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
@@ -96,6 +96,8 @@ config ENCRYPTED_HIBERNATION
bool "Encryption support for userspace snapshots"
depends on HIBERNATION_SNAPSHOT_DEV
depends on CRYPTO_AEAD2=y
+ depends on TCG_TPM2_RESTRICT_PCR
+ depends on TRUSTED_KEYS=y
help
Enable support for kernel-based encryption of hibernation snapshots
created by uswsusp tools.
@@ -4,13 +4,23 @@
#include <linux/crypto.h>
#include <crypto/aead.h>
#include <crypto/gcm.h>
+#include <keys/trusted-type.h>
+#include <linux/key-type.h>
#include <linux/random.h>
#include <linux/mm.h>
+#include <linux/tpm.h>
#include <linux/uaccess.h>
#include "power.h"
#include "user.h"
+/* 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}};
+
/* Encrypt more data from the snapshot into the staging area. */
static int snapshot_encrypt_refill(struct snapshot_data *data)
{
@@ -313,6 +323,16 @@ void snapshot_teardown_encryption(struct snapshot_data *data)
{
int i;
+ /*
+ * Do NULL checks so this function can safely be called from error paths
+ * and other places where this context may not be fully set up.
+ */
+ if (data->key) {
+ key_revoke(data->key);
+ key_put(data->key);
+ data->key = NULL;
+ }
+
if (data->aead_req) {
aead_request_free(data->aead_req);
data->aead_req = NULL;
@@ -381,10 +401,82 @@ static int snapshot_setup_encryption_common(struct snapshot_data *data)
return rc;
}
+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;
+ }
+
+ ret = tpm2_pcr_reset(chip, 23);
+ if (ret)
+ goto out;
+
+ 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;
+
+ key = key_alloc(&key_type_trusted, "swsusp", GLOBAL_ROOT_UID,
+ GLOBAL_ROOT_GID, cred, 0, KEY_ALLOC_NOT_IN_QUOTA,
+ NULL);
+
+ if (IS_ERR(key)) {
+ ret = PTR_ERR(key);
+ key = NULL;
+ goto out;
+ }
+
+ ret = key_instantiate_and_link(key, keyinfo, sizeof(keyinfo), NULL,
+ NULL);
+ if (ret != 0)
+ goto out;
+
+ data->key = key;
+ key = NULL;
+
+out:
+ if (key) {
+ key_revoke(key);
+ key_put(key);
+ }
+
+ kfree(digests);
+ tpm2_pcr_reset(chip, 23);
+
+out_dev:
+ put_device(&chip->dev);
+ return ret;
+}
+
int snapshot_get_encryption_key(struct snapshot_data *data,
struct uswsusp_key_blob __user *key)
{
- u8 aead_key[SNAPSHOT_ENCRYPTION_KEY_SIZE];
+ struct trusted_key_payload *payload;
u8 nonce[USWSUSP_KEY_NONCE_SIZE];
int rc;
@@ -400,21 +492,28 @@ int snapshot_get_encryption_key(struct snapshot_data *data,
get_random_bytes(nonce, sizeof(nonce));
memcpy(&data->nonce_low, &nonce[0], sizeof(data->nonce_low));
memcpy(&data->nonce_high, &nonce[8], sizeof(data->nonce_high));
- /* Build a random key */
- get_random_bytes(aead_key, sizeof(aead_key));
- rc = crypto_aead_setkey(data->aead_tfm, aead_key, sizeof(aead_key));
+
+ /* Create a kernel key, and set it. */
+ rc = snapshot_create_kernel_key(data);
+ if (rc)
+ goto fail;
+
+ payload = data->key->payload.data[0];
+ /* Install the key */
