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PKCS #11 Functions

 


Chapter 7
PKCS #11 Functions

This chapter describes the core PKCS #11 functions that an application needs for communicating with cryptographic modules. In particular, these functions are used for obtaining certificates, keys, and passwords.

PK11_FindCertFromNickname
PK11_FindKeyByAnyCert
PK11_GetSlotName
PK11_GetTokenName
PK11_IsHW
PK11_IsPresent
PK11_IsReadOnly
PK11_SetPasswordFunc

 

PK11_FindCertFromNickname

Finds a certificate from its nickname.

Syntax
#include <pk11func.h>
#include <certt.h>
CERTCertificate *PK11_FindCertFromNickname(
   char *nickname,
   void *wincx);
Parameters

This function has the following parameters:

nickname

A pointer to the nickname in the certificate database or to the nickname in the token.

wincx

A pointer to application data for the password callback function. This pointer is set with SSL_SetPKCS11PinArg during SSL configuration. To retrieve its current value, use SSL_RevealPinArg.

Returns

The function returns one of these values:

Description

A nickname is an alias for a certificate subject. There may be multiple certificates with the same subject, and hence the same nickname. This function will return the newest certificate that matches the subject, based on the NotBefore / NotAfter fields of the certificate. When you are finished with the certificate structure returned by PK11_FindCertFromNickname, you must free it by calling CERT_DestroyCertificate.

The PK11_FindCertFromNickname function calls the password callback function set with PK11_SetPasswordFunc and passes it the pointer specified by the wincx parameter.

 

PK11_FindKeyByAnyCert

Finds the private key associated with a specified certificate in any available slot.

Syntax
#include <pk11func.h>
#include <certt.h>
#include <keyt.h>
SECKEYPrivateKey *PK11_FindKeyByAnyCert(
   CERTCertificate *cert,
   void *wincx);
Parameters

This function has the following parameters:

cert

A pointer to a certificate structure in the certificate database.

wincx

A pointer to application data for the password callback function. This pointer is set with SSL_SetPKCS11PinArg during SSL configuration. To retrieve its current value, use SSL_RevealPinArg.

Returns

The function returns one of these values:

Description

When you are finished with the private key structure returned by PK11_FindKeyByAnyCert, you must free it by calling SECKEY_DestroyPrivateKey.

The PK11_FindKeyByAnyCert function calls the password callback function set with PK11_SetPasswordFunc and passes it the pointer specified by the wincx parameter.

 

PK11_GetSlotName

Gets the name of a slot.

Syntax
#include <pk11func.h>
char *PK11_GetSlotName(PK11SlotInfo *slot);
Parameters

This function has the following parameter:

slot

A pointer to a slot info structure.

Returns

The function returns one of these values:

Description

If the slot is freed, the string with the slot name may also be freed. If you want to preserve it, copy the string before freeing the slot. Do not try to free the string yourself.

PK11_GetTokenName

Gets the name of the token.

Syntax
#include <pk11func.h>
char *PK11_GetTokenName(PK11SlotInfo *slot);
Parameters

This function has the following parameter:

slot

A pointer to a slot info structure.

Returns

The function returns one of these values:

Description

If the slot is freed, the string with the token name may also be freed. If you want to preserve it, copy the string before freeing the slot. Do not try to free the string yourself.

PK11_IsHW

Finds out whether a slot is implemented in hardware or software.

Syntax
#include <pk11func.h>
#include <prtypes.h>
PRBool PK11_IsHW(PK11SlotInfo *slot);
Parameters

This function has the following parameter:

slot

A pointer to a slot info structure.

Returns

The function returns one of these values:

PK11_IsPresent

Finds out whether the token for a slot is available.

Syntax
#include <pk11func.h>
#include <prtypes.h>
PRBool PK11_IsPresent(PK11SlotInfo *slot);
Parameters

This function has the following parameter:

slot

A pointer to a slot info structure.

Returns

The function returns one of these values:

PK11_IsReadOnly

Finds out whether a slot is read-only.

Syntax
#include <pk11func.h>
#include <prtypes.h>
PRBool PK11_IsReadOnly(PK11SlotInfo *slot);
Parameters

This function has the following parameter:

slot

A pointer to a slot info structure.

Returns

The function returns one of these values:

PK11_SetPasswordFunc

Defines a callback function used by the NSS libraries whenever information protected by a password needs to be retrieved from the key or certificate databases.

Syntax
#include <pk11func.h>
#include <prtypes.h>
void PK11_SetPasswordFunc(PK11PasswordFunc func);
Parameter

This function has the following parameter:

func

A pointer to the callback function to set.

Description

During the course of an SSL operation, it may be necessary for the user to log in to a PKCS #11 token (either a smart card or soft token) to access protected information, such as a private key. Such information is protected with a password that can be retrieved by calling an application-supplied callback function. The callback function is identified in a call to PK11_SetPasswordFunc that takes place during NSS initialization.

The callback function set up by PK11_SetPasswordFunc has the following prototype:

typedef char *(*PK11PasswordFunc)(
   PK11SlotInfo *slot,
   PRBool retry,
   void *arg);

This callback function has the following parameters:

slot

A pointer to a slot info structure.

retry

Set to PR_TRUE if this is a retry. This implies that the callback has previously returned the wrong password.

arg

A pointer supplied by the application that can be used to pass state information. Can be NULL.

 

This callback function returns one of these values:

Many tokens keep track of the number of attempts to enter a password and do not allow further attempts after a certain point. Therefore, if the retry argument is PR_TRUE, indicating that the password was tried and is wrong, the callback function should return NULL to indicate that it is unsuccessful, rather than attempting to return the same password again. Failing to terminate when the retry argument is PR_TRUE can result in an endless loop.

Several functions in the NSS libraries use the password callback function to obtain the password before performing operations that involve the protected information. The third parameter to the password callback function is application-defined and can be used for any purpose. For example, Communicator uses the parameter to pass information about which window is associated with the modal dialog box requesting the password from the user. When NSS libraries call the password callback function, the value they pass in the third parameter is determined by SSL_SetPKCS11PinArg.

See Also

For examples of password callback functions, see the samples in the Samples directory.

 

Document Tags and Contributors

 Contributors to this page: Sheppy, kwilson
 Last updated by: Sheppy,