ObjectDatabase: we should fail when asked to read too much

ObjectDatabase.CreateBlob() accepts a number of bytes to read. It
currently however treats this as a max, rather than a hard size, which
seems ripe for introducing bugs.

Assert that we should throw when asked to read too much from a Stream.

2 files changed, 18 insertions, 0 deletions

diff --git a/LibGit2Sharp/Core/Proxy.cs b/LibGit2Sharp/Core/Proxy.cs
index f3fc97dd..e09a7fa0 100644
--- a/LibGit2Sharp/Core/Proxy.cs
+++ b/LibGit2Sharp/Core/Proxy.cs
@@ -69,6 +69,12 @@ namespace LibGit2Sharp.Core
             {
                 var oid = new GitOid();
                 int res = NativeMethods.git_blob_create_fromchunks(ref oid, repo, hintpath, fileCallback, IntPtr.Zero);
+
+                if (res == (int)GitErrorCode.User)
+                {
+                    throw new EndOfStreamException("The stream ended unexpectedly"); 
+                }
+
                 Ensure.ZeroResult(res);
 
                 return oid;
diff --git a/LibGit2Sharp/ObjectDatabase.cs b/LibGit2Sharp/ObjectDatabase.cs
index f40ec4e8..b200649e 100644
--- a/LibGit2Sharp/ObjectDatabase.cs
+++ b/LibGit2Sharp/ObjectDatabase.cs
@@ -138,7 +138,19 @@ namespace LibGit2Sharp
                     }
                 }
 
+                if (bytesToRead == 0)
+                {
+                    return 0;
+                }
+
                 int numberOfReadBytes = stream.Read(local, 0, bytesToRead);
+
+                if (numberOfBytesToConsume.HasValue
+                    && numberOfReadBytes == 0)
+                {
+                    return (int)GitErrorCode.User;
+                }
+
                 totalNumberOfReadBytes += numberOfReadBytes;
 
                 Marshal.Copy(local, 0, content, numberOfReadBytes);