Add armor.encode and armor.decode

Fixes #17

README.md

@@ -43,6 +43,41 @@ const out = await d.decrypt(ciphertext, "text")
 console.log(out)
 ```
 
+### ASCII armoring
+
+age encrypted files (the inputs of `Decrypter.decrypt` and outputs of
+`Encrypter.encrypt`) are binary files, of type `Uint8Array`. There is an official ASCII
+"armor" format, based on PEM, which provides a way to encode an encrypted file as text.
+
+```ts
+import * as age from "age-encryption"
+
+const identity = await age.generateIdentity()
+const recipient = await age.identityToRecipient(identity)
+console.log(identity)
+console.log(recipient)
+
+const e = new age.Encrypter()
+e.addRecipient(recipient)
+const ciphertext = await e.encrypt("Hello, age!")
+const armored = age.armor.encode(ciphertext)
+
+console.log(armored)
+// -----BEGIN AGE ENCRYPTED FILE-----
+// YWdlLWVuY3J5cHRpb24ub3JnL3YxCi0+IFgyNTUxOSB0QXVkQmNwZ3ZzYnNRZDJP
+// WlFId3hyeFNmRS9SdUVUTkFhY1FXSno5VUFBClNOSWhEbnhoK21TaEs3SWRGdklw
+// OW9pdlBZbDg3SEVSQ1FZZHBvUS90YjgKLS0tIGRCVXNNWmdJS0ZkNlNZbStPZWh4
+// N2FBNUJZdTFxMmYwVTEzUWwvTFVNeUkKrNZnrZjMlXvoCHz0FUS/bp9129XtSV1Q
+// 2twDjjAOwgBtBYoji9gKWgOG4w==
+// -----END AGE ENCRYPTED FILE-----
+
+const d = new age.Decrypter()
+d.addIdentity(identity)
+const decoded = age.armor.decode(armored)
+const out = await d.decrypt(decoded, "text")
+console.log(out)
+```
+
 #### Encrypt and decrypt a file with a passphrase
 
