entropy.transceivers: implement support for FtpInterface.get_file_md5 in FtpServerHandler

The aim is to make php handlers not always required when there is a FTP
server that supports "SITE MD5" commands (like proftpd with mod_md5).
This commit makes FtpServerHandler able to handle such feature and avoid
using any other external hook. If server support is found, this verification
is enough. If support is broken, FtpServerHandler will try to fallback to
previously supported features, if enabled (use_handlers variable).
Moreover, FtpServerHandler now makes use of entropy.tools.is_valid_md5
instead of just checking if provided strings are long 32 chars.

libraries/entropy/transceivers.py

@@ -1111,7 +1111,8 @@ class FtpServerHandler:
         self.critical_files = critical_files
         self.handlers_data = handlers_data.copy()
 
-    def handler_verify_upload(self, local_filepath, uri, counter, maxcount, tries):
+    def handler_verify_upload(self, local_filepath, uri, counter, maxcount,
+            tries, remote_md5 = None):
 
         crippled_uri = self.entropyTools.extract_ftp_host_from_uri(uri)
 
@@ -1130,6 +1131,68 @@ class FtpServerHandler:
             back = True
         )
 
+        valid_remote_md5 = True
+        # if remote server supports MD5 commands, remote_md5 is filled
+        if isinstance(remote_md5, basestring):
+            valid_md5 = self.entropyTools.is_valid_md5(remote_md5)
+            ckres = False
+            if valid_md5: # seems valid
+                ckres = self.entropyTools.compare_md5(local_filepath,
+                    remote_md5)
+            if ckres:
+                self.Entropy.updateProgress(
+                    "[%s|#%s|(%s/%s)] %s: %s: %s" % (
+                        blue(crippled_uri),
+                        darkgreen(str(tries)),
+                        blue(str(counter)),
+                        bold(str(maxcount)),
+                        blue(_("digest verification")),
+                        os.path.basename(local_filepath),
+                        darkgreen(_("so far, so good!")),
+                    ),
+                    importance = 0,
+                    type = "info",
+                    header = red(" @@ ")
+                )
+                return True
+            # ouch!
+            elif not valid_md5:
+                # mmmh... malformed md5, try with handlers
+                self.Entropy.updateProgress(
+                    "[%s|#%s|(%s/%s)] %s: %s: %s" % (
+                        blue(crippled_uri),
+                        darkgreen(str(tries)),
+                        blue(str(counter)),
+                        bold(str(maxcount)),
+                        blue(_("digest verification")),
+                        os.path.basename(local_filepath),
+                        bold(_("malformed md5 provided to function")),
+                    ),
+                    importance = 0,
+                    type = "warning",
+                    header = brown(" @@ ")
+                )
+            else: # it's really bad!
+                self.Entropy.updateProgress(
+                    "[%s|#%s|(%s/%s)] %s: %s: %s" % (
+                        blue(crippled_uri),
+                        darkgreen(str(tries)),
+                        blue(str(counter)),
+                        bold(str(maxcount)),
+                        blue(_("digest verification")),
+                        os.path.basename(local_filepath),
+                        bold(_("remote md5 is invalid")),
+                    ),
+                    importance = 0,
+                    type = "warning",
+                    header = brown(" @@ ")
+                )
+                valid_remote_md5 = False
+
+        if not self.use_handlers:
+            # handlers usage is disabled
+            return valid_remote_md5 # always valid
+
         checksum = self.Entropy.get_remote_package_checksum(
             self.repo,
             os.path.basename(local_filepath),
@@ -1150,8 +1213,8 @@ class FtpServerHandler:
                 type = "info",
                 header = red(" @@ ")
             )
-            return True
-        elif isinstance(checksum,bool) and not checksum:
+            return valid_remote_md5
+        elif isinstance(checksum, bool) and not checksum:
             self.Entropy.updateProgress(
                 "[%s|#%s|(%s/%s)] %s: %s: %s" % (
                     blue(crippled_uri),
@@ -1167,7 +1230,7 @@ class FtpServerHandler:
                 header = brown(" @@ ")
             )
             return False
-        elif len(checksum) == 32:
+        elif self.entropyTools.is_valid_md5(checksum):
             # valid? checking
             ckres = self.entropyTools.compare_md5(local_filepath,checksum)
             if ckres:
@@ -1217,7 +1280,7 @@ class FtpServerHandler:
                 type = "warning",
                 header = brown(" @@ ")
             )
-            return True
+            return valid_remote_md5
 
     def go(self):
 
@@ -1306,8 +1369,12 @@ class FtpServerHandler:
                         header = red(" @@ ")
                     )
                     rc = syncer(*myargs)
-                    if rc and self.use_handlers and not self.download:
-                        rc = self.handler_verify_upload(mypath, uri, counter, maxcount, tries)
+                    if rc and not self.download:
+                        # try with "SITE MD5 command first"
+                        # proftpd's mod_md5 supports it
+                        remote_md5 = ftp.get_file_md5(os.path.basename(mypath))
+                        rc = self.handler_verify_upload(mypath, uri,
+                            counter, maxcount, tries, remote_md5 = remote_md5)
                     if rc:
                         self.Entropy.updateProgress(
                             "[%s|#%s|(%s/%s)] %s %s: %s" % (