tdf#101094 (32): Use a partial GET as a fall-back for HEAD...

... partial GET means a GET with no data returned, to test for
resource 'real' availability in case HEAD fails or is disabled.
At  the same time disable use of HEAD method on the resource
for the whole access procedure.

This change is needed to manage web servers that don't permit the
use of either HEAD or OPTIONS methods.
To accomodate pure web sites that enable only GET to fetch contents.

Change-Id: If52316ddd6ce637fb7d2ef518423de246ee2dcfb
Reviewed-on: https://gerrit.libreoffice.org/28992
Tested-by: Giuseppe Castagno <giuseppe.castagno@acca-esse.eu>
Reviewed-by: Giuseppe Castagno <giuseppe.castagno@acca-esse.eu>

ucb/source/ucp/webdav-neon/DAVTypes.cxx

@@ -24,6 +24,7 @@ DAVOptions::DAVOptions() :
     m_isClass1( false ),
     m_isClass2( false ),
     m_isClass3( false ),
+    m_isHeadAllowed( true ),
     m_isLocked( false ),
     m_aAllowedMethods(),
     m_nStaleTime( 0 ),
@@ -38,6 +39,7 @@ DAVOptions::DAVOptions( const DAVOptions & rOther ) :
     m_isClass1( rOther.m_isClass1 ),
     m_isClass2( rOther.m_isClass2 ),
     m_isClass3( rOther.m_isClass3 ),
+    m_isHeadAllowed( rOther.m_isHeadAllowed ),
     m_isLocked( rOther.m_isLocked ),
     m_aAllowedMethods( rOther.m_aAllowedMethods ),
     m_nStaleTime( rOther.m_nStaleTime ),
@@ -173,5 +175,32 @@ bool DAVOptionsCache::isResourceFound( const OUString & rURL )
     return true;
 }
 
+bool DAVOptionsCache::isHeadAllowed( const OUString & rURL )
+{
+    osl::MutexGuard aGuard( m_aMutex );
+    OUString aEncodedUrl( ucb_impl::urihelper::encodeURI( NeonUri::unescape( rURL ) ) );
+    normalizeURLLastChar( aEncodedUrl );
+
+    DAVOptionsMap::iterator it;
+    it = m_aTheCache.find( aEncodedUrl );
+    if ( it != m_aTheCache.end() )
+    {
+        // first check for stale
+        TimeValue t1;
+        osl_getSystemTime( &t1 );
+        if( (*it).second.getStaleTime() < t1.Seconds )
+        {
+            m_aTheCache.erase( it );
+            return true; // to force again OPTIONS method
+        }
+
+        // check if the resource was present on server
+        return (*it).second.isHeadAllowed();
+    }
+    // this value is needed because some web server don't implement
+    // OPTIONS method, so the resource is considered found,
+    // until detected otherwise
+    return true;
+}
 
 /* vim:set shiftwidth=4 softtabstop=4 expandtab cinoptions=b1,g0,N-s cinkeys+=0=break: */

ucb/source/ucp/webdav-neon/DAVTypes.hxx

@@ -81,6 +81,8 @@ namespace webdav_ucp
         bool    m_isClass1;
         bool    m_isClass2;
         bool    m_isClass3;
+        // for server that do not implement it
+        bool    m_isHeadAllowed;
         // Internally used to maintain locked stated of the resource, only
         // if it's a Class 2 resource
         bool    m_isLocked;
@@ -111,6 +113,9 @@ namespace webdav_ucp
         bool isClass3() { return m_isClass3; };
         void setClass3( bool Class3 = true ) { m_isClass3 = Class3; };
 
+        bool isHeadAllowed() { return m_isHeadAllowed; };
+        void setHeadAllowed( bool HeadAllowed = true ) { m_isHeadAllowed = HeadAllowed; };
+
         sal_uInt32  getStaleTime() const { return m_nStaleTime ; };
         void setStaleTime( const sal_uInt32 nStaleTime ) { m_nStaleTime = nStaleTime; };
 
@@ -133,6 +138,7 @@ namespace webdav_ucp
             m_isClass1 = false;
             m_isClass2 = false;
             m_isClass3 = false;
+            m_isHeadAllowed = true;
             m_isLocked = false;
             m_aAllowedMethods.clear();
             m_nStaleTime = 0;
@@ -177,6 +183,8 @@ namespace webdav_ucp
         */
         bool isResourceFound( const OUString & rURL );
 
+        bool isHeadAllowed( const OUString & rURL );
+
     private:
 
