[PATCH v2 1/4] sha1sum: use AF_ALG when available

[Matteo Croce]

Linux supports accessing kernel crypto API via AF_ALG since
version 2.6.38. Coreutils uses libcrypto when available and fallbacks to
generic C implementation of various hashing functions.

Add a generic afalg_stream() function which uses AF_ALG to calculate the
hash of a stream and use sendfile() when possible (regular file with size
less or equal than 0x7ffff000 (2,147,479,552) bytes, AKA MAX_RW_COUNT).

Use afalg_stream() only in sha1sum for now, but other hashes are possible.
The speed gain really depends on the CPU type, on systems which doesn't use
libcrypto ranges from ~10% to 320%.

This is a test on a Intel(R) Xeon(R) CPU E3-1265L V2 and Debian stretch:

    $ truncate -s 2GB 2g.bin
    $ time sha1sum 2g.bin
    752ef2367f479e79e4f0cded9c270c2890506ab0  2g.bin

    real    0m4.829s
    user    0m4.437s
    sys     0m0.391s
    $ time ./sha1sum-afalg 2g.bin
    752ef2367f479e79e4f0cded9c270c2890506ab0  2g.bin

    real    0m3.164s
    user    0m0.000s
    sys     0m3.162s

Signed-off-by: Matteo Croce <address@hidden>
---
 lib/af_alg.c        | 124 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 lib/af_alg.h        |  51 +++++++++++++++++++++
 lib/sha1.c          |  19 +++++++-
 modules/crypto/sha1 |   4 +-
 4 files changed, 196 insertions(+), 2 deletions(-)
 create mode 100644 lib/af_alg.c
 create mode 100644 lib/af_alg.h

