add support of DHCID record type

Related-to RFC-4701

Author: hunts

README.md

@@ -86,7 +86,7 @@ This is a list adopted from <https://github.com/miekg/dns/blob/master/README.md>
 - [x] 4509 - SHA256 Hash in DS
 - [x] 4592 - Wildcards in the DNS
 - [x] 4635 - HMAC SHA TSIG
-- [ ] 4701 - DHCID
+- [x] 4701 - DHCID
 - [x] 4892 - id.server
 - [x] 5001 - NSID
 - [x] 5155 - NSEC3 record

src/records/dhcid.test.ts

@@ -0,0 +1,42 @@
+import { expect } from "chai";
+import { parseRecord } from ".";
+import { RR } from "../rr";
+import { RRType } from "../types";
+
+describe("test DHCID", () => {
+    // https://datatracker.ietf.org/doc/html/rfc4701#section-3.6
+    const examples = [
+        // Example 1: DHCPv6 client identifier with FQDN "chi6.example.com"
+        [
+            `chi6.example.com. 3600 IN DHCID ( AAIBY2/AuCccgoJbsaxcQc9TUapptP69l
+                                     OjxfNuVAA2kjEA= )`,
+            `chi6.example.com.\t\t3600\tIN\tDHCID\tAAIBY2/AuCccgoJbsaxcQc9TUapptP69lOjxfNuVAA2kjEA=`,
+        ],
+        // Example 2: DHCP client-identifier option (IPv4 client) with FQDN "chi.example.com"
+        [
+            `chi.example.com. 3600 IN DHCID ( AAEBOSD+XR3Os/0LozeXVqcNc7FwCfQdW
+                                     L3b/NaiUDlW2No= )`,
+            `chi.example.com.\t\t3600\tIN\tDHCID\tAAEBOSD+XR3Os/0LozeXVqcNc7FwCfQdWL3b/NaiUDlW2No=`,
+        ],
+        // Example 3: MAC address as identity with FQDN "client.example.com"
+        [
+            `client.example.com. 3600 IN DHCID ( AAABxLmlskllE0MVjd57zHcWmEH3pCQ6V
+                                     ytcKD//7es/deY= )`,
+            `client.example.com.\t\t3600\tIN\tDHCID\tAAABxLmlskllE0MVjd57zHcWmEH3pCQ6VytcKD//7es/deY=`,
+        ],
+    ];
+
+    for (const i in examples) {
+        let record: RR | undefined;
+
+        it(`should parse DHCID example ${+i + 1}`, () => {
+            record = parseRecord(examples[i][0]);
+            expect(record.header.type).to.equal(RRType.DHCID);
+        });
+
+        it(`should present DHCID example ${+i + 1}`, () => {
+            const out = record?.present();
+            expect(out).to.equal(examples[i][1]);
+        });
+    }
+});

src/records/dhcid.ts

@@ -0,0 +1,75 @@
+import { stringToBinary, binaryToString } from "../encoding";
+import { ParseError } from "../error";
+import { Slice } from "../packet";
+import { RR } from "../rr";
+import { Writer } from "../buffer";
+import { CharacterString } from "../char";
+import { Uint16, Uint8 } from "../types";
+
+/**
+ * The DHCID (DHCP Identifier) record is used to associate a DHCP client identity with a domain name.
+ *
+ * The record contains a digest generated from the client's identifier and FQDN,
+ * ensuring only the rightful DHCP client can update the DNS entry.
+ *
+ * RDATA format (RFC 4701):
+ * ```
+ *  0                   1                   2                   3
+ *  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * |    identifier type (16 bits)  |  digest type  |               |
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+               +
+ * |                        digest (binary)                        |
+ * |                                                               |
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * ```
+ *
+ * Specified by {@link https://datatracker.ietf.org/doc/html/rfc4701 | RFC 4701}
+ */
+export class DHCID extends RR {
+    identifierType!: Uint16; // 2 bytes
+    digestType!: Uint8;      // 1 byte
+    digest!: Uint8Array;     // variable length
+
+    unpackRdata(rdata: Slice): void {
+        this.identifierType = rdata.readUint16();
+        this.digestType = rdata.readUint8();
+        this.digest = rdata.readUint8Array();
+    }
+
+    packRdata(buf: Writer): number {
+        let n = buf.writeUint16(this.identifierType);
+        n += buf.writeUint8(this.digestType);
+        n += buf.write(this.digest);
+        return n;
+    }
+
+    parseRdata(rdata: CharacterString[]): void {
+        if (rdata.length === 0) {
+            throw new ParseError("Missing fields in DHCID RDATA");
+        }
+
+        const str = rdata.reduce((v, cur) => v += cur.raw(), "");
+        const data = stringToBinary(str, "base64");
+
+        // At lease has 3 bytes, the first two bytes is the identifier type and
+        // the third one is digest type.
+        if (data.byteLength < 3) {
+            throw new ParseError("Invalid DHCID RDATA");
+        }
+
+        this.identifierType = (data[0] << 8) | data[1];
+        this.digestType = data[2];
+
+        this.digest = data.slice(3);
+    }
+
+    presentRdata(): string {
+        const data = new Uint8Array(3 + this.digest.byteLength);
+        data[0] = this.identifierType >>> 8;
+        data[1] = this.identifierType & 0xff;
+        data[2] = this.digestType;
+        data.set(this.digest, 3);
+        return binaryToString(data, "base64");
+    }
+}

src/records/index.ts

@@ -29,6 +29,7 @@ import { Lexer, scanHeader, scanRdata } from "../scan";
 import { BufferReader, CharReader } from "../buffer";
 import { APL } from "./apl";
 import { IPSECKEY } from "./ipseckey";
+import { DHCID } from "./dhcid";
 import { Unknown } from "./unknown";
 
 export { A, isA } from "./a";
@@ -55,6 +56,7 @@ export { NSAP, NSAPPTR } from "./nsap";
 export { NAPTR } from "./naptr";
 export { APL } from "./apl";
 export { IPSECKEY } from "./ipseckey";
+export { DHCID } from "./dhcid";
 export { Unknown } from "./unknown";
 
 /**
@@ -207,6 +209,9 @@ function initRecord(h: Header): RR {
             record = new IPSECKEY(h);
             break;
         }
+        case RRType.DHCID:
+            record = new DHCID(h);
+            break;
         default:
             record = new Unknown(h);
             break;