HttpHeaders consistently ignores invalid date header values

Issue: SPR-14144

spring-web/src/main/java/org/springframework/http/HttpHeaders.java

@@ -779,12 +779,7 @@ public class HttpHeaders implements MultiValueMap<String, String>, Serializable
 	 * January 1, 1970 GMT. Returns -1 when the date is unknown.
 	 */
 	public long getExpires() {
-		try {
+		return getFirstDate(EXPIRES, false);
-			return getFirstDate(EXPIRES);
-		}
-		catch (IllegalArgumentException ex) {
-			return -1;
-		}
 	}
 
 	/**
@@ -802,7 +797,7 @@ public class HttpHeaders implements MultiValueMap<String, String>, Serializable
 	 * January 1, 1970 GMT. Returns -1 when the date is unknown.
 	 */
 	public long getIfModifiedSince() {
-		return getFirstDate(IF_MODIFIED_SINCE);
+		return getFirstDate(IF_MODIFIED_SINCE, false);
 	}
 
 	/**
@@ -867,7 +862,7 @@ public class HttpHeaders implements MultiValueMap<String, String>, Serializable
 	 * January 1, 1970 GMT. Returns -1 when the date is unknown.
 	 */
 	public long getLastModified() {
-		return getFirstDate(LAST_MODIFIED);
+		return getFirstDate(LAST_MODIFIED, false);
 	}
 
 	/**
@@ -969,12 +964,33 @@ public class HttpHeaders implements MultiValueMap<String, String>, Serializable
 	 * Parse the first header value for the given header name as a date,
 	 * return -1 if there is no value, or raise {@link IllegalArgumentException}
 	 * if the value cannot be parsed as a date.
+	 * @param headerName the header name
+	 * @return the parsed date header, or -1 if none
 	 */
 	public long getFirstDate(String headerName) {
+		return getFirstDate(headerName, true);
+	}
+
+	/**
+	 * Parse the first header value for the given header name as a date,
+	 * return -1 if there is no value or also in case of an invalid value
+	 * (if {@code rejectInvalid=false}), or raise {@link IllegalArgumentException}
+	 * if the value cannot be parsed as a date.
+	 * @param headerName the header name
+	 * @param rejectInvalid whether to reject invalid values with an
+	 * {@link IllegalArgumentException} ({@code true}) or rather return -1
+	 * in that case ({@code false})
+	 * @return the parsed date header, or -1 if none (or invalid)
+ 	 */
+	private long getFirstDate(String headerName, boolean rejectInvalid) {
 		String headerValue = getFirst(headerName);
 		if (headerValue == null) {
+			// No header value sent at all
 			return -1;
 		}
+		if (headerValue.length() >= 3) {
+			// Short "0" or "-1" like values are never valid HTTP date headers...
+			// Let's only bother with SimpleDateFormat parsing for long enough values.
 			for (String dateFormat : DATE_FORMATS) {
 				SimpleDateFormat simpleDateFormat = new SimpleDateFormat(dateFormat, Locale.US);
 				simpleDateFormat.setTimeZone(GMT);
@@ -985,9 +1001,13 @@ public class HttpHeaders implements MultiValueMap<String, String>, Serializable
 					// ignore
 				}
 			}
+		}
+		if (rejectInvalid) {
 			throw new IllegalArgumentException("Cannot parse date value \"" + headerValue +
 					"\" for \"" + headerName + "\" header");
 		}
+		return -1;
+	}
 
 	/**
 	 * Set the given date under the given header name after formatting it as a string

spring-web/src/test/java/org/springframework/http/HttpHeadersTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2015 the original author or authors.
+ * Copyright 2002-2016 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.
@@ -30,14 +30,9 @@ import java.util.Locale;
 import java.util.TimeZone;
 
 import org.hamcrest.Matchers;
-
 import org.junit.Test;
 
-import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.*;
-import static org.junit.Assert.assertThat;
-import static org.junit.Assert.assertTrue;
-import static org.junit.Assert.assertFalse;
-import static org.junit.Assert.assertNull;
 
 /**
  * Unit tests for {@link org.springframework.http.HttpHeaders}.
@@ -215,9 +210,7 @@ public class HttpHeadersTests {
 		assertEquals("Invalid Expires header", "Thu, 18 Dec 2008 10:20:00 GMT", headers.getFirst("expires"));
 	}
 
-	// SPR-10648 (example is from INT-3063)
+	@Test  // SPR-10648 (example is from INT-3063)
-
-	@Test
 	public void expiresInvalidDate() {
 		headers.set("Expires", "-1");
 		assertEquals(-1, headers.getExpires());
@@ -234,6 +227,18 @@ public class HttpHeadersTests {
 				headers.getFirst("if-modified-since"));
 	}
 
+	@Test  // SPR-14144
+	public void invalidIfModifiedSinceHeader() {
+		headers.set(HttpHeaders.IF_MODIFIED_SINCE, "0");
+		assertEquals(-1, headers.getIfModifiedSince());
+
+		headers.set(HttpHeaders.IF_MODIFIED_SINCE, "-1");
+		assertEquals(-1, headers.getIfModifiedSince());
+
+		headers.set(HttpHeaders.IF_MODIFIED_SINCE, "XXX");
+		assertEquals(-1, headers.getIfModifiedSince());
+	}
+
 	@Test
 	public void pragma() {
 		String pragma = "no-cache";