* [PATCH v3] KEYS: trusted: allow module init if TPM is inactive or deactivated
@ 2019-08-05 16:44 Roberto Sassu
2019-08-05 17:20 ` Tyler Hicks
` (2 more replies)
0 siblings, 3 replies; 4+ messages in thread
From: Roberto Sassu @ 2019-08-05 16:44 UTC (permalink / raw)
To: jarkko.sakkinen, jejb, zohar, jgg, tyhicks
Cc: linux-integrity, linux-security-module, keyrings, linux-kernel,
crazyt2019+lml, nayna, silviu.vlasceanu, Roberto Sassu
Commit c78719203fc6 ("KEYS: trusted: allow trusted.ko to initialize w/o a
TPM") allows the trusted module to be loaded even if a TPM is not found, to
avoid module dependency problems.
However, trusted module initialization can still fail if the TPM is
inactive or deactivated. tpm_get_random() returns an error.
This patch removes the call to tpm_get_random() and instead extends the PCR
specified by the user with zeros. The security of this alternative is
equivalent to the previous one, as either option prevents with a PCR update
unsealing and misuse of sealed data by a user space process.
Even if a PCR is extended with zeros, instead of random data, it is still
computationally infeasible to find a value as input for a new PCR extend
operation, to obtain again the PCR value that would allow unsealing.
Fixes: 240730437deb ("KEYS: trusted: explicitly use tpm_chip structure...")
Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
Reviewed-by: Tyler Hicks <tyhicks@canonical.com>
Suggested-by: Mimi Zohar <zohar@linux.ibm.com>
---
security/keys/trusted.c | 13 -------------
1 file changed, 13 deletions(-)
diff --git a/security/keys/trusted.c b/security/keys/trusted.c
index 9a94672e7adc..ade699131065 100644
--- a/security/keys/trusted.c
+++ b/security/keys/trusted.c
@@ -1228,24 +1228,11 @@ static int __init trusted_shash_alloc(void)
static int __init init_digests(void)
{
- u8 digest[TPM_MAX_DIGEST_SIZE];
- int ret;
- int i;
-
- ret = tpm_get_random(chip, digest, TPM_MAX_DIGEST_SIZE);
- if (ret < 0)
- return ret;
- if (ret < TPM_MAX_DIGEST_SIZE)
- return -EFAULT;
-
digests = kcalloc(chip->nr_allocated_banks, sizeof(*digests),
GFP_KERNEL);
if (!digests)
return -ENOMEM;
- for (i = 0; i < chip->nr_allocated_banks; i++)
- memcpy(digests[i].digest, digest, TPM_MAX_DIGEST_SIZE);
-
return 0;
}
--
2.17.1
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH v3] KEYS: trusted: allow module init if TPM is inactive or deactivated
2019-08-05 16:44 [PATCH v3] KEYS: trusted: allow module init if TPM is inactive or deactivated Roberto Sassu
@ 2019-08-05 17:20 ` Tyler Hicks
2019-08-05 22:12 ` Jarkko Sakkinen
2019-08-09 15:50 ` Jarkko Sakkinen
2 siblings, 0 replies; 4+ messages in thread
From: Tyler Hicks @ 2019-08-05 17:20 UTC (permalink / raw)
To: Roberto Sassu
Cc: jarkko.sakkinen, jejb, zohar, jgg, linux-integrity,
linux-security-module, keyrings, linux-kernel, crazyt2019+lml,
nayna, silviu.vlasceanu
On 2019-08-05 18:44:27, Roberto Sassu wrote:
> Commit c78719203fc6 ("KEYS: trusted: allow trusted.ko to initialize w/o a
> TPM") allows the trusted module to be loaded even if a TPM is not found, to
> avoid module dependency problems.
>
> However, trusted module initialization can still fail if the TPM is
> inactive or deactivated. tpm_get_random() returns an error.
>
> This patch removes the call to tpm_get_random() and instead extends the PCR
> specified by the user with zeros. The security of this alternative is
> equivalent to the previous one, as either option prevents with a PCR update
> unsealing and misuse of sealed data by a user space process.
>
> Even if a PCR is extended with zeros, instead of random data, it is still
> computationally infeasible to find a value as input for a new PCR extend
> operation, to obtain again the PCR value that would allow unsealing.
>
> Fixes: 240730437deb ("KEYS: trusted: explicitly use tpm_chip structure...")
> Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
> Reviewed-by: Tyler Hicks <tyhicks@canonical.com>
The approach changed a fair bit from v2 to v3 so I'll confirm that my
Reviewed-by still stands.
