drivers/char/tpm/tpm2-sessions.c | 20 ++++++-------------- include/linux/tpm.h | 21 +++++++++++++++++++++ 2 files changed, 27 insertions(+), 14 deletions(-)
tpm2_start_auth_session() does not mask TPM RC correctly from the callers:
[ 28.766528] tpm tpm0: A TPM error (2307) occurred start auth session
Process TPM RCs inside tpm2_start_auth_session(), and map them to POSIX
error codes.
Cc: stable@vger.kernel.org # v6.10+
Fixes: 699e3efd6c64 ("tpm: Add HMAC session start and end functions")
Reported-by: Herbert Xu <herbert@gondor.apana.org.au>
Closes: https://lore.kernel.org/linux-integrity/Z_NgdRHuTKP6JK--@gondor.apana.org.au/
Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
---
v4:
- tpm_to_ret()
v3:
- rc > 0
v2:
- Investigate TPM rc only after destroying tpm_buf.
---
drivers/char/tpm/tpm2-sessions.c | 20 ++++++--------------
include/linux/tpm.h | 21 +++++++++++++++++++++
2 files changed, 27 insertions(+), 14 deletions(-)
diff --git a/drivers/char/tpm/tpm2-sessions.c b/drivers/char/tpm/tpm2-sessions.c
index 3f89635ba5e8..102e099f22c1 100644
--- a/drivers/char/tpm/tpm2-sessions.c
+++ b/drivers/char/tpm/tpm2-sessions.c
@@ -40,11 +40,6 @@
*
* These are the usage functions:
*
- * tpm2_start_auth_session() which allocates the opaque auth structure
- * and gets a session from the TPM. This must be called before
- * any of the following functions. The session is protected by a
- * session_key which is derived from a random salt value
- * encrypted to the NULL seed.
* tpm2_end_auth_session() kills the session and frees the resources.
* Under normal operation this function is done by
* tpm_buf_check_hmac_response(), so this is only to be used on
@@ -963,16 +958,13 @@ static int tpm2_load_null(struct tpm_chip *chip, u32 *null_key)
}
/**
- * tpm2_start_auth_session() - create a HMAC authentication session with the TPM
- * @chip: the TPM chip structure to create the session with
+ * tpm2_start_auth_session() - Create an a HMAC authentication session
+ * @chip: A TPM chip
*
- * This function loads the NULL seed from its saved context and starts
- * an authentication session on the null seed, fills in the
- * @chip->auth structure to contain all the session details necessary
- * for performing the HMAC, encrypt and decrypt operations and
- * returns. The NULL seed is flushed before this function returns.
+ * Loads the ephemeral key (null seed), and starts an HMAC authenticated
+ * session. The null seed is flushed before the return.
*
- * Return: zero on success or actual error encountered.
+ * Returns zero on success, or a POSIX error code.
*/
int tpm2_start_auth_session(struct tpm_chip *chip)
{
@@ -1024,7 +1016,7 @@ int tpm2_start_auth_session(struct tpm_chip *chip)
/* hash algorithm for session */
tpm_buf_append_u16(&buf, TPM_ALG_SHA256);
- rc = tpm_transmit_cmd(chip, &buf, 0, "start auth session");
+ rc = tpm_to_ret(tpm_transmit_cmd(chip, &buf, 0, "StartAuthSession"));
tpm2_flush_context(chip, null_key);
if (rc == TPM2_RC_SUCCESS)
diff --git a/include/linux/tpm.h b/include/linux/tpm.h
index 6c3125300c00..c826d5a9d894 100644
--- a/include/linux/tpm.h
+++ b/include/linux/tpm.h
@@ -257,8 +257,29 @@ enum tpm2_return_codes {
TPM2_RC_TESTING = 0x090A, /* RC_WARN */
TPM2_RC_REFERENCE_H0 = 0x0910,
TPM2_RC_RETRY = 0x0922,
+ TPM2_RC_SESSION_MEMORY = 0x0903,
};
+/*
+ * Convert a return value from tpm_transmit_cmd() to a POSIX return value. The
+ * fallback return value is -EFAULT.
