wip

static/js/crypto.mjs

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+export default class Crypto {
+	constructor(key) {//{{{
+		if(key === null)
+			throw new Error("No key provided")
+
+		if(typeof key === 'string')
+			this.key = sjcl.codec.base64.toBits(base64_key)
+		else
+			this.key = key
+
+		this.aes = new sjcl.cipher.aes(this.key)
+	}//}}}
+
+	static generate_key() {//{{{
+		return sjcl.random.randomWords(8)
+	}//}}}
+	static pass_to_key(pass, salt = null) {//{{{
+		if(salt === null)
+			salt = sjcl.random.randomWords(4) // 128 bits (16 bytes)
+		let key = sjcl.misc.pbkdf2(pass, salt, 10000)
+
+		return {
+			salt,
+			key,
+		}
+	}//}}}
+
+	encrypt(plaintext_data_in_bits, counter, return_encoded = true) {//{{{
+		// 8 bytes of random data, (1 word = 4 bytes) * 2
+		// with 8 bytes of byte encoded counter is used as
+		// IV to guarantee a non-repeated IV (which is a catastrophe).
+		// Assumes counter value is kept unique. Counter is taken from
+		// Postgres sequence.
+		let random_bits = sjcl.random.randomWords(2)
+		let iv_bytes = sjcl.codec.bytes.fromBits(random_bits)
+		for (let i = 0; i < 8; ++i) {
+			let mask = 0xffn << BigInt(i*8)
+			let counter_i_byte = (counter & mask) >> BigInt(i*8)
+			iv_bytes[15-i] = Number(counter_i_byte)
+		}
+		let iv = sjcl.codec.bytes.toBits(iv_bytes)
+
+		let encrypted = sjcl.mode['ccm'].encrypt(
+			this.aes,
+			plaintext_data_in_bits,
+			iv,
+		)
+
+		// Returning 16 bytes (4 words) IV + encrypted data.
+		if(return_encoded)
+			return sjcl.codec.base64.fromBits(
+				iv.concat(encrypted)
+			)
+		else
+			return iv.concat(encrypted)
+	}//}}}
+	decrypt(encrypted_base64_data) {//{{{
+		try {
+			let encoded = sjcl.codec.base64.toBits(encrypted_base64_data)
+			let iv = encoded.slice(0, 4) // in words (4 bytes), not bytes
+			let encrypted_data = encoded.slice(4)
+			return sjcl.mode['ccm'].decrypt(this.aes, encrypted_data, iv)
+		} catch(err) {
+			if(err.message == `ccm: tag doesn't match`)
+				throw('Decryption failed')
+			else
+				throw(err)
+		}
+	}//}}}
+}
+
+// vim: foldmethod=marker