//! Retrieve rightmost thing of label
Term
rightMostTerm (Term t)
{
if (t != NULL)
{
t = deVar (t);
if (realTermTuple (t))
{
return rightMostTerm (TermOp2 (t));
}
}
return t;
}
/**
* Try to unify (a subterm of) tbig with tsmall.
*
* Callback is called with a list of substitutions, and a list of terms that
* need to be decrypted in order for this to work.
*
* E.g. subtermUnify ( {{m}k1}k2, m ) yields a list : {{m}k1}k2, {m}k1 (where
* the {m}k1 is the last added node to the list)
*
* The callback should return true for the iteration to proceed, or false to abort.
* The final result is this flag.
*
* This is the actual procedure used by the Arachne algorithm in archne.c
*/
int
subtermUnify (Term tbig, Term tsmall, Termlist tl, Termlist keylist,
int (*callback) (), void *state)
{
int proceed;
struct su_kcb_state kcb_state;
kcb_state.oldstate = state;
kcb_state.callback = callback;
kcb_state.keylist = keylist;
proceed = true;
// Devar
tbig = deVar (tbig);
tsmall = deVar (tsmall);
// Three options:
// 1. simple unification
proceed = proceed && unify (tbig, tsmall, tl, keycallback, &kcb_state);
// [2/3]: complex
if (switches.intruder)
{
// 2. interm unification
// Only if there is an intruder
if (realTermTuple (tbig))
{
proceed = proceed
&& subtermUnify (TermOp1 (tbig), tsmall, tl, keylist, callback,
state);
proceed = proceed
&& subtermUnify (TermOp2 (tbig), tsmall, tl, keylist, callback,
state);
}
// 3. unification with encryption needed
if (realTermEncrypt (tbig))
{
// extend the keylist
keylist = termlistAdd (keylist, tbig);
proceed = proceed
&& subtermUnify (TermOp (tbig), tsmall, tl, keylist, callback,
state);
// remove last item again
keylist = termlistDelTerm (keylist);
}
}
// Athena problem case: open variable about to be unified.
/**
* In this case we really need to consider the problematic Athena case for untyped variables.
*/
if (isTermVariable (tbig))
{
// Check the type: can it contain tuples, encryptions?
if (isOpenVariable (tbig))
{
// This one needs to be pursued by further constraint adding
/**
* Currently, this is not implemented yet. TODO.
* This is actually the main Athena problem that we haven't solved yet.
*/
// Mark that we don't have a full proof, and possibly remark in proof output.
markNoFullProof (tbig, tsmall);
}
}
return proceed;
}
