On Fri, Nov 11, 2022 at 03:16:33PM -0800, Evan Green wrote:
> We'll also go through the motions of having PCR23 set to a known value at
> the time of key creation and unsealing. Currently there's nothing that
> enforces the contents of PCR23 as a condition to unseal the key blob,
> that will come in a later change.
This patch doesn't really make sense without the later patch
"PM: hibernate: seal the encryption key with a PCR policy".
Maybe they should be merged into one patch?
> +/* sha256("To sleep, perchance to dream") */
> +static struct tpm_digest known_digest = { .alg_id = TPM_ALG_SHA256,
> + .digest = {0x92, 0x78, 0x3d, 0x79, 0x2d, 0x00, 0x31, 0xb0, 0x55, 0xf9,
> + 0x1e, 0x0d, 0xce, 0x83, 0xde, 0x1d, 0xc4, 0xc5, 0x8e, 0x8c,
> + 0xf1, 0x22, 0x38, 0x6c, 0x33, 0xb1, 0x14, 0xb7, 0xec, 0x05,
> + 0x5f, 0x49}};
This can be const.
> +static int snapshot_create_kernel_key(struct snapshot_data *data)
> +{
> + /* Create a key sealed by the SRK. */
> + char *keyinfo = "new\t32\tkeyhandle=0x81000000";
> + const struct cred *cred = current_cred();
> + struct tpm_digest *digests = NULL;
> + struct key *key = NULL;
> + struct tpm_chip *chip;
> + int ret, i;
> +
> + chip = tpm_default_chip();
> + if (!chip)
> + return -ENODEV;
> +
> + if (!(tpm_is_tpm2(chip))) {
> + ret = -ENODEV;
> + goto out_dev;
> + }
tpm_is_tpm2() can return an error value.
> + digests = kcalloc(chip->nr_allocated_banks, sizeof(struct tpm_digest),
> + GFP_KERNEL);
> + if (!digests) {
> + ret = -ENOMEM;
> + goto out;
> + }
> +
> + for (i = 0; i < chip->nr_allocated_banks; i++) {
> + digests[i].alg_id = chip->allocated_banks[i].alg_id;
> + if (digests[i].alg_id == known_digest.alg_id)
> + memcpy(&digests[i], &known_digest, sizeof(known_digest));
> + }
> +
> + ret = tpm_pcr_extend(chip, 23, digests);
> + if (ret != 0)
> + goto out;
So, PCR 23 will not actually be extended properly if there is not a SHA-256
bank? Wouldn't it make more sense to return an error in that case?
> +static int snapshot_load_kernel_key(struct snapshot_data *data,
> + struct uswsusp_key_blob *blob)
> +{
> +
> + char *keytemplate = "load\t%s\tkeyhandle=0x81000000";
Make this const.
> + blobstring = kmalloc(blob->blob_len * 2, GFP_KERNEL);
> + if (!blobstring) {
> + ret = -ENOMEM;
> + goto out;
> + }
> +
> + bin2hex(blobstring, blob->blob, blob->blob_len);
> + keyinfo = kasprintf(GFP_KERNEL, keytemplate, blobstring);
There's no need for bin2hex(). Just use the %*phN format specifier instead:
const char *keytemplate = "load\t%*phN\tkeyhandle=0x81000000";
keyinfo = kasprintf(GFP_KERNEL, keytemplate, blob->blob_len, blob->blob);
- Eric