         /// remove the last '/' in aUrl, if it exists

ucb/source/ucp/webdav-neon/webdavcontent.cxx

@@ -1589,6 +1589,10 @@ uno::Reference< sdbc::XRow > Content::getPropertyValues(
                         // clean cached value of PROPFIND property names
                         // PROPPATCH can change them
                         removeCachedPropertyNames( xResAccess->getURL() );
+                        // test if HEAD allowed, if not, throw, will be catched immediately
+                        if ( !aStaticDAVOptionsCache.isHeadAllowed( xResAccess->getURL() ) )
+                            throw DAVException( DAVException::DAV_HTTP_ERROR, "405 Not Implemented" );
+
                         xResAccess->HEAD( aHeaderNames, resource, xEnv );
                         m_bDidGetOrHead = true;
 
@@ -4075,7 +4079,7 @@ void Content::getResourceOptions(
                             // instead of SC_NOT_IMPLEMENTED or SC_METHOD_NOT_ALLOWED.
                             // So check if this is an available resource, or a real 'Not Found' event.
                             sal_uInt32 nLifeTime = m_nOptsCacheLifeNotFound;
-                            if( isResourceAvailable(xEnv, rResAccess ) )
+                            if( isResourceAvailable( xEnv, rResAccess, rDAVOptions ) )
                             {
                                 nLifeTime = m_nOptsCacheLifeNotImpl;
                                 rDAVOptions.setResourceFound(); // means it exists, but it's not DAV
@@ -4134,17 +4138,54 @@ void Content::getResourceOptions(
 
 //static
 bool Content::isResourceAvailable( const css::uno::Reference< css::ucb::XCommandEnvironment >& xEnv,
-                                  const std::unique_ptr< DAVResourceAccess > & rResAccess )
+                                  const std::unique_ptr< DAVResourceAccess > & rResAccess,
+                                  DAVOptions& rDAVOptions )
 {
+    std::vector< rtl::OUString > aHeaderNames;
+    DAVResource aResource;
+
     try
     {
-        // To check for the physical URL resource availability, using a simple HEAD command
+        // To check for the physical URL resource availability, first
-        // if HEAD is successfull, set element found.
+        // try using a simple HEAD command
-        std::vector< OUString > aHeaderNames;
+        // if HEAD is successfull, set element found,
-        DAVResource resource;
+        rResAccess->HEAD( aHeaderNames, aResource, xEnv );
-        rResAccess->HEAD( aHeaderNames, resource, xEnv );
         return true;
     }
+    catch ( DAVException const & e )
+    {
+        if ( e.getStatus() == SC_NOT_IMPLEMENTED ||
+             e.getStatus() == SC_METHOD_NOT_ALLOWED ||
+             e.getStatus() == SC_NOT_FOUND )
+        {
+            SAL_WARN( "ucb.ucp.webdav", "HEAD not implemented: fall back to a partial GET" );
+            // set in cached OPTIONS "HEAD not implemented"
+            // so it won't be used again on this resource
+            rDAVOptions.setHeadAllowed( false );
+            try
+            {
+                // do a GET with a payload of 0, the server does not
+                // support HEAD (or has HEAD disabled)
+                DAVRequestHeaders aPartialGet;
+                aPartialGet.push_back(
+                    DAVRequestHeader(
+                        OUString( "Range" ),
+                        OUString( "bytes=0-0" )));
+
+                rResAccess->GET( aPartialGet,
+                                 aHeaderNames,
+                                 aResource,
+                                 xEnv );
+                return true;
+            }
+            catch (...)
+            {
+                return false;
+            }
+        }
+        else
+            return false;
+    }
     catch ( ... )
     {
         // some error... so set as not found
@@ -4152,6 +4193,7 @@ bool Content::isResourceAvailable( const css::uno::Reference< css::ucb::XCommand
         // in rResAccess function method.
         return false;
     }
+    return false;
 }
 
 

ucb/source/ucp/webdav-neon/webdavcontent.hxx

@@ -329,7 +329,8 @@ public:
         throw ( css::uno::Exception, std::exception );
 
     static bool isResourceAvailable( const css::uno::Reference< css::ucb::XCommandEnvironment >& xEnv,
-                             const std::unique_ptr< DAVResourceAccess > & rResAccess);
+                             const std::unique_ptr< DAVResourceAccess > & rResAccess,
+                                     DAVOptions& rDAVOptions );
 
     static void removeCachedPropertyNames( const OUString & rURL );
 };