PKCS11 » History » Revision 4
Revision 3 (Andreas Kuckartz, 01/09/2013 02:45 PM) → Revision 4/7 (Andreas Kuckartz, 01/09/2013 03:03 PM)
h1. PKCS11
The main goal of the PKCS#11-interface of the Open eCard App is to provide the functionality, which is required by Mozilla’s Firefox browser.
Mozilla’s overall crypto architecture as taken from [Grif09] is depicted in Figure 1.
!mozilla-crypto-architecture.jpg!
_Figure 1: Mozilla's Cryptographic Architecture ([Grif09], p. 22)_
The important part is the usage of the PKCS#11-interface by the “Core Crypto Code” within the “Network Security Services” as explained in [NSS-PKCS#11].
As this browser is a successor of Netscape’s Communicator it is expected that the PKCS#11-usage in today’s Firefox is similar to the PKCS#11-usage explained in [NSS-PKCS#11].
h2. Required Functions
h3. General-Purpose Functions
Among the general-purpose functions defined in Section 11.4 of [NSS-PKCS#11] the following functions need to be supported:
* @C_Initialize@
* @C_Finalize@
* @C_GetFunctionList@
* @C_GetInfo@
*C_Initialize*
As explained in [NSS-PKCS#11] the Netscape Security Library calls @C_Initialize@ on startup or when it loads a new module. The Netscape Security Library always passes @NULL@, as required by the PKCS #11 specification, in the single @C_Initialize@ parameter @pReserved@. This function will use the IFD-function @EstablishContext@ to initialize the IFD-module.
*C_Finalize*
As explained in [NSS-PKCS#11] the Netscape Security Library calls @C_Finalize@ on shutdown and whenever it unloads a module.
This function will use the IFD-function @ReleaseContext@ to initialize the IFD-module.
*C_GetInfo*
The Netscape Security Library calls @C_GetInfo@ on startup or when it loads a new module. The version numbers, manufacturer IDs, and so on are displayed when the user views the information. The supplied library names are used as the default library names; currently, these names should not include any double quotation marks.
This function will only return static information and does not involve any IFD-function.
*C_GetFunctionList*
As explained in [NSS-PKCS#11] the Netscape Security Library calls @C_GetFunctionList@ on startup or when it loads a new module. In [NSS-PKCS#11] it is recommended that for a not implemented function there should at least be a stub that returns @CKR_FUNCTION_NOT_SUPPORTED@.
This function will only return static information and does not involve any IFD-function.
h3. Slot and Token Management
*C_GetSlotList*
As explained in [NSS-PKCS#11] the Netscape Security Library calls @C_GetSlotList@ on startup or when it loads a new module, requests all the module's slots, and keeps track of the list from that point on. The slots are expected to remain static: that is, the module never has more slots or fewer slots than the number on the original list. This means that the function @C_WaitForSlotEvent@ is not used by the Netscape Security Library.
This function uses the following IFD-functions:
* @ListIFDs@
* @GetIFDCapabilities@
* @GetStatus@
*C_GetSlotInfo*
As explained in [NSS-PKCS#11] the Netscape Security Library calls @C_GetSlotInfo@ on startup or when it loads a new module and reads in the information that can be viewed on the slot information page. If the @CKF_REMOVABLE_DEVICE@ flag is set, the Netscape Security Library also calls @C_GetSlotInfo@ whenever it looks up slots to make sure the token is present. If the @CKF_REMOVABLE_DEVICE@ flag is not set, the Netscape Security Library uses that token information without checking again.
If the @CKF_REMOVABLE_DEVICE@ flag is not set, the @CKF_TOKEN_PRESENT@ flag must be set, or else the Netscape Security Library marks the slot as bad and will never use it.
The Netscape Security Library doesn't currently use the @CKF_HW_SLOT@ flag.
For a particular slot this function returns the following structure:
<pre><code class="c">
typedef struct CK_SLOT_INFO {
CK_UTF8CHAR slotDescription[64];
CK_UTF8CHAR manufacturerID[32];
CK_FLAGS flags;
CK_VERSION hardwareVersion;
CK_VERSION firmwareVersion;
} CK_SLOT_INFO;
</code></pre>
_Listing 1: @CK_SLOT_INFO@ structure_
*C_GetTokenInfo*
If a token is a permanent device (that is, if the @CKF_REMOVABLE_DEVICE@ flag is not set), the Netscape Security Library calls @C_GetTokenInfo@ only on startup or when it loads a new module. If the token is a removable device, the Netscape Security Library may call @C_GetTokenInfo@ anytime it's looking for a new token to check whether the token is write protected, whether it can generate random numbers, and so on.
The Netscape Security Library expects @CK_TOKEN_INFO@ label to contain the name of the token.
