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Message-Id: <3b83ee0e-a20f-3a96-6f25-9c7a2aa68fbd@linux.vnet.ibm.com>
Date: Mon, 22 May 2017 10:29:24 -0400
From: Stefan Berger <stefanb@...ux.vnet.ibm.com>
To: Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
Cc: tpmdd-devel@...ts.sourceforge.net,
linux-security-module@...r.kernel.org,
jgunthorpe@...idianresearch.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 2/2] tpm: vtpm_proxy: Implement request_locality
function.
On 05/20/2017 08:40 AM, Jarkko Sakkinen wrote:
> On Mon, May 15, 2017 at 12:51:45PM -0400, Stefan Berger wrote:
>> Implement the request_locality function. To set the locality on the
>> backend we define vendor-specific TPM 1.2 and TPM 2 ordinals and send
>> a command to the backend to set the locality for the next commands.
>>
>> To avoid recursing into requesting the locality, we set the
>> TPM_TRASNMIT_RAW flag when calling tpm_trasnmit_cmd. To avoid recursing
>> into TPM 2 space related commands, we set the space parameter to NULL.
>>
>> Signed-off-by: Stefan Berger <stefanb@...ux.vnet.ibm.com>
>> ---
>> drivers/char/tpm/tpm-interface.c | 1 +
>> drivers/char/tpm/tpm_vtpm_proxy.c | 36 ++++++++++++++++++++++++++++++++++++
>> include/uapi/linux/vtpm_proxy.h | 4 ++++
>> 3 files changed, 41 insertions(+)
>>
>> diff --git a/drivers/char/tpm/tpm-interface.c b/drivers/char/tpm/tpm-interface.c
>> index 2eacda2..876d45f 100644
>> --- a/drivers/char/tpm/tpm-interface.c
>> +++ b/drivers/char/tpm/tpm-interface.c
>> @@ -537,6 +537,7 @@ ssize_t tpm_transmit_cmd(struct tpm_chip *chip, struct tpm_space *space,
>>
>> return 0;
>> }
>> +EXPORT_SYMBOL_GPL(tpm_transmit_cmd);
>>
>> #define TPM_DIGEST_SIZE 20
>> #define TPM_RET_CODE_IDX 6
>> diff --git a/drivers/char/tpm/tpm_vtpm_proxy.c b/drivers/char/tpm/tpm_vtpm_proxy.c
>> index 751059d..66024bf 100644
>> --- a/drivers/char/tpm/tpm_vtpm_proxy.c
>> +++ b/drivers/char/tpm/tpm_vtpm_proxy.c
>> @@ -371,6 +371,41 @@ static bool vtpm_proxy_tpm_req_canceled(struct tpm_chip *chip, u8 status)
>> return ret;
>> }
>>
>> +static int vtpm_proxy_request_locality(struct tpm_chip *chip, int locality)
>> +{
>> + struct tpm_buf buf;
>> + int rc;
>> + const struct tpm_output_header *header;
>> +
>> + if (chip->flags & TPM_CHIP_FLAG_TPM2)
>> + rc = tpm_buf_init(&buf, TPM2_ST_SESSIONS,
>> + TPM2_CC_SET_LOCALITY);
>> + else
>> + rc = tpm_buf_init(&buf, TPM_TAG_RQU_COMMAND,
>> + TPM_ORD_SET_LOCALITY);
>> + if (rc)
>> + return rc;
>> + tpm_buf_append_u8(&buf, locality);
>> +
>> + rc = tpm_transmit_cmd(chip, NULL, buf.data, tpm_buf_length(&buf), 0,
>> + TPM_TRANSMIT_UNLOCKED | TPM_TRANSMIT_RAW,
>> + "attempting to set locality");
>> + if (rc < 0) {
>> + locality = rc;
>> + goto out;
>> + }
>> +
>> + header = (const struct tpm_output_header *)buf.data;
>> + rc = be32_to_cpu(header->return_code);
>> + if (rc)
>> + locality = -1;
>> +
>> +out:
>> + tpm_buf_destroy(&buf);
>> +
>> + return locality;
>> +}
>> +
> This looks good.
>
>> static const struct tpm_class_ops vtpm_proxy_tpm_ops = {
>> .flags = TPM_OPS_AUTO_STARTUP,
>> .recv = vtpm_proxy_tpm_op_recv,
>> @@ -380,6 +415,7 @@ static const struct tpm_class_ops vtpm_proxy_tpm_ops = {
>> .req_complete_mask = VTPM_PROXY_REQ_COMPLETE_FLAG,
>> .req_complete_val = VTPM_PROXY_REQ_COMPLETE_FLAG,
>> .req_canceled = vtpm_proxy_tpm_req_canceled,
>> + .request_locality = vtpm_proxy_request_locality,
>> };
>>
>> /*
>> diff --git a/include/uapi/linux/vtpm_proxy.h b/include/uapi/linux/vtpm_proxy.h
>> index a69e991..58ac73c 100644
>> --- a/include/uapi/linux/vtpm_proxy.h
>> +++ b/include/uapi/linux/vtpm_proxy.h
>> @@ -46,4 +46,8 @@ struct vtpm_proxy_new_dev {
>>
>> #define VTPM_PROXY_IOC_NEW_DEV _IOWR(0xa1, 0x00, struct vtpm_proxy_new_dev)
>>
>> +/* vendor specific commands to set locality */
>> +#define TPM2_CC_SET_LOCALITY 0x20001000
>> +#define TPM_ORD_SET_LOCALITY 0x20001000
>> +
> Maybe we should just have VTPM_CC_SET_LOCALITY? No reason to have TPM
> version specific constant names. I wonder what would be the best range
> for these CCs. Maybe 0xF0xxxxxxxx would be better?
