utils.py

#!/usr/bin/env python

# Utility functions
# Copyright (C) 2000, 2001, 2002, 2003, 2004, 2005, 2006  James Troup <james@nocrew.org>

################################################################################

# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.

# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.

# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

################################################################################

import codecs, commands, email.Header, os, pwd, re, select, socket, shutil, \
       sys, tempfile, traceback
import apt_pkg
import database

################################################################################

re_comments = re.compile(r"\#.*")
re_no_epoch = re.compile(r"^\d+\:")
re_no_revision = re.compile(r"-[^-]+$")
re_arch_from_filename = re.compile(r"/binary-[^/]+/")
re_extract_src_version = re.compile (r"(\S+)\s*\((.*)\)")
re_isadeb = re.compile (r"(.+?)_(.+?)_(.+)\.u?deb$")
re_issource = re.compile (r"(.+)_(.+?)\.(orig\.tar\.gz|diff\.gz|tar\.gz|dsc)$")

re_single_line_field = re.compile(r"^(\S*)\s*:\s*(.*)")
re_multi_line_field = re.compile(r"^\s(.*)")
re_taint_free = re.compile(r"^[-+~/\.\w]+$")

re_parse_maintainer = re.compile(r"^\s*(\S.*\S)\s*\<([^\>]+)\>")

re_srchasver = re.compile(r"^(\S+)\s+\((\S+)\)$")

changes_parse_error_exc = "Can't parse line in .changes file"
invalid_dsc_format_exc = "Invalid .dsc file"
nk_format_exc = "Unknown Format: in .changes file"
no_files_exc = "No Files: field in .dsc or .changes file."
cant_open_exc = "Can't open file"
unknown_hostname_exc = "Unknown hostname"
cant_overwrite_exc = "Permission denied; can't overwrite existent file."
file_exists_exc = "Destination file exists"
sendmail_failed_exc = "Sendmail invocation failed"
tried_too_hard_exc = "Tried too hard to find a free filename."

default_config = "/etc/dak/dak.conf"
default_apt_config = "/etc/dak/apt.conf"

################################################################################

class Error(Exception):
    """Base class for exceptions in this module."""
    pass

class ParseMaintError(Error):
    """Exception raised for errors in parsing a maintainer field.

    Attributes:
       message -- explanation of the error
    """

    def __init__(self, message):
        self.args = message,
        self.message = message

################################################################################

def open_file(filename, mode='r'):
    try:
	f = open(filename, mode)
    except IOError:
        raise cant_open_exc, filename
    return f

################################################################################

def our_raw_input(prompt=""):
    if prompt:
        sys.stdout.write(prompt)
    sys.stdout.flush()
    try:
        ret = raw_input()
        return ret
    except EOFError:
        sys.stderr.write("\nUser interrupt (^D).\n")
        raise SystemExit

################################################################################

def extract_component_from_section(section):
    component = ""

    if section.find('/') != -1:
        component = section.split('/')[0]
    if component.lower() == "non-us" and section.find('/') != -1:
        s = component + '/' + section.split('/')[1]
        if Cnf.has_key("Component::%s" % s): # Avoid e.g. non-US/libs
            component = s

    if section.lower() == "non-us":
        component = "non-US/main"

    # non-US prefix is case insensitive
    if component.lower()[:6] == "non-us":
        component = "non-US"+component[6:]

    # Expand default component
    if component == "":
        if Cnf.has_key("Component::%s" % section):
            component = section
        else:
            component = "main"
    elif component == "non-US":
        component = "non-US/main"

    return (section, component)

################################################################################

def parse_changes(filename, signing_rules=0):
    """Parses a changes file and returns a dictionary where each field is a
key.  The mandatory first argument is the filename of the .changes
file.

signing_rules is an optional argument:

 o If signing_rules == -1, no signature is required.
 o If signing_rules == 0 (the default), a signature is required.
 o If signing_rules == 1, it turns on the same strict format checking
   as dpkg-source.

