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-rw-r--r--src/cmd/internal/notsha256/sha256.go141
1 files changed, 141 insertions, 0 deletions
diff --git a/src/cmd/internal/notsha256/sha256.go b/src/cmd/internal/notsha256/sha256.go
new file mode 100644
index 0000000..080b344
--- /dev/null
+++ b/src/cmd/internal/notsha256/sha256.go
@@ -0,0 +1,141 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package notsha256 implements the NOTSHA256 algorithm,
+// a hash defined as bitwise NOT of SHA256.
+// It is used in situations where exact fidelity to SHA256 is unnecessary.
+// In particular, it is used in the compiler toolchain,
+// which cannot depend directly on cgo when GOEXPERIMENT=boringcrypto
+// (and in that mode the real sha256 uses cgo).
+package notsha256
+
+import (
+ "encoding/binary"
+ "hash"
+)
+
+// The size of a checksum in bytes.
+const Size = 32
+
+// The blocksize in bytes.
+const BlockSize = 64
+
+const (
+ chunk = 64
+ init0 = 0x6A09E667
+ init1 = 0xBB67AE85
+ init2 = 0x3C6EF372
+ init3 = 0xA54FF53A
+ init4 = 0x510E527F
+ init5 = 0x9B05688C
+ init6 = 0x1F83D9AB
+ init7 = 0x5BE0CD19
+)
+
+// digest represents the partial evaluation of a checksum.
+type digest struct {
+ h [8]uint32
+ x [chunk]byte
+ nx int
+ len uint64
+}
+
+func (d *digest) Reset() {
+ d.h[0] = init0
+ d.h[1] = init1
+ d.h[2] = init2
+ d.h[3] = init3
+ d.h[4] = init4
+ d.h[5] = init5
+ d.h[6] = init6
+ d.h[7] = init7
+ d.nx = 0
+ d.len = 0
+}
+
+// New returns a new hash.Hash computing the NOTSHA256 checksum.
+// state of the hash.
+func New() hash.Hash {
+ d := new(digest)
+ d.Reset()
+ return d
+}
+
+func (d *digest) Size() int {
+ return Size
+}
+
+func (d *digest) BlockSize() int { return BlockSize }
+
+func (d *digest) Write(p []byte) (nn int, err error) {
+ nn = len(p)
+ d.len += uint64(nn)
+ if d.nx > 0 {
+ n := copy(d.x[d.nx:], p)
+ d.nx += n
+ if d.nx == chunk {
+ block(d, d.x[:])
+ d.nx = 0
+ }
+ p = p[n:]
+ }
+ if len(p) >= chunk {
+ n := len(p) &^ (chunk - 1)
+ block(d, p[:n])
+ p = p[n:]
+ }
+ if len(p) > 0 {
+ d.nx = copy(d.x[:], p)
+ }
+ return
+}
+
+func (d *digest) Sum(in []byte) []byte {
+ // Make a copy of d so that caller can keep writing and summing.
+ d0 := *d
+ hash := d0.checkSum()
+ return append(in, hash[:]...)
+}
+
+func (d *digest) checkSum() [Size]byte {
+ len := d.len
+ // Padding. Add a 1 bit and 0 bits until 56 bytes mod 64.
+ var tmp [64]byte
+ tmp[0] = 0x80
+ if len%64 < 56 {
+ d.Write(tmp[0 : 56-len%64])
+ } else {
+ d.Write(tmp[0 : 64+56-len%64])
+ }
+
+ // Length in bits.
+ len <<= 3
+ binary.BigEndian.PutUint64(tmp[:], len)
+ d.Write(tmp[0:8])
+
+ if d.nx != 0 {
+ panic("d.nx != 0")
+ }
+
+ var digest [Size]byte
+
+ binary.BigEndian.PutUint32(digest[0:], d.h[0]^0xFFFFFFFF)
+ binary.BigEndian.PutUint32(digest[4:], d.h[1]^0xFFFFFFFF)
+ binary.BigEndian.PutUint32(digest[8:], d.h[2]^0xFFFFFFFF)
+ binary.BigEndian.PutUint32(digest[12:], d.h[3]^0xFFFFFFFF)
+ binary.BigEndian.PutUint32(digest[16:], d.h[4]^0xFFFFFFFF)
+ binary.BigEndian.PutUint32(digest[20:], d.h[5]^0xFFFFFFFF)
+ binary.BigEndian.PutUint32(digest[24:], d.h[6]^0xFFFFFFFF)
+ binary.BigEndian.PutUint32(digest[28:], d.h[7]^0xFFFFFFFF)
+
+ return digest
+}
+
+// Sum256 returns the SHA256 checksum of the data.
+func Sum256(data []byte) [Size]byte {
+ var d digest
+ d.Reset()
+ d.Write(data)
+ return d.checkSum()
+}