SSH config: fix negated patterns

Negated patterns were handled wrongly. According to the OpenBSD
ssh_config man page,[1] a negated pattern never matches. Negated
patterns make only sense if there are positive patterns; the
negated pattern then can define exceptions for the positive
patterns.

OpenSshConfigFile did this wrongly. It handled "!foo" as "matching
everything but foo", but actually the semantics is "if the input is
"foo", this entry doesn't apply. If the input is anything else,
other patterns determine whether the entry may apply.".

[1] https://man.openbsd.org/ssh_config

Change-Id: I50f6e46581b7ece4c949eddf62f4a265573ec29e
Signed-off-by: Thomas Wolf <thomas.wolf@paranor.ch>

1 files changed, 50 insertions, 58 deletions

diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/internal/transport/ssh/OpenSshConfigFile.java b/org.eclipse.jgit/src/org/eclipse/jgit/internal/transport/ssh/OpenSshConfigFile.java
index de6a346cb2..e4753df00c 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/internal/transport/ssh/OpenSshConfigFile.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/internal/transport/ssh/OpenSshConfigFile.java
@@ -1,6 +1,6 @@
 /*
  * Copyright (C) 2008, 2017, Google Inc.
- * Copyright (C) 2017, 2018, Thomas Wolf <thomas.wolf@paranor.ch> and others
+ * Copyright (C) 2017, 2021, Thomas Wolf <thomas.wolf@paranor.ch> and others
  *
  * This program and the accompanying materials are made available under the
  * terms of the Eclipse Distribution License v. 1.0 which is available at
@@ -21,7 +21,8 @@ import java.time.Instant;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.HashMap;
-import java.util.LinkedHashMap;
+import java.util.Iterator;
+import java.util.LinkedList;
 import java.util.List;
 import java.util.Map;
 import java.util.Set;
@@ -82,12 +83,6 @@ import org.eclipse.jgit.util.SystemReader;
  */
 public class OpenSshConfigFile implements SshConfigStore {
 
-	/**
-	 * "Host" name of the HostEntry for the default options before the first
-	 * host block in a config file.
-	 */
-	private static final String DEFAULT_NAME = ""; //$NON-NLS-1$
-
 	/** The user's home directory, as key files may be relative to here. */
 	private final File home;
 
@@ -105,11 +100,9 @@ public class OpenSshConfigFile implements SshConfigStore {
 	 * fully resolved entries created from that.
 	 */
 	private static class State {
-		// Keyed by pattern; if a "Host" line has multiple patterns, we generate
-		// duplicate HostEntry objects
-		Map<String, HostEntry> entries = new LinkedHashMap<>();
+		List<HostEntry> entries = new LinkedList<>();
 
-		// Keyed by user@hostname:port
+		// Previous lookups, keyed by user@hostname:port
 		Map<String, HostEntry> hosts = new HashMap<>();
 
 		@Override
@@ -165,14 +158,16 @@ public class OpenSshConfigFile implements SshConfigStore {
 			return h;
 		}
 		HostEntry fullConfig = new HostEntry();
-		// Initialize with default entries at the top of the file, before the
-		// first Host block.
-		fullConfig.merge(cache.entries.get(DEFAULT_NAME));
-		for (Map.Entry<String, HostEntry> e : cache.entries.entrySet()) {
-			String pattern = e.getKey();
-			if (isHostMatch(pattern, hostName)) {
-				fullConfig.merge(e.getValue());
-			}
+		Iterator<HostEntry> entries = cache.entries.iterator();
+		if (entries.hasNext()) {
+			// Should always have at least the first top entry containing
+			// key-value pairs before the first Host block
+			fullConfig.merge(entries.next());
+			entries.forEachRemaining(entry -> {
+				if (entry.matches(hostName)) {
+					fullConfig.merge(entry);
+				}
+			});
 		}
 		fullConfig.substitute(hostName, port, userName, localUserName, home);
 		cache.hosts.put(cacheKey, fullConfig);
@@ -208,20 +203,19 @@ public class OpenSshConfigFile implements SshConfigStore {
 		return state;
 	}
 
