[PATCH 00/10] Encrypted Hibernation

[PATCH 00/10] Encrypted Hibernation

[Evan Green]

We are exploring enabling hibernation in some new scenarios. However,
our security team has a few requirements, listed below:
1. The hibernate image must be encrypted with protection derived from
   both the platform (eg TPM) and user authentication data (eg
   password).
2. Hibernation must not be a vector by which a malicious userspace can
   escalate to the kernel.

Requirement #1 can be achieved solely with uswsusp, however requirement
2 necessitates mechanisms in the kernel to guarantee integrity of the
hibernate image. The kernel needs a way to authenticate that it generated
the hibernate image being loaded, and that the image has not been tampered
with. Adding support for in-kernel AEAD encryption with a TPM-sealed key
allows us to achieve both requirements with a single computation pass.

Matthew Garrett published a series [1] that aligns closely with this
goal. His series utilized the fact that PCR23 is a resettable PCR that
can be blocked from access by usermode. The TPM can create a sealed key
tied to PCR23 in two ways. First, the TPM can attest to the value of
PCR23 when the key was created, which the kernel can use on resume to
verify that the kernel must have created the key (since it is the only
one capable of modifying PCR23). It can also create a policy that enforces
PCR23 be set to a specific value as a condition of unsealing the key,
preventing usermode from unsealing the key by talking directly to the
TPM.

This series adopts that primitive as a foundation, tweaking and building
on it a bit. Where Matthew's series used the TPM-backed key to encrypt a
hash of the image, this series uses the key directly as a gcm(aes)
encryption key, which the kernel uses to encrypt and decrypt the
hibernate image in chunks of 16 pages. This provides both encryption and
integrity, which turns out to be a noticeable performance improvement over
separate passes for encryption and hashing.

The series also introduces the concept of mixing user key material into
the encryption key. This allows usermode to introduce key material
based on unspecified external authentication data (in our case derived
from something like the user password or PIN), without requiring
usermode to do a separate encryption pass.

Matthew also documented issues his series had [2] related to generating
fake images by booting alternate kernels without the PCR23 limiting.
With access to PCR23 on the same machine, usermode can create fake
hibernate images that are indistinguishable to the new kernel from
genuine ones. His post outlines a solution that involves adding more
PCRs into the creation data and policy, with some gyrations to make this
work well on a standard PC.

Our approach would be similar: on our machines PCR 0 indicates whether
the system is booted in secure/verified mode or developer mode. By
adding PCR0 to the policy, we can reject hibernate images made in
developer mode while in verified mode (or vice versa).

Additionally, mixing in the user authentication data limits both
data exfiltration attacks (eg a stolen laptop) and forged hibernation
image attacks to attackers that already know the authentication data (eg
user's password). This, combined with our relatively sealed userspace
(dm-verity on the rootfs), and some judicious clearing of the hibernate
image (such as across an OS update) further reduce the risk of an online
attack. The remaining attack space of a forgery from someone with
physical access to the device and knowledge of the authentication data
is out of scope for us, given that flipping to developer mode or
reflashing RO firmware trivially achieves the same thing.

A couple of patches still need to be written on top of this series. The
generalized functionality to OR in additional PCRs via Kconfig (like PCR
0 or 5) still needs to be added. We'll also need a patch that disallows
unencrypted forms of resume from hibernation, to fully close the door
to malicious userspace. However, I wanted to get this series out first
and get reactions from upstream before continuing to add to it.

[1] https://patchwork.kernel.org/project/linux-pm/cover/20210220013255.1083202-1-matthewgarrett@google.com/
[2] https://mjg59.dreamwidth.org/58077.html


Evan Green (6):
  security: keys: trusted: Verify creation data
  PM: hibernate: Add kernel-based encryption
  PM: hibernate: Use TPM-backed keys to encrypt image
  PM: hibernate: Mix user key in encrypted hibernate
  PM: hibernate: Verify the digest encryption key
  PM: hibernate: seal the encryption key with a PCR policy

Matthew Garrett (4):
  tpm: Add support for in-kernel resetting of PCRs
  tpm: Allow PCR 23 to be restricted to kernel-only use
  security: keys: trusted: Parse out individual components of the key
    blob
  security: keys: trusted: Allow storage of PCR values in creation data

 Documentation/power/userland-swsusp.rst       |    8 +
 .../security/keys/trusted-encrypted.rst       |    4 +
 drivers/char/tpm/Kconfig                      |   10 +
 drivers/char/tpm/tpm-dev-common.c             |    8 +
 drivers/char/tpm/tpm-interface.c              |   28 +
 drivers/char/tpm/tpm.h                        |   23 +
 drivers/char/tpm/tpm1-cmd.c                   |   69 ++
 drivers/char/tpm/tpm2-cmd.c                   |   58 +
 drivers/char/tpm/tpm2-space.c                 |    2 +-
 include/keys/trusted-type.h                   |    9 +
 include/linux/tpm.h                           |   12 +
 include/uapi/linux/suspend_ioctls.h           |   28 +-
 kernel/power/Kconfig                          |   15 +
 kernel/power/Makefile                         |    1 +
 kernel/power/power.h                          |    1 +
 kernel/power/snapenc.c                        | 1076 +++++++++++++++++
 kernel/power/snapshot.c                       |    5 +
 kernel/power/user.c                           |   44 +-
 kernel/power/user.h                           |  114 ++
 security/keys/trusted-keys/trusted_tpm1.c     |    9 +
 security/keys/trusted-keys/trusted_tpm2.c     |  164 ++-
 21 files changed, 1670 insertions(+), 18 deletions(-)
 create mode 100644 kernel/power/snapenc.c
 create mode 100644 kernel/power/user.h

-- 
2.31.0

[PATCH 03/10] security: keys: trusted: Parse out individual components of the key blob

[Evan Green]

From: Matthew Garrett <matthewgarrett@google.com>

Performing any sort of state validation of a sealed TPM blob requires
being able to access the individual members in the response. Parse the
blob sufficiently to be able to stash pointers to each member, along
with the length.