The rules for (signing_rules == 1)-mode are:

  o The PGP header consists of "-----BEGIN PGP SIGNED MESSAGE-----"
    followed by any PGP header data and must end with a blank line.

  o The data section must end with a blank line and must be followed by
    "-----BEGIN PGP SIGNATURE-----".
"""

    error = ""
    changes = {}

    changes_in = open_file(filename)
    lines = changes_in.readlines()

    if not lines:
	raise changes_parse_error_exc, "[Empty changes file]"

    # Reindex by line number so we can easily verify the format of
    # .dsc files...
    index = 0
    indexed_lines = {}
    for line in lines:
        index += 1
        indexed_lines[index] = line[:-1]

    inside_signature = 0

    num_of_lines = len(indexed_lines.keys())
    index = 0
    first = -1
    while index < num_of_lines:
        index += 1
        line = indexed_lines[index]
        if line == "":
            if signing_rules == 1:
                index += 1
                if index > num_of_lines:
                    raise invalid_dsc_format_exc, index
                line = indexed_lines[index]
                if not line.startswith("-----BEGIN PGP SIGNATURE"):
                    raise invalid_dsc_format_exc, index
                inside_signature = 0
                break
            else:
                continue
        if line.startswith("-----BEGIN PGP SIGNATURE"):
            break
        if line.startswith("-----BEGIN PGP SIGNED MESSAGE"):
            inside_signature = 1
            if signing_rules == 1:
                while index < num_of_lines and line != "":
                    index += 1
                    line = indexed_lines[index]
            continue
        # If we're not inside the signed data, don't process anything
        if signing_rules >= 0 and not inside_signature:
            continue
        slf = re_single_line_field.match(line)
        if slf:
            field = slf.groups()[0].lower()
            changes[field] = slf.groups()[1]
	    first = 1
            continue
        if line == " .":
            changes[field] += '\n'
            continue
        mlf = re_multi_line_field.match(line)
        if mlf:
            if first == -1:
                raise changes_parse_error_exc, "'%s'\n [Multi-line field continuing on from nothing?]" % (line)
            if first == 1 and changes[field] != "":
                changes[field] += '\n'
            first = 0
	    changes[field] += mlf.groups()[0] + '\n'
            continue
	error += line

    if signing_rules == 1 and inside_signature:
        raise invalid_dsc_format_exc, index

    changes_in.close()
    changes["filecontents"] = "".join(lines)

    if changes.has_key("source"):
        # Strip the source version in brackets from the source field,
	# put it in the "source-version" field instead.
        srcver = re_srchasver.search(changes["source"])
	if srcver:
            changes["source"] = srcver.group(1)
	    changes["source-version"] = srcver.group(2)

    if error:
	raise changes_parse_error_exc, error

    return changes

################################################################################

# Dropped support for 1.4 and ``buggy dchanges 3.4'' (?!) compared to di.pl

def build_file_list(changes, is_a_dsc=0):
    files = {}

    # Make sure we have a Files: field to parse...
    if not changes.has_key("files"):
	raise no_files_exc

    # Make sure we recognise the format of the Files: field
    format = changes.get("format", "")
    if format != "":
	format = float(format)
    if not is_a_dsc and (format < 1.5 or format > 2.0):
	raise nk_format_exc, format

    # Parse each entry/line:
    for i in changes["files"].split('\n'):
        if not i:
            break
        s = i.split()
        section = priority = ""
        try:
            if is_a_dsc:
                (md5, size, name) = s
            else:
                (md5, size, section, priority, name) = s
        except ValueError:
            raise changes_parse_error_exc, i

        if section == "":
            section = "-"
        if priority == "":
            priority = "-"

        (section, component) = extract_component_from_section(section)

        files[name] = Dict(md5sum=md5, size=size, section=section,
                           priority=priority, component=component)

    return files

################################################################################

def force_to_utf8(s):
    """Forces a string to UTF-8.  If the string isn't already UTF-8,
it's assumed to be ISO-8859-1."""
    try:
        unicode(s, 'utf-8')
        return s
    except UnicodeError:
        latin1_s = unicode(s,'iso8859-1')
        return latin1_s.encode('utf-8')

def rfc2047_encode(s):
    """Encodes a (header) string per RFC2047 if necessary.  If the
string is neither ASCII nor UTF-8, it's assumed to be ISO-8859-1."""
    try:
        codecs.lookup('ascii')[1](s)
        return s
    except UnicodeError:
        pass
    try:
        codecs.lookup('utf-8')[1](s)
        h = email.Header.Header(s, 'utf-8', 998)
        return str(h)
    except UnicodeError:
        h = email.Header.Header(s, 'iso-8859-1', 998)
        return str(h)

