#! /usr/local/bin/python """Support module for CGI (Common Gateway Interface) scripts. This module defines a number of utilities for use by CGI scripts written in Python. """ # XXX Perhaps there should be a slimmed version that doesn't contain # all those backwards compatible and debugging classes and functions? # History # ------- # # Michael McLay started this module. Steve Majewski changed the # interface to SvFormContentDict and FormContentDict. The multipart # parsing was inspired by code submitted by Andreas Paepcke. Guido van # Rossum rewrote, reformatted and documented the module and is currently # responsible for its maintenance. # __version__ = "2.5" # Imports # ======= import string import sys import os import urllib import mimetools import rfc822 import UserDict from StringIO import StringIO # Logging support # =============== logfile = "" # Filename to log to, if not empty logfp = None # File object to log to, if not None def initlog(*allargs): """Write a log message, if there is a log file. Even though this function is called initlog(), you should always use log(); log is a variable that is set either to initlog (initially), to dolog (once the log file has been opened), or to nolog (when logging is disabled). The first argument is a format string; the remaining arguments (if any) are arguments to the % operator, so e.g. log("%s: %s", "a", "b") will write "a: b" to the log file, followed by a newline. If the global logfp is not None, it should be a file object to which log data is written. If the global logfp is None, the global logfile may be a string giving a filename to open, in append mode. This file should be world writable!!! If the file can't be opened, logging is silently disabled (since there is no safe place where we could send an error message). """ global logfp, log if logfile and not logfp: try: logfp = open(logfile, "a") except IOError: pass if not logfp: log = nolog else: log = dolog apply(log, allargs) def dolog(fmt, *args): """Write a log message to the log file. See initlog() for docs.""" logfp.write(fmt%args + "\n") def nolog(*allargs): """Dummy function, assigned to log when logging is disabled.""" pass log = initlog # The current logging function # Parsing functions # ================= # Maximum input we will accept when REQUEST_METHOD is POST # 0 ==> unlimited input maxlen = 0 def parse(fp=None, environ=os.environ, keep_blank_values=0, strict_parsing=0): """Parse a query in the environment or from a file (default stdin) Arguments, all optional: fp : file pointer; default: sys.stdin environ : environment dictionary; default: os.environ keep_blank_values: flag indicating whether blank values in URL encoded forms should be treated as blank strings. A true value indicates that blanks should be retained as blank strings. The default false value indicates that blank values are to be ignored and treated as if they were not included. strict_parsing: flag indicating what to do with parsing errors. If false (the default), errors are silently ignored. If true, errors raise a ValueError exception. """ if not fp: fp = sys.stdin if not environ.has_key('REQUEST_METHOD'): environ['REQUEST_METHOD'] = 'GET' # For testing stand-alone if environ['REQUEST_METHOD'] == 'POST': ctype, pdict = parse_header(environ['CONTENT_TYPE']) if ctype == 'multipart/form-data': return parse_multipart(fp, pdict) elif ctype == 'application/x-www-form-urlencoded': clength = string.atoi(environ['CONTENT_LENGTH']) if maxlen and clength > maxlen: raise ValueError, 'Maximum content length exceeded' qs = fp.read(clength) else: qs = '' # Unknown content-type if environ.has_key('QUERY_STRING'): if qs: qs = qs + '&' qs = qs + environ['QUERY_STRING'] elif sys.argv[1:]: if qs: qs = qs + '&' qs = qs + sys.argv[1] environ['QUERY_STRING'] = qs # XXX Shouldn't, really elif environ.has_key('QUERY_STRING'): qs = environ['QUERY_STRING'] else: if sys.argv[1:]: qs = sys.argv[1] else: qs = "" environ['QUERY_STRING'] = qs # XXX Shouldn't, really return parse_qs(qs, keep_blank_values, strict_parsing) def parse_qs(qs, keep_blank_values=0, strict_parsing=0): """Parse a query given as a string argument. Arguments: qs: URL-encoded query string to be parsed keep_blank_values: flag indicating whether blank values in URL encoded queries should be treated as blank strings. A true value indicates that blanks should be retained as blank strings. The default false value indicates that blank values are to be ignored and treated as if they were not included. strict_parsing: flag indicating what to do with parsing errors. If false (the default), errors are silently ignored. If true, errors raise a ValueError exception. """ dict = {} for name, value in parse_qsl(qs, keep_blank_values, strict_parsing): if dict.has_key(name): dict[name].append(value) else: dict[name] = [value] return dict def parse_qsl(qs, keep_blank_values=0, strict_parsing=0): """Parse a query given as a string argument. Arguments: qs: URL-encoded query string to be parsed keep_blank_values: flag indicating whether blank values in URL encoded queries should be treated as blank strings. A true value indicates that blanks should be retained as blank strings. The default false value indicates that blank values are to be ignored and treated as if they were not included. strict_parsing: flag indicating what to do with parsing errors. If false (the default), errors are silently ignored. If true, errors raise a ValueError exception. Returns a list, as G-d intended. """ pairs = [s2 for s1 in qs.split('&') for s2 in s1.split(';')] r = [] for name_value in pairs: nv = name_value.split('=', 1) if len(nv) != 2: if strict_parsing: raise ValueError, "bad query field: %s" % `name_value` continue if len(nv[1]) or keep_blank_values: name = urllib.unquote(string.replace(nv[0], '+', ' ')) value = urllib.unquote(string.replace(nv[1], '+', ' ')) r.append((name, value)) return r def parse_multipart(fp, pdict): """Parse multipart input. Arguments: fp : input file pdict: dictionary containing other parameters of conten-type header Returns a dictionary just like parse_qs(): keys are the field names, each value is a list of values for that field. This is easy to use but not much good if you are expecting megabytes to be uploaded -- in that case, use the FieldStorage class instead which is much more flexible. Note that content-type is the raw, unparsed contents of the content-type header. XXX This does not parse nested multipart parts -- use FieldStorage for that. XXX This should really be subsumed by FieldStorage altogether -- no point in having two implementations of the same parsing algorithm. """ if pdict.has_key('boundary'): boundary = pdict['boundary'] else: boundary = "" nextpart = "--" + boundary lastpart = "--" + boundary + "--" partdict = {} terminator = "" while terminator != lastpart: bytes = -1 data = None if terminator: # At start of next part. Read headers first. headers = mimetools.Message(fp) clength = headers.getheader('content-length') if clength: try: bytes = string.atoi(clength) except string.atoi_error: pass if bytes > 0: if maxlen and bytes > maxlen: raise ValueError, 'Maximum content length exceeded' data = fp.read(bytes) else: data = "" # Read lines until end of part. lines = [] while 1: line = fp.readline() if not line: terminator = lastpart # End outer loop break if line[:2] == "--": terminator = string.strip(line) if terminator in (nextpart, lastpart): break lines.append(line) # Done with part. if data is None: continue if bytes < 0: if lines: # Strip final line terminator line = lines[-1] if line[-2:] == "\r\n": line = line[:-2] elif line[-1:] == "\n": line = line[:-1] lines[-1] = line data = string.joinfields(lines, "") line = headers['content-disposition'] if not line: continue key, params = parse_header(line) if key != 'form-data': continue if params.has_key('name'): name = params['name'] else: continue if partdict.has_key(name): partdict[name].append(data) else: partdict[name] = [data] return partdict def parse_header(line): """Parse a Content-type like header. Return the main content-type and a dictionary of options. """ plist = map(string.strip, string.splitfields(line, ';')) key = string.lower(plist[0]) del plist[0] pdict = {} for p in plist: i = string.find(p, '=') if i >= 0: name = string.lower(string.strip(p[:i])) value = string.strip(p[i+1:]) if len(value) >= 2 and value[0] == value[-1] == '"': value = value[1:-1] pdict[name] = value return key, pdict # Classes for field storage # ========================= class MiniFieldStorage: """Like FieldStorage, for use when no file uploads are possible.""" # Dummy attributes filename = None list = None type = None file = None type_options = {} disposition = None disposition_options = {} headers = {} def __init__(self, name, value): """Constructor from field name and value.""" self.name = name self.value = value # self.file = StringIO(value) def __repr__(self): """Return printable representation.""" return "MiniFieldStorage(%s, %s)" % (`self.name`, `self.value`) class FieldStorage: """Store a sequence of fields, reading multipart/form-data. This class provides naming, typing, files stored on disk, and more. At the top level, it is accessible like a dictionary, whose keys are the field names. (Note: None can occur as a field name.) The items are either a Python list (if there's multiple values) or another FieldStorage or MiniFieldStorage object. If it's a single object, it has the following attributes: name: the field name, if specified; otherwise None filename: the filename, if specified; otherwise None; this is the client side filename, *not* the file name on which it is stored (that's a temporary file you don't deal with) value: the value as a *string*; for file uploads, this transparently reads the file every time you request the value file: the file(-like) object from which you can read the data; None if the data is stored a simple string type: the content-type, or None if not specified type_options: dictionary of options specified on the content-type line disposition: content-disposition, or None if not specified disposition_options: dictionary of corresponding options headers: a dictionary(-like) object (sometimes rfc822.Message or a subclass thereof) containing *all* headers The class is subclassable, mostly for the purpose of overriding the make_file() method, which is called internally to come up with a file open for reading and writing. This makes it possible to override the default choice of storing all files in a temporary directory and unlinking them as soon as they have been opened. """ def __init__(self, fp=None, headers=None, outerboundary="", environ=os.environ, keep_blank_values=0, strict_parsing=0): """Constructor. Read multipart/* until last part. Arguments, all optional: fp : file pointer; default: sys.stdin (not used when the request method is GET) headers : header dictionary-like object; default: taken from environ as per CGI spec outerboundary : terminating multipart boundary (for internal use only) environ : environment dictionary; default: os.environ keep_blank_values: flag indicating whether blank values in URL encoded forms should be treated as blank strings. A true