+ */
+static inline ssize_t tpm_to_ret(ssize_t ret)
+{
+ /* Already a POSIX error: */
+ if (ret < 0)
+ return ret;
+
+ switch (ret) {
+ case TPM2_RC_SUCCESS:
+ return 0;
+ case TPM2_RC_SESSION_MEMORY:
+ return -ENOMEM;
+ default:
+ return -EFAULT;
+ }
+}
+
enum tpm2_command_codes {
TPM2_CC_FIRST = 0x011F,
TPM2_CC_HIERARCHY_CONTROL = 0x0121,
--
2.39.5On Mon, Apr 07, 2025 at 03:28:05PM +0300, Jarkko Sakkinen wrote:
>tpm2_start_auth_session() does not mask TPM RC correctly from the callers:
>
>[ 28.766528] tpm tpm0: A TPM error (2307) occurred start auth session
>
>Process TPM RCs inside tpm2_start_auth_session(), and map them to POSIX
>error codes.
>
>Cc: stable@vger.kernel.org # v6.10+
>Fixes: 699e3efd6c64 ("tpm: Add HMAC session start and end functions")
>Reported-by: Herbert Xu <herbert@gondor.apana.org.au>
>Closes: https://lore.kernel.org/linux-integrity/Z_NgdRHuTKP6JK--@gondor.apana.org.au/
>Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
>---
>v4:
>- tpm_to_ret()
>v3:
>- rc > 0
>v2:
>- Investigate TPM rc only after destroying tpm_buf.
>---
> drivers/char/tpm/tpm2-sessions.c | 20 ++++++--------------
> include/linux/tpm.h | 21 +++++++++++++++++++++
> 2 files changed, 27 insertions(+), 14 deletions(-)
>
>diff --git a/drivers/char/tpm/tpm2-sessions.c b/drivers/char/tpm/tpm2-sessions.c
>index 3f89635ba5e8..102e099f22c1 100644
>--- a/drivers/char/tpm/tpm2-sessions.c
>+++ b/drivers/char/tpm/tpm2-sessions.c
>@@ -40,11 +40,6 @@
> *
> * These are the usage functions:
> *
>- * tpm2_start_auth_session() which allocates the opaque auth structure
>- * and gets a session from the TPM. This must be called before
>- * any of the following functions. The session is protected by a
>- * session_key which is derived from a random salt value
>- * encrypted to the NULL seed.
> * tpm2_end_auth_session() kills the session and frees the resources.
> * Under normal operation this function is done by
> * tpm_buf_check_hmac_response(), so this is only to be used on
>@@ -963,16 +958,13 @@ static int tpm2_load_null(struct tpm_chip *chip, u32 *null_key)
> }
>
> /**
>- * tpm2_start_auth_session() - create a HMAC authentication session with the TPM
>- * @chip: the TPM chip structure to create the session with
>+ * tpm2_start_auth_session() - Create an a HMAC authentication session
>+ * @chip: A TPM chip
> *
>- * This function loads the NULL seed from its saved context and starts
>- * an authentication session on the null seed, fills in the
>- * @chip->auth structure to contain all the session details necessary
>- * for performing the HMAC, encrypt and decrypt operations and
>- * returns. The NULL seed is flushed before this function returns.
>+ * Loads the ephemeral key (null seed), and starts an HMAC authenticated
>+ * session. The null seed is flushed before the return.
> *
>- * Return: zero on success or actual error encountered.
>+ * Returns zero on success, or a POSIX error code.
