Visual FoxPro Requires Chilkat v11.6.0+

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.

Background. Only the secret, ad, encoding, passwordCharset, and maxMemoryKb options are used during verification; everything else is ignored. Because the memory cost is taken from the hash string, setting maxMemoryKb for hashes from an untrusted source prevents an enormous claimed cost from exhausting memory; it is checked before any allocation. The method returns 1 for a match, 0 for no match, and -1 if the verification could not be performed; always test for a match with == 1.

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LOCAL loCrypt
LOCAL lcPassword
LOCAL lcPhcHash
LOCAL loJson
LOCAL lnVerifyResult

loCrypt = CreateObject('Chilkat.Crypt2')

*  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('Chilkat.JsonObject')
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