1 files changed, 213 insertions, 0 deletions

diff --git a/gl/af_alg.c b/gl/af_alg.c
new file mode 100644
index 00000000..748af70b
--- /dev/null
+++ b/gl/af_alg.c
@@ -0,0 +1,213 @@
+/* af_alg.c - Compute message digests from file streams and buffers.
+   Copyright (C) 2018-2021 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