Re: [PATCH v4 4/4] tpm: migrate tpm2_get_random() to use struct tpm_buf

From: Nayna Jain
Date: Fri May 18 2018 - 01:14:52 EST



On 03/26/2018 05:44 PM, Jarkko Sakkinen wrote:
In order to make struct tpm_buf the first class object for constructing
TPM commands, migrate tpm2_get_random() to use it. In addition, removed
remaining references to struct tpm2_cmd. All of them use it to acquire
the length of the response, which can be achieved by using
tpm_buf_length().

Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@xxxxxxxxxxxxxxx>
---
drivers/char/tpm/tpm.h | 19 ++++-----
drivers/char/tpm/tpm2-cmd.c | 98 ++++++++++++++++++---------------------------
2 files changed, 49 insertions(+), 68 deletions(-)

diff --git a/drivers/char/tpm/tpm.h b/drivers/char/tpm/tpm.h
index 7f2d0f489e9c..aa849a1b2641 100644
--- a/drivers/char/tpm/tpm.h
+++ b/drivers/char/tpm/tpm.h
@@ -421,23 +421,24 @@ struct tpm_buf {
u8 *data;
};

-static inline int tpm_buf_init(struct tpm_buf *buf, u16 tag, u32 ordinal)
+static inline void tpm_buf_reset(struct tpm_buf *buf, u16 tag, u32 ordinal)
{
struct tpm_input_header *head;
+ head = (struct tpm_input_header *)buf->data;
+ head->tag = cpu_to_be16(tag);
+ head->length = cpu_to_be32(sizeof(*head));
+ head->ordinal = cpu_to_be32(ordinal);
+}

+static inline int tpm_buf_init(struct tpm_buf *buf, u16 tag, u32 ordinal)
+{
buf->data_page = alloc_page(GFP_HIGHUSER);
if (!buf->data_page)
return -ENOMEM;

buf->flags = 0;
buf->data = kmap(buf->data_page);
-
- head = (struct tpm_input_header *) buf->data;
-
- head->tag = cpu_to_be16(tag);
- head->length = cpu_to_be32(sizeof(*head));
- head->ordinal = cpu_to_be32(ordinal);
-
+ tpm_buf_reset(buf, tag, ordinal);
return 0;
}

@@ -566,7 +567,7 @@ static inline u32 tpm2_rc_value(u32 rc)
int tpm2_pcr_read(struct tpm_chip *chip, int pcr_idx, u8 *res_buf);
int tpm2_pcr_extend(struct tpm_chip *chip, int pcr_idx, u32 count,
struct tpm2_digest *digests);
-int tpm2_get_random(struct tpm_chip *chip, u8 *out, size_t max);
+int tpm2_get_random(struct tpm_chip *chip, u8 *dest, size_t max);
void tpm2_flush_context_cmd(struct tpm_chip *chip, u32 handle,
unsigned int flags);
int tpm2_seal_trusted(struct tpm_chip *chip,
diff --git a/drivers/char/tpm/tpm2-cmd.c b/drivers/char/tpm/tpm2-cmd.c
index b3b52f9eb65f..d5c222f98515 100644
--- a/drivers/char/tpm/tpm2-cmd.c
+++ b/drivers/char/tpm/tpm2-cmd.c
@@ -27,25 +27,6 @@ enum tpm2_session_attributes {
TPM2_SA_CONTINUE_SESSION = BIT(0),
};

-struct tpm2_get_random_in {
- __be16 size;
-} __packed;
-
-struct tpm2_get_random_out {
- __be16 size;
- u8 buffer[TPM_MAX_RNG_DATA];
-} __packed;
-
-union tpm2_cmd_params {
- struct tpm2_get_random_in getrandom_in;
- struct tpm2_get_random_out getrandom_out;
-};
-
-struct tpm2_cmd {
- tpm_cmd_header header;
- union tpm2_cmd_params params;
-} __packed;
-
struct tpm2_hash {
unsigned int crypto_id;
unsigned int tpm_id;
@@ -300,67 +281,70 @@ int tpm2_pcr_extend(struct tpm_chip *chip, int pcr_idx, u32 count,
}


-#define TPM2_GETRANDOM_IN_SIZE \
- (sizeof(struct tpm_input_header) + \
- sizeof(struct tpm2_get_random_in))
-
-static const struct tpm_input_header tpm2_getrandom_header = {
- .tag = cpu_to_be16(TPM2_ST_NO_SESSIONS),
- .length = cpu_to_be32(TPM2_GETRANDOM_IN_SIZE),
- .ordinal = cpu_to_be32(TPM2_CC_GET_RANDOM)
-};
+struct tpm2_get_random_out {
+ __be16 size;
+ u8 buffer[TPM_MAX_RNG_DATA];
+} __packed;