-	private Map<String, HostEntry> parse(BufferedReader reader)
+	private List<HostEntry> parse(BufferedReader reader)
 			throws IOException {
-		final Map<String, HostEntry> entries = new LinkedHashMap<>();
-		final List<HostEntry> current = new ArrayList<>(4);
-		String line;
+		final List<HostEntry> entries = new LinkedList<>();
 
 		// The man page doesn't say so, but the openssh parser (readconf.c)
 		// starts out in active mode and thus always applies any lines that
 		// occur before the first host block. We gather those options in a
 		// HostEntry for DEFAULT_NAME.
 		HostEntry defaults = new HostEntry();
-		current.add(defaults);
-		entries.put(DEFAULT_NAME, defaults);
+		HostEntry current = defaults;
+		entries.add(defaults);
 
+		String line;
 		while ((line = reader.readLine()) != null) {
 			// OpenSsh ignores trailing comments on a line. Anything after the
 			// first # on a line is trimmed away (yes, even if the hash is
@@ -246,38 +240,17 @@ public class OpenSshConfigFile implements SshConfigStore {
 			String argValue = parts.length > 1 ? parts[1].trim() : ""; //$NON-NLS-1$
 
 			if (StringUtils.equalsIgnoreCase(SshConstants.HOST, keyword)) {
-				current.clear();
-				for (String name : parseList(argValue)) {
-					if (name == null || name.isEmpty()) {
-						// null should not occur, but better be safe than sorry.
-						continue;
-					}
-					HostEntry c = entries.get(name);
-					if (c == null) {
-						c = new HostEntry();
-						entries.put(name, c);
-					}
-					current.add(c);
-				}
-				continue;
-			}
-
-			if (current.isEmpty()) {
-				// We received an option outside of a Host block. We
-				// don't know who this should match against, so skip.
+				current = new HostEntry(parseList(argValue));
+				entries.add(current);
 				continue;
 			}
 
 			if (HostEntry.isListKey(keyword)) {
 				List<String> args = validate(keyword, parseList(argValue));
-				for (HostEntry entry : current) {
-					entry.setValue(keyword, args);
-				}
+				current.setValue(keyword, args);
 			} else if (!argValue.isEmpty()) {
 				argValue = validate(keyword, dequote(argValue));
-				for (HostEntry entry : current) {
-					entry.setValue(keyword, argValue);
-				}
+				current.setValue(keyword, argValue);
 			}
 		}
 
@@ -358,13 +331,6 @@ public class OpenSshConfigFile implements SshConfigStore {
 		return value;
 	}
 
-	private static boolean isHostMatch(String pattern, String name) {
-		if (pattern.startsWith("!")) { //$NON-NLS-1$
-			return !patternMatchesHost(pattern.substring(1), name);
-		}
-		return patternMatchesHost(pattern, name);
-	}
-
 	private static boolean patternMatchesHost(String pattern, String name) {
 		if (pattern.indexOf('*') >= 0 || pattern.indexOf('?') >= 0) {
 			final FileNameMatcher fn;
@@ -511,6 +477,32 @@ public class OpenSshConfigFile implements SshConfigStore {
 
 		private Map<String, List<String>> listOptions;
 
+		private final List<String> patterns;
+
+		// Constructor used to build the merged entry; never matches anything
+		HostEntry() {
+			this.patterns = Collections.emptyList();
+		}
+
+		HostEntry(List<String> patterns) {
+			this.patterns = patterns;
+		}
+
+		boolean matches(String hostName) {
+			boolean doesMatch = false;
+			for (String pattern : patterns) {
+				if (pattern.startsWith("!")) { //$NON-NLS-1$
+					if (patternMatchesHost(pattern.substring(1), hostName)) {
+						return false;
+					}
+				} else if (!doesMatch
+						&& patternMatchesHost(pattern, hostName)) {
+					doesMatch = true;
+				}
+			}
+			return doesMatch;
+		}
+
 		private static String toKey(String key) {
 			String k = ALIASES.get(key);
 			return k != null ? k : key;