Modulelibsodium-bindings-0.0.1.1Haskell2010

LibSodium.Bindings.PasswordHashing

24 values

Packagelibsodium-bindings-0.0.1.1
Exports24
LanguageHaskell2010
LicenceBSD-3-Clause
SourcePasswordHashing.hs

Introduction

0 declarations

This modules provides an API that can be used both for key derivation using a low-entropy input and password storage.

Guidelines for choosing the parameters

Start by determining how much memory the function can use. What will be the highest number of threads/processes evaluating the function simultaneously (ideally, no more than 1 per CPU core)? How much physical memory is guaranteed to be available?

Set memlimit to the amount of memory you want to reserve for password hashing.

Then set opslimit to 3 and measure the time it takes to hash a password.

If this is way too long for your application, reduce memlimit, but keep opslimit set to 3.

If the function is so fast that you can afford it to be more computationally intensive without any usability issues, then increase opslimit.

For online use (e.g. logging in on a website), a 1 second computation is likely to be the acceptable maximum.

For interactive use (e.g. a desktop application), a 5 second pause after having entered a password is acceptable if the password doesn't need to be entered more than once per session.

For non-interactive and infrequent use (e.g. restoring an encrypted backup), an even slower computation can be an option.

However, the best defense against brute-force password cracking is to use strong passwords. Libraries such as passwdqc can help enforce this.

Operations

4 declarations

valuecryptoPWHash

:: Ptr CUChar
out parameter. It represents the address of a dedicated storage area of outlen bytes.
-> CLLong
outlen parameter. It is the length of the key derived from the passwd parameter. This should be a least cryptoPWHashBytesMin and at most cryptoPWHashBytesMax.
-> Ptr CChar
passwd parameter. It is a pointer to the password that is to be derived.
-> CULLong
passwdlen parameter. It is the size of the password.
-> Ptr CUChar
salt parameter. It is of a fixed length established by cryptoPWHashSaltBytes. It should be unpredictable. randombytesBuf is the best way to fill the cryptoPWHashSaltBytes of the salt.
-> CULLong
opslimit parameter. It represents the maximum amount of computations to perform. Raising this number will make the function require more CPU cycles to compute a key. This number must be between cryptoPWHashOpsLimitMin and cryptoPWHashOpsLimitMax.
-> CSize
memlimit parameter. It is the maximum amount of RAM in bytes that the function will use. This number must be between cryptoPWHashMemLimitMin cryptoPWHashMemLimitMax
-> CInt
alg parameter. It is an identifier for the algorithm to use and should be set to one of the following values: cryptoPWHashAlgDefault, cryptoPWHashAlgArgon2I13 or cryptoPWHashAlgArgon2ID13.
-> IO CInt
The return code is 0 on success and -1 if the computation didn't complete, usually because the operating system refused to allocate the amount of requested memory.

This functions derives a key from a password. The computed key is then stored in the out parameter.

See: crypto_pwhash()

valuecryptoPWHashStr

:: Ptr CChar
out parameter. It must be of size cryptoPWHashStrBytes.
-> Ptr CChar
passwd parameter. Points to a password to be stored.
-> CULLong
passwdlen parameter. Length of the password.
-> CULLong
opslimit parameter. It represents the maximum amount of computations to perform.
-> CSize
memlimit parameter. It is the maximum amount of RAM in bytes that the function will use.
-> IO CInt
The function returns 0 on success and -1 if it didn't complete successfully.

This function is used for password storage, like an SQL database. It stores an ASCII-encoded string into its out parameter, which includes:

The result of a memory-hard, CPU-intensive hash function applied to the password passwd of length passwdlen;
The automatically generated salt used for the previous computation;
The other parameters required to verify the password, including the algorithm identifier, its version, opslimit, and memlimit.

The out parameter must be a dedicated storage area that's large enough to hold cryptoPWHashStrBytes bytes, but the actual output string may be shorter.

See: crypto_pwhash_str()

valuecryptoPWHashStrVerify

:: Ptr CChar
str parameter. It must be zero-terminated.
-> Ptr CChar
passwd parameter.
-> CULLong
passwdlen parameter.
-> IO CInt
It returns 0 if the verification succeeds and -1 on error.

This function verifies that the str parameter is a valid password verification string (as generated by cryptoPWHashStr), for a passwd whose length is passwdlen.

See: crypto_pwhash_str_verify()

valuecryptoPWHashStrNeedsRehash

:: Ptr CChar
str parameter.
-> CULLong
opslimit parameter.
-> CSize
memlimit parameter.
-> IO CInt
The function returns 0 if the parameters already match the given ones, and returns 1 on error. In particular, It will return 1 if the string appears to be correct but doesn't match the given parameters. In that situation, applications may want to compute a new hash using the current parameters the next time the user logs in.