 ```ts
@@ -108,8 +143,6 @@ and support the `deriveBits` key usage. It doesn't need to be extractable.
 ```ts
 const keyPair = await crypto.subtle.generateKey({ name: "X25519" }, false, ["deriveBits"])
 const identity = (keyPair as CryptoKeyPair).privateKey
-const recipient = await age.identityToRecipient(identity)
-
 const recipient = await age.identityToRecipient(identity)
 console.log(recipient)
 

lib/armor.ts

@@ -0,0 +1,50 @@
+import { base64 } from "@scure/base"
+// eslint-disable-next-line @typescript-eslint/no-unused-vars
+import { type Encrypter, type Decrypter } from "./index.js"
+
+/**
+ * Encode an age encrypted file using the ASCII armor format, a strict subset of
+ * PEM that starts with `-----BEGIN AGE ENCRYPTED FILE-----`.
+ *
+ * @param file - The raw encrypted file (returned by {@link Encrypter.encrypt}).
+ *
+ * @returns The ASCII armored file, with a final newline.
+ */
+export function encode(file: Uint8Array): string {
+    const lines: string[] = []
+    lines.push("-----BEGIN AGE ENCRYPTED FILE-----\n")
+    for (let i = 0; i < file.length; i += 48) {
+        let end = i + 48
+        if (end > file.length) end = file.length
+        lines.push(base64.encode(file.subarray(i, end)) + "\n")
+    }
+    lines.push("-----END AGE ENCRYPTED FILE-----\n")
+    return lines.join("")
+}
+
+/**
+ * Decode an age encrypted file from the ASCII armor format, a strict subset of
+ * PEM that starts with `-----BEGIN AGE ENCRYPTED FILE-----`.
+ *
+ * Extra whitespace before and after the file is ignored, and newlines can be
+ * CRLF or LF, but otherwise the format is parsed strictly.
+ *
+ * @param file - The ASCII armored file.
+ *
+ * @returns The raw encrypted file (to be passed to {@link Decrypter.decrypt}).
+ */
+export function decode(file: string): Uint8Array {
+    const lines = file.trim().replaceAll("\r\n", "\n").split("\n")
+    if (lines[0] !== "-----BEGIN AGE ENCRYPTED FILE-----") {
+        throw Error("invalid header")
+    }
+    if (lines[lines.length - 1] !== "-----END AGE ENCRYPTED FILE-----") {
+        throw Error("invalid footer")
+    }
+    lines.shift()
+    lines.pop()
+    if (lines.some((l, i) => i === lines.length - 1 ? l.length > 64 : l.length !== 64)) {
+        throw Error("line too long")
+    }
+    return base64.decode(lines.join(""))
+}

lib/index.ts

@@ -6,6 +6,8 @@ import { ScryptIdentity, ScryptRecipient, X25519Identity, X25519Recipient } from
 import { encodeHeader, encodeHeaderNoMAC, parseHeader, Stanza } from "./format.js"
 import { decryptSTREAM, encryptSTREAM } from "./stream.js"
 
+export * as armor from "./armor.js"
+
 export { Stanza }
 
 /**

tests/examples/identity.js

@@ -1,15 +1,18 @@
-import { Encrypter, Decrypter, generateIdentity, identityToRecipient } from "age-encryption"
+import * as age from "age-encryption"
 
-const identity = await generateIdentity()
-const recipient = await identityToRecipient(identity)
+const identity = await age.generateIdentity()
+const recipient = await age.identityToRecipient(identity)
 console.log(identity)
 console.log(recipient)
 
-const e = new Encrypter()
+const e = new age.Encrypter()
 e.addRecipient(recipient)
 const ciphertext = await e.encrypt("Hello, age!")
+const armored = age.armor.encode(ciphertext)
+console.log(armored)
 
-const d = new Decrypter()
+const d = new age.Decrypter()
 d.addIdentity(identity)
-const out = await d.decrypt(ciphertext, "text")
+const decoded = age.armor.decode(armored)
+const out = await d.decrypt(decoded, "text")
 console.log(out)

tests/testkit.test.ts

@@ -5,7 +5,7 @@ import { forceWebCryptoOff } from "../lib/x25519.js"
 import { hkdf } from "@noble/hashes/hkdf"
 import { sha256 } from "@noble/hashes/sha256"
 import { hex, base64 } from "@scure/base"
-import { Decrypter } from "../lib/index.js"
+import { Decrypter, armor } from "../lib/index.js"
 
 declare module "@vitest/browser/context" {
     interface BrowserCommands {
@@ -50,35 +50,45 @@ describe("CCTV testkit", async function () {
     }
 
     for (const vec of vectors) {
-        if (vec.meta.armored) continue
+        let body = () => vec.body
+        if (vec.meta.armored) {
+            body = () => armor.decode(new TextDecoder().decode(vec.body))
+        }
         if (vec.meta.expect === "success") {
             it(vec.name + " should succeed", async function () {
                 const d = new Decrypter()
                 if (vec.meta.passphrase) d.addPassphrase(vec.meta.passphrase)
                 if (vec.meta.identity) d.addIdentity(vec.meta.identity)
-                const plaintext = await d.decrypt(vec.body)
+                const plaintext = await d.decrypt(body())
                 assert.equal(hex.encode(sha256(plaintext)), vec.meta.payload)
             })
             if (vec.meta.identity) {
                 it(vec.name + " should succeed without Web Crypto", async function () {
                     withoutWebCrypto()
                     const d = new Decrypter()
                     d.addIdentity(vec.meta.identity)
-                    const plaintext = await d.decrypt(vec.body)
+                    const plaintext = await d.decrypt(body())
                     assert.equal(hex.encode(sha256(plaintext)), vec.meta.payload)
                 })
             }
+            if (vec.meta.armored) {
+                it(vec.name + " should round-trip armor", function () {
+                    const normalize = (s: string) => s.replaceAll("\r\n", "\n").trim()
+                    assert.deepEqual(normalize(armor.encode(body())),
+                        normalize(new TextDecoder().decode(vec.body)))
+                })
+            }
             it(vec.name + " should round-trip header encoding", function () {
-                const h = parseHeader(vec.body)
+                const h = parseHeader(body())
                 assert.deepEqual(encodeHeaderNoMAC(h.stanzas), h.headerNoMAC)
                 const hh = encodeHeader(h.stanzas, h.MAC)
                 const got = new Uint8Array(hh.length + h.rest.length)
                 got.set(hh)
                 got.set(h.rest, hh.length)
-                assert.deepEqual(got, vec.body)
+                assert.deepEqual(got, body())
             })
             it(vec.name + " should round-trip STREAM encryption", function () {
-                const h = parseHeader(vec.body)
+                const h = parseHeader(body())
                 const nonce = h.rest.subarray(0, 16)
                 const streamKey = hkdf(sha256, hex.decode(vec.meta["file key"]), nonce, "payload", 32)
                 const payload = h.rest.subarray(16)
@@ -90,14 +100,14 @@ describe("CCTV testkit", async function () {
                 const d = new Decrypter()
                 if (vec.meta.passphrase) d.addPassphrase(vec.meta.passphrase)
                 if (vec.meta.identity) d.addIdentity(vec.meta.identity)
-                await expect(d.decrypt(vec.body)).rejects.toThrow()
+                await expect(async () => await d.decrypt(body())).rejects.toThrow()
             })
             if (vec.meta.identity) {
                 it(vec.name + " should fail without Web Crypto", async function () {
                     withoutWebCrypto()
                     const d = new Decrypter()
                     d.addIdentity(vec.meta.identity)
-                    await expect(d.decrypt(vec.body)).rejects.toThrow()
+                    await expect(async () => await d.decrypt(body())).rejects.toThrow()
                 })
             }
         }