Added x-forwarded-client-cert server interceptor

grpc-contrib/src/main/java/com/salesforce/grpc/contrib/xfcc/XForwardedClientCert.java

@@ -0,0 +1,121 @@
+/*
+ *  Copyright (c) 2017, salesforce.com, inc.
+ *  All rights reserved.
+ *  Licensed under the BSD 3-Clause license.
+ *  For full license text, see LICENSE.txt file in the repo root  or https://opensource.org/licenses/BSD-3-Clause
+ */
+
+package com.salesforce.grpc.contrib.xfcc;
+
+import io.grpc.Context;
+
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.Collections;
+import java.util.List;
+
+/**
+ * x-forwarded-client-cert (XFCC) is a proxy header which indicates certificate information of part or all of the
+ * clients or proxies that a request has flowed through, on its way from the client to the server.
+ */
+public final class XForwardedClientCert {
+    /**
+     * The metadata key used to access any present {@link XForwardedClientCert} objects.
+     */
+    public static final Context.Key<List<XForwardedClientCert>> XFCC_CONTEXT_KEY = Context.key("x-forwarded-client-cert");
+
+    private String by = "";
+    private String hash = "";
+    private String sanUri = "";
+    private List<String> sanDns = new ArrayList<>();
+    private String subject = "";
+
+    void setBy(String by) {
+        this.by = by;
+    }
+
+    void setHash(String hash) {
+        this.hash = hash;
+    }
+
+    void setSanUri(String sanUri) {
+        this.sanUri = sanUri;
+    }
+
+    void setSubject(String subject) {
+        this.subject = subject;
+    }
+
+    void addSanDns(String sanDns) {
+        this.sanDns.add(sanDns);
+    }
+
+    /**
+     * @return The Subject Alternative Name (SAN) of the current proxy’s certificate.
+     */
+    public String getBy() {
+        return by;
+    }
+
+    /**
+     * @return The SHA 256 digest of the current client certificate.
+     */
+    public String getHash() {
+        return hash;
+    }
+
+    /**
+     * @return The URI type Subject Alternative Name field of the current client certificate.
+     */
+    public String getSanUri() {
+        return sanUri;
+    }
+
+    /**
+     * @return The DNS type Subject Alternative Name field(s) of the current client certificate.
+     */
+    public Collection<String> getSanDns() {
+        return Collections.unmodifiableCollection(sanDns);
+    }
+
+    /**
+     * @return The Subject field of the current client certificate.
+     */
+    public String getSubject() {
+        return subject;
+    }
+
+    @Override
+    public String toString() {
+        List<String> kvp = new ArrayList<>();
+        if (!by.isEmpty()) {
+            kvp.add("By=" + enquote(by));
+        }
+        if (!hash.isEmpty()) {
+            kvp.add("Hash=" + enquote(hash));
+        }
+        if (!sanUri.isEmpty()) {
+            kvp.add("URI=" + enquote(sanUri));
+        }
+        for (String dns : sanDns) {
+            kvp.add("DNS=" + enquote(dns));
+        }
+        if (!subject.isEmpty()) {
+            kvp.add("Subject=" + enquote(subject));
+        }
+
+        return String.join(";", kvp);
+    }
+
+    private String enquote(String value) {
+        // Escape inner quotes with \"
+        value = value.replace("\"", "\\\"");
+
+        // Wrap in quotes if ,;= is present
+        if (value.contains(",") || value.contains(";") || value.contains("=")) {
+            value = "\"" + value + "\"";
+        }
+
+        return value;
+    }
+}

grpc-contrib/src/main/java/com/salesforce/grpc/contrib/xfcc/XfccMarshaller.java

@@ -0,0 +1,32 @@
+/*
+ *  Copyright (c) 2017, salesforce.com, inc.
+ *  All rights reserved.
+ *  Licensed under the BSD 3-Clause license.
+ *  For full license text, see LICENSE.txt file in the repo root  or https://opensource.org/licenses/BSD-3-Clause
+ */
+
+package com.salesforce.grpc.contrib.xfcc;
+
+import io.grpc.Metadata;
+
+import java.util.List;
+import java.util.stream.Collectors;
+
+/**
+ * {@code XfccMarshaller} parses the {@code x-forwarded-client-cert} (XFCC) header populated by TLS-terminating
+ * reverse proxies. For example, Istio and Linkerd.
+ *
+ * @see <a href="https://www.envoyproxy.io/docs/envoy/latest/configuration/http_conn_man/headers.html#config-http-conn-man-headers-x-forwarded-client-cert">Envoy XFCC Header</a>
+ * @see <a href="https://github.com/linkerd/linkerd/issues/1153">Linkerd XFCC Header</a>
+ */
+public final class XfccMarshaller implements Metadata.AsciiMarshaller<List<XForwardedClientCert>> {
+    @Override
+    public String toAsciiString(List<XForwardedClientCert> value) {
+        return value.stream().map(XForwardedClientCert::toString).collect(Collectors.joining(","));
+    }
+
+    @Override
+    public List<XForwardedClientCert> parseAsciiString(String serialized) {
+        return XfccParser.parse(serialized);
+    }
+}

