lib/af_alg.h

   1 /* af_alg.h - Compute message digests from file streams.
   2    Copyright (C) 2018 Free Software Foundation, Inc.
   3
   4    This program is free software; you can redistribute it and/or modify it
   5    under the terms of the GNU General Public License as published by the
   6    Free Software Foundation; either version 2, or (at your option) any
   7    later version.
   8
   9    This program is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12    GNU General Public License for more details.
  13
  14    You should have received a copy of the GNU General Public License
  15    along with this program; if not, see <https://www.gnu.org/licenses/>.  */
  16
  17 /* Written by Matteo Croce <mcroce@redhat.com>, 2018.
  18    Documentation by Bruno Haible <bruno@clisp.org>, 2018.  */
  19
  20 /* Declare specific functions for computing message digests
  21    using the Linux kernel crypto API, if available.  This kernel API gives
  22    access to specialized crypto instructions (that would also be available
  23    in user space) or to crypto devices (not directly available in user space).
  24
  25    For a more complete set of facilities that use the Linux kernel crypto API,
  26    look at libkcapi.  */
  27
  28 #ifndef AF_ALG_H
  29 # define AF_ALG_H 1
  30
  31 # include <stdio.h>
  32 # include <errno.h>
  33
  34 # ifdef __cplusplus
  35 extern "C" {
  36 # endif
  37
  38 # if HAVE_LINUX_IF_ALG_H
  39
  40 /* Compute a message digest of the contents of a file.
  41    STREAM is an open file stream.  Regular files are handled more efficiently.
  42    ALG is the message digest algorithm; see the file /proc/crypto.
  43    RESBLOCK points to a block of HASHLEN bytes, for the result.
  44    HASHLEN must be the length of the message digest, in bytes, in particular:
  45
  46       alg    | hashlen
  47       -------+--------
  48       md5    | 16
  49       sha1   | 20
  50       sha224 | 28
  51       sha256 | 32
  52       sha384 | 48
  53       sha512 | 64
  54
  55    If successful, fill RESBLOCK and return 0.
  56    Upon failure, return a negated error number.  */
  57 int
  58 afalg_stream (FILE *stream, const char *alg, void *resblock, ssize_t hashlen);
  59
  60 # else
  61
  62 static int
  63 afalg_stream (FILE *stream, const char *alg, void *resblock, ssize_t hashlen)
  64 {
  65   return -EAFNOSUPPORT;
  66 }
  67
  68 # endif
  69
  70 # ifdef __cplusplus
  71 }
  72 # endif
  73
  74 #endif /* AF_ALG_H */