diff --git a/lib/af_alg.c b/lib/af_alg.c
new file mode 100644
index 000000000..cb6086b4d
--- /dev/null
+++ b/lib/af_alg.c
@@ -0,0 +1,124 @@
+/* af_alg.c - Functions to compute message digest from file streams using
+   Linux kernel crypto API.
+   Copyright (C) 2018 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   This program is free software; you can redistribute it and/or modify it
+   under the terms of the GNU General Public License as published by the
+   Free Software Foundation; either version 2, or (at your option) any
+   later version.
+
+   This program 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 General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, see <https://www.gnu.org/licenses/>.  */
+
+/* Written by Matteo Croce <address@hidden>, 2018. */
+
+#include <config.h>
+
+#include <sys/socket.h>
+
+#ifdef AF_ALG
+
+#include <unistd.h>
+#include <string.h>
+#include <linux/if_alg.h>
+#include <sys/stat.h>
+#include <sys/sendfile.h>
+
+#include "af_alg.h"
+
+/* from linux/include/linux/fs.h: (INT_MAX & PAGE_MASK) */
+#define MAX_RW_COUNT 0x7FFFF000
+#define BLOCKSIZE 32768
+
+int
+afalg_stream (FILE * stream, void *resblock, const char *alg, ssize_t hashlen)
+{
+  struct sockaddr_alg salg = {
+    .salg_family = AF_ALG,
+    .salg_type = "hash",
+  };
+  int ret, cfd, ofd;
+  char buf[BLOCKSIZE];
+  ssize_t size;
+  struct stat st;
+
+  if (strlen (alg) >= sizeof(salg.salg_name))
+    return -EINVAL;
+
+  cfd = socket (AF_ALG, SOCK_SEQPACKET, 0);
+  if (cfd < 0)
+    return -EAFNOSUPPORT;
+
+  strcpy ((char *) salg.salg_name, alg);
+
+  ret = bind (cfd, (struct sockaddr *) &salg, sizeof (salg));
+  if (ret < 0)
+    {
+      ret = -EAFNOSUPPORT;
+      goto out_cfd;
+    }
+
+  ofd = accept (cfd, NULL, 0);
+  if (ofd < 0)
+    {
+      ret = -EAFNOSUPPORT;
+      goto out_cfd;
+    }
+
+  /* if file is a regular file, attempt sendfile() to pipe the data */
+  if (!fstat (fileno (stream), &st) && S_ISREG (st.st_mode) &&
+      st.st_size <= MAX_RW_COUNT)
+    {
+      if (sendfile (ofd, fileno (stream), NULL, st.st_size) != st.st_size)
+        {
+          ret = -EIO;
+          goto out_ofd;
+        }
+      else
+        {
+          ret = 0;
+        }
+    }
+  else
+    {
+      /* sendfile() not possible, do a classic read-write loop */
+      while ((size = fread (buf, 1, sizeof (buf), stream)))
+        {
+          if (send (ofd, buf, size, size == sizeof (buf) ? MSG_MORE : 0) == -1)
+            {
+              ret = -EIO;
+              goto out_ofd;
+            }
+        }
+      if (ferror (stream))
+        {
+          ret = -EIO;
+          goto out_ofd;
+        }
+    }
+
+  size = read (ofd, resblock, hashlen);
+  if (size != hashlen)
+    {
+      fprintf (stderr, "Error from read (%zd vs %zd bytes): %s\n",
+               size, hashlen, strerror (errno));
+      ret = -EIO;
+    }
+  else
+    {
+      ret = 0;
+    }
+out_ofd:
+  close (ofd);
+out_cfd:
+  close (cfd);
+  return ret;
+}
+
+#endif
diff --git a/lib/af_alg.h b/lib/af_alg.h
new file mode 100644
index 000000000..36a95f4bc
--- /dev/null
+++ b/lib/af_alg.h
@@ -0,0 +1,51 @@
+/* af_alg.h - Declaration of functions to compute message digest from
+   file streams using Linux kernel crypto API.
+   Copyright (C) 2018 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   This program is free software; you can redistribute it and/or modify it
+   under the terms of the GNU General Public License as published by the
+   Free Software Foundation; either version 2, or (at your option) any
+   later version.
+
+   This program 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 General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, see <https://www.gnu.org/licenses/>.  */
+
+/* Written by Matteo Croce <address@hidden>, 2018. */
+
+#ifndef AF_ALG_H
+# define AF_ALG_H 1
+
+# include <stdio.h>
+# include <errno.h>
+# include <sys/socket.h>
+
+# ifdef __cplusplus
+extern "C" {
+# endif
+
+#ifdef AF_ALG
+
+int
+afalg_stream (FILE * stream, void *resblock, const char *alg, ssize_t hashlen);
+
+#else
+
+static int
+afalg_stream (FILE * stream, void *resblock, const char *alg, ssize_t hashlen)
+{
+  return -EAFNOSUPPORT;
+}
+
+#endif
+
+# ifdef __cplusplus
+}
+# endif
+
+#endif
diff --git a/lib/sha1.c b/lib/sha1.c
index 37d46b68e..21b4b323a 100644
--- a/lib/sha1.c
+++ b/lib/sha1.c
@@ -33,6 +33,12 @@
 #include <stdlib.h>
 #include <string.h>
 
+#include <sys/socket.h>
+
+#ifdef AF_ALG
+# include "af_alg.h"
+#endif
+
 #if USE_UNLOCKED_IO
 # include "unlocked-io.h"
 #endif
@@ -130,8 +136,19 @@ sha1_stream (FILE *stream, void *resblock)
 {
   struct sha1_ctx ctx;
   size_t sum;
+  char *buffer;
+#ifdef AF_ALG
+  int ret;
+
+  ret = afalg_stream(stream, resblock, "sha1", SHA1_DIGEST_SIZE);
+  if (!ret)
+      return 0;
+
+  if (ret == -EIO)
+      return 1;
+#endif
 
-  char *buffer = malloc (BLOCKSIZE + 72);
+  buffer = malloc (BLOCKSIZE + 72);
   if (!buffer)
     return 1;
 
diff --git a/modules/crypto/sha1 b/modules/crypto/sha1
index d65f99418..30b7153e2 100644
--- a/modules/crypto/sha1
+++ b/modules/crypto/sha1
@@ -5,6 +5,8 @@ Files:
 lib/gl_openssl.h
 lib/sha1.h
 lib/sha1.c
+lib/af_alg.h
+lib/af_alg.c
 m4/gl-openssl.m4
 m4/sha1.m4
 
@@ -17,7 +19,7 @@ configure.ac:
 gl_SHA1
 
 Makefile.am:
-lib_SOURCES += sha1.c
+lib_SOURCES += sha1.c af_alg.c
 
 Include:
 "sha1.h"
-- 
2.14.3