1 files changed, 132 insertions, 0 deletions
diff --git a/core/crypto/rsa.js b/core/crypto/rsa.js
new file mode 100644
index 0000000..68e8e86
--- /dev/null
+++ b/core/crypto/rsa.js
@@ -0,0 +1,132 @@
+import Base64 from "../base64.js";
+import { modPow, bigIntToU8Array, u8ArrayToBigInt } from "./bigint.js";
+
+export class RSACipher {
+    constructor() {
+        this._keyLength = 0;
+        this._keyBytes = 0;
+        this._n = null;
+        this._e = null;
+        this._d = null;
+        this._nBigInt = null;
+        this._eBigInt = null;
+        this._dBigInt = null;
+        this._extractable = false;
+    }
+
+    get algorithm() {
+        return { name: "RSA-PKCS1-v1_5" };
+    }
+
+    _base64urlDecode(data) {
+        data = data.replace(/-/g, "+").replace(/_/g, "/");
+        data = data.padEnd(Math.ceil(data.length / 4) * 4, "=");
+        return Base64.decode(data);
+    }
+
+    _padArray(arr, length) {
+        const res = new Uint8Array(length);
+        res.set(arr, length - arr.length);
+        return res;
+    }
+
+    static async generateKey(algorithm, extractable, _keyUsages) {
+        const cipher = new RSACipher;
+        await cipher._generateKey(algorithm, extractable);
+        return { privateKey: cipher };
+    }
+
+    async _generateKey(algorithm, extractable) {
+        this._keyLength = algorithm.modulusLength;
+        this._keyBytes = Math.ceil(this._keyLength / 8);
+        const key = await window.crypto.subtle.generateKey(
+            {
+                name: "RSA-OAEP",
+                modulusLength: algorithm.modulusLength,
+                publicExponent: algorithm.publicExponent,
+                hash: {name: "SHA-256"},
+            },
+            true, ["encrypt", "decrypt"]);
+        const privateKey = await window.crypto.subtle.exportKey("jwk", key.privateKey);
+        this._n = this._padArray(this._base64urlDecode(privateKey.n), this._keyBytes);
+        this._nBigInt = u8ArrayToBigInt(this._n);
+        this._e = this._padArray(this._base64urlDecode(privateKey.e), this._keyBytes);
+        this._eBigInt = u8ArrayToBigInt(this._e);
+        this._d = this._padArray(this._base64urlDecode(privateKey.d), this._keyBytes);
+        this._dBigInt = u8ArrayToBigInt(this._d);
+        this._extractable = extractable;
+    }
+
+    static async importKey(key, _algorithm, extractable, keyUsages) {
+        if (keyUsages.length !== 1 || keyUsages[0] !== "encrypt") {
+            throw new Error("only support importing RSA public key");
+        }
+        const cipher = new RSACipher;
+        await cipher._importKey(key, extractable);
+        return cipher;
+    }
+
+    async _importKey(key, extractable) {
+        const n = key.n;
+        const e = key.e;
+        if (n.length !== e.length) {
+            throw new Error("the sizes of modulus and public exponent do not match");
+        }
+        this._keyBytes = n.length;
+        this._keyLength = this._keyBytes * 8;
+        this._n = new Uint8Array(this._keyBytes);
+        this._e = new Uint8Array(this._keyBytes);
+        this._n.set(n);
+        this._e.set(e);
+        this._nBigInt = u8ArrayToBigInt(this._n);
+        this._eBigInt = u8ArrayToBigInt(this._e);
+        this._extractable = extractable;
+    }
+
+    async encrypt(_algorithm, message) {
+        if (message.length > this._keyBytes - 11) {
+            return null;
+        }
+        const ps = new Uint8Array(this._keyBytes - message.length - 3);
+        window.crypto.getRandomValues(ps);
+        for (let i = 0; i < ps.length; i++) {
+            ps[i] = Math.floor(ps[i] * 254 / 255 + 1);
+        }
+        const em = new Uint8Array(this._keyBytes);
+        em[1] = 0x02;
+        em.set(ps, 2);
+        em.set(message, ps.length + 3);
+        const emBigInt = u8ArrayToBigInt(em);
+        const c = modPow(emBigInt, this._eBigInt, this._nBigInt);
+        return bigIntToU8Array(c, this._keyBytes);
+    }
+
+    async decrypt(_algorithm, message) {
+        if (message.length !== this._keyBytes) {
+            return null;
+        }
+        const msgBigInt = u8ArrayToBigInt(message);
+        const emBigInt = modPow(msgBigInt, this._dBigInt, this._nBigInt);
+        const em = bigIntToU8Array(emBigInt, this._keyBytes);
+        if (em[0] !== 0x00 || em[1] !== 0x02) {
+            return null;
+        }
+        let i = 2;
+        for (; i < em.length; i++) {
+            if (em[i] === 0x00) {
+                break;
+            }
+        }
+        if (i === em.length) {
+            return null;
+        }
+        return em.slice(i + 1, em.length);
+    }
+
+    async exportKey() {
+        if (!this._extractable) {
+            throw new Error("key is not extractable");
+        }
+        return { n: this._n, e: this._e, d: this._d };
+    }
+}