D4ConstraintEvaluator.cc

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// -*- mode: c++; c-basic-offset:4 -*-
 
// This file is part of libdap, A C++ implementation of the OPeNDAP Data
// Access Protocol.
 
// Copyright (c) 2002,2003 OPeNDAP, Inc.
// Author: James Gallagher <jgallagher@opendap.org>
//
// This library 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.
//
// This library 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 this library; if not, write to the Free Software
// Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
//
// You can contact OPeNDAP, Inc. at PO Box 112, Saunderstown, RI. 02874-0112.
 
#include <iterator>
#include <sstream>
#include <string>
 
#include "D4CEScanner.h"
#include "D4ConstraintEvaluator.h"
#include "d4_ce_parser.tab.hh"
 
#include "D4Group.h"
#include "D4Maps.h"
#include "D4Sequence.h"
#include "DMR.h"
 
#include "D4FilterClause.h"
#include "D4RValue.h"
 
// Always define this for a production release.
#define PREVENT_XXS_VIA_CE 1
#if NDEBUG && !PREVENT_XXS_VIA_CE
#error("Never release libdap with PREVENT_XXS_VIA_CE turned off")
#endif
 
namespace libdap {
 
bool D4ConstraintEvaluator::parse(const std::string &expr) {
    d_expr = expr; // set for error messages. See the %initial-action section of .yy
 
    // empty expressions are valid but fail the parser. jhrg 2/23/24
    if (expr.empty()) {
        d_dmr->set_ce_empty(true);
        return true;
    }
 
    std::istringstream iss(expr);
    D4CEScanner scanner(iss);
    D4CEParser parser(scanner, *this /* driver */);
 
    if (trace_parsing()) {
        parser.set_debug_level(1);
        parser.set_debug_stream(std::cerr);
    }
 
    return parser.parse() == 0;
}

[[noreturn]] void D4ConstraintEvaluator::throw_not_found(const string & /* id */, const string & /* ident */) {
#if PREVENT_XXS_VIA_CE
    throw Error(no_such_variable,
                string("The constraint expression referenced a variable that was not found in the dataset."));
#else
    throw Error(no_such_variable, d_expr + ": The variable " + id + " was not found in the dataset (" + ident + ").");
#endif
}
 
[[noreturn]] void D4ConstraintEvaluator::throw_not_array(const string & /* id */, const string & /* ident */) {
#if PREVENT_XXS_VIA_CE
    throw Error(no_such_variable,
                string("The constraint expression referenced an Array that was not found in the dataset."));
#else
    throw Error(no_such_variable, d_expr + ": The variable '" + id + "' is not an Array variable (" + ident + ").");
#endif
}
 
void D4ConstraintEvaluator::search_for_and_mark_arrays(BaseType *btp) {
    DBG(cerr << "Entering D4ConstraintEvaluator::search_for_and_mark_arrays...(" << btp->name() << ")" << endl);
 
    if (!btp->is_constructor_type())
        throw InternalErr(__FILE__, __LINE__,
                          "D4ConstraintEvaluator::search_for_and_mark_arrays(): Expected a Constructor type.");
 
    auto ctor = static_cast<Constructor *>(btp);
    for (auto var : ctor->variables()) {
        switch (var->type()) {
        case dods_array_c:
            DBG(cerr << "Found an array: " << (*i)->name() << endl);
            mark_array_variable(var);
            break;
        case dods_structure_c:
        case dods_sequence_c:
            DBG(cerr << "Found a ctor: " << (*i)->name() << endl);
            search_for_and_mark_arrays(var);
            break;
        default:
            break;
        }
    }
}

BaseType *D4ConstraintEvaluator::mark_variable(BaseType *btp) {
    if (!btp)
        throw InternalErr(__FILE__, __LINE__,
                          "D4ConstraintEvaluator::mark_variable(): Expected a non-null BaseType pointer.");
 
