# copyright 2003-2010 LOGILAB S.A. (Paris, FRANCE), all rights reserved.
# contact http://www.logilab.fr/ -- mailto:contact@logilab.fr
#
# This file is part of CubicWeb.
#
# CubicWeb is free software: you can redistribute it and/or modify it under the
# terms of the GNU Lesser General Public License as published by the Free
# Software Foundation, either version 2.1 of the License, or (at your option)
# any later version.
#
# CubicWeb 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 Lesser General Public License for more
# details.
#
# You should have received a copy of the GNU Lesser General Public License along
# with CubicWeb. If not, see <http://www.gnu.org/licenses/>.
"""RQL rewriting utilities : insert rql expression snippets into rql syntax
tree.
This is used for instance for read security checking in the repository.
"""
__docformat__ = "restructuredtext en"
from rql import nodes as n, stmts, TypeResolverException
from yams import BadSchemaDefinition
from logilab.common.graph import has_path
from cubicweb import Unauthorized, typed_eid
def add_types_restriction(schema, rqlst, newroot=None, solutions=None):
if newroot is None:
assert solutions is None
if hasattr(rqlst, '_types_restr_added'):
return
solutions = rqlst.solutions
newroot = rqlst
rqlst._types_restr_added = True
else:
assert solutions is not None
rqlst = rqlst.stmt
eschema = schema.eschema
allpossibletypes = {}
for solution in solutions:
for varname, etype in solution.iteritems():
if not varname in newroot.defined_vars or eschema(etype).final:
continue
allpossibletypes.setdefault(varname, set()).add(etype)
for varname in sorted(allpossibletypes):
try:
var = newroot.defined_vars[varname]
except KeyError:
continue
stinfo = var.stinfo
if stinfo.get('uidrel') is not None:
continue # eid specified, no need for additional type specification
try:
typerel = rqlst.defined_vars[varname].stinfo.get('typerel')
except KeyError:
assert varname in rqlst.aliases
continue
if newroot is rqlst and typerel is not None:
mytyperel = typerel
else:
for vref in newroot.defined_vars[varname].references():
rel = vref.relation()
if rel and rel.is_types_restriction():
mytyperel = rel
break
else:
mytyperel = None
possibletypes = allpossibletypes[varname]
if mytyperel is not None:
# variable as already some types restriction. new possible types
# can only be a subset of existing ones, so only remove no more
# possible types
for cst in mytyperel.get_nodes(n.Constant):
if not cst.value in possibletypes:
cst.parent.remove(cst)
try:
stinfo['possibletypes'].remove(cst.value)
except KeyError:
# restriction on a type not used by this query, may
# occurs with X is IN(...)
pass
else:
# we have to add types restriction
if stinfo.get('scope') is not None:
rel = var.scope.add_type_restriction(var, possibletypes)
else:
# tree is not annotated yet, no scope set so add the restriction
# to the root
rel = newroot.add_type_restriction(var, possibletypes)
stinfo['typerel'] = rel
stinfo['possibletypes'] = possibletypes
def remove_solutions(origsolutions, solutions, defined):
"""when a rqlst has been generated from another by introducing security
assertions, this method returns solutions which are contained in orig
solutions
"""
newsolutions = []
for origsol in origsolutions:
for newsol in solutions[:]:
for var, etype in origsol.items():
try:
if newsol[var] != etype:
try:
defined[var].stinfo['possibletypes'].remove(newsol[var])
except KeyError:
pass
break
except KeyError:
# variable has been rewritten
continue
else:
newsolutions.append(newsol)
solutions.remove(newsol)
return newsolutions
class Unsupported(Exception):
"""raised when an rql expression can't be inserted in some rql query
because it create an unresolvable query (eg no solutions found)
"""
class RQLRewriter(object):
"""insert some rql snippets into another rql syntax tree
this class *isn't thread safe*
"""
def __init__(self, session):
self.session = session
vreg = session.vreg
self.schema = vreg.schema
self.annotate = vreg.rqlhelper.annotate
self._compute_solutions = vreg.solutions
def compute_solutions(self):
self.annotate(self.select)
try:
self._compute_solutions(self.session, self.select, self.kwargs)
except TypeResolverException:
raise Unsupported(str(self.select))
if len(self.select.solutions) < len(self.solutions):
raise Unsupported()
