregate is a cumulative hash over TPM registers 0 - 7.  With
> > + * TPM 1.2 the boot_aggregate was based on reading the SHA1 PCRs, but
> > with
> > + * TPM 2.0 hash agility, TPM chips could support multiple TPM PCR banks,
> > + * allowing firmware to configure and enable different banks.
> > + *
> > + * Knowing which TPM bank is read to calculate the boot_aggregate digest
> > + * needs to be conveyed to a verifier.  For this reason, use the same
> > + * hash algorithm for reading the TPM PCRs as for calculating the boot
> > + * aggregate digest as stored in the measurement list.
> >   */
> >  static int __init ima_calc_boot_aggregate_tfm(char *digest,
> >  					      struct crypto_shash *tfm)
> >  {
> >  	struct tpm_digest d = { .alg_id = TPM_ALG_SHA1, .digest = {0} };
> > +	enum hash_algo crypto_id;
> >  	int rc;
> >  	u32 i;
> >  	SHASH_DESC_ON_STACK(shash, tfm);
> > @@ -673,6 +694,28 @@ static int __init ima_calc_boot_aggregate_tfm(char
> > *digest,
> >  	if (rc != 0)
> >  		return rc;
> > 
> > +	crypto_id = get_hash_algo(crypto_shash_alg_name(tfm));
> 
> Wouldn't be better to determine the index of ima_tpm_chip->allocated_banks
> in patch 1/2 and pass that index here, to avoid another search?

Both your suggestion and Lakshmi's suggestion change the parameters to
ima_calc_boot_aggregate_tfm(), which I was trying to avoid for now.  I
want it to be as easy as possible to backport.

Going forward, you might be correct.