> */
> int tpm2_start_auth_session(struct tpm_chip *chip)
> {
>@@ -1024,7 +1016,7 @@ int tpm2_start_auth_session(struct tpm_chip *chip)
> /* hash algorithm for session */
> tpm_buf_append_u16(&buf, TPM_ALG_SHA256);
>
>- rc = tpm_transmit_cmd(chip, &buf, 0, "start auth session");
>+ rc = tpm_to_ret(tpm_transmit_cmd(chip, &buf, 0, "StartAuthSession"));
> tpm2_flush_context(chip, null_key);
>
> if (rc == TPM2_RC_SUCCESS)
>diff --git a/include/linux/tpm.h b/include/linux/tpm.h
>index 6c3125300c00..c826d5a9d894 100644
>--- a/include/linux/tpm.h
>+++ b/include/linux/tpm.h
>@@ -257,8 +257,29 @@ enum tpm2_return_codes {
> TPM2_RC_TESTING = 0x090A, /* RC_WARN */
> TPM2_RC_REFERENCE_H0 = 0x0910,
> TPM2_RC_RETRY = 0x0922,
>+ TPM2_RC_SESSION_MEMORY = 0x0903,
nit: the other values are in ascending order, should we keep it or is it
not important?
(more a question for me than for the patch)
> };
>
>+/*
>+ * Convert a return value from tpm_transmit_cmd() to a POSIX return value. The
>+ * fallback return value is -EFAULT.
>+ */
>+static inline ssize_t tpm_to_ret(ssize_t ret)
>+{
>+ /* Already a POSIX error: */
>+ if (ret < 0)
>+ return ret;
>+
>+ switch (ret) {
>+ case TPM2_RC_SUCCESS:
>+ return 0;
>+ case TPM2_RC_SESSION_MEMORY:
>+ return -ENOMEM;
>+ default:
>+ return -EFAULT;
>+ }
>+}
I like this and in the future we could reuse it in different places like
tpm2_load_context() and tpm2_save_context().
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
BTW for my understading, looking at that code (sorry if the answer is
obvious, but I'm learning) I'm confused about the use of
tpm2_rc_value().
For example in tpm2_load_context() we have:
rc = tpm_transmit_cmd(chip, &tbuf, 4, NULL);
...
} else if (tpm2_rc_value(rc) == TPM2_RC_HANDLE ||
rc == TPM2_RC_REFERENCE_H0) {
While in tpm2_save_context(), we have:
rc = tpm_transmit_cmd(chip, &tbuf, 0, NULL);
...
} else if (tpm2_rc_value(rc) == TPM2_RC_REFERENCE_H0) {
So to check TPM2_RC_REFERENCE_H0 we are using tpm2_rc_value() only
sometimes, what's the reason?
Thanks,
Stefano
On Mon, Apr 07, 2025 at 03:51:21PM +0200, Stefano Garzarella wrote:
> On Mon, Apr 07, 2025 at 03:28:05PM +0300, Jarkko Sakkinen wrote:
> > tpm2_start_auth_session() does not mask TPM RC correctly from the callers:
> >
> > [ 28.766528] tpm tpm0: A TPM error (2307) occurred start auth session
> >
> > Process TPM RCs inside tpm2_start_auth_session(), and map them to POSIX
> > error codes.
> >
> > Cc: stable@vger.kernel.org # v6.10+
> > Fixes: 699e3efd6c64 ("tpm: Add HMAC session start and end functions")
> > Reported-by: Herbert Xu <herbert@gondor.apana.org.au>
> > Closes: https://lore.kernel.org/linux-integrity/Z_NgdRHuTKP6JK--@gondor.apana.org.au/
> > Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
> > ---
> > v4:
> > - tpm_to_ret()
> > v3:
> > - rc > 0
> > v2:
> > - Investigate TPM rc only after destroying tpm_buf.
> > ---
> > drivers/char/tpm/tpm2-sessions.c | 20 ++++++--------------
> > include/linux/tpm.h | 21 +++++++++++++++++++++
> > 2 files changed, 27 insertions(+), 14 deletions(-)
> >
> > diff --git a/drivers/char/tpm/tpm2-sessions.c b/drivers/char/tpm/tpm2-sessions.c
> > index 3f89635ba5e8..102e099f22c1 100644
> > --- a/drivers/char/tpm/tpm2-sessions.c
> > +++ b/drivers/char/tpm/tpm2-sessions.c
> > @@ -40,11 +40,6 @@
> > *
> > * These are the usage functions:
> > *
> > - * tpm2_start_auth_session() which allocates the opaque auth structure
> > - * and gets a session from the TPM. This must be called before
> > - * any of the following functions. The session is protected by a
> > - * session_key which is derived from a random salt value
> > - * encrypted to the NULL seed.