def rewrite(self, select, snippets, solutions, kwargs, existingvars=None):
"""
snippets: (varmap, list of rql expression)
with varmap a *tuple* (select var, snippet var)
"""
self.select = self.insert_scope = select
self.solutions = solutions
self.kwargs = kwargs
self.u_varname = None
self.removing_ambiguity = False
self.exists_snippet = {}
self.pending_keys = []
self.existingvars = existingvars
# we have to annotate the rqlst before inserting snippets, even though
# we'll have to redo it latter
self.annotate(select)
self.insert_snippets(snippets)
if not self.exists_snippet and self.u_varname:
# U has been inserted than cancelled, cleanup
select.undefine_variable(select.defined_vars[self.u_varname])
# clean solutions according to initial solutions
newsolutions = remove_solutions(solutions, select.solutions,
select.defined_vars)
assert len(newsolutions) >= len(solutions), (
'rewritten rql %s has lost some solutions, there is probably '
'something wrong in your schema permission (for instance using a '
'RQLExpression which insert a relation which doesn\'t exists in '
'the schema)\nOrig solutions: %s\nnew solutions: %s' % (
select, solutions, newsolutions))
if len(newsolutions) > len(solutions):
newsolutions = self.remove_ambiguities(snippets, newsolutions)
select.solutions = newsolutions
add_types_restriction(self.schema, select)
def insert_snippets(self, snippets, varexistsmap=None):
self.rewritten = {}
for varmap, rqlexprs in snippets:
if varexistsmap is not None and not varmap in varexistsmap:
continue
self.varmap = varmap
selectvar, snippetvar = varmap
assert snippetvar in 'SOX'
self.revvarmap = {snippetvar: selectvar}
self.varinfo = vi = {}
try:
vi['const'] = typed_eid(selectvar) # XXX gae
vi['rhs_rels'] = vi['lhs_rels'] = {}
except ValueError:
try:
vi['stinfo'] = sti = self.select.defined_vars[selectvar].stinfo
except KeyError:
# variable has been moved to a newly inserted subquery
# we should insert snippet in that subquery
subquery = self.select.aliases[selectvar].query
assert len(subquery.children) == 1
subselect = subquery.children[0]
RQLRewriter(self.session).rewrite(subselect, [(varmap, rqlexprs)],
subselect.solutions, self.kwargs)
continue
if varexistsmap is None:
vi['rhs_rels'] = dict( (r.r_type, r) for r in sti['rhsrelations'])
vi['lhs_rels'] = dict( (r.r_type, r) for r in sti['relations']
if not r in sti['rhsrelations'])
else:
vi['rhs_rels'] = vi['lhs_rels'] = {}
parent = None
inserted = False
for rqlexpr in rqlexprs:
self.current_expr = rqlexpr
if varexistsmap is None:
try:
new = self.insert_snippet(varmap, rqlexpr.snippet_rqlst, parent)
except Unsupported:
continue
inserted = True
if new is not None:
self.exists_snippet[rqlexpr] = new
parent = parent or new
else:
# called to reintroduce snippet due to ambiguity creation,
# so skip snippets which are not introducing this ambiguity
exists = varexistsmap[varmap]
if self.exists_snippet[rqlexpr] is exists:
self.insert_snippet(varmap, rqlexpr.snippet_rqlst, exists)
if varexistsmap is None and not inserted:
# no rql expression found matching rql solutions. User has no access right
raise Unauthorized()
def insert_snippet(self, varmap, snippetrqlst, parent=None):
new = snippetrqlst.where.accept(self)
existing = self.existingvars
self.existingvars = None
try:
return self._insert_snippet(varmap, parent, new)
finally:
self.existingvars = existing
def _insert_snippet(self, varmap, parent, new):
if new is not None:
if self.varinfo.get('stinfo', {}).get('optrelations'):
assert parent is None
self.insert_scope = self.snippet_subquery(varmap, new)
self.insert_pending()
self.insert_scope = self.select
return
new = n.Exists(new)
if parent is None:
self.insert_scope.add_restriction(new)
else:
grandpa = parent.parent
or_ = n.Or(parent, new)
grandpa.replace(parent, or_)
if not self.removing_ambiguity:
try:
self.compute_solutions()
except Unsupported:
# some solutions have been lost, can't apply this rql expr
if parent is None:
self.select.remove_node(new, undefine=True)
else:
parent.parent.replace(or_, or_.children[0])
self._cleanup_inserted(new)
raise
else:
self.insert_scope = new
self.insert_pending()
self.insert_scope = self.select
return new
self.insert_pending()
def insert_pending(self):
"""pending_keys hold variable referenced by U has_<action>_permission X
relation.