Also, we have positive test results from an affected user:
https://bugzilla.kernel.org/show_bug.cgi?id=203953#c10
Tyler
> Suggested-by: Mimi Zohar <zohar@linux.ibm.com>
> ---
> security/keys/trusted.c | 13 -------------
> 1 file changed, 13 deletions(-)
>
> diff --git a/security/keys/trusted.c b/security/keys/trusted.c
> index 9a94672e7adc..ade699131065 100644
> --- a/security/keys/trusted.c
> +++ b/security/keys/trusted.c
> @@ -1228,24 +1228,11 @@ static int __init trusted_shash_alloc(void)
>
> static int __init init_digests(void)
> {
> - u8 digest[TPM_MAX_DIGEST_SIZE];
> - int ret;
> - int i;
> -
> - ret = tpm_get_random(chip, digest, TPM_MAX_DIGEST_SIZE);
> - if (ret < 0)
> - return ret;
> - if (ret < TPM_MAX_DIGEST_SIZE)
> - return -EFAULT;
> -
> digests = kcalloc(chip->nr_allocated_banks, sizeof(*digests),
> GFP_KERNEL);
> if (!digests)
> return -ENOMEM;
>
> - for (i = 0; i < chip->nr_allocated_banks; i++)
> - memcpy(digests[i].digest, digest, TPM_MAX_DIGEST_SIZE);
> -
> return 0;
> }
>
> --
> 2.17.1
>
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH v3] KEYS: trusted: allow module init if TPM is inactive or deactivated
2019-08-05 16:44 [PATCH v3] KEYS: trusted: allow module init if TPM is inactive or deactivated Roberto Sassu
2019-08-05 17:20 ` Tyler Hicks
@ 2019-08-05 22:12 ` Jarkko Sakkinen
2019-08-09 15:50 ` Jarkko Sakkinen
2 siblings, 0 replies; 4+ messages in thread
From: Jarkko Sakkinen @ 2019-08-05 22:12 UTC (permalink / raw)
To: Roberto Sassu
Cc: jejb, zohar, jgg, tyhicks, linux-integrity,
linux-security-module, keyrings, linux-kernel, crazyt2019+lml,
nayna, silviu.vlasceanu
On Mon, Aug 05, 2019 at 06:44:27PM +0200, Roberto Sassu wrote:
> Commit c78719203fc6 ("KEYS: trusted: allow trusted.ko to initialize w/o a
> TPM") allows the trusted module to be loaded even if a TPM is not found, to
> avoid module dependency problems.
>
> However, trusted module initialization can still fail if the TPM is
> inactive or deactivated. tpm_get_random() returns an error.
>
> This patch removes the call to tpm_get_random() and instead extends the PCR
> specified by the user with zeros. The security of this alternative is
> equivalent to the previous one, as either option prevents with a PCR update
> unsealing and misuse of sealed data by a user space process.
>
> Even if a PCR is extended with zeros, instead of random data, it is still
> computationally infeasible to find a value as input for a new PCR extend
> operation, to obtain again the PCR value that would allow unsealing.
>
> Fixes: 240730437deb ("KEYS: trusted: explicitly use tpm_chip structure...")
> Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
> Reviewed-by: Tyler Hicks <tyhicks@canonical.com>
> Suggested-by: Mimi Zohar <zohar@linux.ibm.com>
Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
/Jarkko
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH v3] KEYS: trusted: allow module init if TPM is inactive or deactivated
2019-08-05 16:44 [PATCH v3] KEYS: trusted: allow module init if TPM is inactive or deactivated Roberto Sassu
2019-08-05 17:20 ` Tyler Hicks
2019-08-05 22:12 ` Jarkko Sakkinen
@ 2019-08-09 15:50 ` Jarkko Sakkinen
2 siblings, 0 replies; 4+ messages in thread
From: Jarkko Sakkinen @ 2019-08-09 15:50 UTC (permalink / raw)
To: Roberto Sassu
Cc: jejb, zohar, jgg, tyhicks, linux-integrity,
linux-security-module, keyrings, linux-kernel, crazyt2019+lml,
nayna, silviu.vlasceanu
On Mon, Aug 05, 2019 at 06:44:27PM +0200, Roberto Sassu wrote:
> Commit c78719203fc6 ("KEYS: trusted: allow trusted.ko to initialize w/o a
> TPM") allows the trusted module to be loaded even if a TPM is not found, to
> avoid module dependency problems.
>
> However, trusted module initialization can still fail if the TPM is
> inactive or deactivated. tpm_get_random() returns an error.
>
> This patch removes the call to tpm_get_random() and instead extends the PCR
> specified by the user with zeros. The security of this alternative is
> equivalent to the previous one, as either option prevents with a PCR update
> unsealing and misuse of sealed data by a user space process.
>
> Even if a PCR is extended with zeros, instead of random data, it is still
> computationally infeasible to find a value as input for a new PCR extend
> operation, to obtain again the PCR value that would allow unsealing.
>
> Fixes: 240730437deb ("KEYS: trusted: explicitly use tpm_chip structure...")
> Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
> Reviewed-by: Tyler Hicks <tyhicks@canonical.com>
> Suggested-by: Mimi Zohar <zohar@linux.ibm.com>
OK so this has been now applied. I'm going to do a PR over
the weekend, which means that the fix will land to 5.3.
/Jarkko
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2019-08-09 15:50 UTC | newest]
Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2019-08-05 16:44 [PATCH v3] KEYS: trusted: allow module init if TPM is inactive or deactivated Roberto Sassu
2019-08-05 17:20 ` Tyler Hicks
2019-08-05 22:12 ` Jarkko Sakkinen
2019-08-09 15:50 ` Jarkko Sakkinen
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).