    DBG(cerr << "In D4ConstraintEvaluator::mark_variable... (" << btp->name() << "; " << btp->type_name() << ")"
             << endl);
 
    btp->set_send_p(true);
 
    if (btp->type() == dods_array_c) {
        mark_array_variable(btp);
    }
 
    // Test for Constructors and marks arrays they contain
    if (btp->is_constructor_type()) {
        search_for_and_mark_arrays(btp);
    } else if (btp->type() == dods_array_c && btp->var() && btp->var()->is_constructor_type()) {
        search_for_and_mark_arrays(btp->var());
    }
 
    // Now set the parent variables
    BaseType *parent = btp->get_parent();
    while (parent) {
        parent->BaseType::set_send_p(true); // Just set the parent using BaseType's impl.
        parent = parent->get_parent();
    }
 
    return btp;
}
 
static bool array_uses_shared_dimension(Array *map, const D4Dimension *source_dim) {
    for (auto d = map->dim_begin(), e = map->dim_end(); d != e; ++d) {
        if (source_dim->name() == (*d).name)
            return true;
    }
 
    return false;
}

 
// Note: If a Map is not part of the current projection, do not include mention of it
// in the response DMR (CDMR)
BaseType *D4ConstraintEvaluator::mark_array_variable(BaseType *btp) {
    if (btp->type() != dods_array_c)
        throw InternalErr(__FILE__, __LINE__, "D4ConstraintEvaluator::mark_array_variable(): Expected an Array type.");
 
    auto *a = static_cast<Array *>(btp);
 
    // If an array appears in a CE without the slicing operators ([]) we still have to
    // call add_constraint(...) for all of it's sdims for them to appear in
    // the Constrained DMR.
    if (d_indexes.empty()) {
        for (auto d = a->dim_begin(), de = a->dim_end(); d != de; ++d) {
            D4Dimension *dim = a->dimension_D4dim(d);
            if (dim) {
                a->add_constraint(d, dim);
            }
        }
    } else {
        // Test that the indexes and dimensions match in number
        if (d_indexes.size() != a->dimensions())
            throw Error(malformed_expr, "The index constraint for '" + btp->name() + "' does not match its rank.");
 
        auto d = a->dim_begin();
        for (auto const &index : d_indexes) {
            if (d == a->dim_end())
                throw Error(malformed_expr, "The index constraint for '" + btp->name() + "' does not match its rank.");
 
            if (index.stride > (a->dimension_stop_ll(d, false) - a->dimension_start_ll(d, false)) + 1)
                throw Error(malformed_expr,
                            "For '" + btp->name() +
                                "', the index stride value is greater than the number of elements in the Array");
            if (!index.rest && index.stop > (a->dimension_stop_ll(d, false) - a->dimension_start_ll(d, false)) + 1)
                throw Error(malformed_expr,
                            "For '" + btp->name() +
                                "', the index stop value is greater than the number of elements in the Array");
 
            D4Dimension *dim = a->dimension_D4dim(d);
 
            // In a DAP4 CE, specifying '[]' as an array dimension slice has two meanings.
            // It can mean 'all the elements' of the dimension or 'apply the slicing inherited
            // from the shared dimension'. The latter might be provide 'all the elements'
            // but regardless, the Array object must record the CE correctly.
 
            if (dim && index.empty) {
                // This case corresponds to a CE that uses the '[]' notation for a
                // particular dimension - meaning, use the Shared Dimension size for
                // this dimension's 'slice'.
                a->add_constraint(d, dim); // calls set_used_by_projected_var(true) + more
            } else {
                // This case corresponds to a 'local dimension slice' (See sections 8.6.2 and
                // 8.7 of the spec as of 4/12/16). When a local dimension slice is used, drop
                // the Map(s) that include that dimension. This enables people to constrain
                // an Array when some of the Array's dimensions don't use Shared Dimensions
                // but others do.
                use_explicit_projection(a, d, index);
            }
 