Once the snippet introducing this has been inserted and solutions
recomputed, we have to insert snippet defined for <action> of entity
types taken by X
"""
while self.pending_keys:
key, action = self.pending_keys.pop()
try:
varname = self.rewritten[key]
except KeyError:
try:
varname = self.revvarmap[key[-1]]
except KeyError:
# variable isn't used anywhere else, we can't insert security
raise Unauthorized()
ptypes = self.select.defined_vars[varname].stinfo['possibletypes']
if len(ptypes) > 1:
# XXX dunno how to handle this
self.session.error(
'cant check security of %s, ambigous type for %s in %s',
self.select, varname, key[0]) # key[0] == the rql expression
raise Unauthorized()
etype = iter(ptypes).next()
eschema = self.schema.eschema(etype)
if not eschema.has_perm(self.session, action):
rqlexprs = eschema.get_rqlexprs(action)
if not rqlexprs:
raise Unauthorized()
self.insert_snippets([((varname, 'X'), rqlexprs)])
def snippet_subquery(self, varmap, transformedsnippet):
"""introduce the given snippet in a subquery"""
subselect = stmts.Select()
selectvar = varmap[0]
subselectvar = subselect.get_variable(selectvar)
subselect.append_selected(n.VariableRef(subselectvar))
snippetrqlst = n.Exists(transformedsnippet.copy(subselect))
aliases = [selectvar]
stinfo = self.varinfo['stinfo']
need_null_test = False
for rel in stinfo['relations']:
rschema = self.schema.rschema(rel.r_type)
if rschema.final or (rschema.inlined and
not rel in stinfo['rhsrelations']):
rel.children[0].name = selectvar # XXX explain why
subselect.add_restriction(rel.copy(subselect))
for vref in rel.children[1].iget_nodes(n.VariableRef):
if isinstance(vref.variable, n.ColumnAlias):
# XXX could probably be handled by generating the subquery
# into the detected subquery
raise BadSchemaDefinition(
"cant insert security because of usage two inlined "
"relations in this query. You should probably at "
"least uninline %s" % rel.r_type)
subselect.append_selected(vref.copy(subselect))
aliases.append(vref.name)
self.select.remove_node(rel)
# when some inlined relation has to be copied in the subquery,
# we need to test that either value is NULL or that the snippet
# condition is satisfied
if rschema.inlined and rel.optional:
need_null_test = True
if need_null_test:
snippetrqlst = n.Or(
n.make_relation(subselectvar, 'is', (None, None), n.Constant,
operator='IS'),
snippetrqlst)
subselect.add_restriction(snippetrqlst)
if self.u_varname:
# generate an identifier for the substitution
argname = subselect.allocate_varname()
while argname in self.kwargs:
argname = subselect.allocate_varname()
subselect.add_constant_restriction(subselect.get_variable(self.u_varname),
'eid', unicode(argname), 'Substitute')
self.kwargs[argname] = self.session.user.eid
add_types_restriction(self.schema, subselect, subselect,
solutions=self.solutions)
myunion = stmts.Union()
myunion.append(subselect)
aliases = [n.VariableRef(self.select.get_variable(name, i))
for i, name in enumerate(aliases)]
self.select.add_subquery(n.SubQuery(aliases, myunion), check=False)
self._cleanup_inserted(transformedsnippet)
try:
self.compute_solutions()
except Unsupported:
# some solutions have been lost, can't apply this rql expr
self.select.remove_subquery(self.select.with_[-1])
raise
return subselect
def remove_ambiguities(self, snippets, newsolutions):
# the snippet has introduced some ambiguities, we have to resolve them
# "manually"
variantes = self.build_variantes(newsolutions)
# insert "is" where necessary
varexistsmap = {}
self.removing_ambiguity = True
