84 lines
2.5 KiB
CoffeeScript
84 lines
2.5 KiB
CoffeeScript
utf8Bytes = (str) ->
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new TextEncoder 'utf-8'
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.encode str
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fromUtf8Bytes = (bytes) ->
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new TextDecoder 'utf-8'
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.decode bytes
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hex = (buf) -> (Array::map.call new Uint8Array(buf),
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(x) => ('00' + x.toString 16).slice(-2)).join ''
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fromHex = (str) ->
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new Uint8Array str.match(/.{1,2}/g).map (byte) => parseInt byte, 16
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HMAC_SHA256_KEY = (buf) ->
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crypto.subtle.importKey 'raw', buf,
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{ name: 'HMAC', hash: 'SHA-256' }, true, [ 'sign' ]
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HMAC_SHA256 = (key, str) ->
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cryptoKey = await HMAC_SHA256_KEY key
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buf = utf8Bytes str
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await crypto.subtle.sign "HMAC", cryptoKey, buf
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SHA256 = (str) ->
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crypto.subtle.digest "SHA-256", utf8Bytes str
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# For client-side encryption of files,
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# always use AES-128-GCM
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# Encrypt a File object
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# Returns hexed key, iv, encrypted file name and mime type, and the encrypted ArrayBuffer
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encryptFile = (file) ->
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# Generate a key to use
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keyParams =
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name: 'AES-GCM'
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length: 128
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keyUsage = ['encrypt', 'decrypt']
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key = await crypto.subtle.generateKey keyParams, true, keyUsage
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# Generate IV and configure the cipher
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iv = crypto.getRandomValues new Uint8Array 16
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algoParams =
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name: 'AES-GCM'
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iv: iv
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tagLength: 128
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# Encrypt
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encrypted = await crypto.subtle.encrypt algoParams, key, await file.arrayBuffer()
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name = hex await crypto.subtle.encrypt algoParams, key, utf8Bytes file.name
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mime = 'application/vnd.angry.paste+' + hex await crypto.subtle.encrypt algoParams, key, utf8Bytes file.type
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exportedKey = hex await crypto.subtle.exportKey 'raw', key
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[exportedKey, hex(iv), name, mime, encrypted]
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importKeyAndIv = (key, iv) ->
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key = fromHex key
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iv = fromHex iv
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key = await crypto.subtle.importKey 'raw', key,
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{ name: "AES-GCM" }, false, ['encrypt', 'decrypt']
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algoParams =
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name: 'AES-GCM'
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iv: iv
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tagLength: 128
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[key, algoParams]
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# Decrypt the name and mime-type of an encrypted file
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decryptMetadata = (key, iv, name, mime) ->
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[key, algoParams] = await importKeyAndIv key, iv
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name = fromUtf8Bytes await crypto.subtle.decrypt algoParams, key, fromHex name
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mime = fromHex mime.replace /^application\/vnd\.angry\.paste\+/, ""
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mime = fromUtf8Bytes await crypto.subtle.decrypt algoParams, key, mime
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[name, mime]
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# Decrypt an encrypted ArrayBuffer
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decryptFile = (key, iv, file) ->
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[key, algoParams] = await importKeyAndIv key, iv
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await crypto.subtle.decrypt algoParams, key, file
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export {
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utf8Bytes,
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hex,
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HMAC_SHA256,
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SHA256,
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encryptFile,
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decryptMetadata,
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decryptFile
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}
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