Fix lowerCaseHostname to lower-case scheme and host properly
Closes https://github.com/keycloak/keycloak/issues/24792

Signed-off-by: rmartinc <rmartinc@redhat.com>

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

@@ -72,10 +72,8 @@
            if (validRedirect.startsWith("/")) {
                validRedirect = relativeToAbsoluteURI(session, rootUrl, validRedirect);
                logger.debugv("replacing relative valid redirect with: {0}", validRedirect);
                resolveValidRedirects.add(validRedirect);
            } else {
                resolveValidRedirects.add(validRedirect);
            }
            resolveValidRedirects.add(lowerCaseHostname(validRedirect));
        }
        return resolveValidRedirects;
    }
@@ -116,7 +114,7 @@
            // 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);
            decodedRedirectUri = getNormalizedRedirectUri(decodedRedirect, true);
            if (decodedRedirectUri == null) return null;

            String r = decodedRedirectUri;
@@ -141,21 +139,25 @@
            }

            // 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);
            redirectUri = getNormalizedRedirectUri(originalRedirect, false);

            // 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);
            }

            if (valid != null && redirectUri.startsWith("/")) {
            if (valid != null && !originalRedirect.isAbsolute()) {
                // return absolute if the original URI is relative
                if (!redirectUri.startsWith("/")) {
                    redirectUri = "/" + redirectUri;
                }
                redirectUri = relativeToAbsoluteURI(session, rootUrl, redirectUri);
            }

            String scheme = decodedRedirect.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)) {
                if (!valid.startsWith(scheme.toLowerCase() + ":") && !"http".equalsIgnoreCase(scheme) && !"https".equalsIgnoreCase(scheme)) {
                    logger.debugf("Invalid URI because scheme is not allowed: %s", redirectUri);
                    valid = null;
                }
@@ -185,12 +187,14 @@
        return uri;
    }

    private static String getNormalizedRedirectUri(URI uri) {
    private static String getNormalizedRedirectUri(URI uri, boolean lower) {
        String redirectUri = null;
        if (uri != null) {
            redirectUri = uri.normalize().toString();
            if (lower) {
            redirectUri = lowerCaseHostname(redirectUri);
        }
        }
        return redirectUri;
    }

@@ -204,9 +208,11 @@
            KeycloakUriBuilder uriBuilder = KeycloakUriBuilder.fromUri(redirectUri, false).preserveDefaultPort();
            String origQuery = uriBuilder.getQuery();
            String origFragment = uriBuilder.getFragment();
            String origUserInfo = uriBuilder.getUserInfo();
            String encodedRedirectUri = uriBuilder
                    .replaceQuery(null)
                    .fragment(null)
                    .userInfo(null)
                    .buildAsString();
            String decodedRedirectUri = null;

@@ -217,6 +223,7 @@
                    return KeycloakUriBuilder.fromUri(decodedRedirectUri, false).preserveDefaultPort()
                            .replaceQuery(origQuery)
                            .fragment(origFragment)
                            .userInfo(origUserInfo)
                            .buildAsString();
                } else {
                    // Next attempt
@@ -231,12 +238,15 @@
    }

    private static String lowerCaseHostname(String redirectUri) {
        int n = redirectUri.indexOf('/', 7);
        if (n == -1) {
            return redirectUri.toLowerCase();
        } else {
            return redirectUri.substring(0, n).toLowerCase() + redirectUri.substring(n);
        // lower case host and scheme which are case-insensitive by spec
        KeycloakUriBuilder uriBuilder = KeycloakUriBuilder.fromUri(redirectUri, false).preserveDefaultPort();
        if (uriBuilder.getScheme() != null) {
            uriBuilder.scheme(uriBuilder.getScheme().toLowerCase());
        }
        if (uriBuilder.getHost() != null) {
            uriBuilder.host(uriBuilder.getHost().toLowerCase());
        }
        return uriBuilder.buildAsString();
    }

    private static String relativeToAbsoluteURI(KeycloakSession session, String rootUrl, String relative) {