################################################################################

# <Culus> 'The standard sucks, but my tool is supposed to interoperate
#          with it. I know - I'll fix the suckage and make things
#          incompatible!'

def fix_maintainer (maintainer):
    """Parses a Maintainer or Changed-By field and returns:
  (1) an RFC822 compatible version,
  (2) an RFC2047 compatible version,
  (3) the name
  (4) the email

The name is forced to UTF-8 for both (1) and (3).  If the name field
contains '.' or ',' (as allowed by Debian policy), (1) and (2) are
switched to 'email (name)' format."""
    maintainer = maintainer.strip()
    if not maintainer:
        return ('', '', '', '')

    if maintainer.find("<") == -1:
        email = maintainer
        name = ""
    elif (maintainer[0] == "<" and maintainer[-1:] == ">"):
        email = maintainer[1:-1]
        name = ""
    else:
        m = re_parse_maintainer.match(maintainer)
        if not m:
            raise ParseMaintError, "Doesn't parse as a valid Maintainer field."
        name = m.group(1)
        email = m.group(2)

    # Get an RFC2047 compliant version of the name
    rfc2047_name = rfc2047_encode(name)

    # Force the name to be UTF-8
    name = force_to_utf8(name)

    if name.find(',') != -1 or name.find('.') != -1:
        rfc822_maint = "%s (%s)" % (email, name)
        rfc2047_maint = "%s (%s)" % (email, rfc2047_name)
    else:
        rfc822_maint = "%s <%s>" % (name, email)
        rfc2047_maint = "%s <%s>" % (rfc2047_name, email)

    if email.find("@") == -1 and email.find("buildd_") != 0:
        raise ParseMaintError, "No @ found in email address part."

    return (rfc822_maint, rfc2047_maint, name, email)

################################################################################

# sendmail wrapper, takes _either_ a message string or a file as arguments
def send_mail (message, filename=""):
	# If we've been passed a string dump it into a temporary file
	if message:
            filename = tempfile.mktemp()
            fd = os.open(filename, os.O_RDWR|os.O_CREAT|os.O_EXCL, 0700)
            os.write (fd, message)
            os.close (fd)

	# Invoke sendmail
	(result, output) = commands.getstatusoutput("%s < %s" % (Cnf["Dinstall::SendmailCommand"], filename))
	if (result != 0):
            raise sendmail_failed_exc, output

	# Clean up any temporary files
	if message:
            os.unlink (filename)

################################################################################

def poolify (source, component):
    if component:
	component += '/'
    # FIXME: this is nasty
    component = component.lower().replace("non-us/", "non-US/")
    if source[:3] == "lib":
	return component + source[:4] + '/' + source + '/'
    else:
	return component + source[:1] + '/' + source + '/'

################################################################################

def move (src, dest, overwrite = 0, perms = 0664):
    if os.path.exists(dest) and os.path.isdir(dest):
	dest_dir = dest
    else:
	dest_dir = os.path.dirname(dest)
    if not os.path.exists(dest_dir):
	umask = os.umask(00000)
	os.makedirs(dest_dir, 02775)
	os.umask(umask)
    #print "Moving %s to %s..." % (src, dest)
    if os.path.exists(dest) and os.path.isdir(dest):
	dest += '/' + os.path.basename(src)
    # Don't overwrite unless forced to
    if os.path.exists(dest):
        if not overwrite:
            fubar("Can't move %s to %s - file already exists." % (src, dest))
        else:
            if not os.access(dest, os.W_OK):
                fubar("Can't move %s to %s - can't write to existing file." % (src, dest))
    shutil.copy2(src, dest)
    os.chmod(dest, perms)
    os.unlink(src)

def copy (src, dest, overwrite = 0, perms = 0664):
    if os.path.exists(dest) and os.path.isdir(dest):
	dest_dir = dest
    else:
	dest_dir = os.path.dirname(dest)
    if not os.path.exists(dest_dir):
	umask = os.umask(00000)
	os.makedirs(dest_dir, 02775)
	os.umask(umask)
    #print "Copying %s to %s..." % (src, dest)
    if os.path.exists(dest) and os.path.isdir(dest):
	dest += '/' + os.path.basename(src)
    # Don't overwrite unless forced to
    if os.path.exists(dest):
        if not overwrite:
            raise file_exists_exc
        else:
            if not os.access(dest, os.W_OK):
                raise cant_overwrite_exc
    shutil.copy2(src, dest)
    os.chmod(dest, perms)

