2018-09-03 01:18:46

by Jarkko Sakkinen

Subject: [PATCH] tpm: fix response size validation in tpm_get_random()

When checking whether the response is large enough to be able to contain
the received random bytes in tpm_get_random() and tpm2_get_random(),
they fail to take account the header size, which should be added to the
minimum size. This commit fixes this issue.

Cc: [email protected]
Fixes: c659af78eb7b ("tpm: Check size of response before accessing data")
Signed-off-by: Jarkko Sakkinen <[email protected]>
---
drivers/char/tpm/tpm-interface.c | 3 ++-
drivers/char/tpm/tpm2-cmd.c | 4 +++-
2 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/char/tpm/tpm-interface.c b/drivers/char/tpm/tpm-interface.c
index 1a803b0cf980..318a7078b2ba 100644
--- a/drivers/char/tpm/tpm-interface.c
+++ b/drivers/char/tpm/tpm-interface.c
@@ -1321,7 +1321,8 @@ int tpm_get_random(struct tpm_chip *chip, u8 *out, size_t max)
}

rlength = be32_to_cpu(tpm_cmd.header.out.length);
- if (rlength < offsetof(struct tpm_getrandom_out, rng_data) +
+ if (rlength < TPM_HEADER_SIZE +
+ offsetof(struct tpm_getrandom_out, rng_data) +
recd) {
total = -EFAULT;
break;
diff --git a/drivers/char/tpm/tpm2-cmd.c b/drivers/char/tpm/tpm2-cmd.c
index c31b490bd41d..3acf4fd4e5a5 100644
--- a/drivers/char/tpm/tpm2-cmd.c
+++ b/drivers/char/tpm/tpm2-cmd.c
@@ -329,7 +329,9 @@ int tpm2_get_random(struct tpm_chip *chip, u8 *dest, size_t max)
&buf.data[TPM_HEADER_SIZE];
recd = min_t(u32, be16_to_cpu(out->size), num_bytes);
if (tpm_buf_length(&buf) <
- offsetof(struct tpm2_get_random_out, buffer) + recd) {
+ TPM_HEADER_SIZE +
+ offsetof(struct tpm2_get_random_out, buffer) +
+ recd) {
err = -EFAULT;
goto out;
}
--
2.17.1

2018-09-05 11:15:48

by Jarkko Sakkinen

Subject: Re: [PATCH] tpm: fix response size validation in tpm_get_random()

On Mon, Sep 03, 2018 at 04:10:04AM +0300, Jarkko Sakkinen wrote:
> When checking whether the response is large enough to be able to contain
> the received random bytes in tpm_get_random() and tpm2_get_random(),
> they fail to take account the header size, which should be added to the
> minimum size. This commit fixes this issue.
>
> Cc: [email protected]
> Fixes: c659af78eb7b ("tpm: Check size of response before accessing data")
> Signed-off-by: Jarkko Sakkinen <[email protected]>

Stefan, you did the original commit. Does this look right to you?

/Jarkko

2018-09-05 13:18:17

by Stefan Berger

Subject: Re: [PATCH] tpm: fix response size validation in tpm_get_random()

On 09/02/2018 09:10 PM, Jarkko Sakkinen wrote:
> When checking whether the response is large enough to be able to contain
> the received random bytes in tpm_get_random() and tpm2_get_random(),
> they fail to take account the header size, which should be added to the
> minimum size. This commit fixes this issue.
>
> Cc: [email protected]
> Fixes: c659af78eb7b ("tpm: Check size of response before accessing data")
> Signed-off-by: Jarkko Sakkinen <[email protected]>
> ---
> drivers/char/tpm/tpm-interface.c | 3 ++-
> drivers/char/tpm/tpm2-cmd.c | 4 +++-
> 2 files changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/char/tpm/tpm-interface.c b/drivers/char/tpm/tpm-interface.c
> index 1a803b0cf980..318a7078b2ba 100644
> --- a/drivers/char/tpm/tpm-interface.c
> +++ b/drivers/char/tpm/tpm-interface.c
> @@ -1321,7 +1321,8 @@ int tpm_get_random(struct tpm_chip *chip, u8 *out, size_t max)
> }
>
> rlength = be32_to_cpu(tpm_cmd.header.out.length);
> - if (rlength < offsetof(struct tpm_getrandom_out, rng_data) +
> + if (rlength < TPM_HEADER_SIZE +
> + offsetof(struct tpm_getrandom_out, rng_data) +
> recd) {
> total = -EFAULT;
> break;
> diff --git a/drivers/char/tpm/tpm2-cmd.c b/drivers/char/tpm/tpm2-cmd.c
> index c31b490bd41d..3acf4fd4e5a5 100644
> --- a/drivers/char/tpm/tpm2-cmd.c
> +++ b/drivers/char/tpm/tpm2-cmd.c
> @@ -329,7 +329,9 @@ int tpm2_get_random(struct tpm_chip *chip, u8 *dest, size_t max)
> &buf.data[TPM_HEADER_SIZE];
> recd = min_t(u32, be16_to_cpu(out->size), num_bytes);
> if (tpm_buf_length(&buf) <
> - offsetof(struct tpm2_get_random_out, buffer) + recd) {
> + TPM_HEADER_SIZE +
> + offsetof(struct tpm2_get_random_out, buffer) +
> + recd) {
> err = -EFAULT;
> goto out;
> }

Reviewed-by: Stefan Berger <[email protected]>