From: Matthew Garrett <mjg59@google.com>
Signed-off-by: Matthew Garrett <mjg59@google.com>

Signed-off-by: Evan Green <evgreen@chromium.org>
---
Matthew's original version of this patch is at:
https://patchwork.kernel.org/patch/12096489/

 include/keys/trusted-type.h               |  8 +++
 security/keys/trusted-keys/trusted_tpm2.c | 67 ++++++++++++++++++++++-
 2 files changed, 73 insertions(+), 2 deletions(-)

diff --git a/include/keys/trusted-type.h b/include/keys/trusted-type.h
index d89fa2579ac056..8a793ae1ad9f70 100644
--- a/include/keys/trusted-type.h
+++ b/include/keys/trusted-type.h
@@ -22,15 +22,23 @@
 #define MAX_BLOB_SIZE			512
 #define MAX_PCRINFO_SIZE		64
 #define MAX_DIGEST_SIZE			64
+#define MAX_CREATION_DATA		412
+#define MAX_TK				76
 
 struct trusted_key_payload {
 	struct rcu_head rcu;
 	unsigned int key_len;
 	unsigned int blob_len;
+	unsigned int creation_len;
+	unsigned int creation_hash_len;
+	unsigned int tk_len;
 	unsigned char migratable;
 	unsigned char old_format;
 	unsigned char key[MAX_KEY_SIZE + 1];
 	unsigned char blob[MAX_BLOB_SIZE];
+	unsigned char *creation;
+	unsigned char *creation_hash;
+	unsigned char *tk;
 };
 
 struct trusted_key_options {
diff --git a/security/keys/trusted-keys/trusted_tpm2.c b/security/keys/trusted-keys/trusted_tpm2.c
index 0165da386289c3..296a00f872ba40 100644
--- a/security/keys/trusted-keys/trusted_tpm2.c
+++ b/security/keys/trusted-keys/trusted_tpm2.c
@@ -215,6 +215,63 @@ static void tpm2_buf_append_auth(struct tpm_buf *buf, u32 session_handle,
 		tpm_buf_append(buf, hmac, hmac_len);
 }
 
+static int tpm2_unpack_blob(struct trusted_key_payload *payload)
+{
+	int tmp, offset;
+
+	/* Find the length of the private data */
+	tmp = be16_to_cpup((__be16 *) &payload->blob[0]);
+	offset = tmp + 2;
+	if (offset > payload->blob_len)
+		return -EFAULT;
+
+	/* Find the length of the public data */
+	tmp = be16_to_cpup((__be16 *) &payload->blob[offset]);
+	offset += tmp + 2;
+	if (offset > payload->blob_len)
+		return -EFAULT;
+
+	/* Find the length of the creation data and store it */
+	tmp = be16_to_cpup((__be16 *) &payload->blob[offset]);
+	if (tmp > MAX_CREATION_DATA)
+		return -E2BIG;
+
+	if ((offset + tmp + 2) > payload->blob_len)
+		return -EFAULT;
+
+	payload->creation = &payload->blob[offset + 2];
+	payload->creation_len = tmp;
+	offset += tmp + 2;
+
+	/* Find the length of the creation hash and store it */
+	tmp = be16_to_cpup((__be16 *) &payload->blob[offset]);
+	if (tmp > MAX_DIGEST_SIZE)
+		return -E2BIG;
+
+	if ((offset + tmp + 2) > payload->blob_len)
+		return -EFAULT;
+
+	payload->creation_hash = &payload->blob[offset + 2];
+	payload->creation_hash_len = tmp;
+	offset += tmp + 2;
+
+	/*
+	 * Store the creation ticket. TPMT_TK_CREATION is two bytes of tag,
+	 * four bytes of handle, and then the digest length and digest data
+	 */
+	tmp = be16_to_cpup((__be16 *) &payload->blob[offset + 6]);
+	if (tmp > MAX_TK)
+		return -E2BIG;
+
+	if ((offset + tmp + 8) > payload->blob_len)
+		return -EFAULT;
+
+	payload->tk = &payload->blob[offset];
+	payload->tk_len = tmp + 8;
+
+	return 0;
+}
+
 /**
  * tpm2_seal_trusted() - seal the payload of a trusted key
  *
@@ -229,6 +286,7 @@ int tpm2_seal_trusted(struct tpm_chip *chip,
 		      struct trusted_key_options *options)
 {
 	int blob_len = 0;
+	unsigned int offset;
 	struct tpm_buf buf;
 	u32 hash;
 	u32 flags;
@@ -317,15 +375,17 @@ int tpm2_seal_trusted(struct tpm_chip *chip,
 		rc = -E2BIG;
 		goto out;
 	}
-	if (tpm_buf_length(&buf) < TPM_HEADER_SIZE + 4 + blob_len) {
+	offset = TPM_HEADER_SIZE + 4;
+	if (tpm_buf_length(&buf) < offset + blob_len) {
 		rc = -EFAULT;
 		goto out;
 	}
 
 	blob_len = tpm2_key_encode(payload, options,
-				   &buf.data[TPM_HEADER_SIZE + 4],
+				   &buf.data[offset],
 				   blob_len);
 
+	rc = tpm2_unpack_blob(payload);
 out:
 	tpm_buf_destroy(&buf);
 
@@ -431,7 +491,10 @@ static int tpm2_load_cmd(struct tpm_chip *chip,
 	if (!rc)
 		*blob_handle = be32_to_cpup(
 			(__be32 *) &buf.data[TPM_HEADER_SIZE]);
+	else
+		goto out;
 
+	rc = tpm2_unpack_blob(payload);
 out:
 	if (blob != payload->blob)
 		kfree(blob);
-- 
2.31.0

[PATCH 04/10] security: keys: trusted: Allow storage of PCR values in creation data

[Evan Green]

From: Matthew Garrett <matthewgarrett@google.com>

When TPMs generate keys, they can also generate some information
describing the state of the PCRs at creation time. This data can then
later be certified by the TPM, allowing verification of the PCR values.
This allows us to determine the state of the system at the time a key
was generated. Add an additional argument to the trusted key creation
options, allowing the user to provide the set of PCRs that should have
their values incorporated into the creation data.

