Perform exact string match if redirect URI contains userinfo, encoded slashes or parent access (#131) (#28872)

Closes keycloak/keycloak-private#113
Closes keycloak/keycloak-private#134

Signed-off-by: rmartinc <rmartinc@redhat.com>
Co-authored-by: Stian Thorgersen <stianst@gmail.com>

 src/main/java/org/keycloak/protocol/cas/utils/RedirectUtils.java

@@ -18,8 +18,6 @@
package org.keycloak.protocol.oidc.utils;

import org.jboss.logging.Logger;
import org.keycloak.common.util.Encode;
import org.keycloak.common.util.KeycloakUriBuilder;
import org.keycloak.common.util.UriUtils;
import org.keycloak.models.ClientModel;
import org.keycloak.models.Constants;
@@ -34,6 +32,7 @@
import java.util.Collection;
import java.util.Set;
import java.util.TreeSet;
import java.util.regex.Pattern;
import java.util.stream.Collectors;

/**
@@ -111,16 +110,13 @@
                return null;
            }

            // Make the validations against fully decoded and normalized redirect-url. This also allows wildcards (case when client configured "Valid redirect-urls" contain wildcards)
            String decodedRedirectUri = decodeRedirectUri(redirectUri);
            URI decodedRedirect = toUri(decodedRedirectUri);
            decodedRedirectUri = getNormalizedRedirectUri(decodedRedirect);
            if (decodedRedirectUri == null) return null;
            // check if the passed URI allows wildcards
            boolean allowWildcards = areWildcardsAllowed(originalRedirect);

            String r = decodedRedirectUri;
            String r = redirectUri;
            Set<String> resolveValidRedirects = resolveValidRedirects(session, rootUrl, validRedirects);

            String valid = matchesRedirects(resolveValidRedirects, r, true);
            String valid = matchesRedirects(resolveValidRedirects, r, allowWildcards);

            if (valid == null && (r.startsWith(Constants.INSTALLED_APP_URL) || r.startsWith(Constants.INSTALLED_APP_LOOPBACK)) && r.indexOf(':', Constants.INSTALLED_APP_URL.length()) >= 0) {
                int i = r.indexOf(':', Constants.INSTALLED_APP_URL.length());
@@ -135,15 +131,7 @@

                r = sb.toString();

                valid = matchesRedirects(resolveValidRedirects, r, true);
            }

            // Return the original redirectUri, which can be partially encoded - for example http://localhost:8280/foo/bar%20bar%2092%2F72/3 . Just make sure it is normalized
            redirectUri = getNormalizedRedirectUri(originalRedirect);

            // We try to check validity also for original (encoded) redirectUrl, but just in case it exactly matches some "Valid Redirect URL" specified for client (not wildcards allowed)
            if (valid == null) {
                valid = matchesRedirects(resolveValidRedirects, redirectUri, false);
                valid = matchesRedirects(resolveValidRedirects, r, allowWildcards);
            }

            if (valid != null && !originalRedirect.isAbsolute()) {
@@ -154,7 +142,7 @@
                redirectUri = relativeToAbsoluteURI(session, rootUrl, redirectUri);
            }

            String scheme = decodedRedirect.getScheme();
            String scheme = originalRedirect.getScheme();
            if (valid != null && scheme != null) {
                // check the scheme is valid, it should be http(s) or explicitly allowed by the validation
                if (!valid.startsWith(scheme + ":") && !"http".equalsIgnoreCase(scheme) && !"https".equalsIgnoreCase(scheme)) {
@@ -179,51 +167,22 @@
            try {
                uri = URI.create(redirectUri);
            } catch (IllegalArgumentException cause) {
                logger.debug("Invalid redirect uri", cause);
                logger.debugf(cause, "Invalid redirect uri %s", redirectUri);
            } catch (Exception cause) {
                logger.debug("Unexpected error when parsing redirect uri", cause);
                logger.debugf(cause, "Unexpected error when parsing redirect uri %s", redirectUri);
            }
        }
        return uri;
    }

    private static String getNormalizedRedirectUri(URI uri) {
        String redirectUri = null;
        if (uri != null) {
            redirectUri = uri.normalize().toString();
        }
        return redirectUri;
    }
    // any access to parent folder /../ is unsafe with or without encoding
    private final static Pattern UNSAFE_PATH_PATTERN = Pattern.compile(
            "(/|%2[fF]|%5[cC]|\\\\)(%2[eE]|\\.){2}(/|%2[fF]|%5[cC]|\\\\)|(/|%2[fF]|%5[cC]|\\\\)(%2[eE]|\\.){2}$");