for (erqlexpr, varmap, oldvarname), etype in variantes[0].iteritems():
varname = self.rewritten[(erqlexpr, varmap, oldvarname)]
var = self.select.defined_vars[varname]
exists = var.references()[0].scope
exists.add_constant_restriction(var, 'is', etype, 'etype')
varexistsmap[varmap] = exists
# insert ORED exists where necessary
for variante in variantes[1:]:
self.insert_snippets(snippets, varexistsmap)
for key, etype in variante.iteritems():
varname = self.rewritten[key]
try:
var = self.select.defined_vars[varname]
except KeyError:
# not a newly inserted variable
continue
exists = var.references()[0].scope
exists.add_constant_restriction(var, 'is', etype, 'etype')
# recompute solutions
#select.annotated = False # avoid assertion error
self.compute_solutions()
# clean solutions according to initial solutions
return remove_solutions(self.solutions, self.select.solutions,
self.select.defined_vars)
def build_variantes(self, newsolutions):
variantes = set()
for sol in newsolutions:
variante = []
for key, newvar in self.rewritten.iteritems():
variante.append( (key, sol[newvar]) )
variantes.add(tuple(variante))
# rebuild variantes as dict
variantes = [dict(variante) for variante in variantes]
# remove variable which have always the same type
for key in self.rewritten:
it = iter(variantes)
etype = it.next()[key]
for variante in it:
if variante[key] != etype:
break
else:
for variante in variantes:
del variante[key]
return variantes
def _cleanup_inserted(self, node):
# cleanup inserted variable references
for vref in node.iget_nodes(n.VariableRef):
vref.unregister_reference()
if not vref.variable.stinfo['references']:
# no more references, undefine the variable
del self.select.defined_vars[vref.name]
def _may_be_shared_with(self, sniprel, target, searchedvarname):
"""if the snippet relation can be skipped to use a relation from the
original query, return that relation node
"""
rschema = self.schema.rschema(sniprel.r_type)
try:
if target == 'object':
orel = self.varinfo['lhs_rels'][sniprel.r_type]
cardindex = 0
ttypes_func = rschema.objects
rdef = rschema.rdef
else: # target == 'subject':
orel = self.varinfo['rhs_rels'][sniprel.r_type]
cardindex = 1
ttypes_func = rschema.subjects
rdef = lambda x, y: rschema.rdef(y, x)
except KeyError:
# may be raised by self.varinfo['xhs_rels'][sniprel.r_type]
return None
# can't share neged relation or relations with different outer join
if (orel.neged(strict=True) or sniprel.neged(strict=True)
or (orel.optional and orel.optional != sniprel.optional)):
return None
# if cardinality is in '?1', we can ignore the snippet relation and use
# variable from the original query
for etype in self.varinfo['stinfo']['possibletypes']:
for ttype in ttypes_func(etype):
if rdef(etype, ttype).cardinality[cardindex] in '+*':
return None
return orel
def _use_orig_term(self, snippet_varname, term):
key = (self.current_expr, self.varmap, snippet_varname)
if key in self.rewritten:
insertedvar = self.select.defined_vars.pop(self.rewritten[key])
for inserted_vref in insertedvar.references():
inserted_vref.parent.replace(inserted_vref, term.copy(self.select))
self.rewritten[key] = term.name
def _get_varname_or_term(self, vname):
if vname == 'U':
if self.u_varname is None:
select = self.select
self.u_varname = select.allocate_varname()
# generate an identifier for the substitution
argname = select.allocate_varname()
while argname in self.kwargs:
argname = select.allocate_varname()
# insert "U eid %(u)s"
select.add_constant_restriction(
select.get_variable(self.u_varname),
'eid', unicode(argname), 'Substitute')
