mirror of
https://github.com/edk2-porting/linux-next.git
synced 2024-12-21 11:44:01 +08:00
a2fbbcea7b
Each text file under Documentation follows a different format. Some doesn't even have titles! Change its representation to follow the adopted standard, using ReST markups for it to be parseable by Sphinx: - comment the internal index; - use the proper markups for titles; - mark literal blocks. Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com> Signed-off-by: Jonathan Corbet <corbet@lwn.net>
102 lines
3.0 KiB
Plaintext
102 lines
3.0 KiB
Plaintext
==================================
|
|
Digital Signature Verification API
|
|
==================================
|
|
|
|
:Author: Dmitry Kasatkin
|
|
:Date: 06.10.2011
|
|
|
|
|
|
.. CONTENTS
|
|
|
|
1. Introduction
|
|
2. API
|
|
3. User-space utilities
|
|
|
|
|
|
Introduction
|
|
============
|
|
|
|
Digital signature verification API provides a method to verify digital signature.
|
|
Currently digital signatures are used by the IMA/EVM integrity protection subsystem.
|
|
|
|
Digital signature verification is implemented using cut-down kernel port of
|
|
GnuPG multi-precision integers (MPI) library. The kernel port provides
|
|
memory allocation errors handling, has been refactored according to kernel
|
|
coding style, and checkpatch.pl reported errors and warnings have been fixed.
|
|
|
|
Public key and signature consist of header and MPIs::
|
|
|
|
struct pubkey_hdr {
|
|
uint8_t version; /* key format version */
|
|
time_t timestamp; /* key made, always 0 for now */
|
|
uint8_t algo;
|
|
uint8_t nmpi;
|
|
char mpi[0];
|
|
} __packed;
|
|
|
|
struct signature_hdr {
|
|
uint8_t version; /* signature format version */
|
|
time_t timestamp; /* signature made */
|
|
uint8_t algo;
|
|
uint8_t hash;
|
|
uint8_t keyid[8];
|
|
uint8_t nmpi;
|
|
char mpi[0];
|
|
} __packed;
|
|
|
|
keyid equals to SHA1[12-19] over the total key content.
|
|
Signature header is used as an input to generate a signature.
|
|
Such approach insures that key or signature header could not be changed.
|
|
It protects timestamp from been changed and can be used for rollback
|
|
protection.
|
|
|
|
API
|
|
===
|
|
|
|
API currently includes only 1 function::
|
|
|
|
digsig_verify() - digital signature verification with public key
|
|
|
|
|
|
/**
|
|
* digsig_verify() - digital signature verification with public key
|
|
* @keyring: keyring to search key in
|
|
* @sig: digital signature
|
|
* @sigen: length of the signature
|
|
* @data: data
|
|
* @datalen: length of the data
|
|
* @return: 0 on success, -EINVAL otherwise
|
|
*
|
|
* Verifies data integrity against digital signature.
|
|
* Currently only RSA is supported.
|
|
* Normally hash of the content is used as a data for this function.
|
|
*
|
|
*/
|
|
int digsig_verify(struct key *keyring, const char *sig, int siglen,
|
|
const char *data, int datalen);
|
|
|
|
User-space utilities
|
|
====================
|
|
|
|
The signing and key management utilities evm-utils provide functionality
|
|
to generate signatures, to load keys into the kernel keyring.
|
|
Keys can be in PEM or converted to the kernel format.
|
|
When the key is added to the kernel keyring, the keyid defines the name
|
|
of the key: 5D2B05FC633EE3E8 in the example bellow.
|
|
|
|
Here is example output of the keyctl utility::
|
|
|
|
$ keyctl show
|
|
Session Keyring
|
|
-3 --alswrv 0 0 keyring: _ses
|
|
603976250 --alswrv 0 -1 \_ keyring: _uid.0
|
|
817777377 --alswrv 0 0 \_ user: kmk
|
|
891974900 --alswrv 0 0 \_ encrypted: evm-key
|
|
170323636 --alswrv 0 0 \_ keyring: _module
|
|
548221616 --alswrv 0 0 \_ keyring: _ima
|
|
128198054 --alswrv 0 0 \_ keyring: _evm
|
|
|
|
$ keyctl list 128198054
|
|
1 key in keyring:
|
|
620789745: --alswrv 0 0 user: 5D2B05FC633EE3E8
|