Verify an Argon2 Password with a Secret and Memory Guard

Demonstrates Crypt2.Argon2VerifyPassword when the hash was created with a secret (pepper) or ad, and the use of maxMemoryKb to guard against untrusted hash strings.

loCrypt = createobject("CkCrypt2")

//  The password should come from a secure source rather than being hard-coded.
lcPassword = "correct horse battery staple"

lcPhcHash = "$argon2id$v=19$m=131072,t=4,p=2$c29tZXJhbmRvbXNhbHQ$3fJ7v1qKcVJ0lHqXjBQZ8mYm3sNTfSPRt0bqDl9kEyM"

//  When the hash was created with a secret (pepper) or ad, the same values must be supplied to verify.
//  Only the secret, ad, encoding, passwordCharset, and maxMemoryKb members of the options are used;
//  everything else is ignored.
loJson = createobject("CkJsonObject")
loJson.UpdateString("secret","application-wide-pepper")
loJson.UpdateString("secretEncoding","utf-8")

//  maxMemoryKb guards against a hash from an untrusted source claiming an enormous memory cost.  The
//  memory cost is taken from the hash string, so this limit is checked before any memory is allocated.
//  It defaults to 2 GB.
loJson.UpdateInt("maxMemoryKb",262144)

//  Argon2VerifyPassword returns 1 if the password matched, 0 if it did not match, and -1 if the
//  verification could not be performed.  Always test for a match with == 1.
lnVerifyResult = loCrypt.Argon2VerifyPassword(lcPassword,loJson.Emit(),lcPhcHash)
if (lnVerifyResult = 1) then
    ? "The password is verified."
else
    if (lnVerifyResult = 0) then
        ? "The password does not match."
    else
        ? "The verification could not be performed: " + loCrypt.LastErrorText
    endif

endif



release loCrypt
release loJson