From f3f349a0cf0598fdf3a40d909075974c7bc992bc Mon Sep 17 00:00:00 2001
From: Matthew White <mehw.is.me@inventati.org>
Date: Tue, 16 Aug 2016 23:12:56 +0200
Subject: [PATCH] Add file size computation in Metalink module

* NEWS: Mention Metalink's file size verification
* src/metalink.c (retrieve_from_metalink): Add file size computation
* doc/metalink.txt: Update document. Remove resolved bugs

Reject downloaded files when they do not agree with their Metalink/XML
metalink:size: https://tools.ietf.org/html/rfc5854#section-4.2.14

At the moment of writing, Metalink/HTTP headers do not provide a file
size field. This information could be obtained from the Content-Length
header field: https://tools.ietf.org/html/rfc6249#section-7
---
 NEWS             |  4 ++++
 doc/metalink.txt | 11 ++++-------
 src/metalink.c   | 35 +++++++++++++++++++++++++++++++++++
 3 files changed, 43 insertions(+), 7 deletions(-)

diff --git a/NEWS b/NEWS
index 60112506..04718d59 100644
--- a/NEWS
+++ b/NEWS
@@ -9,6 +9,10 @@ Please send GNU Wget bug reports to <bug-wget@gnu.org>.
 
 * Changes in Wget X.Y.Z
 
+* When processing a Metalink file, reject downloaded files which don't
+  agree with their own metalink:size value:
+  https://tools.ietf.org/html/rfc5854#section-4.2.16
+
 * When processing a Metalink file, with --continue resume partially
   downloaded files and keep fully downloaded files even if they fail
   the verification.
diff --git a/doc/metalink.txt b/doc/metalink.txt
index 0f3706a9..904ef2e0 100644
--- a/doc/metalink.txt
+++ b/doc/metalink.txt
@@ -67,7 +67,8 @@ References:
 When a Metalink/XML file is parsed:
 1. create the metalink:file "path/file" tree;
 2. download the metalink:url file as "path/file";
-3. verify the "path/file" checksum.
+3. verify the "path/file" size, if declared;
+4. verify the "path/file" checksum.
 
 All the above conform to the RFC5854 standard.
 
@@ -79,11 +80,6 @@ References:
 
 If more metalink:file elements are the same, wget downloads them all.
 
-4.4 Bugs
-========
-
-The download is OK even when metalink:file size is wrong.
-
 5. `wget --metalink-over-http`
 ******************************
 
@@ -107,7 +103,8 @@ References:
 When a Metalink/HTTP header is parsed:
 1. extract metalink metadata from the header;
 2. download the file from the mirror with the highest priority;
-3. verify the file's checksum.
+3. verify the file's size, if declared;
+4. verify the file's checksum.
 
 All the above comform to the usual Wget's download behaviour and to
 the RFC6249 standard.
diff --git a/src/metalink.c b/src/metalink.c
index 03a0bb13..ee0ed085 100644
--- a/src/metalink.c
+++ b/src/metalink.c
@@ -240,6 +240,41 @@ retrieve_from_metalink (const metalink_t* metalink)
                   continue;
                 }
 
+              logprintf (LOG_VERBOSE, _("Computing size for %s\n"), quote (filename));
+
+              if (!mfile->size)
+                {
+                  logprintf (LOG_VERBOSE, _("File size not declared. Skipping check.\n"));
+                }
+              else
+                {
+                  wgint local_file_size = file_size (filename);
+
+                  if (local_file_size == -1)
+                    {
+                      logprintf (LOG_NOTQUIET, _("Could not get downloaded file's size.\n"));
+                      fclose (local_file);
+                      local_file = NULL;
+                      continue;
+                    }
+
+                  /* FIXME: what about int64?  */
+                  DEBUGP (("Declared size: %lld\n", mfile->size));
+                  DEBUGP (("Computed size: %lld\n", (long long) local_file_size));
+
+                  if (local_file_size != (wgint) mfile->size)
+                    {
+                      logprintf (LOG_NOTQUIET, _("Size mismatch for file %s.\n"), quote (filename));
+                      fclose (local_file);
+                      local_file = NULL;
+                      continue;
+                    }
+                  else
+                    {
+                      logputs (LOG_VERBOSE, _("Size matches.\n"));
+                    }
+                }
+
               for (mchksum_ptr = mfile->checksums; *mchksum_ptr; mchksum_ptr++)
                 {
                   char md2[MD2_DIGEST_SIZE];