From dcd5856b11c685ca6d4629212d2978ce196ea65c Mon Sep 17 00:00:00 2001
From: Michael Vogt <mvo@debian.org>
Date: Tue, 26 Aug 2014 19:08:37 -0700
Subject: Pass ExpectedSize to tthe backend method

This ensures that we can stop downloading if the server send
too much data by accident (or by a malicious attempt)
---
 methods/http.cc   | 10 +++++++++-
 methods/http.h    |  4 +++-
 methods/server.cc |  5 +++++
 methods/server.h  |  4 +++-
 4 files changed, 20 insertions(+), 3 deletions(-)

(limited to 'methods')

diff --git a/methods/http.cc b/methods/http.cc
index c734d3799..916fa464f 100644
--- a/methods/http.cc
+++ b/methods/http.cc
@@ -63,7 +63,8 @@ const unsigned int CircleBuf::BW_HZ=10;
 // CircleBuf::CircleBuf - Circular input buffer				/*{{{*/
 // ---------------------------------------------------------------------
 /* */
-CircleBuf::CircleBuf(unsigned long long Size) : Size(Size), Hash(0)
+CircleBuf::CircleBuf(unsigned long long Size) 
+   : Size(Size), Hash(0), TotalWriten(0)
 {
    Buf = new unsigned char[Size];
    Reset();
@@ -79,6 +80,7 @@ void CircleBuf::Reset()
    InP = 0;
    OutP = 0;
    StrPos = 0;
+   TotalWriten = 0;
    MaxGet = (unsigned long long)-1;
    OutQueue = string();
    if (Hash != 0)
@@ -216,6 +218,8 @@ bool CircleBuf::Write(int Fd)
 	 
 	 return false;
       }
+
+      TotalWriten += Res;
       
       if (Hash != 0)
 	 Hash->Add(Buf + (OutP%Size),Res);
@@ -649,6 +653,10 @@ bool HttpServerState::Go(bool ToFile, FileFd * const File)
 	 return _error->Errno("write",_("Error writing to output file"));
    }
 
+   if (ExpectedSize > 0 && In.TotalWriten > ExpectedSize)
+      return _error->Error("Writing more data than expected (%llu > %llu)",
+                           In.TotalWriten, ExpectedSize);
+
    // Handle commands from APT
    if (FD_ISSET(STDIN_FILENO,&rfds))
    {
diff --git a/methods/http.h b/methods/http.h
index 5406ce4a7..c98fe8e5f 100644
--- a/methods/http.h
+++ b/methods/http.h
@@ -63,6 +63,8 @@ class CircleBuf
 
    public:
    Hashes *Hash;
+   // total amount of data that got written so far
+   unsigned long long TotalWriten;
 
    // Read data in
    bool Read(int Fd);
@@ -81,8 +83,8 @@ class CircleBuf
    bool ReadSpace() const {return Size - (InP - OutP) > 0;};
    bool WriteSpace() const {return InP - OutP > 0;};
 
-   // Dump everything
    void Reset();
+   // Dump everything
    void Stats();
 
    CircleBuf(unsigned long long Size);
diff --git a/methods/server.cc b/methods/server.cc
index c91d3b218..1b6511c59 100644
--- a/methods/server.cc
+++ b/methods/server.cc
@@ -531,6 +531,11 @@ int ServerMethod::Loop()
 
 	    // Run the data
 	    bool Result = true;
+
+            // ensure we don't fetch too much
+            if (Queue->ExpectedSize > 0)
+               Server->ExpectedSize = Queue->ExpectedSize;
+
             if (Server->HaveContent)
 	       Result = Server->RunData(File);
 
diff --git a/methods/server.h b/methods/server.h
index 5299b3954..0d7333140 100644
--- a/methods/server.h
+++ b/methods/server.h
@@ -49,6 +49,8 @@ struct ServerState
    URI Proxy;
    unsigned long TimeOut;
 
+   unsigned long long ExpectedSize;
+
    protected:
    ServerMethod *Owner;
 
@@ -73,7 +75,7 @@ struct ServerState
    bool Comp(URI Other) const {return Other.Host == ServerName.Host && Other.Port == ServerName.Port;};
    virtual void Reset() {Major = 0; Minor = 0; Result = 0; Code[0] = '\0'; Size = 0;
 		 StartPos = 0; Encoding = Closes; time(&Date); HaveContent = false;
-		 State = Header; Persistent = false; Pipeline = true;};
+		 State = Header; Persistent = false; Pipeline = true; ExpectedSize = 0;};
    virtual bool WriteResponse(std::string const &Data) = 0;
 
    /** \brief Transfer the data from the socket */
-- 
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