value indicates that blanks should be retained as blank strings. The default false value indicates that blank values are to be ignored and treated as if they were not included. strict_parsing: flag indicating what to do with parsing errors. If false (the default), errors are silently ignored. If true, errors raise a ValueError exception. """ method = 'GET' self.keep_blank_values = keep_blank_values self.strict_parsing = strict_parsing if environ.has_key('REQUEST_METHOD'): method = string.upper(environ['REQUEST_METHOD']) if method == 'GET' or method == 'HEAD': if environ.has_key('QUERY_STRING'): qs = environ['QUERY_STRING'] elif sys.argv[1:]: qs = sys.argv[1] else: qs = "" fp = StringIO(qs) if headers is None: headers = {'content-type': "application/x-www-form-urlencoded"} if headers is None: headers = {} if method == 'POST': # Set default content-type for POST to what's traditional headers['content-type'] = "application/x-www-form-urlencoded" if environ.has_key('CONTENT_TYPE'): headers['content-type'] = environ['CONTENT_TYPE'] if environ.has_key('CONTENT_LENGTH'): headers['content-length'] = environ['CONTENT_LENGTH'] self.fp = fp or sys.stdin self.headers = headers self.outerboundary = outerboundary # Process content-disposition header cdisp, pdict = "", {} if self.headers.has_key('content-disposition'): cdisp, pdict = parse_header(self.headers['content-disposition']) self.disposition = cdisp self.disposition_options = pdict self.name = None if pdict.has_key('name'): self.name = pdict['name'] self.filename = None if pdict.has_key('filename'): self.filename = pdict['filename'] # Process content-type header # # Honor any existing content-type header. But if there is no # content-type header, use some sensible defaults. Assume # outerboundary is "" at the outer level, but something non-false # inside a multi-part. The default for an inner part is text/plain, # but for an outer part it should be urlencoded. This should catch # bogus clients which erroneously forget to include a content-type # header. # # See below for what we do if there does exist a content-type header, # but it happens to be something we don't understand. if self.headers.has_key('content-type'): ctype, pdict = parse_header(self.headers['content-type']) elif self.outerboundary or method != 'POST': ctype, pdict = "text/plain", {} else: ctype, pdict = 'application/x-www-form-urlencoded', {} self.type = ctype self.type_options = pdict self.innerboundary = "" if pdict.has_key('boundary'): self.innerboundary = pdict['boundary'] clen = -1 if self.headers.has_key('content-length'): try: clen = string.atoi(self.headers['content-length']) except: pass if maxlen and clen > maxlen: raise ValueError, 'Maximum content length exceeded' self.length = clen self.list = self.file = None self.done = 0 if ctype == 'application/x-www-form-urlencoded': self.read_urlencoded() elif ctype[:10] == 'multipart/': self.read_multi(environ, keep_blank_values, strict_parsing) else: self.read_single() def __repr__(self): """Return a printable representation.""" return "FieldStorage(%s, %s, %s)" % ( `self.name`, `self.filename`, `self.value`) def __getattr__(self, name): if name != 'value': raise AttributeError, name if self.file: self.file.seek(0) value = self.file.read() self.file.seek(0) elif self.list is not None: value = self.list else: value = None return value def __getitem__(self, key): """Dictionary style indexing.""" if self.list is None: raise TypeError, "not indexable" found = [] for item in self.list: if item.name == key: found.append(item) if not found: raise KeyError, key if len(found) == 1: return found[0] else: return found def getvalue(self, key, default=None): """Dictionary style get() method, including 'value' lookup.""" if self.has_key(key): value = self[key] if type(value) is type([]): return map(lambda v: v.value, value) else: return value.value else: return default def keys(self): """Dictionary style keys() method.""" if self.list is None: raise TypeError, "not indexable" keys = [] for item in self.list: if item.name not in keys: keys.append(item.name) return keys def has_key(self, key): """Dictionary style has_key() method.""" if self.list is None: raise TypeError, "not indexable" for item in self.list: if item.name == key: return 1 return 0 def __len__(self): """Dictionary style len(x) support.""" return len(self.keys()) def read_urlencoded(self): """Internal: read data in query string format.""" qs = self.fp.read(self.length) self.list = list = [] for key, value in parse_qsl(qs, self.keep_blank_values, self.strict_parsing): list.append(MiniFieldStorage(key, value)) self.skip_lines() FieldStorageClass = None def read_multi(self, environ, keep_blank_values, strict_parsing): """Internal: read a part that is itself multipart.""" self.list = [] klass = self.FieldStorageClass or self.