Mimi
Roberto Sassu Feb. 4, 2020, 1:37 p.m. UTC | #4
> -----Original Message-----
> From: linux-integrity-owner@vger.kernel.org [mailto:linux-integrity-
> owner@vger.kernel.org] On Behalf Of Mimi Zohar
> Sent: Thursday, January 30, 2020 5:23 PM
> To: linux-integrity@vger.kernel.org
> Cc: Jerry Snitselaar <jsnitsel@redhat.com>; James Bottomley
> <James.Bottomley@HansenPartnership.com>; linux-
> kernel@vger.kernel.org; Mimi Zohar <zohar@linux.ibm.com>
> Subject: [PATCH v3 2/2] ima: support calculating the boot_aggregate based
> on different TPM banks
> 
> Calculating the boot_aggregate attempts to read the TPM SHA1 bank,
> assuming it is always enabled.  With TPM 2.0 hash agility, TPM chips
> could support multiple TPM PCR banks, allowing firmware to configure and
> enable different banks.
> 
> Instead of hard coding the TPM 2.0 bank hash algorithm used for calculating
> the boot-aggregate, use the same hash algorithm for reading the TPM PCRs
> as
> for calculating the boot aggregate digest.  Preference is given to the
> configured IMA default hash algorithm.
> 
> For TPM 1.2 SHA1 is the only supported hash algorithm.
> 
> Reported-by: Jerry Snitselaar <jsnitsel@redhat.com>
> Suggested-by: Roberto Sassu <roberto.sassu@huawei.com>
> Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>
> ---
>  security/integrity/ima/ima_crypto.c | 45
> ++++++++++++++++++++++++++++++++++++-
>  1 file changed, 44 insertions(+), 1 deletion(-)
> 
> diff --git a/security/integrity/ima/ima_crypto.c
> b/security/integrity/ima/ima_crypto.c
> index 7967a6904851..a020aaefdea8 100644
> --- a/security/integrity/ima/ima_crypto.c
> +++ b/security/integrity/ima/ima_crypto.c
> @@ -656,13 +656,34 @@ static void __init ima_pcrread(u32 idx, struct
> tpm_digest *d)
>  		pr_err("Error Communicating to TPM chip\n");
>  }
> 
> +static enum hash_algo get_hash_algo(const char *algname)
> +{
> +	int i;
> +
> +	for (i = 0; i < HASH_ALGO__LAST; i++) {
> +		if (strcmp(algname, hash_algo_name[i]) == 0)
> +			break;
> +	}
> +
> +	return i;
> +}
> +
>  /*
> - * Calculate the boot aggregate hash
> + * The boot_aggregate is a cumulative hash over TPM registers 0 - 7.  With
> + * TPM 1.2 the boot_aggregate was based on reading the SHA1 PCRs, but
> with
> + * TPM 2.0 hash agility, TPM chips could support multiple TPM PCR banks,
> + * allowing firmware to configure and enable different banks.
> + *
> + * Knowing which TPM bank is read to calculate the boot_aggregate digest
> + * needs to be conveyed to a verifier.  For this reason, use the same
> + * hash algorithm for reading the TPM PCRs as for calculating the boot
> + * aggregate digest as stored in the measurement list.
>   */
>  static int __init ima_calc_boot_aggregate_tfm(char *digest,
>  					      struct crypto_shash *tfm)
>  {
>  	struct tpm_digest d = { .alg_id = TPM_ALG_SHA1, .digest = {0} };
> +	enum hash_algo crypto_id;
>  	int rc;
>  	u32 i;
>  	SHASH_DESC_ON_STACK(shash, tfm);
> @@ -673,6 +694,28 @@ static int __init ima_calc_boot_aggregate_tfm(char
> *digest,
>  	if (rc != 0)
>  		return rc;
> 
> +	crypto_id = get_hash_algo(crypto_shash_alg_name(tfm));
> +	if (crypto_id == HASH_ALGO__LAST) {
> +		pr_devel("unknown hash algorithm (%s), failing to read
> PCRs.\n",
> +			 crypto_shash_alg_name(tfm));
> +		return 0;
> +	}
> +
> +	for (i = 0; i < ima_tpm_chip->nr_allocated_banks; i++) {
> +		if (ima_tpm_chip->allocated_banks[i].crypto_id ==
> crypto_id) {
> +			d.alg_id = ima_tpm_chip->allocated_banks[i].alg_id;
> +			break;
> +		}
> +	}
> +	if (i == ima_tpm_chip->nr_allocated_banks) {
> +		pr_devel("TPM %s bank not allocated, failing to read
> PCRs.\n",
> +			 crypto_shash_alg_name(tfm));
> +		return 0;
> +	}
> +
> +	pr_devel("calculating the boot-aggregregate based on TPM
> bank: %04x\n",
> +		  d.alg_id);
> +
>  	/* cumulative sha1 over tpm registers 0-7 */
>  	for (i = TPM_PCR0; i < TPM_PCR8; i++) {
>  		ima_pcrread(i, &d);

The third argument of crypto_shash_update() should be
crypto_shash_digestsize(tfm).

