crypto/sha512: fix casting of d.nx in UnmarshalBinary

Fixes #29541

Change-Id: I006915b020b6e710298c32c05e3de77a7f9b54f3
GitHub-Last-Rev: c7a90a4bbe17fd1904c0942e8b343264fb85cba1
GitHub-Pull-Request: golang/go#29542
Reviewed-on: https://go-review.googlesource.com/c/156277
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

diff --git a/src/crypto/sha512/sha512.go b/src/crypto/sha512/sha512.go
index 24fde7dce708b85094df8b5869bc9a8808109919..c685319480c24470578f88649d5de9cba8a0de3f 100644 (file)
--- a/src/crypto/sha512/sha512.go
+++ b/src/crypto/sha512/sha512.go
@@ -191,7 +191,7 @@ func (d *digest) UnmarshalBinary(b []byte) error {
        b, d.h[7] = consumeUint64(b)
        b = b[copy(d.x[:], b):]
        b, d.len = consumeUint64(b)
-       d.nx = int(d.len) % chunk
+       d.nx = int(d.len % chunk)
        return nil
 }
 

diff --git a/src/crypto/sha512/sha512_test.go b/src/crypto/sha512/sha512_test.go
index 4423cf5f18952d1389e0665c292cf882c3ee0fb3..96a1aa69a4fcc090e7f4b08da4eb9e189078de4f 100644 (file)
--- a/src/crypto/sha512/sha512_test.go
+++ b/src/crypto/sha512/sha512_test.go
@@ -11,6 +11,7 @@ import (
        "crypto/rand"
        "encoding"
        "encoding/hex"
+       "fmt"
        "hash"
        "io"
        "testing"
@@ -831,6 +832,62 @@ func TestBlockGeneric(t *testing.T) {
        }
 }
 
+// Tests for unmarshaling hashes that have hashed a large amount of data
+// The initial hash generation is omitted from the test, because it takes a long time.
+// The test contains some already-generated states, and their expected sums
+// Tests a problem that is outlined in Github issue #29541
+// The problem is triggered when an amount of data has been hashed for which
+// the data length has a 1 in the 32nd bit. When casted to int, this changes
+// the sign of the value, and causes the modulus operation to return a
+// different result.
+type unmarshalTest struct {
+       state string
+       sum   string
+}
+
+var largeUnmarshalTests = []unmarshalTest{
+       // Data length: 6_565_544_823
+       unmarshalTest{
+               state: "sha\aηe\x0f\x0f\xe1r]#\aoJ!.{5B\xe4\x140\x91\xdd\x00a\xe1\xb3E&\xb9\xbb\aJ\x9f^\x9f\x03ͺD\x96H\x80\xb0X\x9d\xdeʸ\f\xf7:\xd5\xe6'\xb9\x93f\xddA\xf0~\xe1\x02\x14\x00\x01\x02\x03\x04\x05\x06\a\b\t\n\v\f\r\x0e\x0f\x10\x11\x12\x13\x14\x15\x16\x17\x18\x19\x1a\x1b\x1c\x1d\x1e\x1f !\"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^_`abcdefghijklmnopqrstuv\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x01\x87VCw",
+               sum:   "12d612357a1dbc74a28883dff79b83e7d2b881ae40d7a67fd7305490bc8a641cd1ce9ece598192080d6e9ac7e75d5988567a58a9812991299eb99a04ecb69523",
+       },
+       unmarshalTest{
+               state: "sha\a2\xd2\xdc\xf5\xd7\xe2\xf9\x97\xaa\xe7}Fϱ\xbc\x8e\xbf\x12h\x83Z\xa1\xc7\xf5p>bfS T\xea\xee\x1e\xa6Z\x9c\xa4ڶ\u0086\bn\xe47\x8fsGs3\xe0\xda\\\x9dqZ\xa5\xf6\xd0kM\xa1\xf2\x00\x01\x02\x03\x04\x05\x06\a\b\t\n\v\f\r\x0e\x0f\x10\x11\x12\x13\x14\x15\x16\x17\x18\x19\x1a\x1b\x1c\x1d\x1e\x1f !\"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^_`abcdefghijklmnopqrstuv\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x01\xa7VCw",
+               sum:   "94a04b9a901254cd94ca0313557e4be3ab1ca86e920c1f3efdc22d361e9ae12be66bc6d6dc5db79a0a4aa6eca6f293c1e9095bbae127ae405f6c325478343299",
+       },
+}
+
+func safeSum(h hash.Hash) (sum []byte, err error) {
+       defer func() {
+               if r := recover(); r != nil {
+                       err = fmt.Errorf("sum panic: %v", r)
+               }
+       }()
+
+       return h.Sum(nil), nil
+}
+
+func TestLargeHashes(t *testing.T) {
+       for i, test := range largeUnmarshalTests {
+
+               h := New()
+               if err := h.(encoding.BinaryUnmarshaler).UnmarshalBinary([]byte(test.state)); err != nil {
+                       t.Errorf("test %d could not unmarshal: %v", i, err)
+                       continue
+               }
+
+               sum, err := safeSum(h)
+               if err != nil {
+                       t.Errorf("test %d could not sum: %v", i, err)
+                       continue
+               }
+
+               if fmt.Sprintf("%x", sum) != test.sum {
+                       t.Errorf("test %d sum mismatch: expect %s got %x", i, test.sum, sum)
+               }
+       }
+}
+
 var bench = New()
 var buf = make([]byte, 8192)