https://github.com/torvalds/linux
Revision fedc1ed0f11be666de066b0c78443254736a942e authored by Linus Torvalds on 31 March 2014, 00:26:08 UTC, committed by Linus Torvalds on 31 March 2014, 00:26:08 UTC
Pull vfs fixes from Al Viro: "Switch mnt_hash to hlist, turning the races between __lookup_mnt() and hash modifications into false negatives from __lookup_mnt() (instead of hangs)" On the false negatives from __lookup_mnt(): "The *only* thing we care about is not getting stuck in __lookup_mnt(). If it misses an entry because something in front of it just got moved around, etc, we are fine. We'll notice that mount_lock mismatch and that'll be it" * 'for-linus-2' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: switch mnt_hash to hlist don't bother with propagate_mnt() unless the target is shared keep shadowed vfsmounts together resizable namespace.c hashes
Tip revision: fedc1ed0f11be666de066b0c78443254736a942e authored by Linus Torvalds on 31 March 2014, 00:26:08 UTC
Merge branch 'for-linus-2' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs
Merge branch 'for-linus-2' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs
Tip revision: fedc1ed
digsig.txt
Digital Signature Verification API
CONTENTS
1. Introduction
2. API
3. User-space utilities
1. 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.
2. 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);
3. 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
Dmitry Kasatkin
06.10.2011
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