+ rc = crypto_aead_setkey(data->aead_tfm, payload->key, SNAPSHOT_ENCRYPTION_KEY_SIZE);
if (rc)
goto fail;
- /* Hand the key back to user mode (to be changed!) */
- rc = put_user(sizeof(struct uswsusp_key_blob), &key->blob_len);
+ /* Hand the key back to user mode in sealed form. */
+ rc = put_user(payload->blob_len, &key->blob_len);
if (rc)
goto fail;
- rc = copy_to_user(&key->blob, &aead_key, sizeof(aead_key));
+ rc = copy_to_user(&key->blob, &payload->blob, payload->blob_len);
if (rc)
goto fail;
+ /* The nonce just gets handed back in the clear. */
rc = copy_to_user(&key->nonce, &nonce, sizeof(nonce));
if (rc)
goto fail;
@@ -426,10 +525,99 @@ int snapshot_get_encryption_key(struct snapshot_data *data,
return rc;
}
+static int snapshot_load_kernel_key(struct snapshot_data *data,
+ struct uswsusp_key_blob *blob)
+{
+
+ char *keytemplate = "load\t%s\tkeyhandle=0x81000000";
+ const struct cred *cred = current_cred();
+ struct tpm_digest *digests = NULL;
+ char *blobstring = NULL;
+ struct key *key = NULL;
+ struct tpm_chip *chip;
+ char *keyinfo = NULL;
+ int i, ret;
+
+ chip = tpm_default_chip();
+ if (!chip)
+ return -ENODEV;
+
+ if (!(tpm_is_tpm2(chip))) {
+ ret = -ENODEV;
+ goto out_dev;
+ }
+
+ ret = tpm2_pcr_reset(chip, 23);
+ if (ret)
+ goto out;
+
+ digests = kcalloc(chip->nr_allocated_banks, sizeof(struct tpm_digest),
+ GFP_KERNEL);
+ if (!digests)
+ 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;
+
+ 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);
+ if (!keyinfo) {
+ ret = -ENOMEM;
+ goto out;
+ }
+
+ key = key_alloc(&key_type_trusted, "swsusp", GLOBAL_ROOT_UID,
+ GLOBAL_ROOT_GID, cred, 0, KEY_ALLOC_NOT_IN_QUOTA,
+ NULL);
+
+ if (IS_ERR(key)) {
+ ret = PTR_ERR(key);
+ key = NULL;
+ goto out;
+ }
+
+ ret = key_instantiate_and_link(key, keyinfo, strlen(keyinfo) + 1, NULL,
+ NULL);
+ if (ret != 0)
+ goto out;
+
+ data->key = key;
+ key = NULL;
+
+out:
+ if (key) {
+ key_revoke(key);
+ key_put(key);
+ }
+
+ kfree(keyinfo);
+ kfree(blobstring);
+ kfree(digests);
+ tpm2_pcr_reset(chip, 23);
+
+out_dev:
+ put_device(&chip->dev);
+ return ret;
+}
+
int snapshot_set_encryption_key(struct snapshot_data *data,
struct uswsusp_key_blob __user *key)
{
struct uswsusp_key_blob blob;
+ struct trusted_key_payload *payload;
int rc;
/* It's too late if data's been pushed in. */
@@ -445,13 +633,18 @@ int snapshot_set_encryption_key(struct snapshot_data *data,
if (rc)
goto crypto_setup_fail;
- if (blob.blob_len != sizeof(struct uswsusp_key_blob)) {
+ if (blob.blob_len > sizeof(key->blob)) {
rc = -EINVAL;
goto crypto_setup_fail;
}
+ rc = snapshot_load_kernel_key(data, &blob);
+ if (rc)
+ goto crypto_setup_fail;
+
+ payload = data->key->payload.data[0];
rc = crypto_aead_setkey(data->aead_tfm,
- blob.blob,
+ payload->key,
SNAPSHOT_ENCRYPTION_KEY_SIZE);
if (rc)
@@ -31,6 +31,7 @@ struct snapshot_data {
uint64_t crypt_total;
uint64_t nonce_low;
uint64_t nonce_high;
+ struct key *key;
#endif
};