Ignore trailing slash in Origin header

See gh-26892

spring-web/src/main/java/org/springframework/web/cors/CorsConfiguration.java

@@ -551,6 +551,9 @@ public class CorsConfiguration {
 		if (!StringUtils.hasText(requestOrigin)) {
 			return null;
 		}
+		if (requestOrigin.endsWith("/")) {
+			requestOrigin = requestOrigin.substring(0, requestOrigin.length() - 1);
+		}
 		if (!ObjectUtils.isEmpty(this.allowedOrigins)) {
 			if (this.allowedOrigins.contains(ALL)) {
 				validateAllowCredentials();

spring-web/src/test/java/org/springframework/web/cors/CorsConfigurationTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2020 the original author or authors.
+ * Copyright 2002-2021 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -291,6 +291,7 @@ public class CorsConfigurationTests {
 
 		config.setAllowedOrigins(Collections.singletonList("https://domain.com"));
 		assertThat(config.checkOrigin("https://domain.com")).isEqualTo("https://domain.com");
+		assertThat(config.checkOrigin("https://domain.com/")).isEqualTo("https://domain.com");
 
 		config.setAllowCredentials(false);
 		assertThat(config.checkOrigin("https://domain.com")).isEqualTo("https://domain.com");

spring-web/src/test/java/org/springframework/web/cors/DefaultCorsProcessorTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2020 the original author or authors.
+ * Copyright 2002-2021 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -170,10 +170,19 @@ public class DefaultCorsProcessorTests {
 		this.conf.addAllowedOrigin("https://DOMAIN2.com");
 
 		this.processor.processRequest(this.conf, this.request, this.response);
+		assertThat(this.response.getStatus()).isEqualTo(HttpServletResponse.SC_OK);
 		assertThat(this.response.containsHeader(HttpHeaders.ACCESS_CONTROL_ALLOW_ORIGIN)).isTrue();
-		assertThat(this.response.getHeaders(HttpHeaders.VARY)).contains(HttpHeaders.ORIGIN,
-				HttpHeaders.ACCESS_CONTROL_REQUEST_METHOD, HttpHeaders.ACCESS_CONTROL_REQUEST_HEADERS);
+	}
+
+	@Test // gh-26892
+	public void actualRequestTrailingSlashOriginMatch() throws Exception {
+		this.request.setMethod(HttpMethod.GET.name());
+		this.request.addHeader(HttpHeaders.ORIGIN, "https://domain2.com/");
+		this.conf.addAllowedOrigin("https://domain2.com");
+
+		this.processor.processRequest(this.conf, this.request, this.response);
 		assertThat(this.response.getStatus()).isEqualTo(HttpServletResponse.SC_OK);
+		assertThat(this.response.containsHeader(HttpHeaders.ACCESS_CONTROL_ALLOW_ORIGIN)).isTrue();
 	}
 
 	@Test

spring-web/src/test/java/org/springframework/web/cors/reactive/DefaultCorsProcessorTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2020 the original author or authors.
+ * Copyright 2002-2021 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -172,10 +172,22 @@ public class DefaultCorsProcessorTests {
 		this.processor.process(this.conf, exchange);
 
 		ServerHttpResponse response = exchange.getResponse();
+		assertThat((Object) response.getStatusCode()).isNull();
 		assertThat(response.getHeaders().containsKey(ACCESS_CONTROL_ALLOW_ORIGIN)).isTrue();
-		assertThat(response.getHeaders().get(VARY)).contains(ORIGIN,
-				ACCESS_CONTROL_REQUEST_METHOD, ACCESS_CONTROL_REQUEST_HEADERS);
+	}
+
+	@Test // gh-26892
+	public void actualRequestTrailingSlashOriginMatch() {
+		ServerWebExchange exchange = MockServerWebExchange.from(MockServerHttpRequest
+				.method(HttpMethod.GET, "http://localhost/test.html")
+				.header(HttpHeaders.ORIGIN, "https://domain2.com/"));
+
+		this.conf.addAllowedOrigin("https://domain2.com");
+		this.processor.process(this.conf, exchange);
+
+		ServerHttpResponse response = exchange.getResponse();
 		assertThat((Object) response.getStatusCode()).isNull();
+		assertThat(response.getHeaders().containsKey(ACCESS_CONTROL_ALLOW_ORIGIN)).isTrue();
 	}
 
 	@Test