239 lines
6.6 KiB
Markdown
239 lines
6.6 KiB
Markdown
# crypto Module
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| Since | Origin / Contributor | Maintainer | Source |
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| :----- | :-------------------- | :---------- | :------ |
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| 2015-06-02 | [DiUS](https://github.com/DiUS), [Johny Mattsson](https://github.com/jmattsson) | [Johny Mattsson](https://github.com/jmattsson) | [crypto.c](../../app/modules/crypto.c)|
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The crypto modules provides various functions for working with cryptographic algorithms.
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The following encryption/decryption algorithms/modes are supported:
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- `"AES-ECB"` for 128-bit AES in ECB mode (NOT recommended)
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- `"AES-CBC"` for 128-bit AES in CBC mode
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The following hash algorithms are supported:
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- MD2 (not available by default, has to be explicitly enabled in `app/include/user_config.h`)
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- MD5
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- SHA1
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- SHA256, SHA384, SHA512 (unless disabled in `app/include/user_config.h`)
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## crypto.encrypt()
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Encrypts Lua strings.
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#### Syntax
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`crypto.encrypt(algo, key, plain [, iv])`
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#### Parameters
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- `algo` the name of a supported encryption algorithm to use
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- `key` the encryption key as a string; for AES encryption this *MUST* be 16 bytes long
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- `plain` the string to encrypt; it will be automatically zero-padded to a 16-byte boundary if necessary
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- `iv` the initilization vector, if using AES-CBC; defaults to all-zero if not given
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#### Returns
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The encrypted data as a binary string. For AES this is always a multiple of 16 bytes in length.
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#### Example
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```lua
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print(encoder.toHex(crypto.encrypt("AES-ECB", "1234567890abcdef", "Hi, I'm secret!")))
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```
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#### See also
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- [`crypto.decrypt()`](#cryptodecrypt)
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## crypto.decrypt()
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Decrypts previously encrypted data.
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#### Syntax
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`crypto.decrypt(algo, key, cipher [, iv])`
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#### Parameters
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- `algo` the name of a supported encryption algorithm to use
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- `key` the encryption key as a string; for AES encryption this *MUST* be 16 bytes long
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- `cipher` the cipher text to decrypt (as obtained from `crypto.encrypt()`)
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- `iv` the initialization vector, if using AES-CBC; defaults to all-zero if not given
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#### Returns
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The decrypted string.
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Note that the decrypted string may contain extra zero-bytes of padding at the end. One way of stripping such padding is to use `:match("(.-)%z*$")` on the decrypted string. Additional care needs to be taken if working on binary data, in which case the real length likely needs to be encoded with the data, and at which point `:sub(1, n)` can be used to strip the padding.
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#### Example
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```lua
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key = "1234567890abcdef"
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cipher = crypto.encrypt("AES-ECB", key, "Hi, I'm secret!")
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print(encoder.toHex(cipher))
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print(crypto.decrypt("AES-ECB", key, cipher))
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```
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#### See also
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- [`crypto.encrypt()`](#cryptoencrypt)
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## crypto.fhash()
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Compute a cryptographic hash of a a file.
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#### Syntax
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`hash = crypto.fhash(algo, filename)`
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#### Parameters
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- `algo` the hash algorithm to use, case insensitive string
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- `filename` the path to the file to hash
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#### Returns
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A binary string containing the message digest. To obtain the textual version (ASCII hex characters), please use [`encoder.toHex()`](encoder.md#encodertohex ).
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#### Example
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```lua
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print(encoder.toHex(crypto.fhash("sha1","myfile.lua")))
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```
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## crypto.hash()
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Compute a cryptographic hash of a Lua string.
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#### Syntax
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`hash = crypto.hash(algo, str)`
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#### Parameters
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`algo` the hash algorithm to use, case insensitive string
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`str` string to hash contents of
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#### Returns
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A binary string containing the message digest. To obtain the textual version (ASCII hex characters), please use [`encoder.toHex()`](encoder.md#encodertohex).
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#### Example
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```lua
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print(encoder.toHex(crypto.hash("sha1","abc")))
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```
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## crypto.new_hash()
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Create a digest/hash object that can have any number of strings added to it. Object has `update` and `finalize` functions.
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#### Syntax
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`hashobj = crypto.new_hash(algo)`
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#### Parameters
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`algo` the hash algorithm to use, case insensitive string
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#### Returns
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Userdata object with `update` and `finalize` functions available.
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#### Example
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```lua
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hashobj = crypto.new_hash("SHA1")
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hashobj:update("FirstString")
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hashobj:update("SecondString")
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digest = hashobj:finalize()
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print(encoder.toHex(digest))
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```
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## crypto.hmac()
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Compute a [HMAC](https://en.wikipedia.org/wiki/Hash-based_message_authentication_code) (Hashed Message Authentication Code) signature for a Lua string.
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#### Syntax
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`signature = crypto.hmac(algo, str, key)`
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#### Parameters
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- `algo` hash algorithm to use, case insensitive string
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- `str` data to calculate the hash for
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- `key` key to use for signing, may be a binary string
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#### Returns
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A binary string containing the HMAC signature. Use [`encoder.toHex()`](encoder.md#encodertohex) to obtain the textual version.
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#### Example
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```lua
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print(encoder.toHex(crypto.hmac("sha1","abc","mysecret")))
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```
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## crypto.new_hmac()
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Create a hmac object that can have any number of strings added to it. Object has `update` and `finalize` functions.
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#### Syntax
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`hmacobj = crypto.new_hmac(algo, key)`
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#### Parameters
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- `algo` the hash algorithm to use, case insensitive string
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- `key` the key to use (may be a binary string)
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#### Returns
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Userdata object with `update` and `finalize` functions available.
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#### Example
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```lua
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hmacobj = crypto.new_hmac("SHA1", "s3kr3t")
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hmacobj:update("FirstString")
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hmacobj:update("SecondString")
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digest = hmacobj:finalize()
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print(encoder.toHex(digest))
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```
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## crypto.mask()
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Applies an XOR mask to a Lua string. Note that this is not a proper cryptographic mechanism, but some protocols may use it nevertheless.
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#### Syntax
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`crypto.mask(message, mask)`
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#### Parameters
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- `message` message to mask
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- `mask` the mask to apply, repeated if shorter than the message
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#### Returns
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The masked message, as a binary string. Use [`encoder.toHex()`](encoder.md#encodertohex) to get a textual representation of it.
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#### Example
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```lua
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print(encoder.toHex(crypto.mask("some message to obscure","X0Y7")))
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```
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## crypto.toBase64()
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Provides a Base64 representation of a (binary) Lua string.
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!!! warning
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This function is deprecated; please use instead [`encoder.toBase64()`](encoder.md#encodertobase64)
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#### Syntax
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`b64 = crypto.toBase64(binary)`
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#### Parameters
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`binary` input string to Base64 encode
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#### Return
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A Base64 encoded string.
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#### Example
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```lua
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print(crypto.toBase64(crypto.hash("sha1","abc")))
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```
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## crypto.toHex()
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Provides an ASCII hex representation of a (binary) Lua string. Each byte in the input string is represented as two hex characters in the output.
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!!! warning
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This function is deprecated; please use instead [`encoder.toHex()`](encoder.md#encodertohex)
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#### Syntax
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`hexstr = crypto.toHex(binary)`
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#### Parameters
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`binary` input string to get hex representation for
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#### Returns
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An ASCII hex string.
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#### Example
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```lua
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print(crypto.toHex(crypto.hash("sha1","abc")))
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```
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