NAME

       keyctl_pkey_query - Query public key parameters

SYNOPSIS

       #include <keyutils.h>

       long keyctl_pkey_query(key_serial_t key, const char *info,
                              struct keyctl_pkey_query *result);

DESCRIPTION

       keyctl_pkey_query()  queries  the  public key parameters associated with a kernel key that supports these
       operations (typically asymmetric-type).  The caller must have search permission on the target key  to  be
       able to query its parameters.

       When invoking the function, key indicates the key to be queried, info points to a space- or tab-separated
       string of "key[=value]" parameters and result points to a buffer in which the result will be placed.

       The parameters that can be used in  the  info  parameter  string  are  dependent  on  the  type  of  key.
       Parameters  can  specify  such  things as encoding types (such as "enc=pkcs1"); see asymmetric-key(7) for
       more information.

       If successful, the result is written into the following struct:

           struct keyctl_pkey_query {
                   unsigned int    supported_ops;
                   unsigned int    key_size;
                   unsigned short  max_data_size;
                   unsigned short  max_sig_size;
                   unsigned short  max_enc_size;
                   unsigned short  max_dec_size;
           };

       The supported_ops field contains a bitmask of the following constants:

           KEYCTL_SUPPORTS_ENCRYPT
           KEYCTL_SUPPORTS_DECRYPT
           KEYCTL_SUPPORTS_SIGN
           KEYCTL_SUPPORTS_VERIFY

       indicating what operations are supported and thus which of the other keyctl_pkey_*()  operations  can  be
       used with this key.

       The  key_size  field  indicates  the  number of bits in the key size and the max_data_size, max_sig_size,
       max_enc_size and max_dec_size fields indicate the maximum sizes in bytes of a blob of data to be  signed,
       a signature blob, a blob to be encrypted and a blob to be decrypted respectively.

RETURN VALUE

       On  success  keyctl_pkey_query()  returns 0.  On error, the value -1 will be returned and errno will have
       been set to an appropriate error.

ERRORS

       ENOKEY The key specified is invalid.

       EKEYEXPIRED
              The key specified has expired.

       EKEYREVOKED
              The key specified has been revoked.

       EACCES The key exists, but is not searchable by the calling process.

       ENOPKG Some facility needed to complete the requested operation is not available.  This is most  probably
              a requested or required digest or encryption algorithm.

       EFAULT Bad address.

LINKING

       This  is  a  library  function  that  can  be  found  in libkeyutils.  When linking, -lkeyutils should be
       specified to the linker.

SEE ALSO

       keyctl(1), add_key(2), keyctl(2), keyctl(3), keyctl_pkey_encrypt(3), keyctl_pkey_sign(3), asymmetric-
       key(7), keyrings(7), keyutils(7)