> > * tpm2_end_auth_session() kills the session and frees the resources.
> > * Under normal operation this function is done by
> > * tpm_buf_check_hmac_response(), so this is only to be used on
> > @@ -963,16 +958,13 @@ static int tpm2_load_null(struct tpm_chip *chip, u32 *null_key)
> > }
> >
> > /**
> > - * tpm2_start_auth_session() - create a HMAC authentication session with the TPM
> > - * @chip: the TPM chip structure to create the session with
> > + * tpm2_start_auth_session() - Create an a HMAC authentication session
> > + * @chip: A TPM chip
> > *
> > - * This function loads the NULL seed from its saved context and starts
> > - * an authentication session on the null seed, fills in the
> > - * @chip->auth structure to contain all the session details necessary
> > - * for performing the HMAC, encrypt and decrypt operations and
> > - * returns. The NULL seed is flushed before this function returns.
> > + * Loads the ephemeral key (null seed), and starts an HMAC authenticated
> > + * session. The null seed is flushed before the return.
> > *
> > - * Return: zero on success or actual error encountered.
> > + * Returns zero on success, or a POSIX error code.
> > */
> > int tpm2_start_auth_session(struct tpm_chip *chip)
> > {
> > @@ -1024,7 +1016,7 @@ int tpm2_start_auth_session(struct tpm_chip *chip)
> > /* hash algorithm for session */
> > tpm_buf_append_u16(&buf, TPM_ALG_SHA256);
> >
> > - rc = tpm_transmit_cmd(chip, &buf, 0, "start auth session");
> > + rc = tpm_to_ret(tpm_transmit_cmd(chip, &buf, 0, "StartAuthSession"));
> > tpm2_flush_context(chip, null_key);
> >
> > if (rc == TPM2_RC_SUCCESS)
> > diff --git a/include/linux/tpm.h b/include/linux/tpm.h
> > index 6c3125300c00..c826d5a9d894 100644
> > --- a/include/linux/tpm.h
> > +++ b/include/linux/tpm.h
> > @@ -257,8 +257,29 @@ enum tpm2_return_codes {
> > TPM2_RC_TESTING = 0x090A, /* RC_WARN */
> > TPM2_RC_REFERENCE_H0 = 0x0910,
> > TPM2_RC_RETRY = 0x0922,
> > + TPM2_RC_SESSION_MEMORY = 0x0903,
>
> nit: the other values are in ascending order, should we keep it or is it not
> important?
>
> (more a question for me than for the patch)
nope
>
> > };
> >
> > +/*
> > + * Convert a return value from tpm_transmit_cmd() to a POSIX return value. The
> > + * fallback return value is -EFAULT.
> > + */
> > +static inline ssize_t tpm_to_ret(ssize_t ret)
> > +{
> > + /* Already a POSIX error: */
> > + if (ret < 0)
> > + return ret;
> > +
> > + switch (ret) {
> > + case TPM2_RC_SUCCESS:
> > + return 0;
> > + case TPM2_RC_SESSION_MEMORY:
> > + return -ENOMEM;
> > + default:
> > + return -EFAULT;
> > + }
> > +}
>
> I like this and in the future we could reuse it in different places like
> tpm2_load_context() and tpm2_save_context().
>
> Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
>
>
> BTW for my understading, looking at that code (sorry if the answer is
> obvious, but I'm learning) I'm confused about the use of tpm2_rc_value().
>
> For example in tpm2_load_context() we have:
>
> rc = tpm_transmit_cmd(chip, &tbuf, 4, NULL);
> ...
> } else if (tpm2_rc_value(rc) == TPM2_RC_HANDLE ||
> rc == TPM2_RC_REFERENCE_H0) {
>
> While in tpm2_save_context(), we have:
>
> rc = tpm_transmit_cmd(chip, &tbuf, 0, NULL);
> ...
