[dak/master 01/10] daklib/gpg.py: small library for PGP-signed files
Signed-off-by: Ansgar Burchardt <ansgar@debian.org>
---
daklib/gpg.py | 187 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
1 files changed, 187 insertions(+), 0 deletions(-)
create mode 100644 daklib/gpg.py
diff --git a/daklib/gpg.py b/daklib/gpg.py
new file mode 100644
index 0000000..5c396ec
--- /dev/null
+++ b/daklib/gpg.py
@@ -0,0 +1,187 @@
+"""Utilities for signed files
+
+@contact: Debian FTP Master <ftpmaster@debian.org>
+@copyright: 2011 Ansgar Burchardt <ansgar@debian.org>
+@license: GNU General Public License version 2 or later
+"""
+
+# 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 errno
+import fcntl
+import os
+import select
+import sys
+
+try:
+ _MAXFD = os.sysconf("SC_OPEN_MAX")
+except:
+ _MAXFD = 256
+
+class GpgException(Exception):
+ pass
+
+class _Pipe(object):
+ """context manager for pipes
+
+ Note: When the pipe is closed by other means than the close_r and close_w
+ methods, you have to set self.r (self.w) to None.
+ """
+ def __enter__(self):
+ (self.r, self.w) = os.pipe()
+ return self
+ def __exit__(self, type, value, traceback):
+ self.close_w()
+ self.close_r()
+ return False
+ def close_r(self):
+ """close reading side of the pipe"""
+ if self.r:
+ os.close(self.r)
+ self.r = None
+ def close_w(self):
+ """close writing part of the pipe"""
+ if self.w:
+ os.close(self.w)
+ self.w = None
+
+class SignedFile(object):
+ """handle files signed with PGP
+
+ The following attributes are available:
+ contents - string with the content (after removing PGP armor)
+ valid - Boolean indicating a valid signature was found
+ fingerprint - fingerprint of the key used for signing
+ primary_fingerprint - fingerprint of the primary key associated to the key used for signing
+ """
+ def __init__(self, data, keyrings, require_signature=True, gpg="/usr/bin/gpg"):
+ """
+ @param data: string containing the message
+ @param keyrings: seqeuence of keyrings
+ @param require_signature: if True (the default), will raise an exception if no valid signature was found
+ @param gpg: location of the gpg binary
+ """
+ self.gpg = gpg
+ self.keyrings = keyrings
+
+ self.valid = False
+ self.fingerprint = None
+ self.primary_fingerprint = None
+
+ self._verify(data, require_signature)
+
+ def _verify(self, data, require_signature):
+ with _Pipe() as stdin:
+ with _Pipe() as contents:
+ with _Pipe() as status:
+ pid = os.fork()
+ if pid == 0:
+ self._exec_gpg(stdin.r, contents.w, sys.stderr.fileno(), status.w)
+ else:
+ stdin.close_r()
+ contents.close_w()
+ status.close_w()
+
+ read = self._do_io([contents.r, status.r], {stdin.w: data})
+ stdin.w = None # was closed by _do_io
+
+ (pid_, exit_code, usage_) = os.wait4(pid, 0)
+
+ self.contents = read[contents.r]
+ self.status = read[status.r]
+
+ if self.status == "":
+ raise GpgException("No status output from GPG. (GPG exited with status code %s)" % exit_code)
+
+ for line in self.status.splitlines():
+ self._parse_status(line)
+
+ if require_signature and not self.valid:
+ raise GpgException("No valid signature found. (GPG exited with status code %s)" % exit_code)
+
+ def _do_io(self, read, write):
+ read_lines = dict( (fd, []) for fd in read )
+ write_pos = dict( (fd, 0) for fd in write )
+
+ read_set = list(read)
+ write_set = write.keys()
+ while len(read_set) > 0 or len(write_set) > 0:
+ r, w, x_ = select.select(read_set, write_set, ())
+ for fd in r:
+ data = os.read(fd, 4096)
+ if data == "":
+ read_set.remove(fd)
+ read_lines[fd].append(data)
+ for fd in w:
+ data = write[fd][write_pos[fd]:]
+ if data == "":
+ os.close(fd)
+ write_set.remove(fd)
+ else:
+ bytes_written = os.write(fd, data)
+ write_pos[fd] += bytes_written
+
+ return dict( (fd, "".join(read_lines[fd])) for fd in read_lines.keys() )
+
+ def _parse_status(self, line):
+ fields = line.split()
+ if fields[0] != "[GNUPG:]":
+ raise GpgException("Unexpected output on status-fd: %s" % line)
+
+ # VALIDSIG <fingerprint in hex> <sig_creation_date> <sig-timestamp>
+ # <expire-timestamp> <sig-version> <reserved> <pubkey-algo>
+ # <hash-algo> <sig-class> <primary-key-fpr>
+ if fields[1] == "VALIDSIG":
+ self.valid = True
+ self.fingerprint = fields[2]
+ self.primary_fingerprint = fields[11]
+
+ if fields[1] == "BADARMOR":
+ raise GpgException("Bad armor.")
+
+ if fields[1] == "NODATA":
+ raise GpgException("No data.")
+
+ if fields[1] == "DECRYPTION_FAILED":
+ raise GpgException("Decryption failed.")
+
+ if fields[1] == "ERROR":
+ raise GpgException("Other error: %s %s" % (fields[2], fields[3]))
+
+ def _exec_gpg(self, stdin, stdout, stderr, statusfd):
+ try:
+ if stdin != 0:
+ os.dup2(stdin, 0)
+ if stdout != 1:
+ os.dup2(stdout, 1)
+ if stderr != 2:
+ os.dup2(stderr, 2)
+ if statusfd != 3:
+ os.dup2(statusfd, 3)
+ for fd in range(4):
+ old = fcntl.fcntl(fd, fcntl.F_GETFD)
+ fcntl.fcntl(fd, fcntl.F_SETFD, old & ~fcntl.FD_CLOEXEC)
+ os.closerange(4, _MAXFD)
+
+ args = [self.gpg, "--status-fd=3", "--no-default-keyring"]
+ for k in self.keyrings:
+ args.append("--keyring=%s" % k)
+ args.extend(["--decrypt", "-"])
+
+ os.execvp(self.gpg, args)
+ finally:
+ sys.exit(1)
+
+# vim: set sw=4 et:
--
1.7.2.5
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