################################################################################

def where_am_i ():
    res = socket.gethostbyaddr(socket.gethostname())
    database_hostname = Cnf.get("Config::" + res[0] + "::DatabaseHostname")
    if database_hostname:
	return database_hostname
    else:
        return res[0]

def which_conf_file ():
    res = socket.gethostbyaddr(socket.gethostname())
    if Cnf.get("Config::" + res[0] + "::DakConfig"):
	return Cnf["Config::" + res[0] + "::DakConfig"]
    else:
	return default_config

def which_apt_conf_file ():
    res = socket.gethostbyaddr(socket.gethostname())
    if Cnf.get("Config::" + res[0] + "::AptConfig"):
	return Cnf["Config::" + res[0] + "::AptConfig"]
    else:
	return default_apt_config

################################################################################

# Escape characters which have meaning to SQL's regex comparison operator ('~')
# (woefully incomplete)

def regex_safe (s):
    s = s.replace('+', '\\\\+')
    s = s.replace('.', '\\\\.')
    return s

################################################################################

# Perform a substition of template
def TemplateSubst(map, filename):
    file = open_file(filename)
    template = file.read()
    for x in map.keys():
        template = template.replace(x,map[x])
    file.close()
    return template

################################################################################

def fubar(msg, exit_code=1):
    sys.stderr.write("E: %s\n" % (msg))
    sys.exit(exit_code)

def warn(msg):
    sys.stderr.write("W: %s\n" % (msg))

################################################################################

# Returns the user name with a laughable attempt at rfc822 conformancy
# (read: removing stray periods).
def whoami ():
    return pwd.getpwuid(os.getuid())[4].split(',')[0].replace('.', '')

################################################################################

def size_type (c):
    t  = " B"
    if c > 10240:
        c = c / 1024
        t = " KB"
    if c > 10240:
        c = c / 1024
        t = " MB"
    return ("%d%s" % (c, t))

################################################################################

def cc_fix_changes (changes):
    o = changes.get("architecture", "")
    if o:
        del changes["architecture"]
    changes["architecture"] = {}
    for j in o.split():
        changes["architecture"][j] = 1

# Sort by source name, source version, 'have source', and then by filename
def changes_compare (a, b):
    try:
        a_changes = parse_changes(a)
    except:
        return -1

    try:
        b_changes = parse_changes(b)
    except:
        return 1

    cc_fix_changes (a_changes)
    cc_fix_changes (b_changes)

    # Sort by source name
    a_source = a_changes.get("source")
    b_source = b_changes.get("source")
    q = cmp (a_source, b_source)
    if q:
        return q

    # Sort by source version
    a_version = a_changes.get("version", "0")
    b_version = b_changes.get("version", "0")
    q = apt_pkg.VersionCompare(a_version, b_version)
    if q:
        return q

    # Sort by 'have source'
    a_has_source = a_changes["architecture"].get("source")
    b_has_source = b_changes["architecture"].get("source")
    if a_has_source and not b_has_source:
        return -1
    elif b_has_source and not a_has_source:
        return 1

    # Fall back to sort by filename
    return cmp(a, b)

################################################################################

def find_next_free (dest, too_many=100):
    extra = 0
    orig_dest = dest
    while os.path.exists(dest) and extra < too_many:
        dest = orig_dest + '.' + repr(extra)
        extra += 1
    if extra >= too_many:
        raise tried_too_hard_exc
    return dest

################################################################################

def result_join (original, sep = '\t'):
    list = []
    for i in xrange(len(original)):
        if original[i] == None:
            list.append("")
        else:
            list.append(original[i])
    return sep.join(list)

################################################################################

def prefix_multi_line_string(str, prefix, include_blank_lines=0):
    out = ""
    for line in str.split('\n'):
        line = line.strip()
        if line or include_blank_lines:
            out += "%s%s\n" % (prefix, line)
    # Strip trailing new line
    if out:
        out = out[:-1]
    return out