            ++d;
        }
    }
 
    d_indexes.clear(); // Clear the info so the next slice expression can be parsed.
 
    return btp;
}

static void array_map_remover(Array *a, const D4Dimension *dim) {
    auto root = dynamic_cast<D4Group *>(a->get_ancestor());
    if (!root)
        throw InternalErr(__FILE__, __LINE__, "Expected a valid ancestor Group.");
 
    for (auto m = a->maps()->map_begin(), e = a->maps()->map_end(); m != e; ++m) {
        // Added a test to ensure 'dim' is not null. This could be the case if
        // execution gets here and the index *i was not empty. jhrg 4/18/17
        auto *map = (*m)->array(root);
        if (dim && array_uses_shared_dimension(map, dim)) {
            D4Map *map_to_be_removed = *m;
            a->maps()->remove_map(map_to_be_removed); // Invalidates the iterator
            delete map_to_be_removed;                 // removed from container; delete
            break;                                    // must leave the for loop because 'm' is now invalid
        }
    }
}

void D4ConstraintEvaluator::use_explicit_projection(Array *a, const Array::Dim_iter &dim_iter,
                                                    const D4ConstraintEvaluator::index &index) {
    // First apply the constraint to the Array's dimension
    a->add_constraint_ll(dim_iter, index.start, index.stride, index.rest ? -1 : index.stop);
 
    // Then, if the Array has Maps, scan those Maps for any that use dimensions
    // that match the name of this particular dimension. If any such Maps are found
    // remove them. This ensures that the Array can be constrained using the  'local
    // dimension slice' without the constrained DMR containing references to Maps
    // that don't exist (or are otherwise nonsensical).
    //
    // This code came about as a fix for problems discovered during testing of
    // local dimension slices. See https://opendap.atlassian.net/browse/HYRAX-98
    // jhrg 4/12/16
    if (!a->maps()->empty()) {
        // Some variables may have several maps that shares the same dimension.
        // When local constraint applies, all these maps should be removed.
        int map_size = a->maps()->size();
        for (int map_index = 0; map_index < map_size; map_index++) {
            array_map_remover(a, a->dimension_D4dim(dim_iter));
        }
    }
}

D4Dimension *D4ConstraintEvaluator::slice_dimension(const std::string &id, const index &i) {
    D4Dimension *dim = dmr()->root()->find_dim(id);
 
    if ((uint64_t)i.stride > dim->size())
        throw Error(malformed_expr,
                    "For '" + id + "', the index stride value is greater than the size of the dimension");
    if (!i.rest && ((uint64_t)i.stop > dim->size() - 1))
        throw Error(malformed_expr, "For '" + id + "', the index stop value is greater than the size of the dimension");
 
    dim->set_constraint(i.start, i.stride, i.rest ? dim->size() - 1 : i.stop);
 
    return dim;
}
 
D4ConstraintEvaluator::index D4ConstraintEvaluator::make_index(const std::string &i) {
    int64_t v = get_int64(i.c_str());
    return {v, 1, v, false, false /*empty*/, ""};
}
 
D4ConstraintEvaluator::index D4ConstraintEvaluator::make_index(const std::string &i, const std::string &s,
                                                               const std::string &e) {
    int64_t initial = get_int64(i.c_str());
    int64_t end = get_int64(e.c_str());
    if (initial > end)
        throw Error(malformed_expr, string("The start value of an array index is past the stop value."));
 
    return {initial, get_int64(s.c_str()), end, false, false /*empty*/, ""};
}
 
D4ConstraintEvaluator::index D4ConstraintEvaluator::make_index(const std::string &i, int64_t s, const std::string &e) {
    int64_t initial = get_int64(i.c_str());
    int64_t end = get_int64(e.c_str());
    if (initial > end)
        throw Error(malformed_expr, string("The start value of an array index is past the stop value."));
 
    return {initial, s, end, false, false /*empty*/, ""};
}
 
D4ConstraintEvaluator::index D4ConstraintEvaluator::make_index(const std::string &i, const std::string &s) {
    return {get_int64(i.c_str()), get_int64(s.c_str()), 0, true, false /*empty*/, ""};
}
 
