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-rw-r--r--internal/configfile/scrypt.go62
1 files changed, 62 insertions, 0 deletions
diff --git a/internal/configfile/scrypt.go b/internal/configfile/scrypt.go
new file mode 100644
index 0000000..31bcbe4
--- /dev/null
+++ b/internal/configfile/scrypt.go
@@ -0,0 +1,62 @@
+package configfile
+
+import (
+ "log"
+ "math"
+ "os"
+
+ "golang.org/x/crypto/scrypt"
+
+ "github.com/rfjakob/gocryptfs/internal/cryptocore"
+ "github.com/rfjakob/gocryptfs/internal/tlog"
+)
+
+const (
+ // ScryptDefaultLogN is the default scrypt logN configuration parameter.
+ // 1 << 16 uses 64MB of memory,
+ // takes 4 seconds on my Atom Z3735F netbook
+ ScryptDefaultLogN = 16
+)
+
+// ScryptKDF is an instance of the scrypt key deriviation function.
+type ScryptKDF struct {
+ Salt []byte
+ N int
+ R int
+ P int
+ KeyLen int
+}
+
+// NewScryptKDF returns a new instance of ScryptKDF.
+func NewScryptKDF(logN int) ScryptKDF {
+ var s ScryptKDF
+ s.Salt = cryptocore.RandBytes(cryptocore.KeyLen)
+ if logN <= 0 {
+ s.N = 1 << ScryptDefaultLogN
+ } else {
+ if logN < 10 {
+ tlog.Fatal.Println("Error: scryptn below 10 is too low to make sense. Aborting.")
+ os.Exit(1)
+ }
+ s.N = 1 << uint32(logN)
+ }
+ s.R = 8 // Always 8
+ s.P = 1 // Always 1
+ s.KeyLen = cryptocore.KeyLen
+ return s
+}
+
+// DeriveKey returns a new key from a supplied password.
+func (s *ScryptKDF) DeriveKey(pw string) []byte {
+ k, err := scrypt.Key([]byte(pw), s.Salt, s.N, s.R, s.P, s.KeyLen)
+ if err != nil {
+ log.Panicf("DeriveKey failed: %v", err)
+ }
+ return k
+}
+
+// LogN - N is saved as 2^LogN, but LogN is much easier to work with.
+// This function gives you LogN = Log2(N).
+func (s *ScryptKDF) LogN() int {
+ return int(math.Log2(float64(s.N)) + 0.5)
+}