################################################################################

def validate_changes_file_arg(filename, require_changes=1):
    """'filename' is either a .changes or .dak file.  If 'filename' is a
.dak file, it's changed to be the corresponding .changes file.  The
function then checks if the .changes file a) exists and b) is
readable and returns the .changes filename if so.  If there's a
problem, the next action depends on the option 'require_changes'
argument:

 o If 'require_changes' == -1, errors are ignored and the .changes
                               filename is returned.
 o If 'require_changes' == 0, a warning is given and 'None' is returned.
 o If 'require_changes' == 1, a fatal error is raised.
"""
    error = None

    orig_filename = filename
    if filename.endswith(".dak"):
        filename = filename[:-4]+".changes"

    if not filename.endswith(".changes"):
        error = "invalid file type; not a changes file"
    else:
        if not os.access(filename,os.R_OK):
            if os.path.exists(filename):
                error = "permission denied"
            else:
                error = "file not found"

    if error:
        if require_changes == 1:
            fubar("%s: %s." % (orig_filename, error))
        elif require_changes == 0:
            warn("Skipping %s - %s" % (orig_filename, error))
            return None
        else: # We only care about the .dak file
            return filename
    else:
        return filename

################################################################################

def real_arch(arch):
    return (arch != "source" and arch != "all")

################################################################################

def join_with_commas_and(list):
	if len(list) == 0: return "nothing"
	if len(list) == 1: return list[0]
	return ", ".join(list[:-1]) + " and " + list[-1]

################################################################################

def pp_deps (deps):
    pp_deps = []
    for atom in deps:
        (pkg, version, constraint) = atom
        if constraint:
            pp_dep = "%s (%s %s)" % (pkg, constraint, version)
        else:
            pp_dep = pkg
        pp_deps.append(pp_dep)
    return " |".join(pp_deps)

################################################################################

def get_conf():
	return Cnf

################################################################################

# Handle -a, -c and -s arguments; returns them as SQL constraints
def parse_args(Options):
    # Process suite
    if Options["Suite"]:
        suite_ids_list = []
        for suite in split_args(Options["Suite"]):
            suite_id = database.get_suite_id(suite)
            if suite_id == -1:
                warn("suite '%s' not recognised." % (suite))
            else:
                suite_ids_list.append(suite_id)
        if suite_ids_list:
            con_suites = "AND su.id IN (%s)" % ", ".join([ str(i) for i in suite_ids_list ])
        else:
            fubar("No valid suite given.")
    else:
        con_suites = ""

    # Process component
    if Options["Component"]:
        component_ids_list = []
        for component in split_args(Options["Component"]):
            component_id = database.get_component_id(component)
            if component_id == -1:
                warn("component '%s' not recognised." % (component))
            else:
                component_ids_list.append(component_id)
        if component_ids_list:
            con_components = "AND c.id IN (%s)" % ", ".join([ str(i) for i in component_ids_list ])
        else:
            fubar("No valid component given.")
    else:
        con_components = ""

    # Process architecture
    con_architectures = ""
    if Options["Architecture"]:
        arch_ids_list = []
        check_source = 0
        for architecture in split_args(Options["Architecture"]):
            if architecture == "source":
                check_source = 1
            else:
                architecture_id = database.get_architecture_id(architecture)
                if architecture_id == -1:
                    warn("architecture '%s' not recognised." % (architecture))
                else:
                    arch_ids_list.append(architecture_id)
        if arch_ids_list:
            con_architectures = "AND a.id IN (%s)" % ", ".join([ str(i) for i in arch_ids_list ])
        else:
            if not check_source:
                fubar("No valid architecture given.")
    else:
        check_source = 1

    return (con_suites, con_architectures, con_components, check_source)

################################################################################

# Inspired(tm) by Bryn Keller's print_exc_plus (See
# http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/52215)

def print_exc():
    tb = sys.exc_info()[2]
    while tb.tb_next:
        tb = tb.tb_next
    stack = []
    frame = tb.tb_frame
    while frame:
        stack.append(frame)
        frame = frame.f_back
    stack.reverse()
    traceback.print_exc()
    for frame in stack:
        print "\nFrame %s in %s at line %s" % (frame.f_code.co_name,
                                             frame.f_code.co_filename,
                                             frame.f_lineno)
        for key, value in frame.f_locals.items():
            print "\t%20s = " % key,
            try:
                print value
            except:
                print "<unable to print>"

