Hi experts,
This patchset is the implementation for signature verification of hibernate
snapshot image. The origin idea is from Jiri Kosina: Let EFI bootloader
generate key-pair in UEFI secure boot environment, then pass it to kernel
for sign/verify S4 image.
Due to there have potential threat from the S4 image hacked, it may causes
kernel lost the trust in UEFI secure boot. Hacker attack the S4 snapshot
image in swap partition through whatever exploit from another trusted OS,
and the exploit may don't need physical access machine.
So, this patchset give the ability to kernel for parsing the RSA private key
from EFI bootloader, then using the private key to generate the signature
of S4 snapshot image. Kernel put the signature to snapshot header, and
verify the signature when kernel try to recover snapshot image to memory.
==============
How To Enable
==============
Set enable the CONFIG_SNAPSHOT_VERIFICATION kernel config. And you can also
choice which hash algorithm should snapshot be signed with. Then rebuild
kernel.
Please note this function need UEFI bootloader's support to generate key-pair
in UEFI secure boot environment, e.g. shim. Current shim implementation by
Gary Lin:
Git:
https://github.com/lcp/shim/tree/s4-key-upstream
RPM:
https://build.opensuse.org/package/show/home:gary_lin:UEFI/shim
Please use the shim from above URL if you want to try. Please remember add
the hash of shim to db in UEFI BIOS because it didn't sign by Microsoft or
any OSV key.
=========
Behavior
=========
The RSA key-pair are generated by EFI bootloader(e.g. shim) in UEFI secure
boot environment, so this function binding with EFI secure boot enabled.
The kernel behavior is:
+ UEFI Secure Boot ON. Kernel found private key from shim:
Kernel will run the signature check when S4.
+ UEFI Secure Boot ON. Kernel didn't find key from shim:
Kernel will lock down S4 function.
+ UEFI Secure Boot OFF
Kernel will disable S4 signature check, and ignore any keys
from EFI bootloader. Unconditional allow hibernate launch.
On EFI bootloader side, the behavior as following:
+ First, kernel will check the following 2 EFI variable:
S4SignKey-fe141863-c070-478e-b8a3-878a5dc9ef21 [BootService]
S4WakeKey-fe141863-c070-478e-b8a3-878a5dc9ef21 [Runtime][Volatile]
S4SignKey and S4WakeKey is a RSA key-pair:
- S4SignKey is a private key that's used to generate signature of S4
snapshot.
The blob format of S4SignKey is PKCS#8 uncompressed format, it should
packaged a RSA private key that's followed PKCS#1.
- S4WakeKey is a public key that's used to verify signature of S4
snapshot.
The blob format of S4WakeKey is X.509 format, it should packaged a RSA
public key that's followed PKCS#1.
+ EFI bootloader must generate RSA key-pair when system boot:
- Bootloader store the public key to EFI boottime variable by itself
- Bootloader put The private key to S4SignKey EFI variable for forward to
kernel.
+ EFI stub kernel will load the S4SignKey blob to RAM before ExitBootServices,
then copy to a memory page to maintain by hibernate_key.c. This private key
will used to sign snapshot when S4.
+ When machine resume from hibernate:
- EFI bootloader should copy the public key from boottime variable to
S4WakeKey EFI variable.
- Bootloader need generates a new key-pair for next round S4 usage.
It should put new private key to S4SignKey variable.
+ EFI bootlaoder need check the following EFI runtime variable for regenerate
new key-pair:
GenS4Key-fe141863-c070-478e-b8a3-878a5dc9ef21
The size of GenS4Key is 1 byte, OS(kernel or userland tool) will set it to
"1" for notify efi bootloader regenerate key-pair.
==============
Implementation
==============
Whole implementation including 3 parts: shim, asymmetric keys and hibernate:
+ shim:
Current solution implemented by Gary Lin:
https://github.com/lcp/shim/tree/s4-key-upstream
Please use shim from the above URL if you want to try. Please remember add
this shim to db because it didn't sign by Microsoft or any OSV key.
+ Asymmetric keys:
This patchset implemented uncompressed PKCS#8 and RSA private key parser,
it also implement the signature generation operation of RSASSA-PKCS1-v_5
in PKCS#1 spec. [RFC3447 sec 8.2.2]
Set CONFIG_PKCS8_PRIVATE_KEY_INFO_PARSER=y will give kernel the abilities
to parsing private key in uncompressed PKCS#8 blob and generate signature.
+ Hibernate:
Set CONFIG_SNAPSHOT_VERIFICATION=y will enable the function of snapshot
signature generation and verification. I reserved 512 byes size in snapshot
header for store the signature that's generated from the digest with SHA
algorithms.
