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# Copyright (C) 2005 by Canonical Ltd
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# This program is free software; you can redistribute it and/or modify
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# it under the terms of the GNU General Public License as published by
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# the Free Software Foundation; either version 2 of the License, or
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# (at your option) any later version.
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# This program is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# GNU General Public License for more details.
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# You should have received a copy of the GNU General Public License
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# along with this program; if not, write to the Free Software
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# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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"""Testament - a summary of a revision for signing.
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A testament can be defined as "something that serves as tangible
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proof or evidence." In bzr we use them to allow people to certify
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particular revisions as authentic.
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The goal is that if two revisions are semantically equal, then they will
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have a byte-for-byte equal testament. We can define different versions of
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"semantically equal" by using different testament classes; e.g. one that
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includes or ignores file-ids.
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We sign a testament rather than the revision XML itself for several reasons.
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The most important is that the form in which the revision is stored
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internally is designed for that purpose, and contains information which need
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not be attested to by the signer. For example the inventory contains the
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last-changed revision for a file, but this is not necessarily something the
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Having unnecessary fields signed makes the signatures brittle when the same
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revision is stored in different branches or when the format is upgraded.
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Handling upgrades is another motivation for using testaments separate from
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the stored revision. We would like to be able to compare a signature
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generated from an old-format tree to newer tree, or vice versa. This could
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be done by comparing the revisions but that makes it unclear about exactly
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what is being compared or not.
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Different signing keys might indicate different levels of trust; we can in
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the future extend this to allow signatures indicating not just that a
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particular version is authentic but that it has other properties.
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The signature can be applied to either the full testament or to just a
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* timestamps are given as integers to avoid rounding errors
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* parents given in lexicographical order
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* indented-text form similar to log; intended to be human readable
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* paths are given with forward slashes
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* files are named using paths for ease of comparison/debugging
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* the testament uses unix line-endings (\n)
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# XXX: At the moment, clients trust that the graph described in a weave
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# is accurate, but that's not covered by the testament. Perhaps the best
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# fix is when verifying a revision to make sure that every file mentioned
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# in the revision has compatible ancestry links.
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# TODO: perhaps write timestamp in a more readable form
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# TODO: Perhaps these should just be different formats in which inventories/
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# revisions can be serialized.
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from cStringIO import StringIO
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def contains_whitespace(s):
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"""True if there are any whitespace characters in s."""
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for ch in string.whitespace:
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def contains_linebreaks(s):
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"""True if there is any vertical whitespace in s."""
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class Testament(object):
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"""Reduced summary of a revision.
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- produced from a revision
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- loaded from a stream
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- compared to a revision
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def from_revision(cls, branch, revision_id):
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"""Produce a new testament from a historical revision"""
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rev = branch.get_revision(revision_id)
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t.revision_id = str(revision_id)
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t.committer = rev.committer
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t.timezone = rev.timezone or 0
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t.timestamp = rev.timestamp
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t.message = rev.message
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t.parent_ids = rev.parent_ids[:]
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t.inventory = branch.get_inventory(revision_id)
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assert not contains_whitespace(t.revision_id)
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assert not contains_linebreaks(t.committer)
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def as_text_lines(self):
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"""Yield text form as a sequence of lines.
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The result is returned in utf-8, because it should be signed or
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hashed in that encoding.
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a('bazaar-ng testament version 1\n')
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a('revision-id: %s\n' % self.revision_id)
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a('committer: %s\n' % self.committer)
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a('timestamp: %d\n' % self.timestamp)
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a('timezone: %d\n' % self.timezone)
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# inventory length contains the root, which is not shown here
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for parent_id in sorted(self.parent_ids):
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assert not contains_whitespace(parent_id)
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a(' %s\n' % parent_id)
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for l in self.message.splitlines():
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for path, ie in self.inventory.iter_entries():
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a(self._entry_to_line(path, ie))
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assert isinstance(l, str), \
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'%r of type %s is not a plain string' % (l, type(l))
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def _escape_path(self, path):
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assert not contains_linebreaks(path)
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return unicode(path.replace('\\', '/').replace(' ', '\ ')).encode('utf-8')
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def _entry_to_line(self, path, ie):
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"""Turn an inventory entry into a testament line"""
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l = ' ' + str(ie.kind)
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l += ' ' + self._escape_path(path)
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assert not contains_whitespace(ie.file_id)
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l += ' ' + unicode(ie.file_id).encode('utf-8')
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if ie.kind == 'file':
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# TODO: avoid switching on kind
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l += ' ' + ie.text_sha1
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elif ie.kind == 'symlink':
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assert ie.symlink_target
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l += ' ' + self._escape_path(ie.symlink_target)
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return ''.join(self.as_text_lines())
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def as_short_text(self):
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"""Return short digest-based testament."""
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map(s.update, self.as_text_lines())
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return ('bazaar-ng testament short form 1\n'
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% (self.revision_id, s.hexdigest()))
added
removed
bzrlib/testament.py