    // Decode redirectUri. Only path is decoded as other elements can be encoded in the original URL or cannot be encoded at all.
    // URL can be decoded multiple times (in case it was encoded multiple times, or some of it's parts were encoded multiple times)
    private static String decodeRedirectUri(String redirectUri) {
        if (redirectUri == null) return null;
        int MAX_DECODING_COUNT = 5; // Max count of attempts for decoding URL (in case it was encoded multiple times)

        try {
            KeycloakUriBuilder uriBuilder = KeycloakUriBuilder.fromUri(redirectUri, false).preserveDefaultPort();
            if (uriBuilder.getPath() == null) {
                return redirectUri;
            }
            String encodedPath = uriBuilder.getPath();
            String decodedPath;

            for (int i = 0; i < MAX_DECODING_COUNT; i++) {
                decodedPath = Encode.decode(encodedPath);
                if (decodedPath.equals(encodedPath)) {
                    // URL path is decoded. We can return it in the original redirect URI
                    return uriBuilder.replacePath(decodedPath, false).buildAsString();
                } else {
                    // Next attempt
                    encodedPath = decodedPath;
                }
            }
        } catch (IllegalArgumentException iae) {
            logger.debugf("Illegal redirect URI used: %s, Details: %s", redirectUri, iae.getMessage());
        }
        logger.debugf("Was not able to decode redirect URI: %s", redirectUri);
        return null;
    private static boolean areWildcardsAllowed(URI redirectUri) {
        // wildcars are only allowed if no user-info and no unsafe pattern in path
        return redirectUri.getRawUserInfo() == null
                && (redirectUri.getRawPath() == null || !UNSAFE_PATH_PATTERN.matcher(redirectUri.getRawPath()).find());
    }

    private static String relativeToAbsoluteURI(KeycloakSession session, String rootUrl, String relative) {
@@ -240,24 +199,20 @@
        return sb.toString();
    }

    // removes the queryString, fragment and userInfo from the redirect
    // to avoid comparing this when wildcards are used
    private static String stripOffRedirectForWildcard(String redirect) {
        return KeycloakUriBuilder.fromUri(redirect, false)
                .preserveDefaultPort()
                .userInfo(null)
                .replaceQuery(null)
                .fragment(null)
                .buildAsString();
    }

    // return the String that matched the redirect or null if not matched
    private static String matchesRedirects(Set<String> validRedirects, String redirect, boolean allowWildcards) {
        logger.tracef("matchesRedirects: redirect URL to check: %s, allow wildcards: %b, Configured valid redirect URLs: %s", redirect, allowWildcards, validRedirects);
        for (String validRedirect : validRedirects) {
            if (validRedirect.endsWith("*") && !validRedirect.contains("?") && allowWildcards) {
                // strip off the userInfo, query or fragment components - we don't check them when wildcards are effective
                String r = stripOffRedirectForWildcard(redirect);
            if ("*".equals(validRedirect)) {
                // the valid redirect * is a full wildcard for http(s) even if the redirect URI does not allow wildcards
                return validRedirect;
            } else if (validRedirect.endsWith("*") && !validRedirect.contains("?") && allowWildcards) {
                // strip off the query or fragment components - we don't check them when wildcards are effective
                int idx = redirect.indexOf('?');
                if (idx == -1) {
                    idx = redirect.indexOf('#');
                }
                String r = idx == -1 ? redirect : redirect.substring(0, idx);
                // strip off *
                int length = validRedirect.length() - 1;
                validRedirect = validRedirect.substring(0, length);