If the @CKF_WRITE_PROTECTED@ flag is set, the Netscape Security Library won't use the token to generate keys.
The Netscape Security Library interprets the combination of the @CKF_LOGIN_REQUIRED@ and @CKF_USER_PIN_INITIALIZED@ flags as shown in the following table.
|_. @CFK_LOGIN_REQUIRED@ |_. @CFK_USER_PIN_INITIALIZED@ |_. Netscape Security Library assumes that: |
| @FALSE@ | @FALSE@ | This is a general access device. The Netscape Security Library will use it without prompting the user for a PIN. |
| @TRUE@ | @FALSE@ | The device is uninitialized. The Netscape Security Library attempts to initialize the device only if it needs to generate a key or needs to set the user PIN. The Netscape Security Library calls @C_InitPIN@ to initialize the device and set the user PIN; if these calls are successful, the key is generated and at that point the @CFK_USER_PIN_INITIALIZED@ flag should change from @FALSE@ to @TRUE@. |
| @FALSE@ | @TRUE@ | This is a general access device that can have a PIN set on it. Because it's a general access device, the Netscape Security Library never prompts for the PIN, even though it's possible to set a PIN with @C_SetPIN@. If the PIN is set successfully, the @CFK_LOGIN_REQUIRED@ flag should change to @TRUE@. The Netscape Security Library uses this combination of flags for its internal token when the key database password is @NULL@. These are not standard PKCS #11 semantics; they are intended for the Netscape Security Library's internal use only. |
| @TRUE@ | @TRUE@ | The device has been initialized and requires authentication. The Netscape Security Library checks whether the user is logged on, and if not prompts the user for a PIN. |
_Table 1: Interpretation of flags ([NSS-PKCS#11], Table 1.1)_
For a typical signature card in operational mode the two flags are @TRUE@. On the other side the two flags for the private key on the eGK, which is used for card2card-authentication, are both @FALSE@.
This function returns the @CK_TOKEN_INFO@ struct for a specific token.
<pre><code class="c">
typedef struct CK_TOKEN_INFO {
CK_UTF8CHAR label[32];
CK_UTF8CHAR manufacturerID[32];
CK_UTF8CHAR model[16];
CK_CHAR serialNumber[16];
CK_FLAGS flags;
CK_ULONG ulMaxSessionCount;
CK_ULONG ulSessionCount;
CK_ULONG ulMaxRwSessionCount;
CK_ULONG ulRwSessionCount;
CK_ULONG ulMaxPinLen;
CK_ULONG ulMinPinLen;
CK_ULONG ulTotalPublicMemory;
CK_ULONG ulFreePublicMemory;
CK_ULONG ulTotalPrivateMemory;
CK_ULONG ulFreePrivateMemory;
CK_VERSION hardwareVersion;
CK_VERSION firmwareVersion;
CK_CHAR utcTime[16];
} CK_TOKEN_INFO;
</code></pre>
_Listing 2: @CK_TOKEN_INFO@ structure ([PKCS#11(v2.3)], p. 37)_
*C_GetMechanismList*
As explained in [NSS-PKCS#11], the Netscape Security Library calls @C_GetMechanismList@ fairly frequently to identify the mechanisms supported by a token.
This function returns the @CK_MECHANISM_INFO@ struct for a specific token.
<pre><code class="c">
typedef struct CK_MECHANISM_INFO {
CK_ULONG ulMinKeySize;
CK_ULONG ulMaxKeySize;
CK_FLAGS flags;
} CK_MECHANISM_INFO;
</code></pre>
_Listing 3: @CK_MECHANISM_INFO@ structure ([PKCS#11(v2.3)], p. 49)_
|_. Bit Flag |_. Mask |_. Meaning |
| @CKF_HW@ | 0x00000001 | True if the mechanism is performed by the device; false if the mechanism is performed in software |
| @CKF_ENCRYPT@ | 0x00000100 | True if the mechanism can be used with @C_EncryptInit@ |
| @CKF_DECRYPT@ | 0x00000200 | True if the mechanism can be used with @C_DecryptInit@ |
| @CKF_DIGEST@ | 0x00000400 | True if the mechanism can be used with @C_DigestInit@ |
| @CKF_SIGN@ | 0x00000800 | True if the mechanism can be used with @C_SignInit@ |
| @CKF_SIGN_RECOVER@ | 0x00001000 | True if the mechanism can be used with @C_SignRecoverInit@ |
| @CKF_VERIFY@ | 0x00002000 | True if the mechanism can be used with @C_VerifyInit@ |
| @CKF_VERIFY_RECOVER@ | 0x00004000 | True if the mechanism can be used with @C_VerifyRecoverInit@ |
| @CKF_GENERATE@ | 0x00008000 | True if the mechanism can be used with @C_GenerateKey@ |
| @CKF_GENERATE_KEY_PAIR@ | 0x00010000 | True if the mechanism can be used with @C_GenerateKeyPair@ |
| @CKF_WRAP@ | 0x00020000 | True if the mechanism can be used with @C_WrapKey@ |
| @CKF_UNWRAP@ | 0x00040000 | True if the mechanism can be used with @C_UnwrapKey@ |
| @CKF_DERIVE@ | 0x00080000 | True if the mechanism can be used with @C_DeriveKey@ |
| @CKF_EXTENSION@ | 0x80000000 | True if there is an extension to the flags; false if no extensions. Must be false for this version. |
_Table 2: Mechanism Information Flags ([PKCS#11(v2.3)], p. 50)_
h3. Session Management
*C_OpenSession*
As explained in [NSS-PKCS#11] the Netscape Security Library calls @C_OpenSession@ whenever it initializes a token and keeps the session open as long as possible. The Netscape Security Library almost never closes a session after it finishes doing something with a token. It uses a single session for all single-part RSA operations such as logging in, logging out, signing, verifying, generating keys, wrapping keys, and so on.