From: Matthew Garrett <mjg59@google.com>
Signed-off-by: Matthew Garrett <mjg59@google.com>

Signed-off-by: Evan Green <evgreen@chromium.org>
---
Matthew's original version of this patch is at:
https://patchwork.kernel.org/patch/12096503/

 .../security/keys/trusted-encrypted.rst       |  4 +++
 include/keys/trusted-type.h                   |  1 +
 security/keys/trusted-keys/trusted_tpm1.c     |  9 +++++++
 security/keys/trusted-keys/trusted_tpm2.c     | 25 +++++++++++++++++--
 4 files changed, 37 insertions(+), 2 deletions(-)

diff --git a/Documentation/security/keys/trusted-encrypted.rst b/Documentation/security/keys/trusted-encrypted.rst
index f614dad7de12f9..7215b067bf128f 100644
--- a/Documentation/security/keys/trusted-encrypted.rst
+++ b/Documentation/security/keys/trusted-encrypted.rst
@@ -170,6 +170,10 @@ Usage::
        policyhandle= handle to an authorization policy session that defines the
                      same policy and with the same hash algorithm as was used to
                      seal the key.
+       creationpcrs= hex integer representing the set of PCR values to be
+                     included in the PCR creation data. The bit corresponding
+		     to each PCR should be 1 to be included, 0 to be ignored.
+		     TPM2 only.
 
 "keyctl print" returns an ascii hex copy of the sealed key, which is in standard
 TPM_STORED_DATA format.  The key length for new keys are always in bytes.
diff --git a/include/keys/trusted-type.h b/include/keys/trusted-type.h
index 8a793ae1ad9f70..b3ac4afe8ba987 100644
--- a/include/keys/trusted-type.h
+++ b/include/keys/trusted-type.h
@@ -54,6 +54,7 @@ struct trusted_key_options {
 	uint32_t policydigest_len;
 	unsigned char policydigest[MAX_DIGEST_SIZE];
 	uint32_t policyhandle;
+	uint32_t creation_pcrs;
 };
 
 struct trusted_key_ops {
diff --git a/security/keys/trusted-keys/trusted_tpm1.c b/security/keys/trusted-keys/trusted_tpm1.c
index aa108bea6739b3..2975827c01bec0 100644
--- a/security/keys/trusted-keys/trusted_tpm1.c
+++ b/security/keys/trusted-keys/trusted_tpm1.c
@@ -713,6 +713,7 @@ enum {
 	Opt_hash,
 	Opt_policydigest,
 	Opt_policyhandle,
+	Opt_creationpcrs,
 };
 
 static const match_table_t key_tokens = {
@@ -725,6 +726,7 @@ static const match_table_t key_tokens = {
 	{Opt_hash, "hash=%s"},
 	{Opt_policydigest, "policydigest=%s"},
 	{Opt_policyhandle, "policyhandle=%s"},
+	{Opt_creationpcrs, "creationpcrs=%s"},
 	{Opt_err, NULL}
 };
 
@@ -858,6 +860,13 @@ static int getoptions(char *c, struct trusted_key_payload *pay,
 				return -EINVAL;
 			opt->policyhandle = handle;
 			break;
+		case Opt_creationpcrs:
+			if (!tpm2)
+				return -EINVAL;
+			res = kstrtoint(args[0].from, 16, &opt->creation_pcrs);
+			if (res < 0)
+				return -EINVAL;
+			break;
 		default:
 			return -EINVAL;
 		}
diff --git a/security/keys/trusted-keys/trusted_tpm2.c b/security/keys/trusted-keys/trusted_tpm2.c
index 296a00f872ba40..b7ddb78e644d17 100644
--- a/security/keys/trusted-keys/trusted_tpm2.c
+++ b/security/keys/trusted-keys/trusted_tpm2.c
@@ -290,7 +290,7 @@ int tpm2_seal_trusted(struct tpm_chip *chip,
 	struct tpm_buf buf;
 	u32 hash;
 	u32 flags;
-	int i;
+	int i, j;
 	int rc;
 
 	for (i = 0; i < ARRAY_SIZE(tpm2_hash_map); i++) {
@@ -359,7 +359,28 @@ int tpm2_seal_trusted(struct tpm_chip *chip,
 	tpm_buf_append_u16(&buf, 0);
 
 	/* creation PCR */
-	tpm_buf_append_u32(&buf, 0);
+	if (options->creation_pcrs) {
+		/* One bank */
+		tpm_buf_append_u32(&buf, 1);
+		/* Which bank to use */
+		tpm_buf_append_u16(&buf, hash);
+		/* Length of the PCR bitmask */
+		tpm_buf_append_u8(&buf, 3);
+		/* PCR bitmask */
+		for (i = 0; i < 3; i++) {
+			char tmp = 0;
+
+			for (j = 0; j < 8; j++) {
+				char bit = (i * 8) + j;
+
+				if (options->creation_pcrs & (1 << bit))
+					tmp |= (1 << j);
+			}
+			tpm_buf_append_u8(&buf, tmp);
+		}
+	} else {
+		tpm_buf_append_u32(&buf, 0);
+	}
 
 	if (buf.flags & TPM_BUF_OVERFLOW) {
 		rc = -E2BIG;
-- 
2.31.0

[PATCH 05/10] security: keys: trusted: Verify creation data

[Evan Green]

If a loaded key contains creation data, ask the TPM to verify that
creation data. This allows users like encrypted hibernate to know that
the loaded and parsed creation data has not been tampered with.