For adapt S4 signature check to secure boot, I have porting 3 patches from
Fedora kernel, authors are Josh Boyer and Matthew Garrett. I also add Cc. to
them.
Please help review this RFC patchset! Appreciate for any comments!
v3:
- Load S4 sign key before ExitBootServices in efi stub.
- In Makefile, moved hibernate_keys.o before hibernate.o for load S4 sign
key before check hibernate image. It makes sure the new sign key will be
transfer to resume target kernel.
- Set "depends on EFI_STUB" in Kconfig.
v2:
- Moved SNAPSHOT_VERIFICATION kernel config to earlier patch.
- Add dummy functions to simplify the ifdef check.
- Sent to opensuse-kernel@xxxxxxxxxxxx for review:
http://lists.opensuse.org/opensuse-kernel/2013-08/msg00025.html
v1:
- Internal review
- github:
https://github.com/joeyli/linux-s4sign/commits/devel-s4sign
Josh Boyer (1):
Secure boot: Add a dummy kernel parameter that will switch on Secure
Boot mode
Lee, Chun-Yi (15):
asymmetric keys: add interface and skeleton for implement signature
generation
asymmetric keys: implement EMSA_PKCS1-v1_5-ENCODE in rsa
asymmetric keys: separate the length checking of octet string from
RSA_I2OSP
asymmetric keys: implement OS2IP in rsa
asymmetric keys: implement RSASP1
asymmetric keys: support parsing PKCS #8 private key information
asymmetric keys: explicitly add the leading zero byte to encoded
message
Hibernate: introduced RSA key-pair to verify signature of snapshot
Hibernate: generate and verify signature of snapshot
Hibernate: Avoid S4 sign key data included in snapshot image
Hibernate: applied SNAPSHOT_VERIFICATION config to switch signature
check
Hibernate: adapt to UEFI secure boot with signature check
Hibernate: show the verification time for monitor performance
Hibernate: introduced SNAPSHOT_SIG_HASH config for select hash
algorithm
Hibernate: notify bootloader regenerate key-pair for snapshot
verification
Matthew Garrett (2):
Secure boot: Add new capability
efi: Enable secure boot lockdown automatically when enabled in
firmware
Documentation/kernel-parameters.txt | 7 +
Documentation/x86/zero-page.txt | 2 +
arch/x86/boot/compressed/eboot.c | 121 ++++++++++
arch/x86/include/asm/bootparam_utils.h | 8 +-
arch/x86/include/asm/efi.h | 9 +
arch/x86/include/uapi/asm/bootparam.h | 4 +-
arch/x86/kernel/setup.c | 7 +
arch/x86/platform/efi/efi.c | 68 ++++++
crypto/asymmetric_keys/Kconfig | 11 +
crypto/asymmetric_keys/Makefile | 16 ++
crypto/asymmetric_keys/pkcs8.asn1 | 19 ++
crypto/asymmetric_keys/pkcs8_info_parser.c | 152 ++++++++++++
crypto/asymmetric_keys/pkcs8_parser.h | 23 ++
crypto/asymmetric_keys/pkcs8_private_key.c | 148 ++++++++++++
crypto/asymmetric_keys/pkcs8_rsakey.asn1 | 29 +++
crypto/asymmetric_keys/private_key.h | 29 +++
crypto/asymmetric_keys/public_key.c | 32 +++
crypto/asymmetric_keys/rsa.c | 283 ++++++++++++++++++++++-
crypto/asymmetric_keys/signature.c | 28 +++
include/crypto/public_key.h | 28 +++
include/keys/asymmetric-subtype.h | 6 +
include/linux/cred.h | 2 +
include/linux/efi.h | 18 ++
include/uapi/linux/capability.h | 6 +-
kernel/cred.c | 17 ++
kernel/power/Kconfig | 77 ++++++-
kernel/power/Makefile | 1 +
kernel/power/hibernate.c | 37 +++
kernel/power/hibernate_keys.c | 329 ++++++++++++++++++++++++++
kernel/power/main.c | 11 +-
kernel/power/power.h | 35 +++
kernel/power/snapshot.c | 345 +++++++++++++++++++++++++++-
kernel/power/swap.c | 22 ++
kernel/power/user.c | 22 ++
34 files changed, 1925 insertions(+), 27 deletions(-)
create mode 100644 crypto/asymmetric_keys/pkcs8.asn1
create mode 100644 crypto/asymmetric_keys/pkcs8_info_parser.c
create mode 100644 crypto/asymmetric_keys/pkcs8_parser.h
create mode 100644 crypto/asymmetric_keys/pkcs8_private_key.c
create mode 100644 crypto/asymmetric_keys/pkcs8_rsakey.asn1
create mode 100644 crypto/asymmetric_keys/private_key.h
create mode 100644 kernel/power/hibernate_keys.c
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