[tor-commits] [stem/master] Completely untested start for descriptor parsing

[atagar@xxxxxxxxxxxxxx]

commit cb819ce76b011c4ee84fa15014c92166bca49577
Author: Damian Johnson <atagar@xxxxxxxxxxxxxx>
Date:   Sat Mar 17 16:19:09 2012 -0700

    Completely untested start for descriptor parsing
    
    Starting on server descriptor parsing. This is gonna need some other classes
    and helper functions (such as an ExitPolicy and is_valid_ip_address()) but
    otherwise should be pretty straight forward.
---
 stem/descriptor/server_descriptor.py |  132 ++++++++++++++++++++++++++++++++++
 1 files changed, 132 insertions(+), 0 deletions(-)

diff --git a/stem/descriptor/server_descriptor.py b/stem/descriptor/server_descriptor.py
new file mode 100644
index 0000000..e9782bc
--- /dev/null
+++ b/stem/descriptor/server_descriptor.py
@@ -0,0 +1,132 @@
+"""
+Parsing for Tor server descriptors, which contains the infrequently changing
+information about a Tor relay (contact information, exit policy, public keys,
+etc). This information is provided from a few sources...
+
+- control port via 'GETINFO desc/*' queries
+- the 'cached-descriptors' file in tor's data directory
+- tor metrics, at https://metrics.torproject.org/data.html
+"""
+
+import re
+
+from stem.descriptor.descriptor import Descriptor
+
+ENTRY_START = "router"
+ENTRY_END   = "router-signature"
+
+KEYWORD_CHAR    = "[a-zA-Z0-9-]"
+WHITESPACE      = "[ \t]"
+KEYWORD_LINE    = re.compile("^(%s+)%s*(%s*)$" % (KEYWORD_CHAR, WHITESPACE, KEYWORD_CHAR))
+SIGNATURE_START = re.compile("^-----BEGIN %s+ PUBLIC KEY-----$" % KEYWORD_CHAR)
+SIGNATURE_END   = re.compile("^-----END %s+ PUBLIC KEY-----$" % KEYWORD_CHAR)
+
+# entries must have exactly one of the following
+REQUIRED_FIELDS = (
+  "published",
+  "onion-key",
+  "signing-key",
+  "bandwidth",
+)
+
+# optional entries that can appear at most once
+SINGLE_FIELDS = (
+  "contact",
+  "uptime",
+  "fingerprint",
+  "hibernating",
+  "read-history",
+  "write-history",
+  "eventdns",
+  "platform",
+  "family",
+)
+
+def parse_server_descriptors_v2(path, descriptor_file):
+  """
+  Iterates over the verion 2 server descriptors in a descriptor file.
+  """
+  
+  pass
+
+class ServerDescriptorV2(Descriptor):
+  """
+  Version 2 server descriptor, as specified in...
+  https://gitweb.torproject.org/torspec.git/blob/HEAD:/dir-spec-v2.txt
+  
+  Attributes:
+    nickname (str)   - relay's nickname (*)
+    address (str)    - IPv4 address of the relay (*)
+    or_port (int)    - port used for relaying (*)
+    socks_port (int) - deprecated attribute, always zero (*)
+    dir_port (int)   - deprecated port used for descriptor mirroring (*)
+    
+    * required fields
+  """
+  
+  nickname = None
+  address = None
+  or_port = None
+  socks_port = None
+  dir_port = None
+  
+  def __init__(self, contents):
+    Descriptor.__init__(self, contents)
+    
+    # A descriptor contains a series of 'keyword lines' which are simply a
+    # keyword followed by an optional value. Lines can also be followed by a
+    # signature block.
+    #
+    # We care about the ordering of 'accept' and 'reject' entries because this
+    # influences the resulting exit policy, but for everything else the order
+    # does not matter so breaking it into key / value pairs.
+    
+    entries = {}
+    exit_policy_lines = []
+    
+    for line in contents.split("\n"):
+      line_match = KEYWORD_LINE.match()
+      
+      if not line_match:
+        raise ValueError("Line contains invalid characters: %s" % line)
+      
+      keyword, value = line_match.groups()
+      
+      if keyword in ("accept", "reject"):
+        exit_policy_lines.append("%s %s" % (keyword, value))
+      elif keyword in entries:
+        entries[keyword].append(value)
+      else:
+        entries[keyword] = [value]
+    
+    # validates restrictions about the entries
+    
+    for keyword in REQUIRED_FIELDS:
+      if not keyword in entries:
+        raise ValueError("Descriptor must have a '%s' entry" % keyword
+    
+    for keyword in SINGLE_FIELDS + REQUIRED_FIELDS:
+      if keyword in entries and len(entries[keyword]) > 1:
+        raise ValueError("The '%s' entry can only appear once in a descriptor" % keyword)
+    
+    # parse all the entries into our attributes
+    
+    for keyword, values in entres.items():
+      if keyword == "router":
+        # "router" nickname address ORPort SocksPort DirPort
+        router_comp = values[0].split()
+        
+        if len(router_comp) != 5:
+          raise ValueError("Router line must have five values: router %s" % values[0]
+        
+        # TODO: also check validity of other fields
+        # Fingerprint = "$" 40*HEXDIG
+        # NicknameChar = "a"-"z" / "A"-"Z" / "0" - "9"
+        # Nickname = 1*19 NicknameChar
+        
+        self.nickname   = router_comp[0]
+        self.address    = router_comp[1]
+        self.or_port    = router_comp[2]
+        self.socks_port = router_comp[3]
+        self.dir_port   = router_comp[4]
+



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