/**
* tpm2_get_random() - get random bytes from the TPM RNG
*
* @chip: TPM chip to use
- * @out: destination buffer for the random bytes
+ * @dest: destination buffer for the random bytes
* @max: the max number of bytes to write to @out
*
* Return:
- * Size of the output buffer, or -EIO on error.
+ * size of the output buffer when the operation is successful.
+ * A negative number for system errors (errno).
*/
-int tpm2_get_random(struct tpm_chip *chip, u8 *out, size_t max)
+int tpm2_get_random(struct tpm_chip *chip, u8 *dest, size_t max)
{
- struct tpm2_cmd cmd;
- u32 recd, rlength;
- u32 num_bytes;
+ struct tpm2_get_random_out *out;
+ struct tpm_buf buf;
+ u32 recd;
+ u32 num_bytes = max;
int err;
int total = 0;
int retries = 5;
- u8 *dest = out;
-
- num_bytes = min_t(u32, max, sizeof(cmd.params.getrandom_out.buffer));
+ u8 *dest_ptr = dest;

- if (!out || !num_bytes ||
- max > sizeof(cmd.params.getrandom_out.buffer))
+ if (!num_bytes || max > TPM_MAX_RNG_DATA)
return -EINVAL;

- do {
- cmd.header.in = tpm2_getrandom_header;
- cmd.params.getrandom_in.size = cpu_to_be16(num_bytes);
+ err = tpm_buf_init(&buf, 0, 0);
+ if (err)
+ return err;

- err = tpm_transmit_cmd(chip, NULL, &cmd, sizeof(cmd),
+ do {
+ tpm_buf_reset(&buf, TPM2_ST_NO_SESSIONS, TPM2_CC_GET_RANDOM);
+ tpm_buf_append_u16(&buf, num_bytes);
+ err = tpm_transmit_cmd(chip, NULL, buf.data, PAGE_SIZE,
offsetof(struct tpm2_get_random_out,
buffer),
0, "attempting get random");
if (err)
- break;
+ goto out;

- recd = min_t(u32, be16_to_cpu(cmd.params.getrandom_out.size),
- num_bytes);
- rlength = be32_to_cpu(cmd.header.out.length);
- if (rlength < offsetof(struct tpm2_get_random_out, buffer) +
- recd)
- return -EFAULT;
- memcpy(dest, cmd.params.getrandom_out.buffer, recd);
+ out = (struct tpm2_get_random_out *)
+ &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) {
+ err = -EFAULT;
+ goto out;
+ }
+ memcpy(dest_ptr, out->buffer, recd);

- dest += recd;
+ dest_ptr += recd;
total += recd;
num_bytes -= recd;
} while (retries-- && total < max);

+ tpm_buf_destroy(&buf);
return total ? total : -EIO;
+out:
+ tpm_buf_destroy(&buf);
+ return err;
}

How about having it as :

ÂÂÂ if (!total)
ÂÂÂ ÂÂÂ err = -EIO;
out:
ÂÂÂ tpm_buf_destroy(&buf);
ÂÂÂ return total?:err;

/**
@@ -434,7 +418,7 @@ int tpm2_seal_trusted(struct tpm_chip *chip,
{
unsigned int blob_len;
struct tpm_buf buf;
- u32 hash, rlength;
+ u32 hash;
int i;
int rc;

@@ -509,8 +493,7 @@ int tpm2_seal_trusted(struct tpm_chip *chip,
rc = -E2BIG;
goto out;
}
- rlength = be32_to_cpu(((struct tpm2_cmd *)&buf)->header.out.length);
- if (rlength < TPM_HEADER_SIZE + 4 + blob_len) {
+ if (tpm_buf_length(&buf) < TPM_HEADER_SIZE + 4 + blob_len) {
rc = -EFAULT;
goto out;
}
@@ -620,7 +603,6 @@ static int tpm2_unseal_cmd(struct tpm_chip *chip,
u16 data_len;
u8 *data;
int rc;
- u32 rlength;

rc = tpm_buf_init(&buf, TPM2_ST_SESSIONS, TPM2_CC_UNSEAL);
if (rc)
@@ -648,9 +630,7 @@ static int tpm2_unseal_cmd(struct tpm_chip *chip,
goto out;
}

- rlength = be32_to_cpu(((struct tpm2_cmd *)&buf)
- ->header.out.length);
- if (rlength < TPM_HEADER_SIZE + 6 + data_len) {
+ if (tpm_buf_length(&buf) < TPM_HEADER_SIZE + 6 + data_len) {
rc = -EFAULT;
goto out;
}
Probably, all the changes related to the use of tpm_buf_length() could be a separate patch in itself ?

Otherwise,

Tested-by: Nayna Jain<nayna@xxxxxxxxxxxxxxxxxx>

Thanks & Regards,
- Nayna