Partially-sourced-from: Matthew Garrett <mjg59@google.com>
Signed-off-by: Evan Green <evgreen@chromium.org>

---
Source material for this change is at:
https://patchwork.kernel.org/project/linux-pm/patch/20210220013255.1083202-9-matthewgarrett@google.com/

 include/linux/tpm.h                       |  1 +
 security/keys/trusted-keys/trusted_tpm2.c | 72 ++++++++++++++++++++++-
 2 files changed, 72 insertions(+), 1 deletion(-)

diff --git a/include/linux/tpm.h b/include/linux/tpm.h
index 8320cbac6f4009..438f8bc0a50582 100644
--- a/include/linux/tpm.h
+++ b/include/linux/tpm.h
@@ -224,6 +224,7 @@ enum tpm2_command_codes {
 	TPM2_CC_SELF_TEST	        = 0x0143,
 	TPM2_CC_STARTUP		        = 0x0144,
 	TPM2_CC_SHUTDOWN	        = 0x0145,
+	TPM2_CC_CERTIFYCREATION	        = 0x014A,
 	TPM2_CC_NV_READ                 = 0x014E,
 	TPM2_CC_CREATE		        = 0x0153,
 	TPM2_CC_LOAD		        = 0x0157,
diff --git a/security/keys/trusted-keys/trusted_tpm2.c b/security/keys/trusted-keys/trusted_tpm2.c
index b7ddb78e644d17..6db30a5fc320c0 100644
--- a/security/keys/trusted-keys/trusted_tpm2.c
+++ b/security/keys/trusted-keys/trusted_tpm2.c
@@ -600,6 +600,69 @@ static int tpm2_unseal_cmd(struct tpm_chip *chip,
 	return rc;
 }
 
+/**
+ * tpm2_certify_creation() - execute a TPM2_CertifyCreation command
+ *
+ * @chip: TPM chip to use
+ * @payload: the key data in clear and encrypted form
+ * @blob_handle: the loaded TPM handle of the key
+ *
+ * Return: 0 on success
+ *         -EINVAL on tpm error status
+ *         < 0 error from tpm_send or tpm_buf_init
+ */
+static int tpm2_certify_creation(struct tpm_chip *chip,
+				 struct trusted_key_payload *payload,
+				 u32 blob_handle)
+{
+	struct tpm_header *head;
+	struct tpm_buf buf;
+	int rc;
+
+	rc = tpm_buf_init(&buf, TPM2_ST_SESSIONS, TPM2_CC_CERTIFYCREATION);
+	if (rc)
+		return rc;
+
+	/* Use TPM_RH_NULL for signHandle */
+	tpm_buf_append_u32(&buf, 0x40000007);
+
+	/* Object handle */
+	tpm_buf_append_u32(&buf, blob_handle);
+
+	/* Auth */
+	tpm_buf_append_u32(&buf, 9);
+	tpm_buf_append_u32(&buf, TPM2_RS_PW);
+	tpm_buf_append_u16(&buf, 0);
+	tpm_buf_append_u8(&buf, 0);
+	tpm_buf_append_u16(&buf, 0);
+
+	/* Qualifying data */
+	tpm_buf_append_u16(&buf, 0);
+
+	/* Creation data hash */
+	tpm_buf_append_u16(&buf, payload->creation_hash_len);
+	tpm_buf_append(&buf, payload->creation_hash,
+		       payload->creation_hash_len);
+
+	/* signature scheme */
+	tpm_buf_append_u16(&buf, TPM_ALG_NULL);
+
+	/* creation ticket */
+	tpm_buf_append(&buf, payload->tk, payload->tk_len);
+
+	rc = tpm_transmit_cmd(chip, &buf, 6, "certifying creation data");
+	if (rc)
+		goto out;
+
+	head = (struct tpm_header *)buf.data;
+
+	if (head->return_code != 0)
+		rc = -EINVAL;
+out:
+	tpm_buf_destroy(&buf);
+	return rc;
+}
+
 /**
  * tpm2_unseal_trusted() - unseal the payload of a trusted key
  *
@@ -625,8 +688,15 @@ int tpm2_unseal_trusted(struct tpm_chip *chip,
 		goto out;
 
 	rc = tpm2_unseal_cmd(chip, payload, options, blob_handle);
-	tpm2_flush_context(chip, blob_handle);
+	if (rc)
+		goto flush;
+
+	if (payload->creation_len)
+		rc = tpm2_certify_creation(chip, payload, blob_handle);
 
+
+flush:
+	tpm2_flush_context(chip, blob_handle);
 out:
 	tpm_put_ops(chip);
 
-- 
2.31.0

Re: [PATCH 00/10] Encrypted Hibernation

[Pavel Machek]

Hi!

> We are exploring enabling hibernation in some new scenarios. However,
> our security team has a few requirements, listed below:
> 1. The hibernate image must be encrypted with protection derived from
>    both the platform (eg TPM) and user authentication data (eg
>    password).
> 2. Hibernation must not be a vector by which a malicious userspace can
>    escalate to the kernel.

Can you (or your security team) explain why requirement 2. is needed?

On normal systems, trusted userspace handles kernel upgrades (for example), 
so it can escalate to kernel priviledges.