The Netscape Security Library opens a separate session for each part of a multipart encryption (bulk encryption). If it runs out of sessions, it uses the initial session for saves and restores.
This function will use the IFD-function @Connect@ to open a session to the token.
*C_CloseSession*
As explained in [NSS-PKCS#11] the Netscape Security Library calls @C_CloseSession@ to close sessions created for bulk encryption.
This function will use the IFD-function @Disconnect@ to close a session to the token.
*C_CloseAllSessions*
As explained in [NSS-PKCS#11] the Netscape Security Library may call @C_CloseAllSessions@ when it closes down a slot.
*C_GetSessionInfo*
The Netscape Security Library calls @C_GetSessionInfo@ frequently.
If a token has been removed during a session, @C_GetSessionInfo@ should return either @CKR_SESSION_CLOSED@ or @CKR_SESSION_HANDLE_INVALID@. If a token has been removed and then the same or another token is inserted, @C_GetSessionInfo@ should return @CKR_SESSION_HANDLE_INVALID@.
*C_Login*
The Netscape Security Library calls @C_Login@ on a token's initial session whenever @CKF_LOGIN_REQUIRED@ is @TRUE@ and the user state indicates that the user isn't logged in.
This function will use the IFD-function @VerifyUser@ to perform the authentication of a user.
*C_Logout*
The Netscape Security Library calls @C_Logout@ on a token's initial session
* when the password is timed out
* when performing any kind of private key operation if "ask always" is turned on
* when changing a password
* when the user logs out
h3. Object Management
In the scope of a TLS-handshake the client needs to read the certificate from the card and send it to the server. This functionality is most likely performed using the following two functions.
*C_GetAttributeValue*
The Netscape Security Library calls @C_GetAttributeValue@ to get the value of attributes for both single objects and multiple objects. This is useful for extracting public keys, nonsecret bulk keys, and so on.
*C_FindObjectsInit, C_FindObjects, C_FindFinal*
The Netscape Security Library calls these functions frequently to look up objects by @CKA_ID@ or @CKA_LABEL@. These values must match the equivalent values for related keys and certificates and must be unique among key pairs on a given token.
The Netscape Security Library also looks up certificates by @CK_ISSUER@ and @CK_SERIAL@. If those fields aren't set on the token, S/MIME won't work.
h3. Cryptographic Operations
In the scope of a TLS-handshake the client needs to sign data, which is constructed based on previously exchanged messages in the handshake. This signature is most likely created using the functions @C_SignInit@, @C_Sign@ and @C_SignFinal@.
h2. References
[Grif09] R. Griffin: Encryption and Key Management Tutorials, Part II: PKCS #11 – Enhancements and Opportunities, Talk at RSA 2009, ftp://ftp.rsasecurity.com/pub/pkcs/pkcs-11/v2-30/TUT-M51_Griffin_PKCS11.pdf
[NSS-PKCS#11] Implementing PKCS #11 for the Netscape Security Library, http://docs.oracle.com/cd/E19957-01/816-6150-10/pkcs.htm
[PKCS#11(v2.3)] RSA Laboratories: PKCS #11 Base Functionality v2.30: Cryptoki – Draft 4, 10 July 2009
h2. Additional links
PKCS11 FAQ
https://developer.mozilla.org/en-US/docs/PKCS11_FAQ
Using the PKCS #11 Module Logger
NSS Technical Note: 2
http://www.mozilla.org/projects/security/pki/nss/tech-notes/tn2.html
Network Security Services (NSS)
(The main NSS page with lots of links to current material)
http://www.mozilla.org/projects/security/pki/nss/