> } else if (tpm2_rc_value(rc) == TPM2_RC_REFERENCE_H0) {
>
> So to check TPM2_RC_REFERENCE_H0 we are using tpm2_rc_value() only
> sometimes, what's the reason?
Good catch, I'll update...
TPM RC is a struct or bitfield.
>
> Thanks,
> Stefano
>
>
BR, Jarkko
On Mon, Apr 07, 2025 at 09:13:37PM +0300, Jarkko Sakkinen wrote:
> On Mon, Apr 07, 2025 at 03:51:21PM +0200, Stefano Garzarella wrote:
> > On Mon, Apr 07, 2025 at 03:28:05PM +0300, Jarkko Sakkinen wrote:
> > > tpm2_start_auth_session() does not mask TPM RC correctly from the callers:
> > >
> > > [ 28.766528] tpm tpm0: A TPM error (2307) occurred start auth session
> > >
> > > Process TPM RCs inside tpm2_start_auth_session(), and map them to POSIX
> > > error codes.
> > >
> > > Cc: stable@vger.kernel.org # v6.10+
> > > Fixes: 699e3efd6c64 ("tpm: Add HMAC session start and end functions")
> > > Reported-by: Herbert Xu <herbert@gondor.apana.org.au>
> > > Closes: https://lore.kernel.org/linux-integrity/Z_NgdRHuTKP6JK--@gondor.apana.org.au/
> > > Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
> > > ---
> > > v4:
> > > - tpm_to_ret()
> > > v3:
> > > - rc > 0
> > > v2:
> > > - Investigate TPM rc only after destroying tpm_buf.
> > > ---
> > > drivers/char/tpm/tpm2-sessions.c | 20 ++++++--------------
> > > include/linux/tpm.h | 21 +++++++++++++++++++++
> > > 2 files changed, 27 insertions(+), 14 deletions(-)
> > >
> > > diff --git a/drivers/char/tpm/tpm2-sessions.c b/drivers/char/tpm/tpm2-sessions.c
> > > index 3f89635ba5e8..102e099f22c1 100644
> > > --- a/drivers/char/tpm/tpm2-sessions.c
> > > +++ b/drivers/char/tpm/tpm2-sessions.c
> > > @@ -40,11 +40,6 @@
> > > *
> > > * These are the usage functions:
> > > *
> > > - * tpm2_start_auth_session() which allocates the opaque auth structure
> > > - * and gets a session from the TPM. This must be called before
> > > - * any of the following functions. The session is protected by a
> > > - * session_key which is derived from a random salt value
> > > - * encrypted to the NULL seed.
> > > * tpm2_end_auth_session() kills the session and frees the resources.
> > > * Under normal operation this function is done by
> > > * tpm_buf_check_hmac_response(), so this is only to be used on
> > > @@ -963,16 +958,13 @@ static int tpm2_load_null(struct tpm_chip *chip, u32 *null_key)
> > > }
> > >
> > > /**
> > > - * tpm2_start_auth_session() - create a HMAC authentication session with the TPM
> > > - * @chip: the TPM chip structure to create the session with
> > > + * tpm2_start_auth_session() - Create an a HMAC authentication session
> > > + * @chip: A TPM chip
> > > *
> > > - * This function loads the NULL seed from its saved context and starts
> > > - * an authentication session on the null seed, fills in the
> > > - * @chip->auth structure to contain all the session details necessary
> > > - * for performing the HMAC, encrypt and decrypt operations and
> > > - * returns. The NULL seed is flushed before this function returns.
> > > + * Loads the ephemeral key (null seed), and starts an HMAC authenticated
> > > + * session. The null seed is flushed before the return.
> > > *
> > > - * Return: zero on success or actual error encountered.
> > > + * Returns zero on success, or a POSIX error code.