################################################################################

def try_with_debug(function):
    try:
        function()
    except SystemExit:
        raise
    except:
        print_exc()

################################################################################

# Function for use in sorting lists of architectures.
# Sorts normally except that 'source' dominates all others.

def arch_compare_sw (a, b):
    if a == "source" and b == "source":
        return 0
    elif a == "source":
        return -1
    elif b == "source":
        return 1

    return cmp (a, b)

################################################################################

# Split command line arguments which can be separated by either commas
# or whitespace.  If dwim is set, it will complain about string ending
# in comma since this usually means someone did 'dak ls -a i386, m68k
# foo' or something and the inevitable confusion resulting from 'm68k'
# being treated as an argument is undesirable.

def split_args (s, dwim=1):
    if s.find(",") == -1:
        return s.split()
    else:
        if s[-1:] == "," and dwim:
            fubar("split_args: found trailing comma, spurious space maybe?")
        return s.split(",")

################################################################################

def Dict(**dict): return dict

########################################

# Our very own version of commands.getouputstatus(), hacked to support
# gpgv's status fd.
def gpgv_get_status_output(cmd, status_read, status_write):
    cmd = ['/bin/sh', '-c', cmd]
    p2cread, p2cwrite = os.pipe()
    c2pread, c2pwrite = os.pipe()
    errout, errin = os.pipe()
    pid = os.fork()
    if pid == 0:
        # Child
        os.close(0)
        os.close(1)
        os.dup(p2cread)
        os.dup(c2pwrite)
        os.close(2)
        os.dup(errin)
        for i in range(3, 256):
            if i != status_write:
                try:
                    os.close(i)
                except:
                    pass
        try:
            os.execvp(cmd[0], cmd)
        finally:
            os._exit(1)

    # Parent
    os.close(p2cread)
    os.dup2(c2pread, c2pwrite)
    os.dup2(errout, errin)

    output = status = ""
    while 1:
        i, o, e = select.select([c2pwrite, errin, status_read], [], [])
        more_data = []
        for fd in i:
            r = os.read(fd, 8196)
            if len(r) > 0:
                more_data.append(fd)
                if fd == c2pwrite or fd == errin:
                    output += r
                elif fd == status_read:
                    status += r
                else:
                    fubar("Unexpected file descriptor [%s] returned from select\n" % (fd))
        if not more_data:
            pid, exit_status = os.waitpid(pid, 0)
            try:
                os.close(status_write)
                os.close(status_read)
                os.close(c2pread)
                os.close(c2pwrite)
                os.close(p2cwrite)
                os.close(errin)
                os.close(errout)
            except:
                pass
            break

    return output, status, exit_status

################################################################################

def process_gpgv_output(status):
    # Process the status-fd output
    keywords = {}
    internal_error = ""
    for line in status.split('\n'):
        line = line.strip()
        if line == "":
            continue
        split = line.split()
        if len(split) < 2:
            internal_error += "gpgv status line is malformed (< 2 atoms) ['%s'].\n" % (line)
            continue
        (gnupg, keyword) = split[:2]
        if gnupg != "[GNUPG:]":
            internal_error += "gpgv status line is malformed (incorrect prefix '%s').\n" % (gnupg)
            continue
        args = split[2:]
        if keywords.has_key(keyword) and (keyword != "NODATA" and keyword != "SIGEXPIRED"):
            internal_error += "found duplicate status token ('%s').\n" % (keyword)
            continue
        else:
            keywords[keyword] = args

    return (keywords, internal_error)

################################################################################

def retrieve_key (filename, keyserver=None, keyring=None):
    """Retrieve the key that signed 'filename' from 'keyserver' and
add it to 'keyring'.  Returns nothing on success, or an error message
on error."""