Best regards,
									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

Re: [PATCH 00/10] Encrypted Hibernation

[Evan Green]

On Fri, May 6, 2022 at 9:08 AM Pavel Machek <pavel@ucw.cz> wrote:
>
> Hi!
>
> > We are exploring enabling hibernation in some new scenarios. However,
> > our security team has a few requirements, listed below:
> > 1. The hibernate image must be encrypted with protection derived from
> >    both the platform (eg TPM) and user authentication data (eg
> >    password).
> > 2. Hibernation must not be a vector by which a malicious userspace can
> >    escalate to the kernel.
>
> Can you (or your security team) explain why requirement 2. is needed?
>
> On normal systems, trusted userspace handles kernel upgrades (for example),
> so it can escalate to kernel priviledges.
>

Our systems are a little more sealed up than a normal distro, we use
Verified Boot [1]. To summarize, RO firmware with an embedded public
key verifies that the kernel+commandline was signed by Google. The
commandline includes the root hash of the rootfs as well (where the
modules live). So when an update is applied (A/B style, including the
whole rootfs), assuming the RO firmware stayed RO (which requires
physical measures to defeat), we can guarantee that the kernel,
commandline, and rootfs have not been tampered with.

Verified boot gives us confidence that on each boot, we're at least
starting from known code. This makes it more challenging for an
attacker to persist an exploit across reboot. With the kernel and
modules verified, we try to make it non-trivial for someone who does
manage to gain root execution once from escalating to kernel
execution. Hibernation would be one obvious escalation route, so we're
hoping to find a way to enable it without handing out that easy
primitive.

[1] https://www.chromium.org/chromium-os/chromiumos-design-docs/verified-boot/

> Best regards,
>                                                                         Pavel
> --
> (english) http://www.livejournal.com/~pavelmachek
> (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

Re: [PATCH 00/10] Encrypted Hibernation

[Rafael J. Wysocki]

On Mon, May 9, 2022 at 6:44 PM Evan Green <evgreen@chromium.org> wrote:
>
> On Fri, May 6, 2022 at 9:08 AM Pavel Machek <pavel@ucw.cz> wrote:
> >
> > Hi!
> >
> > > We are exploring enabling hibernation in some new scenarios. However,
> > > our security team has a few requirements, listed below:
> > > 1. The hibernate image must be encrypted with protection derived from
> > >    both the platform (eg TPM) and user authentication data (eg
> > >    password).
> > > 2. Hibernation must not be a vector by which a malicious userspace can
> > >    escalate to the kernel.
> >
> > Can you (or your security team) explain why requirement 2. is needed?
> >
> > On normal systems, trusted userspace handles kernel upgrades (for example),
> > so it can escalate to kernel priviledges.
> >
>
> Our systems are a little more sealed up than a normal distro, we use
> Verified Boot [1]. To summarize, RO firmware with an embedded public
> key verifies that the kernel+commandline was signed by Google. The
> commandline includes the root hash of the rootfs as well (where the
> modules live). So when an update is applied (A/B style, including the
> whole rootfs), assuming the RO firmware stayed RO (which requires
> physical measures to defeat), we can guarantee that the kernel,
> commandline, and rootfs have not been tampered with.
>
> Verified boot gives us confidence that on each boot, we're at least
> starting from known code. This makes it more challenging for an
> attacker to persist an exploit across reboot. With the kernel and
> modules verified, we try to make it non-trivial for someone who does
> manage to gain root execution once from escalating to kernel
> execution. Hibernation would be one obvious escalation route, so we're
> hoping to find a way to enable it without handing out that easy
> primitive.
>
> [1] https://www.chromium.org/chromium-os/chromiumos-design-docs/verified-boot/

So I guess this really is an RFC.

Honestly, I need more time to go through this and there are pieces of
it that need to be looked at other people (like the TPM-related
changes).

Thanks!

Re: [PATCH 00/10] Encrypted Hibernation

[Evan Green]

Hi Rafael,

On Tue, May 17, 2022 at 9:06 AM Rafael J. Wysocki <rafael@kernel.org> wrote:
>
> On Mon, May 9, 2022 at 6:44 PM Evan Green <evgreen@chromium.org> wrote:
> >
> > On Fri, May 6, 2022 at 9:08 AM Pavel Machek <pavel@ucw.cz> wrote:
> > >
> > > Hi!
> > >
> > > > We are exploring enabling hibernation in some new scenarios. However,
> > > > our security team has a few requirements, listed below:
> > > > 1. The hibernate image must be encrypted with protection derived from
> > > >    both the platform (eg TPM) and user authentication data (eg
> > > >    password).
> > > > 2. Hibernation must not be a vector by which a malicious userspace can
> > > >    escalate to the kernel.
> > >
> > > Can you (or your security team) explain why requirement 2. is needed?
> > >
> > > On normal systems, trusted userspace handles kernel upgrades (for example),
> > > so it can escalate to kernel priviledges.
> > >
> >
> > Our systems are a little more sealed up than a normal distro, we use
> > Verified Boot [1]. To summarize, RO firmware with an embedded public
> > key verifies that the kernel+commandline was signed by Google. The
> > commandline includes the root hash of the rootfs as well (where the
> > modules live). So when an update is applied (A/B style, including the
> > whole rootfs), assuming the RO firmware stayed RO (which requires
> > physical measures to defeat), we can guarantee that the kernel,
> > commandline, and rootfs have not been tampered with.
> >
> > Verified boot gives us confidence that on each boot, we're at least
> > starting from known code. This makes it more challenging for an
> > attacker to persist an exploit across reboot. With the kernel and
> > modules verified, we try to make it non-trivial for someone who does
> > manage to gain root execution once from escalating to kernel
> > execution. Hibernation would be one obvious escalation route, so we're
> > hoping to find a way to enable it without handing out that easy
> > primitive.
> >
> > [1] https://www.chromium.org/chromium-os/chromiumos-design-docs/verified-boot/
>
> So I guess this really is an RFC.

Yes, I suppose it is.

>
> Honestly, I need more time to go through this and there are pieces of
> it that need to be looked at other people (like the TPM-related
> changes).