self.kwargs[argname] = self.session.user.eid
return self.u_varname
key = (self.current_expr, self.varmap, vname)
try:
return self.rewritten[key]
except KeyError:
self.rewritten[key] = newvname = self.select.allocate_varname()
return newvname
# visitor methods ##########################################################
def _visit_binary(self, node, cls):
newnode = cls()
for c in node.children:
new = c.accept(self)
if new is None:
continue
newnode.append(new)
if len(newnode.children) == 0:
return None
if len(newnode.children) == 1:
return newnode.children[0]
return newnode
def _visit_unary(self, node, cls):
newc = node.children[0].accept(self)
if newc is None:
return None
newnode = cls()
newnode.append(newc)
return newnode
def visit_and(self, node):
return self._visit_binary(node, n.And)
def visit_or(self, node):
return self._visit_binary(node, n.Or)
def visit_not(self, node):
return self._visit_unary(node, n.Not)
def visit_exists(self, node):
return self._visit_unary(node, n.Exists)
def keep_var(self, varname):
if varname in 'SO':
return varname in self.existingvars
if varname == 'U':
return True
vargraph = self.current_expr.vargraph
for existingvar in self.existingvars:
#path = has_path(vargraph, varname, existingvar)
if has_path(vargraph, varname, existingvar):
return True
# no path from this variable to an existing variable
return False
def visit_relation(self, node):
lhs, rhs = node.get_variable_parts()
# remove relations where an unexistant variable and or a variable linked
# to an unexistant variable is used.
if self.existingvars:
if not self.keep_var(lhs.name):
return
if node.r_type in ('has_add_permission', 'has_update_permission',
'has_delete_permission', 'has_read_permission'):
assert lhs.name == 'U'
action = node.r_type.split('_')[1]
key = (self.current_expr, self.varmap, rhs.name)
self.pending_keys.append( (key, action) )
return
if isinstance(rhs, n.VariableRef):
if self.existingvars and not self.keep_var(rhs.name):
return
if lhs.name in self.revvarmap and rhs.name != 'U':
orel = self._may_be_shared_with(node, 'object', lhs.name)
if orel is not None:
self._use_orig_term(rhs.name, orel.children[1].children[0])
return
elif rhs.name in self.revvarmap and lhs.name != 'U':
orel = self._may_be_shared_with(node, 'subject', rhs.name)
if orel is not None:
self._use_orig_term(lhs.name, orel.children[0])
return
rel = n.Relation(node.r_type, node.optional)
for c in node.children:
rel.append(c.accept(self))
return rel
def visit_comparison(self, node):
cmp_ = n.Comparison(node.operator)
for c in node.children:
cmp_.append(c.accept(self))
return cmp_
def visit_mathexpression(self, node):
cmp_ = n.MathExpression(node.operator)
for c in cmp.children:
cmp_.append(c.accept(self))
return cmp_
def visit_function(self, node):
"""generate filter name for a function"""
function_ = n.Function(node.name)
for c in node.children:
function_.append(c.accept(self))
return function_
def visit_constant(self, node):
"""generate filter name for a constant"""
return n.Constant(node.value, node.type)
def visit_variableref(self, node):
"""get the sql name for a variable reference"""
if node.name in self.revvarmap:
if self.varinfo.get('const') is not None:
return n.Constant(self.varinfo['const'], 'Int') # XXX gae
return n.VariableRef(self.select.get_variable(
self.revvarmap[node.name]))
vname_or_term = self._get_varname_or_term(node.name)
if isinstance(vname_or_term, basestring):
return n.VariableRef(self.select.get_variable(vname_or_term))
# shared term
return vname_or_term.copy(self.select)