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-rw-r--r--lib/srp.go133
-rw-r--r--lib/srp_test.go69
2 files changed, 202 insertions, 0 deletions
diff --git a/lib/srp.go b/lib/srp.go
new file mode 100644
index 0000000..20208a6
--- /dev/null
+++ b/lib/srp.go
@@ -0,0 +1,133 @@
+// Copyright © 2022 siddharth <s@ricketyspace.net>
+// SPDX-License-Identifier: ISC
+
+package lib
+
+import "math/big"
+
+// SRP - implementation.
+// Reference http://srp.stanford.edu/design.html
+
+// SRP Client UI - Spec
+//
+// > register s@ricketyspace.net
+// Enter password
+// > ******
+// Registering with server...registered!
+// > login s@ricketyspace.net
+// Enter password
+// > ******
+// Logging in...in!
+// s@ricketyspace.net>
+// s@ricketyspace.net> login s@ricketyspace.net
+// login command not allowed when logged in
+// s@ricketyspace.net> register rsd@gnu.org
+// register command not allowed when logged in
+// s@ricketyspace.net> logout
+// Logging out..out!
+// > register s@ricketyspace.net
+// Already registered!
+
+// SRP Server.
+type SRPServer struct {
+ users []SRPUser
+}
+
+// Registered user on the SRP server.
+type SRPUser struct {
+ // Large safe prime. Server and client agree upon the value of
+ // N.
+ n *big.Int
+ // Generator modulo N. Server and client agree upon the value
+ // of N.
+ g *big.Int
+ // Multipier parameter. Server and client agree upon the value
+ // of N.
+ k *big.Int
+ // Hashing object for H() function.
+ h Sha256
+ // User's email address
+ ident string
+ // Salt. Randomly generator by the server.
+ salt []byte
+ // Private key derived from salt and user's pass.
+ x *big.Int
+ // Scrambling parameter.
+ u *big.Int
+ // Secret ephemeral value.
+ b *big.Int
+ // Password verifier.
+ v *big.Int
+ // Session key.
+ sk []byte
+}
+
+// SRP client.
+type SRPClient struct {
+ session SRPClientSession
+}
+
+// User session on the SRP client.
+type SRPClientSession struct {
+ // Large safe prime. Client and server agree upon the value of
+ // N.
+ n *big.Int
+ // Generator modulo N. Client and server agree upon the value
+ // of N.
+ g *big.Int
+ // Multipier parameter. Client and server agree upon the value
+ // of N.
+ k *big.Int
+ // User's email address
+ ident string
+ // Scrambling parameter.
+ u *big.Int
+ // Secret ephemeral value.
+ a *big.Int
+ // Session key.
+ sk []byte
+}
+
+func NewSRPUser(n, g, k, ident, pass string) (*SRPUser, error) {
+ var err error
+ var ok bool
+
+ user := new(SRPUser)
+ user.n, ok = new(big.Int).SetString(StripSpaceChars(n), 16)
+ if !ok {
+ return nil, CPError{"n is invalid"}
+ }
+ user.g, ok = new(big.Int).SetString(StripSpaceChars(g), 16)
+ if !ok {
+ return nil, CPError{"g is invalid"}
+ }
+ user.k, ok = new(big.Int).SetString(StripSpaceChars(k), 16)
+ if !ok {
+ return nil, CPError{"k is invalid"}
+ }
+ user.ident = ident
+ user.x = big.NewInt(0)
+ user.v = big.NewInt(0)
+
+ // Initialize hashing object.
+ user.h = Sha256{}
+ user.h.Init([]uint32{})
+
+ // Generate salt.
+ user.salt, err = RandomBytes(8)
+ if err != nil {
+ return nil, err
+ }
+
+ // Generate private key `x` from salt+pass
+ m := make([]byte, 0)
+ copy(m, user.salt)
+ m = append(m, StrToBytes(pass)...)
+ user.h.Message(m)
+ user.x.SetBytes(user.h.Hash())
+
+ // Generate password verifier `v`
+ user.v.Exp(user.g, user.x, user.n)
+
+ return user, nil
+}
diff --git a/lib/srp_test.go b/lib/srp_test.go
new file mode 100644
index 0000000..d7e3b0d
--- /dev/null
+++ b/lib/srp_test.go
@@ -0,0 +1,69 @@
+// Copyright © 2022 siddharth <s@ricketyspace.net>
+// SPDX-License-Identifier: ISC
+
+package lib
+
+import (
+ "math/big"
+ "testing"
+)
+
+func TestNewSRPUser(t *testing.T) {
+ n := StripSpaceChars(
+ `ffffffffffffffffc90fdaa22168c234c4c6628b80dc1cd129024
+ e088a67cc74020bbea63b139b22514a08798e3404ddef9519b3cd
+ 3a431b302b0a6df25f14374fe1356d6d51c245e485b576625e7ec
+ 6f44c42e9a637ed6b0bff5cb6f406b7edee386bfb5a899fa5ae9f
+ 24117c4b1fe649286651ece45b3dc2007cb8a163bf0598da48361
+ c55d39a69163fa8fd24cf5f83655d23dca3ad961c62f356208552
+ bb9ed529077096966d670c354e4abc9804f1746c08ca237327fff
+ fffffffffffff`)
+ g := "2"
+ k := "3"
+ ident := "s@ricketyspace.net"
+ pass := "d59d6c93af0f37f272d924979"
+ user, err := NewSRPUser(n, g, k, ident, pass)
+ if err != nil {
+ t.Errorf("Error: %v\n", err)
+ return
+ }
+
+ // Check n.
+ bigN, _ := new(big.Int).SetString(StripSpaceChars(n), 16)
+ if user.n.Cmp(bigN) != 0 {
+ t.Error("Error: n not set correctly\n")
+ return
+ }
+ // Check g.
+ bigG, _ := new(big.Int).SetString(StripSpaceChars(g), 16)
+ if user.g.Cmp(bigG) != 0 {
+ t.Error("Error: g not set correctly\n")
+ return
+ }
+ // Check k.
+ bigK, _ := new(big.Int).SetString(StripSpaceChars(k), 16)
+ if user.k.Cmp(bigK) != 0 {
+ t.Error("Error: k not set correctly\n")
+ return
+ }
+ // Check ident.
+ if user.ident != ident {
+ t.Error("Error: user not set correctly\n")
+ return
+ }
+ // Check salt.
+ if len(user.salt) < 8 {
+ t.Error("Error: salt not set correctly\n")
+ return
+ }
+ // Check x.
+ if user.x.Cmp(big.NewInt(1)) < 0 {
+ t.Error("Error: x not set correctly\n")
+ return
+ }
+ // Check v.
+ if user.v.Cmp(big.NewInt(1)) < 0 {
+ t.Error("Error: v not set correctly\n")
+ return
+ }
+}