lib/af_alg.h

   1 /* af_alg.h - Compute message digests from file streams and buffers.
   2    Copyright (C) 2018-2019 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 USE_LINUX_CRYPTO_API
  39
  40 /* Compute a message digest of a memory region.
  41
  42    The memory region starts at BUFFER and is LEN bytes long.
  43
  44    ALG is the message digest algorithm; see the file /proc/crypto.
  45
  46    RESBLOCK points to a block of HASHLEN bytes, for the result.
  47    HASHLEN must be the length of the message digest, in bytes, in particular:
  48
  49       alg    | hashlen
  50       -------+--------
  51       md5    | 16
  52       sha1   | 20
  53       sha224 | 28
  54       sha256 | 32
  55       sha384 | 48
  56       sha512 | 64
  57
  58    If successful, fill RESBLOCK and return 0.
  59    Upon failure, return a negated error number.  */
  60 int
  61 afalg_buffer (const char *buffer, size_t len, const char *alg,
  62               void *resblock, ssize_t hashlen);
  63
  64 /* Compute a message digest of data read from STREAM.
  65
  66    STREAM is an open file stream.  The last operation on STREAM should
  67    not be 'ungetc', and if STREAM is also open for writing it should
  68    have been fflushed since its last write.  Read from the current
  69    position to the end of STREAM.  Handle regular files efficiently.
  70
  71    ALG is the message digest algorithm; see the file /proc/crypto.
  72
  73    RESBLOCK points to a block of HASHLEN bytes, for the result.
  74    HASHLEN must be the length of the message digest, in bytes, in particular:
  75
  76       alg    | hashlen
  77       -------+--------
  78       md5    | 16
  79       sha1   | 20
  80       sha224 | 28
  81       sha256 | 32
  82       sha384 | 48
  83       sha512 | 64
  84
  85    If successful, fill RESBLOCK and return 0.
  86    Upon failure, return a negated error number.
  87    Unless returning 0 or -EIO, restore STREAM's file position so that
  88    the caller can fall back on some other method.  */
  89 int
  90 afalg_stream (FILE *stream, const char *alg,
  91               void *resblock, ssize_t hashlen);
  92
  93 # else
  94
  95 static inline int
  96 afalg_buffer (const char *buffer, size_t len, const char *alg,
  97               void *resblock, ssize_t hashlen)
  98 {
  99   return -EAFNOSUPPORT;
 100 }
 101
 102 static inline int
 103 afalg_stream (FILE *stream, const char *alg,
 104               void *resblock, ssize_t hashlen)
 105 {
 106   return -EAFNOSUPPORT;
 107 }
 108
 109 # endif
 110
 111 # ifdef __cplusplus
 112 }
 113 # endif
 114
 115 #endif /* AF_ALG_H */