Roberto

HUAWEI TECHNOLOGIES Duesseldorf GmbH, HRB 56063
Managing Director: Li Peng, Li Jian, Shi Yanli
Mimi Zohar Feb. 4, 2020, 5:27 p.m. UTC | #5
On Tue, 2020-02-04 at 13:37 +0000, Roberto Sassu wrote:
> > -----Original Message-----
> > From: linux-integrity-owner@vger.kernel.org [mailto:linux-integrity-
> > owner@vger.kernel.org] On Behalf Of Mimi Zohar
> > Sent: Thursday, January 30, 2020 5:23 PM
> > To: linux-integrity@vger.kernel.org
> > Cc: Jerry Snitselaar <jsnitsel@redhat.com>; James Bottomley
> > <James.Bottomley@HansenPartnership.com>; linux-
> > kernel@vger.kernel.org; Mimi Zohar <zohar@linux.ibm.com>
> > Subject: [PATCH v3 2/2] ima: support calculating the boot_aggregate based
> > on different TPM banks
> > 
> > Calculating the boot_aggregate attempts to read the TPM SHA1 bank,
> > assuming it is always enabled.  With TPM 2.0 hash agility, TPM chips
> > could support multiple TPM PCR banks, allowing firmware to configure and
> > enable different banks.
> > 
> > Instead of hard coding the TPM 2.0 bank hash algorithm used for calculating
> > the boot-aggregate, use the same hash algorithm for reading the TPM PCRs
> > as
> > for calculating the boot aggregate digest.  Preference is given to the
> > configured IMA default hash algorithm.
> > 
> > For TPM 1.2 SHA1 is the only supported hash algorithm.
> > 
> > Reported-by: Jerry Snitselaar <jsnitsel@redhat.com>
> > Suggested-by: Roberto Sassu <roberto.sassu@huawei.com>
> > Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>
> > ---
> >  security/integrity/ima/ima_crypto.c | 45
> > ++++++++++++++++++++++++++++++++++++-
> >  1 file changed, 44 insertions(+), 1 deletion(-)
> > 
> > diff --git a/security/integrity/ima/ima_crypto.c
> > b/security/integrity/ima/ima_crypto.c
> > index 7967a6904851..a020aaefdea8 100644
> > --- a/security/integrity/ima/ima_crypto.c
> > +++ b/security/integrity/ima/ima_crypto.c
> > @@ -656,13 +656,34 @@ static void __init ima_pcrread(u32 idx, struct
> > tpm_digest *d)
> >  		pr_err("Error Communicating to TPM chip\n");
> >  }
> > 
> > +static enum hash_algo get_hash_algo(const char *algname)
> > +{
> > +	int i;
> > +
> > +	for (i = 0; i < HASH_ALGO__LAST; i++) {
> > +		if (strcmp(algname, hash_algo_name[i]) == 0)
> > +			break;
> > +	}
> > +
> > +	return i;
> > +}
> > +
> >  /*
> > - * Calculate the boot aggregate hash
> > + * The boot_aggregate is a cumulative hash over TPM registers 0 - 7.  With
> > + * TPM 1.2 the boot_aggregate was based on reading the SHA1 PCRs, but
> > with
> > + * TPM 2.0 hash agility, TPM chips could support multiple TPM PCR banks,
> > + * allowing firmware to configure and enable different banks.
> > + *
> > + * Knowing which TPM bank is read to calculate the boot_aggregate digest
> > + * needs to be conveyed to a verifier.  For this reason, use the same
> > + * hash algorithm for reading the TPM PCRs as for calculating the boot
> > + * aggregate digest as stored in the measurement list.
> >   */
> >  static int __init ima_calc_boot_aggregate_tfm(char *digest,
> >  					      struct crypto_shash *tfm)
> >  {
> >  	struct tpm_digest d = { .alg_id = TPM_ALG_SHA1, .digest = {0} };
> > +	enum hash_algo crypto_id;
> >  	int rc;
> >  	u32 i;
> >  	SHASH_DESC_ON_STACK(shash, tfm);
> > @@ -673,6 +694,28 @@ static int __init ima_calc_boot_aggregate_tfm(char
> > *digest,
> >  	if (rc != 0)
> >  		return rc;
> > 
> > +	crypto_id = get_hash_algo(crypto_shash_alg_name(tfm));
> > +	if (crypto_id == HASH_ALGO__LAST) {
> > +		pr_devel("unknown hash algorithm (%s), failing to read
> > PCRs.\n",
> > +			 crypto_shash_alg_name(tfm));
> > +		return 0;
> > +	}
> > +
> > +	for (i = 0; i < ima_tpm_chip->nr_allocated_banks; i++) {
> > +		if (ima_tpm_chip->allocated_banks[i].crypto_id ==
> > crypto_id) {
> > +			d.alg_id = ima_tpm_chip->allocated_banks[i].alg_id;
> > +			break;
> > +		}
> > +	}
> > +	if (i == ima_tpm_chip->nr_allocated_banks) {
> > +		pr_devel("TPM %s bank not allocated, failing to read
> > PCRs.\n",
> > +			 crypto_shash_alg_name(tfm));
> > +		return 0;
> > +	}
> > +
> > +	pr_devel("calculating the boot-aggregregate based on TPM
> > bank: %04x\n",
> > +		  d.alg_id);
> > +
> >  	/* cumulative sha1 over tpm registers 0-7 */
> >  	for (i = TPM_PCR0; i < TPM_PCR8; i++) {
> >  		ima_pcrread(i, &d);
> 
> The third argument of crypto_shash_update() should be
> crypto_shash_digestsize(tfm).

