[tor-commits] [stem/master] Basic constraint checking for extra-info descriptors

[atagar at torproject.org]

commit 234a90a79624e5503c4bf65db01c14e54fb9b8de
Author: Damian Johnson <atagar at torproject.org>
Date:   Sun May 6 20:52:21 2012 -0700

    Basic constraint checking for extra-info descriptors
    
    Parsing the 'extra-info' line and performing basic validation about extra-info
    descriptor fields (that we have required fields, most fields don't appear more
    than once, etc).
    
    I'll add some unit tests for this after I've added parsing for all of the
    mandatory fields.
---
 stem/descriptor/extrainfo_descriptor.py |  102 +++++++++++++++++++++++++++++++
 stem/descriptor/server_descriptor.py    |    4 +-
 2 files changed, 104 insertions(+), 2 deletions(-)

diff --git a/stem/descriptor/extrainfo_descriptor.py b/stem/descriptor/extrainfo_descriptor.py
index 891ba18..04530c0 100644
--- a/stem/descriptor/extrainfo_descriptor.py
+++ b/stem/descriptor/extrainfo_descriptor.py
@@ -22,6 +22,52 @@ ExtraInfoDescriptor - Tor extra-info descriptor.
 
 import stem.descriptor
 
+# relay descriptors must have exactly one of the following
+REQUIRED_FIELDS = (
+  "extra-info",
+  "published",
+  "router-signature",
+)
+
+# optional entries that can appear at most once
+SINGLE_FIELDS = (
+  "read-history",
+  "write-history",
+  "geoip-db-digest",
+  "bridge-stats-end",
+  "bridge-ips",
+  "dirreq-stats-end",
+  "dirreq-v2-ips",
+  "dirreq-v3-ips",
+  "dirreq-v2-reqs",
+  "dirreq-v3-reqs",
+  "dirreq-v2-share",
+  "dirreq-v3-share",
+  "dirreq-v2-resp",
+  "dirreq-v3-resp",
+  "dirreq-v2-direct-dl",
+  "dirreq-v3-direct-dl",
+  "dirreq-v2-tunneled-dl",
+  "dirreq-v3-tunneled-dl",
+  "dirreq-read-history",
+  "dirreq-write-history",
+  "entry-stats-end",
+  "entry-ips",
+  "cell-stats-end",
+  "cell-processed-cells",
+  "cell-queued-cells",
+  "cell-time-in-queue",
+  "cell-circuits-per-decile",
+  "conn-bi-direct",
+  "exit-stats-end",
+  "exit-kibibytes-written",
+  "exit-kibibytes-read",
+  "exit-streams-opened",
+)
+
+FIRST_FIELD = "extra-info"
+LAST_FIELD = "router-signature"
+
 def parse_file(descriptor_file, validate = True):
   """
   Iterates over the extra-info descriptors in a file.
@@ -108,4 +154,60 @@ class ExtraInfoDescriptor(stem.descriptor.Descriptor):
     self.write_history_end = None
     self.write_history_interval = None
     self.write_history_values = []
+    
+    entries, first_keyword, last_keyword, _ = \
+      stem.descriptor._get_descriptor_components(raw_contents, validate, ())
+    
+    if validate:
+      for keyword in REQUIRED_FIELDS:
+        if not keyword in entries:
+          raise ValueError("Extra-info descriptor must have a '%s' entry" % keyword)
+      
+      for keyword in REQUIRED_FIELDS + SINGLE_FIELDS:
+        if keyword in entries and len(entries[keyword]) > 1:
+          raise ValueError("The '%s' entry can only appear once in an extra-info descriptor" % keyword)
+      if not first_keyword == FIRST_FIELD:
+        raise ValueError("Extra-info descriptor must start with a '%s' entry" % FIRST_FIELD)
+      
+      if not last_keyword == LAST_FIELD:
+        raise ValueError("Descriptor must end with a '%s' entry" % LAST_FIELD)
+    
+    self._parse(entries, validate)
+  
+  def _parse(self, entries, validate):
+    """
+    Parses a series of 'keyword => (value, pgp block)' mappings and applies
+    them as attributes.
+    
+    Arguments:
+      entries (dict)  - descriptor contents to be applied
+      validate (bool) - checks the validity of descriptor content if True
+    
+    Raises:
+      ValueError if an error occures in validation
+    """
+    
+    for keyword, values in entries.items():
+      # most just work with the first (and only) value
+      value, block_contents = values[0]
+      
+      line = "%s %s" % (keyword, value) # original line
+      if block_contents: line += "\n%s" % block_contents
+      
+      if keyword == "extra-info":
+        # "extra-info" Nickname Fingerprint
+        extra_info_comp = value.split()
+        
+        if len(extra_info_comp) != 2:
+          if not validate: continue
+          raise ValueError("Extra-info line must have two values: %s" % line)
+        
+        if validate:
+          if not stem.util.tor_tools.is_valid_nickname(extra_info_comp[0]):
+            raise ValueError("Extra-info line entry isn't a valid nickname: %s" % extra_info_comp[0])
+          elif not stem.util.tor_tools.is_valid_fingerprint(extra_info_comp[1]):
+            raise ValueError("Tor relay fingerprints consist of fourty hex digits: %s" % extra_info_comp[1])
+        
+        self.nickname = extra_info_comp[0]
+        self.fingerprint = extra_info_comp[1]
 
diff --git a/stem/descriptor/server_descriptor.py b/stem/descriptor/server_descriptor.py
index b87ed2a..12b0728 100644
--- a/stem/descriptor/server_descriptor.py
+++ b/stem/descriptor/server_descriptor.py
@@ -543,11 +543,11 @@ class ServerDescriptor(stem.descriptor.Descriptor):
     
     expected_first_keyword = self._first_keyword()
     if expected_first_keyword and not first_keyword == expected_first_keyword:
-      raise ValueError("Descriptor must start with a '%s' entry" % first_keyword)
+      raise ValueError("Descriptor must start with a '%s' entry" % expected_first_keyword)
     
     expected_last_keyword = self._last_keyword()
     if expected_last_keyword and not last_keyword == expected_last_keyword:
-      raise ValueError("Descriptor must end with a '%s' entry" % last_keyword)
+      raise ValueError("Descriptor must end with a '%s' entry" % expected_last_keyword)
     
     if not self.exit_policy:
       raise ValueError("Descriptor must have at least one 'accept' or 'reject' entry")