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-rw-r--r--Documentation/digsig.txt131
1 files changed, 68 insertions, 63 deletions
diff --git a/Documentation/digsig.txt b/Documentation/digsig.txt
index 3f682889068b..f6a8902d3ef7 100644
--- a/Documentation/digsig.txt
+++ b/Documentation/digsig.txt
@@ -1,13 +1,20 @@
+==================================
Digital Signature Verification API
+==================================
-CONTENTS
+:Author: Dmitry Kasatkin
+:Date: 06.10.2011
-1. Introduction
-2. API
-3. User-space utilities
+.. CONTENTS
-1. Introduction
+ 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.
@@ -17,25 +24,25 @@ 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;
+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.
@@ -43,31 +50,33 @@ 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
+===
-API currently includes only 1 function:
+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
+ /**
+ * 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.
@@ -75,22 +84,18 @@ 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
+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