Thanks!  At this point we know the hash algorithm, so we could use
hash_digest_size[].

Mimi

Patch
diff mbox series

diff --git a/security/integrity/ima/ima_crypto.c b/security/integrity/ima/ima_crypto.c
index 7967a6904851..a020aaefdea8 100644
--- a/security/integrity/ima/ima_crypto.c
+++ b/security/integrity/ima/ima_crypto.c
@@ -656,13 +656,34 @@  static void __init ima_pcrread(u32 idx, struct tpm_digest *d)
 		pr_err("Error Communicating to TPM chip\n");
 }
 
+static enum hash_algo get_hash_algo(const char *algname)
+{
+	int i;
+
+	for (i = 0; i < HASH_ALGO__LAST; i++) {
+		if (strcmp(algname, hash_algo_name[i]) == 0)
+			break;
+	}
+
+	return i;
+}
+
 /*
- * Calculate the boot aggregate hash
+ * The boot_aggregate is a cumulative hash over TPM registers 0 - 7.  With
+ * TPM 1.2 the boot_aggregate was based on reading the SHA1 PCRs, but with
+ * TPM 2.0 hash agility, TPM chips could support multiple TPM PCR banks,
+ * allowing firmware to configure and enable different banks.
+ *
+ * Knowing which TPM bank is read to calculate the boot_aggregate digest
+ * needs to be conveyed to a verifier.  For this reason, use the same
+ * hash algorithm for reading the TPM PCRs as for calculating the boot
+ * aggregate digest as stored in the measurement list.
  */
 static int __init ima_calc_boot_aggregate_tfm(char *digest,
 					      struct crypto_shash *tfm)
 {
 	struct tpm_digest d = { .alg_id = TPM_ALG_SHA1, .digest = {0} };
+	enum hash_algo crypto_id;
 	int rc;
 	u32 i;
 	SHASH_DESC_ON_STACK(shash, tfm);
@@ -673,6 +694,28 @@  static int __init ima_calc_boot_aggregate_tfm(char *digest,
 	if (rc != 0)
 		return rc;
 
+	crypto_id = get_hash_algo(crypto_shash_alg_name(tfm));
+	if (crypto_id == HASH_ALGO__LAST) {
+		pr_devel("unknown hash algorithm (%s), failing to read PCRs.\n",
+			 crypto_shash_alg_name(tfm));
+		return 0;
+	}
+
+	for (i = 0; i < ima_tpm_chip->nr_allocated_banks; i++) {
+		if (ima_tpm_chip->allocated_banks[i].crypto_id == crypto_id) {
+			d.alg_id = ima_tpm_chip->allocated_banks[i].alg_id;
+			break;
+		}
+	}
+	if (i == ima_tpm_chip->nr_allocated_banks) {
+		pr_devel("TPM %s bank not allocated, failing to read PCRs.\n",
+			 crypto_shash_alg_name(tfm));
+		return 0;
+	}
+
+	pr_devel("calculating the boot-aggregregate based on TPM bank: %04x\n",
+		  d.alg_id);
+
 	/* cumulative sha1 over tpm registers 0-7 */
 	for (i = TPM_PCR0; i < TPM_PCR8; i++) {
 		ima_pcrread(i, &d);