internal: add a cryptography primitives thing

Signed-off-by: Xe Iaso <me@xeiaso.net>

1 files changed, 42 insertions, 0 deletions

diff --git a/internal/crypto.go b/internal/crypto.go
new file mode 100644
index 0000000..37fae9e
--- /dev/null
+++ b/internal/crypto.go
@@ -0,0 +1,42 @@
+package internal
+
+import (
+	"crypto/md5"
+	"fmt"
+	"hash/fnv"
+)
+
+// Hash is a simple wrapper around the MD5 algorithm implementation in the
+// Go standard library. It takes in data and a salt and returns the hashed
+// representation.
+func Hash(data string, salt string) string {
+	output := md5.Sum([]byte(data + salt))
+	return fmt.Sprintf("%x", output)
+}
+
+// Fnv is a non-cryptographic hashing function based on non-cryptographic hash
+// functions created by Glenn Fowler, Landon Curt Noll, and Phong Vo. This
+// wraps the standard library FNV hash function by representing it as a 32 bit
+// integer. Then it takes that number and "hashes" it by adding the rune's
+// unicode value (as a uint 32) and then takes the modulus of 26, letting the number
+// be represented as a letter of the alphabet. This is not a cryptographically
+// secure operation, it is purely to replace numbers with a human-readable string
+// to satisfy the requirement that any vhost with a "/" in it cannot end in a number
+// (to avoid someone obtaining a vhost that is a cidr mask, it can cause issues).
+func Fnv(data string) string {
+	h := fnv.New32()
+	h.Write([]byte(data))
+
+	hash := h.Sum32()
+
+	alphabet := "abcdefghijklmnopqrstuvwxyz"
+	res := ""
+
+	for _, char := range fmt.Sprintf("%d", hash) {
+		res = res + string(alphabet[(uint32(char)+hash)%26])
+
+		hash = (hash << 1) | (hash >> 31) // "rotate" the number for extra variance
+	}
+
+	return res
+}