    # Defaults for keyserver and keyring
    if not keyserver:
        keyserver = Cnf["Dinstall::KeyServer"]
    if not keyring:
        keyring = Cnf.ValueList("Dinstall::GPGKeyring")[0]

    # Ensure the filename contains no shell meta-characters or other badness
    if not re_taint_free.match(filename):
        return "%s: tainted filename" % (filename)

    # Invoke gpgv on the file
    status_read, status_write = os.pipe(); 
    cmd = "gpgv --status-fd %s --keyring /dev/null %s" % (status_write, filename)
    (_, status, _) = gpgv_get_status_output(cmd, status_read, status_write)

    # Process the status-fd output
    (keywords, internal_error) = process_gpgv_output(status)
    if internal_error:
        return internal_error

    if not keywords.has_key("NO_PUBKEY"):
        return "didn't find expected NO_PUBKEY in gpgv status-fd output"

    fingerprint = keywords["NO_PUBKEY"][0]
    # XXX - gpg sucks.  You can't use --secret-keyring=/dev/null as
    # it'll try to create a lockfile in /dev.  A better solution might
    # be a tempfile or something.
    cmd = "gpg --no-default-keyring --secret-keyring=%s --no-options" \
          % (Cnf["Dinstall::SigningKeyring"])
    cmd += " --keyring %s --keyserver %s --recv-key %s" \
           % (keyring, keyserver, fingerprint)
    (result, output) = commands.getstatusoutput(cmd)
    if (result != 0):
        return "'%s' failed with exit code %s" % (cmd, result)

    return ""

################################################################################

def gpg_keyring_args(keyrings=None):
    if not keyrings:
        keyrings = Cnf.ValueList("Dinstall::GPGKeyring")

    return " ".join(["--keyring %s" % x for x in keyrings])

################################################################################

def check_signature (sig_filename, reject, data_filename="", keyrings=None, autofetch=None):
    """Check the signature of a file and return the fingerprint if the
signature is valid or 'None' if it's not.  The first argument is the
filename whose signature should be checked.  The second argument is a
reject function and is called when an error is found.  The reject()
function must allow for two arguments: the first is the error message,
the second is an optional prefix string.  It's possible for reject()
to be called more than once during an invocation of check_signature().
The third argument is optional and is the name of the files the
detached signature applies to.  The fourth argument is optional and is
a *list* of keyrings to use.  'autofetch' can either be None, True or
False.  If None, the default behaviour specified in the config will be
used."""

    # Ensure the filename contains no shell meta-characters or other badness
    if not re_taint_free.match(sig_filename):
        reject("!!WARNING!! tainted signature filename: '%s'." % (sig_filename))
        return None

    if data_filename and not re_taint_free.match(data_filename):
        reject("!!WARNING!! tainted data filename: '%s'." % (data_filename))
        return None

    if not keyrings:
        keyrings = Cnf.ValueList("Dinstall::GPGKeyring")

    # Autofetch the signing key if that's enabled
    if autofetch == None:
        autofetch = Cnf.get("Dinstall::KeyAutoFetch")
    if autofetch:
        error_msg = retrieve_key(sig_filename)
        if error_msg:
            reject(error_msg)
            return None

    # Build the command line
    status_read, status_write = os.pipe(); 
    cmd = "gpgv --status-fd %s %s %s %s" % (
        status_write, gpg_keyring_args(keyrings), sig_filename, data_filename)

    # Invoke gpgv on the file
    (output, status, exit_status) = gpgv_get_status_output(cmd, status_read, status_write)

    # Process the status-fd output
    (keywords, internal_error) = process_gpgv_output(status)

    # If we failed to parse the status-fd output, let's just whine and bail now
    if internal_error:
        reject("internal error while performing signature check on %s." % (sig_filename))
        reject(internal_error, "")
        reject("Please report the above errors to the Archive maintainers by replying to this mail.", "")
        return None

    bad = ""
    # Now check for obviously bad things in the processed output
    if keywords.has_key("SIGEXPIRED"):
        reject("The key used to sign %s has expired." % (sig_filename))
        bad = 1
    if keywords.has_key("KEYREVOKED"):
        reject("The key used to sign %s has been revoked." % (sig_filename))
        bad = 1
    if keywords.has_key("BADSIG"):
        reject("bad signature on %s." % (sig_filename))
        bad = 1
    if keywords.has_key("ERRSIG") and not keywords.has_key("NO_PUBKEY"):
        reject("failed to check signature on %s." % (sig_filename))
        bad = 1
    if keywords.has_key("NO_PUBKEY"):
        args = keywords["NO_PUBKEY"]
        if len(args) >= 1:
            key = args[0]
        reject("The key (0x%s) used to sign %s wasn't found in the keyring(s)." % (key, sig_filename))
        bad = 1
    if keywords.has_key("BADARMOR"):
        reject("ASCII armour of signature was corrupt in %s." % (sig_filename))
        bad = 1
    if keywords.has_key("NODATA"):
        reject("no signature found in %s." % (sig_filename))
        bad = 1

