Source code
package org.apache.kafka.common.security.ssl;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import java.util.Locale;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import static org.apache.kafka.common.config.internals.BrokerSecurityConfigs.DEFAULT_SSL_PRINCIPAL_MAPPING_RULES;
public class SslPrincipalMapper {
private static final String RULE_PATTERN = "(DEFAULT)|RULE:((\\\\.|[^\\\\/])*)/((\\\\.|[^\\\\/])*)/([LU]?).*?|(.*?)";
private static final Pattern RULE_SPLITTER = Pattern.compile("\\s*(" + RULE_PATTERN + ")\\s*(,\\s*|$)");
private static final Pattern RULE_PARSER = Pattern.compile(RULE_PATTERN);
private final List<Rule> rules;
public SslPrincipalMapper(String sslPrincipalMappingRules) {
this.rules = parseRules(splitRules(sslPrincipalMappingRules));
}
public static SslPrincipalMapper fromRules(String sslPrincipalMappingRules) {
return new SslPrincipalMapper(sslPrincipalMappingRules);
}
private static List<String> splitRules(String sslPrincipalMappingRules) {
if (sslPrincipalMappingRules == null) {
sslPrincipalMappingRules = DEFAULT_SSL_PRINCIPAL_MAPPING_RULES;
}
List<String> result = new ArrayList<>();
Matcher matcher = RULE_SPLITTER.matcher(sslPrincipalMappingRules.trim());
while (matcher.find()) {
result.add(matcher.group(1));
}
return result;
}
private static List<Rule> parseRules(List<String> rules) {
List<Rule> result = new ArrayList<>();
for (String rule : rules) {
Matcher matcher = RULE_PARSER.matcher(rule);
if (!matcher.lookingAt()) {
throw new IllegalArgumentException("Invalid rule: " + rule);
}
if (rule.length() != matcher.end()) {
throw new IllegalArgumentException("Invalid rule: `" + rule + "`, unmatched substring: `" + rule.substring(matcher.end()) + "`");
}
// empty rules are ignored
if (matcher.group(1) != null) {
result.add(new Rule());
} else if (matcher.group(2) != null) {
result.add(new Rule(matcher.group(2),
matcher.group(4),
"L".equals(matcher.group(6)),
"U".equals(matcher.group(6))));
}
}
return result;
}
public String getName(String distinguishedName) throws IOException {
for (Rule r : rules) {
String principalName = r.apply(distinguishedName);
if (principalName != null) {
return principalName;
}
}
throw new NoMatchingRule("No rules apply to " + distinguishedName + ", rules " + rules);
}
@Override
public String toString() {
return "SslPrincipalMapper(rules = " + rules + ")";
}
public static class NoMatchingRule extends IOException {
NoMatchingRule(String msg) {
super(msg);
}
}
private static class Rule {
private static final Pattern BACK_REFERENCE_PATTERN = Pattern.compile("\\$(\\d+)");
private final boolean isDefault;
private final Pattern pattern;
private final String replacement;
private final boolean toLowerCase;
private final boolean toUpperCase;
Rule() {
isDefault = true;
pattern = null;
replacement = null;
toLowerCase = false;
toUpperCase = false;
}
Rule(String pattern, String replacement, boolean toLowerCase, boolean toUpperCase) {
isDefault = false;
this.pattern = pattern == null ? null : Pattern.compile(pattern);
this.replacement = replacement;
this.toLowerCase = toLowerCase;
this.toUpperCase = toUpperCase;
}
String apply(String distinguishedName) {
if (isDefault) {
return distinguishedName;
}
String result = null;
final Matcher m = pattern.matcher(distinguishedName);
if (m.matches()) {
result = distinguishedName.replaceAll(pattern.pattern(), escapeLiteralBackReferences(replacement, m.groupCount()));
}
if (toLowerCase && result != null) {
result = result.toLowerCase(Locale.ENGLISH);
} else if (toUpperCase && result != null) {
result = result.toUpperCase(Locale.ENGLISH);
}
return result;
}
//If we find a back reference that is not valid, then we will treat it as a literal string. For example, if we have 3 capturing
//groups and the Replacement Value has the value is "$1@$4", then we want to treat the $4 as a literal "$4", rather
//than attempting to use it as a back reference.
//This method was taken from Apache Nifi project : org.apache.nifi.authorization.util.IdentityMappingUtil
private String escapeLiteralBackReferences(final String unescaped, final int numCapturingGroups) {
if (numCapturingGroups == 0) {
return unescaped;
}
String value = unescaped;
final Matcher backRefMatcher = BACK_REFERENCE_PATTERN.matcher(value);
while (backRefMatcher.find()) {
final String backRefNum = backRefMatcher.group(1);
if (backRefNum.startsWith("0")) {
continue;
}
int backRefIndex = Integer.parseInt(backRefNum);
// if we have a replacement value like $123, and we have less than 123 capturing groups, then
// we want to truncate the 3 and use capturing group 12; if we have less than 12 capturing groups,
// then we want to truncate the 2 and use capturing group 1; if we don't have a capturing group then
// we want to truncate the 1 and get 0.
while (backRefIndex > numCapturingGroups && backRefIndex >= 10) {
backRefIndex /= 10;
}
if (backRefIndex > numCapturingGroups) {
final StringBuilder sb = new StringBuilder(value.length() + 1);
final int groupStart = backRefMatcher.start(1);
sb.append(value, 0, groupStart - 1);
sb.append("\\");
sb.append(value.substring(groupStart - 1));
value = sb.toString();
}
}
return value;
}
@Override
public String toString() {
StringBuilder buf = new StringBuilder();
if (isDefault) {
buf.append("DEFAULT");
} else {
buf.append("RULE:");
if (pattern != null) {
buf.append(pattern);
}
if (replacement != null) {
buf.append("/");
buf.append(replacement);
}
if (toLowerCase) {
buf.append("/L");
} else if (toUpperCase) {
buf.append("/U");
}
}
return buf.toString();
}
}
}