D4ConstraintEvaluator::index D4ConstraintEvaluator::make_index(const std::string &i, int64_t s) {
    return {get_int64(i.c_str()), s, 0, true, false /*empty*/, ""};
}
 
static string expr_msg(const std::string &op, const std::string &arg1, const std::string &arg2) {
    return "(" + arg1 + " " + op + " " + arg2 + ").";
}

static D4FilterClause::ops get_op_code(const std::string &op) {
    DBGN(cerr << "Entering " << __PRETTY_FUNCTION__ << endl << "op: " << op << endl);
 
    if (op == "<")
        return D4FilterClause::less;
    else if (op == ">")
        return D4FilterClause::greater;
    else if (op == "<=")
        return D4FilterClause::less_equal;
    else if (op == ">=")
        return D4FilterClause::greater_equal;
    else if (op == "==")
        return D4FilterClause::equal;
    else if (op == "!=")
        return D4FilterClause::not_equal;
    else if (op == "~=")
        return D4FilterClause::match;
    else
        throw Error(malformed_expr, "The operator '" + op + "' is not supported.");
}

void D4ConstraintEvaluator::add_filter_clause(const std::string &op, const std::string &arg1,
                                              const std::string &arg2) const {
    DBG(cerr << "Entering: " << __PRETTY_FUNCTION__ << endl);
 
    // Check that there really is a D4Sequence associated with this filter clause.
    auto s = dynamic_cast<D4Sequence *>(top_basetype());
    if (!s)
        throw Error(malformed_expr, "When a filter expression is used, it must be bound to a Sequence variable: " +
                                        expr_msg(op, arg1, arg2));
 
    DBG(cerr << "s->name(): " << s->name() << endl);
 
    // Check that arg1 and 2 are valid
    BaseType *a1 = s->var(arg1);
    BaseType *a2 = s->var(arg2);
    DBG(cerr << "a1: " << a1 << ", a2: " << a2 << endl);
 
    if (a1 && a2)
        throw Error(malformed_expr,
                    "One of the arguments in a filter expression must be a constant: " + expr_msg(op, arg1, arg2));
    if (!(a1 || a2))
        throw Error(malformed_expr, "One of the arguments in a filter expression must be a variable in a Sequence: " +
                                        expr_msg(op, arg1, arg2));
 
    // Now we know a1 XOR a2 is true
    if (a1) {
        s->clauses().add_clause(new D4FilterClause(get_op_code(op), new D4RValue(a1), D4RValueFactory(arg2)));
    } else {
        s->clauses().add_clause(new D4FilterClause(get_op_code(op), D4RValueFactory(arg1), new D4RValue(a2)));
    }
}

string &D4ConstraintEvaluator::remove_quotes(string &s) {
    if (*s.begin() == '\"' && *(s.end() - 1) == '\"') {
        s.erase(s.begin());
        s.erase(s.end() - 1);
    }
 
    return s;
}
 
// This method is called from the parser (see d4_ce_parser.yy, down in the code
// section). This will be called during the call to D4CEParser::parse(), that
// is inside D4ConstraintEvaluator::parse(...)
//
// Including the value passed in for 'l' allows the CE text to leak into
// the error message, a potential XSS attack vector. jhrg 4/15/20
[[noreturn]] void D4ConstraintEvaluator::error(const libdap::location &, const std::string &m) {
    ostringstream oss;
#if PREVENT_XXS_VIA_CE
    oss << "Constraint expression parse error: " << m << ends;
#else
    oss << l << ": " << m << ends;
#endif
    throw Error(malformed_expr, oss.str());
}
 
} /* namespace libdap */