PRF_IPSEC_PRFPLUS_GOSTR3411_2012_{256,512}

[gogost.git] / prfplus / plus.go

diff --git a/prfplus/plus.go b/prfplus/plus.go
new file mode 100644 (file)
index 0000000..84ce70c
--- /dev/null
+++ b/prfplus/plus.go
@@ -0,0 +1,47 @@
+// GoGOST -- Pure Go GOST cryptographic functions library
+// Copyright (C) 2015-2019 Sergey Matveev <stargrave@stargrave.org>
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, version 3 of the License.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+package prfplus
+
+type PRFForPlus interface {
+       BlockSize() int
+       Derive(salt []byte) []byte
+}
+
+// prf+ function as defined in RFC 7296 (IKEv2)
+func PRFPlus(prf PRFForPlus, dst, salt []byte) {
+       in := make([]byte, prf.BlockSize()+len(salt)+1)
+       in[len(in)-1] = byte(0x01)
+       copy(in[prf.BlockSize():], salt)
+       copy(in[:prf.BlockSize()], prf.Derive(in[prf.BlockSize():]))
+       copy(dst, in[:prf.BlockSize()])
+       n := len(dst) / prf.BlockSize()
+       if n == 0 {
+               return
+       }
+       if n*prf.BlockSize() != len(dst) {
+               n++
+       }
+       n--
+       out := dst[prf.BlockSize():]
+       for i := 0; i < n; i++ {
+               in[len(in)-1] = byte(i + 2)
+               copy(in[:prf.BlockSize()], prf.Derive(in))
+               copy(out, in[:prf.BlockSize()])
+               if i+1 != n {
+                       out = out[prf.BlockSize():]
+               }
+       }
+}