> > > */
> > > int tpm2_start_auth_session(struct tpm_chip *chip)
> > > {
> > > @@ -1024,7 +1016,7 @@ int tpm2_start_auth_session(struct tpm_chip *chip)
> > > /* hash algorithm for session */
> > > tpm_buf_append_u16(&buf, TPM_ALG_SHA256);
> > >
> > > - rc = tpm_transmit_cmd(chip, &buf, 0, "start auth session");
> > > + rc = tpm_to_ret(tpm_transmit_cmd(chip, &buf, 0, "StartAuthSession"));
> > > tpm2_flush_context(chip, null_key);
> > >
> > > if (rc == TPM2_RC_SUCCESS)
> > > diff --git a/include/linux/tpm.h b/include/linux/tpm.h
> > > index 6c3125300c00..c826d5a9d894 100644
> > > --- a/include/linux/tpm.h
> > > +++ b/include/linux/tpm.h
> > > @@ -257,8 +257,29 @@ enum tpm2_return_codes {
> > > TPM2_RC_TESTING = 0x090A, /* RC_WARN */
> > > TPM2_RC_REFERENCE_H0 = 0x0910,
> > > TPM2_RC_RETRY = 0x0922,
> > > + TPM2_RC_SESSION_MEMORY = 0x0903,
> >
> > nit: the other values are in ascending order, should we keep it or is it not
> > important?
> >
> > (more a question for me than for the patch)
>
> nope
>
> >
> > > };
> > >
> > > +/*
> > > + * Convert a return value from tpm_transmit_cmd() to a POSIX return value. The
> > > + * fallback return value is -EFAULT.
> > > + */
> > > +static inline ssize_t tpm_to_ret(ssize_t ret)
> > > +{
> > > + /* Already a POSIX error: */
> > > + if (ret < 0)
> > > + return ret;
> > > +
> > > + switch (ret) {
> > > + case TPM2_RC_SUCCESS:
> > > + return 0;
> > > + case TPM2_RC_SESSION_MEMORY:
> > > + return -ENOMEM;
> > > + default:
> > > + return -EFAULT;
> > > + }
> > > +}
> >
> > I like this and in the future we could reuse it in different places like
> > tpm2_load_context() and tpm2_save_context().
> >
> > Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
> >
> >
> > BTW for my understading, looking at that code (sorry if the answer is
> > obvious, but I'm learning) I'm confused about the use of tpm2_rc_value().
> >
> > For example in tpm2_load_context() we have:
> >
> > rc = tpm_transmit_cmd(chip, &tbuf, 4, NULL);
> > ...
> > } else if (tpm2_rc_value(rc) == TPM2_RC_HANDLE ||
> > rc == TPM2_RC_REFERENCE_H0) {
> >
> > While in tpm2_save_context(), we have:
> >
> > rc = tpm_transmit_cmd(chip, &tbuf, 0, NULL);
> > ...
> > } else if (tpm2_rc_value(rc) == TPM2_RC_REFERENCE_H0) {
> >
> > So to check TPM2_RC_REFERENCE_H0 we are using tpm2_rc_value() only
> > sometimes, what's the reason?
>
> Good catch, I'll update...
>
> TPM RC is a struct or bitfield.
Applied to my -next: https://web.git.kernel.org/pub/scm/linux/kernel/git/jarkko/linux-tpmdd.git/log/?h=next
BR, Jarkko
On Mon, Apr 07, 2025 at 03:28:05PM +0300, Jarkko Sakkinen wrote:
> tpm2_start_auth_session() does not mask TPM RC correctly from the callers:
>
> [ 28.766528] tpm tpm0: A TPM error (2307) occurred start auth session
>
> Process TPM RCs inside tpm2_start_auth_session(), and map them to POSIX
> error codes.
>
> Cc: stable@vger.kernel.org # v6.10+
> Fixes: 699e3efd6c64 ("tpm: Add HMAC session start and end functions")
> Reported-by: Herbert Xu <herbert@gondor.apana.org.au>
> Closes: https://lore.kernel.org/linux-integrity/Z_NgdRHuTKP6JK--@gondor.apana.org.au/
> Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
> ---
> v4:
> - tpm_to_ret()
> v3:
> - rc > 0
> v2:
> - Investigate TPM rc only after destroying tpm_buf.
