python3/ashd/ssi.py

   1 """Module for handling server-side-include formatted files
   2
   3 This module is quite incomplete. I might complete it with more
   4 features as I need them. It will probably never be entirely compliant
   5 with Apache's version due to architectural differences.
   6 """
   7
   8 import sys, os, io, time, logging, functools
   9 from . import wsgiutil
  10
  11 log = logging.getLogger("ssi")
  12
  13 def parsecmd(text, p):
  14     try:
  15         while text[p].isspace(): p += 1
  16         cmd = ""
  17         while not text[p].isspace():
  18             cmd += text[p]
  19             p += 1
  20         pars = {}
  21         while True:
  22             while text[p].isspace(): p += 1
  23             if text[p:p + 3] == "-->":
  24                 return cmd, pars, p + 3
  25             key = ""
  26             while text[p].isalnum():
  27                 key += text[p]
  28                 p += 1
  29             if key == "":
  30                 return None, {}, p
  31             while text[p].isspace(): p += 1
  32             if text[p] != '=':
  33                 continue
  34             p += 1
  35             while text[p].isspace(): p += 1
  36             q = text[p]
  37             if q != '"' and q != "'" and q != '`':
  38                 continue
  39             val = ""
  40             p += 1
  41             while text[p] != q:
  42                 val += text[p]
  43                 p += 1
  44             p += 1
  45             pars[key] = val
  46     except IndexError:
  47         return None, {}, len(text)
  48
  49 class context(object):
  50     def __init__(self, out, root):
  51         self.out = out
  52         self.vars = {}
  53         now = time.time()
  54         self.vars["DOCUMENT_NAME"] = os.path.basename(root.path)
  55         self.vars["DATE_GMT"] = time.asctime(time.gmtime(now))
  56         self.vars["DATE_LOCAL"] = time.asctime(time.localtime(now))
  57         self.vars["LAST_MODIFIED"] = time.asctime(time.localtime(root.mtime))
  58
  59 class ssifile(object):
  60     def __init__(self, path):
  61         self.path = path
  62         sb = os.stat(self.path)
  63         self.cache = (sb.st_mode & 0o010) != 0
  64         self.mtime = int(sb.st_mtime)
  65         with open(path) as fp:
  66             self.parts = self.parse(fp.read())
  67
  68     def text(self, text, ctx):
  69         ctx.out.write(text)
  70
  71     def echo(self, var, enc, ctx):
  72         if var in ctx.vars:
  73             ctx.out.write(enc(ctx.vars[var]))
  74
  75     def include(self, path, ctx):
  76         try:
  77             nest = getfile(os.path.join(os.path.dirname(self.path), path))
  78         except Exception:
  79             log.warning("%s: could not find included file %s" % (self.path, path))
  80             return
  81         nest.process(ctx)
  82
  83     def process(self, ctx):
  84         for part in self.parts:
  85             part(ctx)
  86
  87     def resolvecmd(self, cmd, pars):
  88         if cmd == "include":
  89             if "file" in pars:
  90                 return functools.partial(self.include, pars["file"])
  91             elif "virtual" in pars:
  92                 # XXX: For now, just include the file as-is. Change
  93                 # when necessary.
  94                 return functools.partial(self.include, pars["virtual"])
  95             else:
  96                 log.warning("%s: invalid `include' directive" % self.path)
  97                 return None
  98         elif cmd == "echo":
  99             if not "var" in pars:
 100                 log.warning("%s: invalid `echo' directive" % self.path)
 101                 return None
 102             enc = wsgiutil.htmlquote
 103             if "encoding" in pars:
 104                 if pars["encoding"] == "entity":
 105                     enc = wsgiutil.htmlquote
 106             return functools.partial(self.echo, pars["var"], enc)
 107         else:
 108             log.warning("%s: unknown SSI command `%s'" % (self.path, cmd))
 109             return None
 110
 111     def parse(self, text):
 112         ret = []
 113         p = 0
 114         while True:
 115             p2 = text.find("<!--#", p)
 116             if p2 < 0:
 117                 ret.append(functools.partial(self.text, text[p:]))
 118                 return ret
 119             ret.append(functools.partial(self.text, text[p:p2]))
 120             cmd, pars, p = parsecmd(text, p2 + 5)
 121             if cmd is not None:
 122                 cmd = self.resolvecmd(cmd, pars)
 123                 if cmd is not None:
 124                     ret.append(cmd)
 125
 126 filecache = {}
 127
 128 def getfile(path):
 129     path = os.path.normpath(path)
 130     cf = filecache.get(path)
 131     if not cf:
 132         cf = filecache[path] = ssifile(path)
 133     elif int(os.stat(path).st_mtime) != cf.mtime:
 134         cf = filecache[path] = ssifile(path)
 135     return cf
 136
 137 def wsgi(env, startreq):
 138     try:
 139         if env["PATH_INFO"] != "":
 140             return wsgiutil.simpleerror(env, startreq, 404, "Not Found", "The resource specified by the URL does not exist.")
 141         root = getfile(env["SCRIPT_FILENAME"])
 142
 143         if root.cache and "HTTP_IF_MODIFIED_SINCE" in env:
 144             try:
 145                 lmt = wsgiutil.phttpdate(env["HTTP_IF_MODIFIED_SINCE"])
 146                 if root.mtime <= lmt:
 147                     startreq("304 Not Modified", [("Content-Length", "0")])
 148                     return []
 149             except:
 150                 pass
 151
 152         buf = io.StringIO()
 153         root.process(context(buf, root))
 154     except Exception:
 155         return wsgiutil.simpleerror(env, startreq, 500, "Internal Error", "The server encountered an unpexpected error while handling SSI.")
 156     ret = buf.getvalue().encode("utf8")
 157     head = [("Content-Type", "text/html; charset=UTF-8"), ("Content-Length", str(len(ret)))]
 158     if root.cache:
 159         head.append(("Last-Modified", wsgiutil.httpdate(root.mtime)))
 160     startreq("200 OK", head)
 161     return [ret]