1  /* af_alg.h - Compute message digests from file streams and buffers.
       2     Copyright (C) 2018-2023 Free Software Foundation, Inc.
       3  
       4     This file is free software: you can redistribute it and/or modify
       5     it under the terms of the GNU Lesser General Public License as
       6     published by the Free Software Foundation; either version 2.1 of the
       7     License, or (at your option) any later version.
       8  
       9     This file 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 Lesser General Public License for more details.
      13  
      14     You should have received a copy of the GNU Lesser 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 */