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              The key specified has been revoked.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)