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-rw-r--r--lib/srp.go58
-rw-r--r--lib/srp_test.go66
2 files changed, 124 insertions, 0 deletions
diff --git a/lib/srp.go b/lib/srp.go
index 05b61ab..2303793 100644
--- a/lib/srp.go
+++ b/lib/srp.go
@@ -170,6 +170,35 @@ func (u *SRPUser) EphemeralKeyPub() (*big.Int, error) {
return pub, nil
}
+func (u *SRPUser) SetScramblingParam(a *big.Int) error {
+ b, err := u.EphemeralKeyPub()
+ if err != nil {
+ return err
+ }
+ bb := b.Bytes()
+ ab := a.Bytes()
+
+ // Make M=A+B
+ m := make([]byte, 0)
+ m = append(m, ab...)
+ m = append(m, bb...)
+ if len(m) != (len(ab) + len(bb)) {
+ return CPError{"length of m is incorrect"}
+ }
+
+ // Hash M
+ u.h.Message(m)
+ h := u.h.Hash()
+
+ // Set scrambling paramter u
+ u.u = new(big.Int)
+ u.u.SetBytes(h)
+ if u.u.Cmp(big.NewInt(0)) != 1 {
+ return CPError{"u is invalid"}
+ }
+ return nil
+}
+
func NewSRPClientSession(n, g, k, ident string) (*SRPClientSession, error) {
var ok bool
@@ -212,3 +241,32 @@ func (s *SRPClientSession) EphemeralKeyPub() (*big.Int, error) {
return pub, nil
}
+
+func (s *SRPClientSession) SetScramblingParam(b *big.Int) error {
+ a, err := s.EphemeralKeyPub()
+ if err != nil {
+ return err
+ }
+ ab := a.Bytes()
+ bb := b.Bytes()
+
+ // Make M=A+B
+ m := make([]byte, 0)
+ m = append(m, ab...)
+ m = append(m, bb...)
+ if len(m) != (len(ab) + len(bb)) {
+ return CPError{"length of m is incorrect"}
+ }
+
+ // Hash M
+ s.h.Message(m)
+ h := s.h.Hash()
+
+ // Set scrambling paramter u
+ s.u = new(big.Int)
+ s.u.SetBytes(h)
+ if s.u.Cmp(big.NewInt(0)) != 1 {
+ return CPError{"u is invalid"}
+ }
+ return nil
+}
diff --git a/lib/srp_test.go b/lib/srp_test.go
index 3e3c8d6..a819b15 100644
--- a/lib/srp_test.go
+++ b/lib/srp_test.go
@@ -182,3 +182,69 @@ func TestSRPClientSessionEphemeralKeyPub(t *testing.T) {
return
}
}
+
+func TestSRPScramblingParamter(t *testing.T) {
+ n := StripSpaceChars(
+ `ffffffffffffffffc90fdaa22168c234c4c6628b80dc1cd129024
+ e088a67cc74020bbea63b139b22514a08798e3404ddef9519b3cd
+ 3a431b302b0a6df25f14374fe1356d6d51c245e485b576625e7ec
+ 6f44c42e9a637ed6b0bff5cb6f406b7edee386bfb5a899fa5ae9f
+ 24117c4b1fe649286651ece45b3dc2007cb8a163bf0598da48361
+ c55d39a69163fa8fd24cf5f83655d23dca3ad961c62f356208552
+ bb9ed529077096966d670c354e4abc9804f1746c08ca237327fff
+ fffffffffffff`)
+ g := "2"
+ k := "3"
+ ident := "s@ricketyspace.net"
+ pass := "d59d6c93af0f37f272d924979"
+
+ // Init srp server user.
+ user, err := NewSRPUser(n, g, k, ident, pass)
+ if err != nil {
+ t.Errorf("Error: %v\n", err)
+ return
+ }
+
+ // Get server's pub for user.
+ user.EphemeralKeyGen()
+ pubB, err := user.EphemeralKeyPub()
+ if err != nil {
+ t.Errorf("Error: %v\n", err)
+ return
+ }
+
+ // Init srp client session.
+ session, err := NewSRPClientSession(n, g, k, ident)
+ if err != nil {
+ t.Errorf("Error: %v\n", err)
+ return
+ }
+
+ // Get client's pub for user.
+ pubA, err := session.EphemeralKeyPub()
+ if err != nil {
+ t.Errorf("Error: %v\n", err)
+ return
+ }
+
+ // Compute server's scrambling parameter for user.
+ err = user.SetScramblingParam(pubA)
+ if err != nil {
+ t.Errorf("Error: %v\n", err)
+ return
+ }
+
+ // Compute client's scrambling paramter for user.
+ err = session.SetScramblingParam(pubB)
+ if err != nil {
+ t.Errorf("Error: %v\n", err)
+ return
+ }
+
+ // The server's and client's scrambling parameter must be the
+ // same.
+ if user.u.Cmp(session.u) != 0 {
+ t.Error("Error: scrambling parameter of server != client\n")
+ return
+ }
+}