grpc-contrib/src/main/java/com/salesforce/grpc/contrib/xfcc/XfccParser.java

@@ -0,0 +1,119 @@
+/*
+ *  Copyright (c) 2017, salesforce.com, inc.
+ *  All rights reserved.
+ *  Licensed under the BSD 3-Clause license.
+ *  For full license text, see LICENSE.txt file in the repo root  or https://opensource.org/licenses/BSD-3-Clause
+ */
+
+package com.salesforce.grpc.contrib.xfcc;
+
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * {@code XfccParser} parses the {@code x-forwarded-client-cert} (XFCC) header populated by TLS-terminating
+ * reverse proxies.
+ *
+ * @see <a href="https://www.envoyproxy.io/docs/envoy/latest/configuration/http_conn_man/headers.html#config-http-conn-man-headers-x-forwarded-client-cert">Envoy XFCC Header</a>
+ */
+final class XfccParser {
+    private XfccParser() { }
+
+    /**
+     * Given a header string, parse and return a collection of {@link XForwardedClientCert} objects.
+     */
+    static List<XForwardedClientCert> parse(String header) {
+        List<XForwardedClientCert> certs = new ArrayList<>();
+
+        for (String element : quoteAwareSplit(header, ',')) {
+            XForwardedClientCert cert = new XForwardedClientCert();
+            List<String> kvps = quoteAwareSplit(element, ';');
+            for (String kvp : kvps) {
+                List<String> l = quoteAwareSplit(kvp, '=');
+
+                if (l.get(0).toLowerCase().equals("by")) {
+                    cert.setBy(dequote(l.get(1)));
+                }
+                if (l.get(0).toLowerCase().equals("hash")) {
+                    cert.setHash(dequote(l.get(1)));
+                }
+                // Use "SAN:" instead of "URI:" for backward compatibility with previous mesh proxy releases.
+                if (l.get(0).toLowerCase().equals("san") || l.get(0).toLowerCase().equals("uri")) {
+                    cert.setSanUri(dequote(l.get(1)));
+                }
+                if (l.get(0).toLowerCase().equals("dns")) {
+                    cert.addSanDns(dequote(l.get(1)));
+                }
+                if (l.get(0).toLowerCase().equals("subject")) {
+                    cert.setSubject(dequote(l.get(1)));
+                }
+            }
+            certs.add(cert);
+        }
+
+        return certs;
+    }
+
+    // Break str into individual elements, splitting on delim (not in quotes)
+    private static List<String> quoteAwareSplit(String str, char delim) {
+        boolean inQuotes = false;
+        boolean inEscape = false;
+
+        List<String> elements = new ArrayList<>();
+        StringBuilder buffer = new StringBuilder();
+        for (char c : str.toCharArray()) {
+            if (c == delim && !inQuotes) {
+                elements.add(buffer.toString());
+                buffer = new StringBuilder();
+                inEscape = false;
+                continue;
+            }
+
+            if (c == '"') {
+                if (inQuotes) {
+                    if (!inEscape) {
+                        inQuotes = false;
+                    }
+                } else {
+                    inQuotes = true;
+
+                }
+                inEscape = false;
+                buffer.append(c);
+                continue;
+            }
+
+            if (c == '\\') {
+                if (!inEscape) {
+                    inEscape = true;
+                    buffer.append(c);
+                    continue;
+                }
+            }
+
+            // all other characters
+            inEscape = false;
+            buffer.append(c);
+        }
+
+        if (inQuotes) {
+            throw new RuntimeException("Quoted string not closed");
+        }
+
+        elements.add(buffer.toString());
+
+        return elements;
+    }
+
+    // Remove leading and tailing unescaped quotes, remove escaping from escaped internal quotes
+    private static String dequote(String str) {
+        str = str.replace("\\\"", "\"");
+        if (str.startsWith("\"")) {
+            str = str.substring(1);
+        }
+        if (str.endsWith("\"")) {
+            str = str.substring(0, str.length() - 1);
+        }
+        return str;
+    }
+}

grpc-contrib/src/main/java/com/salesforce/grpc/contrib/xfcc/XfccServerInterceptor.java

@@ -0,0 +1,41 @@
+/*
+ *  Copyright (c) 2017, salesforce.com, inc.
+ *  All rights reserved.
+ *  Licensed under the BSD 3-Clause license.
+ *  For full license text, see LICENSE.txt file in the repo root  or https://opensource.org/licenses/BSD-3-Clause
+ */
+
+package com.salesforce.grpc.contrib.xfcc;
+
+import io.grpc.*;
+
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * {@code XfccServerInterceptor} parses the {@code x-forwarded-client-cert} (XFCC) header populated by TLS-terminating
+ * reverse proxies. For example: Envoy, Istio, and Linkerd. If present, the parsed XFCC header is appended to the
+ * gRPC {@code Context}.
+ *
+ * @see <a href="https://www.envoyproxy.io/docs/envoy/latest/configuration/http_conn_man/headers.html#config-http-conn-man-headers-x-forwarded-client-cert">Envoy XFCC Header</a>
+ * @see <a href="https://github.com/linkerd/linkerd/issues/1153">Linkerd XFCC Header</a>
+ */
+public final class XfccServerInterceptor implements ServerInterceptor {
+    private static final Metadata.Key<List<XForwardedClientCert>> XFCC_METADATA_KEY = Metadata.Key.of("x-forwarded-client-cert", new XfccMarshaller());
+
+    @Override
+    public <ReqT, RespT> ServerCall.Listener<ReqT> interceptCall(ServerCall<ReqT, RespT> call, Metadata headers, ServerCallHandler<ReqT, RespT> next) {
+        Iterable<List<XForwardedClientCert>> values = headers.getAll(XFCC_METADATA_KEY);
+        if (values != null) {
+            List<XForwardedClientCert> xfccs = new ArrayList<>();
+            for (List<XForwardedClientCert> value : values) {
+                xfccs.addAll(value);
+            }
+
+            Context xfccContext = Context.current().withValue(XForwardedClientCert.XFCC_CONTEXT_KEY, xfccs);
+            return Contexts.interceptCall(xfccContext, call, headers, next);
+        } else {
+            return next.startCall(call, headers);
+        }
+    }
+}