I am not sure about that.
>
> These are not changes that require a new patch set version but we they
> need to be discussed before merging these changes.
Unfortunately there is one more patch needed. We now need to restrict
that this particular driver command can only be sent from inside the
driver and never via any of the TPM devices (/dev/vtpm%d or
/dev/tpmrm%d). That patch could then either return an error code if
tried or return an error message. In the case of the TPM 2 spaces
commands an error code is returned if a command isn't known. We could
just do that instead of returning a full TPM error message. Here's the
patch that would do that.
To prevent userspace from sending the TPM driver command to set
the locality, we need to check every command that is sent from
user space. To distinguish user space commands from internally
sent commands we introduce an additional state flag
STATE_DRIVER_COMMAND that is set while the driver sends this
command. Similar to the TPM 2 space commands we return an error
code when this command is detected.
Signed-off-by: Stefan Berger <stefanb@...ux.vnet.ibm.com>
---
drivers/char/tpm/tpm_vtpm_proxy.c | 33 +++++++++++++++++++++++++++++++++
1 file changed, 33 insertions(+)
diff --git a/drivers/char/tpm/tpm_vtpm_proxy.c
b/drivers/char/tpm/tpm_vtpm_proxy.c
index 66024bf..d25c361 100644
--- a/drivers/char/tpm/tpm_vtpm_proxy.c
+++ b/drivers/char/tpm/tpm_vtpm_proxy.c
@@ -43,6 +43,7 @@ struct proxy_dev {
#define STATE_OPENED_FLAG BIT(0)
#define STATE_WAIT_RESPONSE_FLAG BIT(1) /* waiting for emulator
response */
#define STATE_REGISTERED_FLAG BIT(2)
+#define STATE_DRIVER_COMMAND BIT(3) /* sending a driver specific
command */
size_t req_len; /* length of queued TPM request */
size_t resp_len; /* length of queued TPM response */
@@ -299,6 +300,28 @@ static int vtpm_proxy_tpm_op_recv(struct tpm_chip
*chip, u8 *buf, size_t count)
return len;
}
+static int vtpm_proxy_is_driver_command(struct tpm_chip *chip,
+ u8 *buf, size_t count)
+{
+ struct tpm_input_header *hdr = (struct tpm_input_header*)buf;
+
+ if (count < sizeof(struct tpm_input_header))
+ return 0;
+
+ if (chip->flags & TPM_CHIP_FLAG_TPM2) {
+ switch (be32_to_cpu(hdr->ordinal)) {
+ case TPM2_CC_SET_LOCALITY:
+ return 1;
+ }
+ } else {
+ switch (be32_to_cpu(hdr->ordinal)) {
+ case TPM_ORD_SET_LOCALITY:
+ return 1;
+ }
+ }
+ return 0;
+}
+
/*
* Called when core TPM driver forwards TPM requests to 'server side'.
*
@@ -321,6 +344,10 @@ static int vtpm_proxy_tpm_op_send(struct tpm_chip
*chip, u8 *buf, size_t count)
return -EIO;
}
+ if (!(proxy_dev->state & STATE_DRIVER_COMMAND) &&
+ vtpm_proxy_is_driver_command(chip, buf, count))
+ return -EFAULT;
+
mutex_lock(&proxy_dev->buf_lock);
if (!(proxy_dev->state & STATE_OPENED_FLAG)) {
@@ -376,6 +403,7 @@ static int vtpm_proxy_request_locality(struct
tpm_chip *chip, int locality)
struct tpm_buf buf;
int rc;
const struct tpm_output_header *header;
+ struct proxy_dev *proxy_dev = dev_get_drvdata(&chip->dev);
if (chip->flags & TPM_CHIP_FLAG_TPM2)
rc = tpm_buf_init(&buf, TPM2_ST_SESSIONS,
@@ -387,9 +415,14 @@ static int vtpm_proxy_request_locality(struct
tpm_chip *chip, int locality)
return rc;
tpm_buf_append_u8(&buf, locality);
+ proxy_dev->state |= STATE_DRIVER_COMMAND;
+
rc = tpm_transmit_cmd(chip, NULL, buf.data, tpm_buf_length(&buf), 0,
TPM_TRANSMIT_UNLOCKED | TPM_TRANSMIT_RAW,
"attempting to set locality");
+
+ proxy_dev->state &= ~STATE_DRIVER_COMMAND;
+
if (rc < 0) {
locality = rc;
goto out;
--
2.4.3
>
>> #endif /* _UAPI_LINUX_VTPM_PROXY_H */
>> --
>> 2.4.3
>>
> /Jarkko
>
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