Re: 'ls' hanging on paramiko-based sftp server

[Alexander V. Lukyanov]

On Mon, May 05, 2008 at 11:27:59AM -0500, Charles Duffy wrote:
> Per subject. I don't understand what the client is waiting for -- 
> according to 'ls' with debug set, every packet sent has received a 
> response. Could the unhandled 'env' requests be related?

I suspect the server sends truncated replies. Please try this patch
(against 3.7.2 version).

-- 
   Alexander.

Index: SFtp.cc
===================================================================
RCS file: /home/lav/cvsroot/lftp/src/SFtp.cc,v
retrieving revision 1.78
diff -u -p -r1.78 SFtp.cc
--- SFtp.cc     8 Apr 2008 19:35:11 -0000       1.78
+++ SFtp.cc     7 May 2008 07:41:53 -0000
@@ -388,7 +388,12 @@ void SFtp::Packet::PackString(Buffer *b,
 SFtp::unpack_status_t SFtp::Packet::UnpackString(const Buffer *b,int 
*offset,int limit,xstring *str_out)
 {
    if(limit-*offset<4)
-      return b->Eof()?UNPACK_PREMATURE_EOF:UNPACK_NO_DATA_YET;
+   {
+      // We unpack strings when we have already received complete packet,
+      // so it is not possible to receive any more data.
+      LogError(2,"bad string in reply (truncated length field)");
+      return UNPACK_WRONG_FORMAT;
+   }
 
    int len=b->UnpackUINT32BE(*offset);
    if(len>limit-*offset-4)
@@ -441,8 +446,8 @@ SFtp::unpack_status_t SFtp::Packet::Unpa
 
 SFtp::unpack_status_t SFtp::UnpackPacket(Buffer *b,SFtp::Packet **p)
 {
-   *p=0;
    Packet *&pp=*p;
+   pp=0;
 
    Packet probe;
    unpack_status_t res=probe.Unpack(b);
@@ -517,8 +522,8 @@ SFtp::unpack_status_t SFtp::UnpackPacket
         ;
       }
       probe.DropData(b);
-      delete *p;
-      *p=0;
+      delete pp;
+      pp=0;
    }
    return res;
 }
@@ -1851,9 +1856,19 @@ SFtp::unpack_status_t SFtp::Reply_STATUS
    UNPACK32(code);
    if(protocol_version>=3)
    {
+      if(unpacked>=limit)
+      {
+        LogError(2,"Status reply lacks `error message' field");
+        return UNPACK_SUCCESS;
+      }
       res=Packet::UnpackString(b,offset,limit,&message);
       if(res!=UNPACK_SUCCESS)
         return res;
+      if(unpacked>=limit)
+      {
+        LogError(2,"Status reply lacks `language tag' field");
+        return UNPACK_SUCCESS;
+      }
       res=Packet::UnpackString(b,offset,limit,&language);
       if(res!=UNPACK_SUCCESS)
         return res;