No problem, thanks for the reply to let me know. I expect some back
and forth in terms of what should be hidden behind abstractions and
where exactly things should live. But I wanted to get this out to
upstream as early as I could, just to get initial reactions on the
overall concept and design. Looking forward to hearing your thoughts
when you get a chance, and let me know if there are others I should be
adding that I've missed.

-Evan

>
> Thanks!

Re: [PATCH 00/10] Encrypted Hibernation

[Evan Green]

On Tue, May 17, 2022 at 10:34 AM Evan Green <evgreen@chromium.org> wrote:
>
> Hi Rafael,
>
> On Tue, May 17, 2022 at 9:06 AM Rafael J. Wysocki <rafael@kernel.org> wrote:
> >
> > On Mon, May 9, 2022 at 6:44 PM Evan Green <evgreen@chromium.org> wrote:
> > >
> > > On Fri, May 6, 2022 at 9:08 AM Pavel Machek <pavel@ucw.cz> wrote:
> > > >
> > > > Hi!
> > > >
> > > > > We are exploring enabling hibernation in some new scenarios. However,
> > > > > our security team has a few requirements, listed below:
> > > > > 1. The hibernate image must be encrypted with protection derived from
> > > > >    both the platform (eg TPM) and user authentication data (eg
> > > > >    password).
> > > > > 2. Hibernation must not be a vector by which a malicious userspace can
> > > > >    escalate to the kernel.
> > > >
> > > > Can you (or your security team) explain why requirement 2. is needed?
> > > >
> > > > On normal systems, trusted userspace handles kernel upgrades (for example),
> > > > so it can escalate to kernel priviledges.
> > > >
> > >
> > > Our systems are a little more sealed up than a normal distro, we use
> > > Verified Boot [1]. To summarize, RO firmware with an embedded public
> > > key verifies that the kernel+commandline was signed by Google. The
> > > commandline includes the root hash of the rootfs as well (where the
> > > modules live). So when an update is applied (A/B style, including the
> > > whole rootfs), assuming the RO firmware stayed RO (which requires
> > > physical measures to defeat), we can guarantee that the kernel,
> > > commandline, and rootfs have not been tampered with.
> > >
> > > Verified boot gives us confidence that on each boot, we're at least
> > > starting from known code. This makes it more challenging for an
> > > attacker to persist an exploit across reboot. With the kernel and
> > > modules verified, we try to make it non-trivial for someone who does
> > > manage to gain root execution once from escalating to kernel
> > > execution. Hibernation would be one obvious escalation route, so we're
> > > hoping to find a way to enable it without handing out that easy
> > > primitive.
> > >
> > > [1] https://www.chromium.org/chromium-os/chromiumos-design-docs/verified-boot/
> >
> > So I guess this really is an RFC.
>
> Yes, I suppose it is.
>
> >
> > Honestly, I need more time to go through this and there are pieces of
> > it that need to be looked at other people (like the TPM-related
> > changes).
>
> No problem, thanks for the reply to let me know. I expect some back
> and forth in terms of what should be hidden behind abstractions and
> where exactly things should live. But I wanted to get this out to
> upstream as early as I could, just to get initial reactions on the
> overall concept and design. Looking forward to hearing your thoughts
> when you get a chance, and let me know if there are others I should be
> adding that I've missed.

Gentle bump in case this dropped off of radars, I'd still appreciate
any feedback folks had on this series.
-Evan

>
> -Evan
>
> >
> > Thanks!

Re: [PATCH 00/10] Encrypted Hibernation

[Evan Green]

On Thu, Jun 16, 2022 at 8:42 AM Evan Green <evgreen@chromium.org> wrote:
>
> On Tue, May 17, 2022 at 10:34 AM Evan Green <evgreen@chromium.org> wrote:
> >
> > Hi Rafael,
> >
> > On Tue, May 17, 2022 at 9:06 AM Rafael J. Wysocki <rafael@kernel.org> wrote:
> > >
> > > On Mon, May 9, 2022 at 6:44 PM Evan Green <evgreen@chromium.org> wrote:
> > > >
> > > > On Fri, May 6, 2022 at 9:08 AM Pavel Machek <pavel@ucw.cz> wrote:
> > > > >
> > > > > Hi!
> > > > >
> > > > > > We are exploring enabling hibernation in some new scenarios. However,
> > > > > > our security team has a few requirements, listed below:
> > > > > > 1. The hibernate image must be encrypted with protection derived from
> > > > > >    both the platform (eg TPM) and user authentication data (eg
> > > > > >    password).
> > > > > > 2. Hibernation must not be a vector by which a malicious userspace can
> > > > > >    escalate to the kernel.
> > > > >
> > > > > Can you (or your security team) explain why requirement 2. is needed?
> > > > >
> > > > > On normal systems, trusted userspace handles kernel upgrades (for example),
> > > > > so it can escalate to kernel priviledges.
> > > > >
> > > >
> > > > Our systems are a little more sealed up than a normal distro, we use
> > > > Verified Boot [1]. To summarize, RO firmware with an embedded public
> > > > key verifies that the kernel+commandline was signed by Google. The
> > > > commandline includes the root hash of the rootfs as well (where the
> > > > modules live). So when an update is applied (A/B style, including the
> > > > whole rootfs), assuming the RO firmware stayed RO (which requires
> > > > physical measures to defeat), we can guarantee that the kernel,
> > > > commandline, and rootfs have not been tampered with.
> > > >
> > > > Verified boot gives us confidence that on each boot, we're at least
> > > > starting from known code. This makes it more challenging for an
> > > > attacker to persist an exploit across reboot. With the kernel and
> > > > modules verified, we try to make it non-trivial for someone who does
> > > > manage to gain root execution once from escalating to kernel
> > > > execution. Hibernation would be one obvious escalation route, so we're
> > > > hoping to find a way to enable it without handing out that easy
> > > > primitive.
> > > >
> > > > [1] https://www.chromium.org/chromium-os/chromiumos-design-docs/verified-boot/
> > >
> > > So I guess this really is an RFC.
> >
> > Yes, I suppose it is.
> >
> > >
> > > Honestly, I need more time to go through this and there are pieces of
> > > it that need to be looked at other people (like the TPM-related
> > > changes).
> >
> > No problem, thanks for the reply to let me know. I expect some back
> > and forth in terms of what should be hidden behind abstractions and
> > where exactly things should live. But I wanted to get this out to
> > upstream as early as I could, just to get initial reactions on the
> > overall concept and design. Looking forward to hearing your thoughts
> > when you get a chance, and let me know if there are others I should be
> > adding that I've missed.
>
> Gentle bump in case this dropped off of radars, I'd still appreciate
> any feedback folks had on this series.

