software.amazon.smithy.model.validation.validators.HttpHeaderTraitValidator Maven / Gradle / Ivy

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/*
 * Copyright 2019 Amazon.com, Inc. or its affiliates. All Rights Reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License").
 * You may not use this file except in compliance with the License.
 * A copy of the License is located at
 *
 *  http://aws.amazon.com/apache2.0
 *
 * or in the "license" file accompanying this file. This file is distributed
 * on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either
 * express or implied. See the License for the specific language governing
 * permissions and limitations under the License.
 */

package software.amazon.smithy.model.validation.validators;

import static java.util.stream.Collectors.groupingBy;
import static java.util.stream.Collectors.mapping;
import static java.util.stream.Collectors.toList;

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.Locale;
import java.util.Optional;
import java.util.Set;
import software.amazon.smithy.model.Model;
import software.amazon.smithy.model.shapes.MemberShape;
import software.amazon.smithy.model.shapes.StructureShape;
import software.amazon.smithy.model.traits.HttpHeaderTrait;
import software.amazon.smithy.model.validation.AbstractValidator;
import software.amazon.smithy.model.validation.ValidationEvent;
import software.amazon.smithy.model.validation.ValidationUtils;
import software.amazon.smithy.utils.SetUtils;

/**
 * Validates that httpHeader traits are case-insensitively unique.
 */
public final class HttpHeaderTraitValidator extends AbstractValidator {

    /** Gather the allowed characters for HTTP headers (tchar from RFC 7230). **/
    private static final Set TCHAR = SetUtils.of(
            // "!" / "#" / "$" / "%" / "&" / "'" / "*" / "+" / "-" / "." / "^" / "_" / "`" / "|" / "~"
            '!', '#', '$', '%', '&', '\'', '*', '+', '-', '.', '^', '_', '`', '|', '~',
            // DIGIT (0-9)
            '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
            // ALPHA (A-Z)
            'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M',
            'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z',
            // ALPHA (a-z)
            'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm',
            'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z'
    );

    private static final Set BLOCKLIST = SetUtils.of(
            "authorization",
            "connection",
            "content-length",
            "expect",
            "host",
            "max-forwards",
            "proxy-authenticate",
            "server",
            "te",
            "trailer",
            "transfer-encoding",
            "upgrade",
            "user-agent",
            "www-authenticate",
            "x-forwarded-for");

    @Override
    public List validate(Model model) {
        if (!model.isTraitApplied(HttpHeaderTrait.class)) {
            return Collections.emptyList();
        }

        List events = new ArrayList<>();

        for (StructureShape structure : model.getStructureShapes()) {
            events.addAll(validateStructure(structure));
        }

        for (MemberShape member : model.getMemberShapesWithTrait(HttpHeaderTrait.class)) {
            HttpHeaderTrait httpHeaderTrait = member.expectTrait(HttpHeaderTrait.class);
            validateHeader(member, httpHeaderTrait).ifPresent(events::add);
        }

        return events;
    }

    private Optional validateHeader(MemberShape member, HttpHeaderTrait trait) {
        String header = trait.getValue();

        if (BLOCKLIST.contains(header.toLowerCase(Locale.ENGLISH))) {
            return Optional.of(danger(member, trait, String.format(
                    "`%s` is not an allowed HTTP header binding", header)));
        }

        for (int i = 0; i < header.length(); i++) {
            if (!TCHAR.contains(header.charAt(i))) {
                return Optional.of(danger(member, trait, String.format(
                        "`%s` is not a valid HTTP header field name according to section 3.2 of RFC 7230", header)));
            }
        }

        return Optional.empty();
    }

    private List validateStructure(StructureShape structure) {
        return structure.getAllMembers().values().stream()
                .filter(member -> member.hasTrait(HttpHeaderTrait.class))
                .collect(groupingBy(shape -> shape.expectTrait(HttpHeaderTrait.class).getValue().toLowerCase(Locale.US),
                                    mapping(MemberShape::getMemberName, toList())))
                .entrySet()
                .stream()
                .filter(entry -> entry.getValue().size() > 1)
                .map(entry -> error(structure, String.format(
                        "`httpHeader` field name binding conflicts found for the `%s` header in the "
                        + "following structure members: %s",
                        entry.getKey(), ValidationUtils.tickedList(entry.getValue()))))
                .collect(toList());
    }
}