> ---
> drivers/char/tpm/tpm2-sessions.c | 20 ++++++--------------
> include/linux/tpm.h | 21 +++++++++++++++++++++
> 2 files changed, 27 insertions(+), 14 deletions(-)
>
> diff --git a/drivers/char/tpm/tpm2-sessions.c b/drivers/char/tpm/tpm2-sessions.c
> index 3f89635ba5e8..102e099f22c1 100644
> --- a/drivers/char/tpm/tpm2-sessions.c
> +++ b/drivers/char/tpm/tpm2-sessions.c
> @@ -40,11 +40,6 @@
> *
> * These are the usage functions:
> *
> - * tpm2_start_auth_session() which allocates the opaque auth structure
> - * and gets a session from the TPM. This must be called before
> - * any of the following functions. The session is protected by a
> - * session_key which is derived from a random salt value
> - * encrypted to the NULL seed.
> * tpm2_end_auth_session() kills the session and frees the resources.
> * Under normal operation this function is done by
> * tpm_buf_check_hmac_response(), so this is only to be used on
> @@ -963,16 +958,13 @@ static int tpm2_load_null(struct tpm_chip *chip, u32 *null_key)
> }
>
> /**
> - * tpm2_start_auth_session() - create a HMAC authentication session with the TPM
> - * @chip: the TPM chip structure to create the session with
> + * tpm2_start_auth_session() - Create an a HMAC authentication session
> + * @chip: A TPM chip
> *
> - * This function loads the NULL seed from its saved context and starts
> - * an authentication session on the null seed, fills in the
> - * @chip->auth structure to contain all the session details necessary
> - * for performing the HMAC, encrypt and decrypt operations and
> - * returns. The NULL seed is flushed before this function returns.
> + * Loads the ephemeral key (null seed), and starts an HMAC authenticated
> + * session. The null seed is flushed before the return.
> *
> - * Return: zero on success or actual error encountered.
> + * Returns zero on success, or a POSIX error code.
> */
> int tpm2_start_auth_session(struct tpm_chip *chip)
> {
> @@ -1024,7 +1016,7 @@ int tpm2_start_auth_session(struct tpm_chip *chip)
> /* hash algorithm for session */
> tpm_buf_append_u16(&buf, TPM_ALG_SHA256);
>
> - rc = tpm_transmit_cmd(chip, &buf, 0, "start auth session");
> + rc = tpm_to_ret(tpm_transmit_cmd(chip, &buf, 0, "StartAuthSession"));
The cool thing here is that e.g., in the case of
tpm2_start_auth_session, there is two implementation options:
1. tpm_to_ret(tpm2_start_auth_session)
2. tpm_to_ret(tpm_transmit_cmd)
Just want to expose this choice..
> tpm2_flush_context(chip, null_key);
>
> if (rc == TPM2_RC_SUCCESS)
> diff --git a/include/linux/tpm.h b/include/linux/tpm.h
> index 6c3125300c00..c826d5a9d894 100644
> --- a/include/linux/tpm.h
> +++ b/include/linux/tpm.h
> @@ -257,8 +257,29 @@ enum tpm2_return_codes {
> TPM2_RC_TESTING = 0x090A, /* RC_WARN */
> TPM2_RC_REFERENCE_H0 = 0x0910,
> TPM2_RC_RETRY = 0x0922,
> + TPM2_RC_SESSION_MEMORY = 0x0903,
> };
>
> +/*
> + * Convert a return value from tpm_transmit_cmd() to a POSIX return value. The
> + * fallback return value is -EFAULT.
> + */
> +static inline ssize_t tpm_to_ret(ssize_t ret)
> +{
> + /* Already a POSIX error: */
> + if (ret < 0)
> + return ret;
> +
> + switch (ret) {
> + case TPM2_RC_SUCCESS:
> + return 0;
> + case TPM2_RC_SESSION_MEMORY:
> + return -ENOMEM;
> + default:
> + return -EFAULT;
> + }
> +}
> +
> enum tpm2_command_codes {
> TPM2_CC_FIRST = 0x011F,
> TPM2_CC_HIERARCHY_CONTROL = 0x0121,
> --
> 2.39.5
>
BR, Jarkko
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