Add wrapper for EVP_BPE_scrypt

[harrybrwn]

Pretty simple, just a wrapper function around EVP_BPE_scrypt with some simple tests.

[qmuntal]

Thanks for submitting. Adding Scrypt support seems like a good addition. Added some comments.

[qmuntal]

The password content is not being modified, so there is no need to create a copy of it. unsafe is our friend here:

Suggested change

	cpassword,
	base(unsafe.StringData(password)),

[qmuntal]

Same as with password, no need to copy salt as it is not being modified:

Suggested change

	(*C.uchar)(csalt),
	base(salt),

[qmuntal]

key can directly be allocated in Go memory and passed to go_openssl_EVP_PBE_scrypt using base(key).

Suggested change

	key := C.malloc(C.size_t(keylen))
	defer C.free(key)
	key := make([]byte, keylen)

[qmuntal]

EVP_PBE_scrypt is defined since OpenSSL 3.0

Suggested change

	DEFINEFUNC_1_1_1(int, EVP_PBE_scrypt, (const char *pass, size_t passlen, const unsigned char *salt, size_t saltlen, uint64_t N, uint64_t r, uint64_t p, uint64_t maxmem, unsigned char *key, size_t keylen), (pass, passlen, salt, saltlen, N, r, p, maxmem, key, keylen))
	DEFINEFUNC_3_0(int, EVP_PBE_scrypt, (const char *pass, size_t passlen, const unsigned char *salt, size_t saltlen, uint64_t N, uint64_t r, uint64_t p, uint64_t maxmem, unsigned char *key, size_t keylen), (pass, passlen, salt, saltlen, N, r, p, maxmem, key, keylen)) \

[qmuntal]

Nit: use Go naming conventions

Suggested change

	func Scrypt(password string, salt []byte, N, r, p, maxmem, keylen uint64) ([]byte, error) {
	func Scrypt(password string, salt []byte, N, r, p, maxMem, keyLen uint64) ([]byte, error) {

[qmuntal]

EVP_PBE_scrypt is supported since OpenSSL 3, and maybe not for all providers. Please implement the SupportsSscrypt() bool function. The implementation will be almost identical to

openssl/pbkdf2.go

Line 15 in eb155da

func SupportsPBKDF2() bool {

, replacing PBKDF2 with SCRYPT and returning false in the OpenSSL 1 case.

Then use this function in the new test cases.