One more bump here, as we'd really love to get encrypted hibernation
to a form upstream would accept if at all possible. We were
considering landing this in our Chrome OS tree for now, then coming
back in a couple months with a "we've been baking this ourselves and
it's going so great, oooh yeah". I'm not sure if upstream would find
that compelling or not. But in any case, some guidance towards making
this more upstream friendly would be well appreciated.

One thing I realized in attempting to pick this myself is that the
trusted key blob format has moved to ASN.1. So I should really move
the creation ticket to the new ASN.1 format (if I can figure out the
right OID for that piece), which would allow me to drop a lot of the
ugly stuff in tpm2_unpack_blob(). Maybe if I get no other comments
I'll work on that and resend.

-Evan

Re: [PATCH 00/10] Encrypted Hibernation

[Matthew Garrett]

On Mon, Aug 1, 2022 at 3:33 PM Evan Green <evgreen@chromium.org> wrote:

> One more bump here, as we'd really love to get encrypted hibernation
> to a form upstream would accept if at all possible. We were
> considering landing this in our Chrome OS tree for now, then coming
> back in a couple months with a "we've been baking this ourselves and
> it's going so great, oooh yeah". I'm not sure if upstream would find
> that compelling or not. But in any case, some guidance towards making
> this more upstream friendly would be well appreciated.
>
> One thing I realized in attempting to pick this myself is that the
> trusted key blob format has moved to ASN.1. So I should really move
> the creation ticket to the new ASN.1 format (if I can figure out the
> right OID for that piece), which would allow me to drop a lot of the
> ugly stuff in tpm2_unpack_blob(). Maybe if I get no other comments
> I'll work on that and resend.

I've been revamping my TPM-backed verified hibernation implementation
based on this work, so I'd definitely be enthusiastic about it being
mergeable.

Re: [PATCH 04/10] security: keys: trusted: Allow storage of PCR values in creation data

[Eric Biggers]

On Wed, May 04, 2022 at 04:20:56PM -0700, Evan Green wrote:
> diff --git a/security/keys/trusted-keys/trusted_tpm1.c b/security/keys/trusted-keys/trusted_tpm1.c
> index aa108bea6739b3..2975827c01bec0 100644
> --- a/security/keys/trusted-keys/trusted_tpm1.c
> +++ b/security/keys/trusted-keys/trusted_tpm1.c
> @@ -713,6 +713,7 @@ enum {
>  	Opt_hash,
>  	Opt_policydigest,
>  	Opt_policyhandle,
> +	Opt_creationpcrs,
>  };
>  
>  static const match_table_t key_tokens = {
> @@ -725,6 +726,7 @@ static const match_table_t key_tokens = {
>  	{Opt_hash, "hash=%s"},
>  	{Opt_policydigest, "policydigest=%s"},
>  	{Opt_policyhandle, "policyhandle=%s"},
> +	{Opt_creationpcrs, "creationpcrs=%s"},
>  	{Opt_err, NULL}
>  };
>  
> @@ -858,6 +860,13 @@ static int getoptions(char *c, struct trusted_key_payload *pay,
>  				return -EINVAL;
>  			opt->policyhandle = handle;
>  			break;
> +		case Opt_creationpcrs:
> +			if (!tpm2)
> +				return -EINVAL;
> +			res = kstrtoint(args[0].from, 16, &opt->creation_pcrs);
> +			if (res < 0)
> +				return -EINVAL;
> +			break;

I thought that TPM1 is deprecated.  Are you sure you need more TPM1 features?

- Eric

Re: [PATCH 04/10] security: keys: trusted: Allow storage of PCR values in creation data

[Evan Green]

On Tue, Aug 2, 2022 at 4:00 PM Eric Biggers <ebiggers@kernel.org> wrote:
>
> On Wed, May 04, 2022 at 04:20:56PM -0700, Evan Green wrote:
> > diff --git a/security/keys/trusted-keys/trusted_tpm1.c b/security/keys/trusted-keys/trusted_tpm1.c
> > index aa108bea6739b3..2975827c01bec0 100644
> > --- a/security/keys/trusted-keys/trusted_tpm1.c
> > +++ b/security/keys/trusted-keys/trusted_tpm1.c
> > @@ -713,6 +713,7 @@ enum {
> >       Opt_hash,
> >       Opt_policydigest,
> >       Opt_policyhandle,
> > +     Opt_creationpcrs,
> >  };
> >
> >  static const match_table_t key_tokens = {
> > @@ -725,6 +726,7 @@ static const match_table_t key_tokens = {
> >       {Opt_hash, "hash=%s"},
> >       {Opt_policydigest, "policydigest=%s"},
> >       {Opt_policyhandle, "policyhandle=%s"},
> > +     {Opt_creationpcrs, "creationpcrs=%s"},
> >       {Opt_err, NULL}
> >  };
> >
> > @@ -858,6 +860,13 @@ static int getoptions(char *c, struct trusted_key_payload *pay,
> >                               return -EINVAL;
> >                       opt->policyhandle = handle;
> >                       break;
> > +             case Opt_creationpcrs:
> > +                     if (!tpm2)
> > +                             return -EINVAL;
> > +                     res = kstrtoint(args[0].from, 16, &opt->creation_pcrs);
> > +                     if (res < 0)
> > +                             return -EINVAL;
> > +                     break;
>
> I thought that TPM1 is deprecated.  Are you sure you need more TPM1 features?