    if bad:
        return None

    # Next check gpgv exited with a zero return code
    if exit_status:
        reject("gpgv failed while checking %s." % (sig_filename))
        if status.strip():
            reject(prefix_multi_line_string(status, " [GPG status-fd output:] "), "")
        else:
            reject(prefix_multi_line_string(output, " [GPG output:] "), "")
        return None

    # Sanity check the good stuff we expect
    if not keywords.has_key("VALIDSIG"):
        reject("signature on %s does not appear to be valid [No VALIDSIG]." % (sig_filename))
        bad = 1
    else:
        args = keywords["VALIDSIG"]
        if len(args) < 1:
            reject("internal error while checking signature on %s." % (sig_filename))
            bad = 1
        else:
            fingerprint = args[0]
    if not keywords.has_key("GOODSIG"):
        reject("signature on %s does not appear to be valid [No GOODSIG]." % (sig_filename))
        bad = 1
    if not keywords.has_key("SIG_ID"):
        reject("signature on %s does not appear to be valid [No SIG_ID]." % (sig_filename))
        bad = 1

    # Finally ensure there's not something we don't recognise
    known_keywords = Dict(VALIDSIG="",SIG_ID="",GOODSIG="",BADSIG="",ERRSIG="",
                          SIGEXPIRED="",KEYREVOKED="",NO_PUBKEY="",BADARMOR="",
                          NODATA="")

    for keyword in keywords.keys():
        if not known_keywords.has_key(keyword):
            reject("found unknown status token '%s' from gpgv with args '%r' in %s." % (keyword, keywords[keyword], sig_filename))
            bad = 1

    if bad:
        return None
    else:
        return fingerprint

################################################################################

# Inspired(tm) by http://www.zopelabs.com/cookbook/1022242603

def wrap(paragraph, max_length, prefix=""):
    line = ""
    s = ""
    have_started = 0
    words = paragraph.split()

    for word in words:
        word_size = len(word)
        if word_size > max_length:
            if have_started:
                s += line + '\n' + prefix
            s += word + '\n' + prefix
        else:
            if have_started:
                new_length = len(line) + word_size + 1
                if new_length > max_length:
                    s += line + '\n' + prefix
                    line = word
                else:
                    line += ' ' + word
            else:
                line = word
        have_started = 1

    if have_started:
        s += line

    return s

################################################################################

# Relativize an absolute symlink from 'src' -> 'dest' relative to 'root'.
# Returns fixed 'src'
def clean_symlink (src, dest, root):
    src = src.replace(root, '', 1)
    dest = dest.replace(root, '', 1)
    dest = os.path.dirname(dest)
    new_src = '../' * len(dest.split('/'))
    return new_src + src

################################################################################

def temp_filename(directory=None, dotprefix=None, perms=0700):
    """Return a secure and unique filename by pre-creating it.
If 'directory' is non-null, it will be the directory the file is pre-created in.
If 'dotprefix' is non-null, the filename will be prefixed with a '.'."""

    if directory:
        old_tempdir = tempfile.tempdir
        tempfile.tempdir = directory

    filename = tempfile.mktemp()

    if dotprefix:
        filename = "%s/.%s" % (os.path.dirname(filename), os.path.basename(filename))
    fd = os.open(filename, os.O_RDWR|os.O_CREAT|os.O_EXCL, perms)
    os.close(fd)

    if directory:
        tempfile.tempdir = old_tempdir

    return filename

################################################################################

apt_pkg.init()

Cnf = apt_pkg.newConfiguration()
apt_pkg.ReadConfigFileISC(Cnf,default_config)

if which_conf_file() != default_config:
	apt_pkg.ReadConfigFileISC(Cnf,which_conf_file())

################################################################################