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/* af_alg.c - Compute message digests from file streams and buffers.
Copyright (C) 2018-2024 Free Software Foundation, Inc.
This file is free software: you can redistribute it and/or modify
it under the terms of the GNU Lesser General Public License as
published by the Free Software Foundation; either version 2.1 of the
License, or (at your option) any later version.
This file is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public License
along with this program. If not, see <https://www.gnu.org/licenses/>. */
/* Written by Matteo Croce <mcroce@redhat.com>, 2018. */
#include <config.h>
#include "af_alg.h"
#if USE_LINUX_CRYPTO_API
#include <unistd.h>
#include <string.h>
#include <stdio.h>
#include <errno.h>
#include <linux/if_alg.h>
#include <sys/stat.h>
#include <sys/sendfile.h>
#include <sys/socket.h>
#include "sys-limits.h"
#define BLOCKSIZE 32768
/* Return a newly created socket for ALG.
On error, return a negative error number. */
static int
alg_socket (char const *alg)
{
struct sockaddr_alg salg = {
.salg_family = AF_ALG,
.salg_type = "hash",
};
/* Copy alg into salg.salg_name, without calling strcpy nor strlen. */
for (size_t i = 0; (salg.salg_name[i] = alg[i]) != '\0'; i++)
if (i == sizeof salg.salg_name - 1)
/* alg is too long. */
return -EINVAL;
int cfd = socket (AF_ALG, SOCK_SEQPACKET | SOCK_CLOEXEC, 0);
if (cfd < 0)
return -EAFNOSUPPORT;
int ofd = (bind (cfd, (struct sockaddr *) &salg, sizeof salg) == 0
? accept4 (cfd, NULL, 0, SOCK_CLOEXEC)
: -1);
close (cfd);
return ofd < 0 ? -EAFNOSUPPORT : ofd;
}
int
afalg_buffer (const char *buffer, size_t len, const char *alg,
void *resblock, ssize_t hashlen)
{
/* On Linux < 4.9, the value for an empty stream is wrong (all zeroes).
See <https://patchwork.kernel.org/patch/9308641/>.
This was not fixed properly until November 2016,
see <https://patchwork.kernel.org/patch/9434741/>. */
if (len == 0)
return -EAFNOSUPPORT;
int ofd = alg_socket (alg);
if (ofd < 0)
return ofd;
int result;
for (;;)
{
ssize_t size = (len > BLOCKSIZE ? BLOCKSIZE : len);
if (send (ofd, buffer, size, MSG_MORE) != size)
{
result = -EAFNOSUPPORT;
break;
}
buffer += size;
len -= size;
if (len == 0)
{
result = read (ofd, resblock, hashlen) == hashlen ? 0 : -EAFNOSUPPORT;
break;
}
}
close (ofd);
return result;
}
int
afalg_stream (FILE *stream, const char *alg,
void *resblock, ssize_t hashlen)
{
int ofd = alg_socket (alg);
if (ofd < 0)
return ofd;
/* If STREAM's size is known and nonzero and not too large, attempt
sendfile to pipe the data. The nonzero restriction avoids issues
with /proc files that pretend to be empty, and lets the classic
read-write loop work around an empty-input bug noted below. */
int fd = fileno (stream);
int result;
struct stat st;
off_t off = ftello (stream);
if (0 <= off && fstat (fd, &st) == 0
&& (S_ISREG (st.st_mode) || S_TYPEISSHM (&st) || S_TYPEISTMO (&st))
&& off < st.st_size && st.st_size - off < SYS_BUFSIZE_MAX)
{
/* Make sure the offset of fileno (stream) reflects how many bytes
have been read from stream before this function got invoked.
Note: fflush on an input stream after ungetc does not work as expected
on some platforms. Therefore this situation is not supported here. */
if (fflush (stream))
result = -EIO;
else
{
off_t nbytes = st.st_size - off;
if (sendfile (ofd, fd, &off, nbytes) == nbytes)
{
if (read (ofd, resblock, hashlen) == hashlen)
{
/* The input buffers of stream are no longer valid. */
if (lseek (fd, off, SEEK_SET) != (off_t)-1)
result = 0;
else
/* The file position of fd has not changed. */
result = -EAFNOSUPPORT;
}
else
/* The file position of fd has not changed. */
result = -EAFNOSUPPORT;
}
else
/* The file position of fd has not changed. */
result = -EAFNOSUPPORT;
}
}
else
{
/* sendfile not possible, do a classic read-write loop. */
/* Number of bytes to seek (backwards) in case of error. */
off_t nseek = 0;
for (;;)
{
char buf[BLOCKSIZE];
/* When the stream is not seekable, start with a single-byte block,
so that we can use ungetc() in the case that send() fails. */
size_t blocksize = (nseek == 0 && off < 0 ? 1 : BLOCKSIZE);
ssize_t size = fread (buf, 1, blocksize, stream);
if (size == 0)
{
/* On Linux < 4.9, the value for an empty stream is wrong (all 0).
See <https://patchwork.kernel.org/patch/9308641/>.
This was not fixed properly until November 2016,
see <https://patchwork.kernel.org/patch/9434741/>. */
result = ferror (stream) ? -EIO : nseek == 0 ? -EAFNOSUPPORT : 0;
break;
}
nseek -= size;
if (send (ofd, buf, size, MSG_MORE) != size)
{
if (nseek == -1)
{
/* 1 byte of pushback buffer is guaranteed on stream, even
if stream is not seekable. */
ungetc ((unsigned char) buf[0], stream);
result = -EAFNOSUPPORT;
}
else if (fseeko (stream, nseek, SEEK_CUR) == 0)
/* The position of stream has been restored. */
result = -EAFNOSUPPORT;
else
result = -EIO;
break;
}
/* Don't assume that EOF is sticky. See:
<https://sourceware.org/bugzilla/show_bug.cgi?id=19476>. */
if (feof (stream))
{
result = 0;
break;
}
}
if (result == 0 && read (ofd, resblock, hashlen) != hashlen)
{
if (nseek == 0 || fseeko (stream, nseek, SEEK_CUR) == 0)
/* The position of stream has been restored. */
result = -EAFNOSUPPORT;
else
result = -EIO;
}
}
close (ofd);
return result;
}
#endif
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