It seems that trusted_tpm1.c is not just TPM1 functions, but also
common functions that call TPM2 primitives. A few of these functions
(like this getoptions()) seem to even error out if !tpm_is_tpm2(chip).

-Evan

Re: [PATCH 00/10] Encrypted Hibernation

[Jarkko Sakkinen]

On Tue, Aug 02, 2022 at 11:36:43AM -0700, Matthew Garrett wrote:
> On Mon, Aug 1, 2022 at 3:33 PM Evan Green <evgreen@chromium.org> wrote:
> 
> > One more bump here, as we'd really love to get encrypted hibernation
> > to a form upstream would accept if at all possible. We were
> > considering landing this in our Chrome OS tree for now, then coming
> > back in a couple months with a "we've been baking this ourselves and
> > it's going so great, oooh yeah". I'm not sure if upstream would find
> > that compelling or not. But in any case, some guidance towards making
> > this more upstream friendly would be well appreciated.
> >
> > One thing I realized in attempting to pick this myself is that the
> > trusted key blob format has moved to ASN.1. So I should really move
> > the creation ticket to the new ASN.1 format (if I can figure out the
> > right OID for that piece), which would allow me to drop a lot of the
> > ugly stuff in tpm2_unpack_blob(). Maybe if I get no other comments
> > I'll work on that and resend.
> 
> I've been revamping my TPM-backed verified hibernation implementation
> based on this work, so I'd definitely be enthusiastic about it being
> mergeable.

BTW, is it tested with QEMU + swtpm?

BR, Jarkko

Re: [PATCH 00/10] Encrypted Hibernation

[Evan Green]

On Wed, Aug 3, 2022 at 5:59 PM Jarkko Sakkinen <jarkko@kernel.org> wrote:
>
> On Tue, Aug 02, 2022 at 11:36:43AM -0700, Matthew Garrett wrote:
> > On Mon, Aug 1, 2022 at 3:33 PM Evan Green <evgreen@chromium.org> wrote:
> >
> > > One more bump here, as we'd really love to get encrypted hibernation
> > > to a form upstream would accept if at all possible. We were
> > > considering landing this in our Chrome OS tree for now, then coming
> > > back in a couple months with a "we've been baking this ourselves and
> > > it's going so great, oooh yeah". I'm not sure if upstream would find
> > > that compelling or not. But in any case, some guidance towards making
> > > this more upstream friendly would be well appreciated.
> > >
> > > One thing I realized in attempting to pick this myself is that the
> > > trusted key blob format has moved to ASN.1. So I should really move
> > > the creation ticket to the new ASN.1 format (if I can figure out the
> > > right OID for that piece), which would allow me to drop a lot of the
> > > ugly stuff in tpm2_unpack_blob(). Maybe if I get no other comments
> > > I'll work on that and resend.
> >
> > I've been revamping my TPM-backed verified hibernation implementation
> > based on this work, so I'd definitely be enthusiastic about it being
> > mergeable.
>
> BTW, is it tested with QEMU + swtpm?

For myself, so far I've been testing on a recent Intel Chromebook. The
H1 (aka cr50) security chip on modern chromebooks implements a subset
[1] of TPM2.0, and is exposed through the standard TPM APIs in the
kernel. I can make sure to test on Qemu as well, is there anything in
particular I should look out for?

-Evan

[1] https://chromium-review.googlesource.com/c/chromiumos/third_party/tpm2/+/3373466

>
> BR, Jarkko

Re: [PATCH 00/10] Encrypted Hibernation

[Jarkko Sakkinen]

On Thu, Aug 04, 2022 at 02:55:35PM -0700, Evan Green wrote:
> On Wed, Aug 3, 2022 at 5:59 PM Jarkko Sakkinen <jarkko@kernel.org> wrote:
> >
> > On Tue, Aug 02, 2022 at 11:36:43AM -0700, Matthew Garrett wrote:
> > > On Mon, Aug 1, 2022 at 3:33 PM Evan Green <evgreen@chromium.org> wrote:
> > >
> > > > One more bump here, as we'd really love to get encrypted hibernation
> > > > to a form upstream would accept if at all possible. We were
> > > > considering landing this in our Chrome OS tree for now, then coming
> > > > back in a couple months with a "we've been baking this ourselves and
> > > > it's going so great, oooh yeah". I'm not sure if upstream would find
> > > > that compelling or not. But in any case, some guidance towards making
> > > > this more upstream friendly would be well appreciated.
> > > >
> > > > One thing I realized in attempting to pick this myself is that the
> > > > trusted key blob format has moved to ASN.1. So I should really move
> > > > the creation ticket to the new ASN.1 format (if I can figure out the
> > > > right OID for that piece), which would allow me to drop a lot of the
> > > > ugly stuff in tpm2_unpack_blob(). Maybe if I get no other comments
> > > > I'll work on that and resend.
> > >
> > > I've been revamping my TPM-backed verified hibernation implementation
> > > based on this work, so I'd definitely be enthusiastic about it being
> > > mergeable.
> >
> > BTW, is it tested with QEMU + swtpm?
> 
> For myself, so far I've been testing on a recent Intel Chromebook. The
> H1 (aka cr50) security chip on modern chromebooks implements a subset
> [1] of TPM2.0, and is exposed through the standard TPM APIs in the
> kernel. I can make sure to test on Qemu as well, is there anything in
> particular I should look out for?

I was just thinking what I could use for testing

BR, Jarkko