__class__ part = klass(self.fp, {}, self.innerboundary, environ, keep_blank_values, strict_parsing) # Throw first part away while not part.done: headers = rfc822.Message(self.fp) part = klass(self.fp, headers, self.innerboundary, environ, keep_blank_values, strict_parsing) self.list.append(part) self.skip_lines() def read_single(self): """Internal: read an atomic part.""" if self.length >= 0: self.read_binary() self.skip_lines() else: self.read_lines() self.file.seek(0) bufsize = 8*1024 # I/O buffering size for copy to file def read_binary(self): """Internal: read binary data.""" self.file = self.make_file('b') todo = self.length if todo >= 0: while todo > 0: data = self.fp.read(min(todo, self.bufsize)) if not data: self.done = -1 break self.file.write(data) todo = todo - len(data) def read_lines(self): """Internal: read lines until EOF or outerboundary.""" self.file = self.make_file('') if self.outerboundary: self.read_lines_to_outerboundary() else: self.read_lines_to_eof() def read_lines_to_eof(self): """Internal: read lines until EOF.""" while 1: line = self.fp.readline() if not line: self.done = -1 break self.file.write(line) def read_lines_to_outerboundary(self): """Internal: read lines until outerboundary.""" next = "--" + self.outerboundary last = next + "--" delim = "" while 1: line = self.fp.readline() if not line: self.done = -1 break if line[:2] == "--": strippedline = string.strip(line) if strippedline == next: break if strippedline == last: self.done = 1 break odelim = delim if line[-2:] == "\r\n": delim = "\r\n" line = line[:-2] elif line[-1] == "\n": delim = "\n" line = line[:-1] else: delim = "" self.file.write(odelim + line) def skip_lines(self): """Internal: skip lines until outer boundary if defined.""" if not self.outerboundary or self.done: return next = "--" + self.outerboundary last = next + "--" while 1: line = self.fp.readline() if not line: self.done = -1 break if line[:2] == "--": strippedline = string.strip(line) if strippedline == next: break if strippedline == last: self.done = 1 break def make_file(self, binary=None): """Overridable: return a readable & writable file. The file will be used as follows: - data is written to it - seek(0) - data is read from it The 'binary' argument is unused -- the file is always opened in binary mode. This version opens a temporary file for reading and writing, and immediately deletes (unlinks) it. The trick (on Unix!) is that the file can still be used, but it can't be opened by another process, and it will automatically be deleted when it is closed or when the current process terminates. If you want a more permanent file, you derive a class which overrides this method. If you want a visible temporary file that is nevertheless automatically deleted when the script terminates, try defining a __del__ method in a derived class which unlinks the temporary files you have created. """ import tempfile return tempfile.TemporaryFile("w+b") # Backwards Compatibility Classes # =============================== class FormContentDict(UserDict.UserDict): """Form content as dictionary with a list of values per field. form = FormContentDict() form[key] -> [value, value, ...] form.has_key(key) -> Boolean form.keys() -> [key, key, ...] form.values() -> [[val, val, ...], [val, val, ...], ...] form.items() -> [(key, [val, val, ...]), (key, [val, val, ...]), ...] form.dict == {key: [val, val, ...], ...} """ def __init__(self, environ=os.environ): self.dict = self.data = parse(environ=environ) self.query_string = environ['QUERY_STRING'] class SvFormContentDict(FormContentDict): """Form content as dictionary expecting a single value per field. If you only expect a single value for each field, then form[key] will return that single value. It will raise an IndexError if that expectation is not true. If you expect a field to have possible multiple values, than you can use form.getlist(key) to get all of the values. values() and items() are a compromise: they return single strings where there is a single value, and lists of strings otherwise. """ def __getitem__(self, key): if len(self.dict[key]) > 1: raise IndexError, 'expecting a single value' return self.dict[key][0] def getlist(self, key): return self.dict[key] def values(self): result = [] for value in self.dict.values(): if len(value) == 1: result.append(value[0]) else: result.append(value) return result def items(self): result = [] for key, value in self.dict.items(): if len(value) == 1: result.append((key, value[0])) else: result.append((key, value)) return result class InterpFormContentDict(SvFormContentDict): """This class is present for backwards compatibility only.""" def __getitem__(self, key): v = SvFormContentDict.__getitem__(self, key) if v[0] in string.digits + '+-.': try: return string.atoi(v) except ValueError: try: return string.atof(v) except ValueError: pass return string.strip(v) def values(self): result = [] for key in self.keys(): try: result.append(self[key]) except IndexError: result.append(self.dict[key]) return result def items(self): result = [] for key in self.keys(): try: result.append((key, self[key])) except IndexError: result.append((key, self.dict[key])) return result class FormContent(FormContentDict): """This class is present for backwards compatibility only.""" def values(self, key): if self.dict.has_key(key) :return self.dict[key] else: return None def indexed_value(self, key, location): if self.dict.has_key(key): if len(self.dict[key]) > location: return self.dict[key][location] else: return None else: return None def value(self, key): if self.dict.has_key(key): return self.dict[key][0] else: return None def length(self, key): return len(self.dict[key]) def stripped(self, key): if self.dict.has_key(key): return string.strip(self.dict[key][0]) else: return None def pars(self): return self.dict # Test/debug code # =============== def test(environ=os.environ): """Robust test CGI script, usable as main program. Write minimal HTTP headers and dump all information provided to the script in HTML form. """ import traceback print "Content-type: text/html" print sys.stderr = sys.stdout try: form = FieldStorage() # Replace with other classes to test those print_directory() print_arguments() print_form(form) print_environ(environ) print_environ_usage() def f(): exec "testing print_exception() -- italics?" def g(f=f): f() print "

What follows is a test, not an actual exception:

" g() except: print_exception() print "

Second try with a small maxlen...

" global maxlen maxlen = 50 try: form = FieldStorage() # Replace with other classes to test those print_directory() print_arguments() print_form(form) print_environ(environ) except: print_exception() def print_exception(type=None, value=None, tb=None, limit=None): if type is None: type, value, tb = sys.exc_info() import traceback print print "

Traceback (most recent call last):

" list = traceback.format_tb(tb, limit) + \ traceback.format_exception_only(type, value) print "
%s%s
" % ( escape(string.join(list[:-1], "")), escape(list[-1]), ) del tb def print_environ(environ=os.environ): """Dump the shell environment as HTML.""" keys = environ.keys() keys.sort() print print "

Shell Environment:

" print "
" for key in keys: print "
", escape(key), "
", escape(environ[key]) print "
" print def print_form(form): """Dump the contents of a form as HTML.""" keys = form.keys() keys.sort() print print "

Form Contents:

" if not keys: print "

No form fields." print "

" for key in keys: print "
" + escape(key) + ":", value = form[key] print "" + escape(`type(value)`) + "" print "
" + escape(`value`) print "
" print def print_directory(): """Dump the current directory as HTML.""" print print "

Current Working Directory:

" try: pwd = os.getcwd() except os.error, msg: print "os.error:", escape(str(msg)) else: print escape(pwd) print def print_arguments(): print print "

Command Line Arguments:

" print print sys.argv print def print_environ_usage(): """Dump a list of environment variables used by CGI as HTML.""" print """

These environment variables could have been set:

In addition, HTTP headers sent by the server may be passed in the environment as well. Here are some common variable names: """ # Utilities # ========= def escape(s, quote=None): """Replace special characters '&', '<' and '>' by SGML entities.""" s = string.replace(s, "&", "&") # Must be done first! s = string.replace(s, "<", "<") s = string.replace(s, ">", ">",) if quote: s = string.replace(s, '"', """) return s # Invoke mainline # =============== # Call test() when this file is run as a script (not imported as a module) if __name__ == '__main__': test()