add Hash() and HashToString() function to the crypto package (#54)

* add Hash() and HashToString() function to the crypto package to have one standard way of hashing across different projects.
Co-authored-by: Lucas Roesler <[email protected]>

go.mod

@@ -30,6 +30,7 @@ require (
 	github.com/uber/jaeger-lib v2.0.0+incompatible // indirect
 	github.com/urfave/negroni v1.0.0
 	go.uber.org/goleak v1.0.0
+	golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2
 	google.golang.org/genproto v0.0.0-20190716160619-c506a9f90610 // indirect
 	google.golang.org/grpc v1.22.0 // indirect
 	gopkg.in/yaml.v2 v2.3.0

go.sum

@@ -197,6 +197,7 @@ golang.org/x/sync v0.0.0-20180314180146-1d60e4601c6f h1:wMNYb4v58l5UBM7MYRLPG6Zh
 golang.org/x/sync v0.0.0-20180314180146-1d60e4601c6f/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sync v0.0.0-20181108010431-42b317875d0f/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sync v0.0.0-20181221193216-37e7f081c4d4/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
+golang.org/x/sync v0.0.0-20190423024810-112230192c58 h1:8gQV6CLnAEikrhgkHFbMAEhagSSnXWGV915qUMm9mrU=
 golang.org/x/sync v0.0.0-20190423024810-112230192c58/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sys v0.0.0-20180419222023-a2a45943ae67/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
 golang.org/x/sys v0.0.0-20180830151530-49385e6e1522/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=

pkg/crypto/hash.go

@@ -0,0 +1,90 @@
+package crypto
+
+import (
+	"bytes"
+	"encoding/hex"
+	"encoding/json"
+	"fmt"
+	"hash"
+	"io"
+	"strings"
+
+	"golang.org/x/crypto/sha3"
+)
+
+var (
+	// DefaultHasher is the default implementation for hashing things
+	// It outputs 32 Bytes and uses a SHA3-256 hash in the current configuration.
+	// Its generic security strength is 256 bits against preimage attacks,
+	// and 128 bits against collision attacks.
+	defaultHasher = basicHasher{sha3.New256()}
+)
+
+// Hash is a convenience function calling the default hasher
+// WARNING: only pass in data that is json-marshalable. If not, the worst case scenario is that you passed in data with circular references and this will just blow up your CPU
+func Hash(data ...interface{}) ([]byte, error) {
+	return defaultHasher.Hash(data...)
+}
+
+// HashToString is a convenience function calling the default hasher and encoding the result as hex string
+func HashToString(data ...interface{}) (string, error) {
+	hash, err := defaultHasher.Hash(data...)
+	if err != nil {
+		return "", err
+	}
+	return hex.EncodeToString(hash), nil
+}
+
+// Hasher provides a method for hashing arbitary data types
+type Hasher interface {
+	Hash(data ...interface{}) ([]byte, error)
+}
+
+type basicHasher struct {
+	hash hash.Hash
+}
+
+func (h basicHasher) Hash(args ...interface{}) ([]byte, error) {
+	h.hash.Reset()
+
+	for _, data := range args {
+		var (
+			reader       io.Reader
+			encoderError error
+		)
+
+		// setup reader for the data
+		switch d := data.(type) {
+		case io.Reader:
+			reader = d
+		case []byte:
+			reader = bytes.NewReader(d)
+		case string:
+			reader = strings.NewReader(d)
+		case fmt.Stringer:
+			reader = strings.NewReader(d.String())
+		default:
+			r, w := io.Pipe()
+			encoder := json.NewEncoder(w)
+			go func() {
+				defer w.Close()
+				encoderError = encoder.Encode(data)
+			}()
+			reader = r
+		}
+
+		// hash all the data
+		_, err := io.Copy(h.hash, reader)
+		if err != nil {
+			return nil, err
+		}
+
+		// check encoder error
+		if encoderError != nil {
+			return nil, encoderError
+		}
+
+	}
+
+	return h.hash.Sum(nil), nil
+}

pkg/crypto/hash_test.go

@@ -0,0 +1,80 @@
+package crypto
+
+import (
+	"encoding/json"
+	"reflect"
+	"strings"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestHash(t *testing.T) {
+	cases := []struct {
+		name           string
+		input          []interface{}
+		expectedOutput string
+		expectedError  error
+	}{
+		{
+			name:           "hash a string",
+			input:          []interface{}{"foobar"},
+			expectedOutput: "09234807e4af85f17c66b48ee3bca89dffd1f1233659f9f940a2b17b0b8c6bc5",
+		},
+		{
+			name:           "reproducable results",
+			input:          []interface{}{"foobar"},
+			expectedOutput: "09234807e4af85f17c66b48ee3bca89dffd1f1233659f9f940a2b17b0b8c6bc5",
+		},
+		{
+			name:           "something else",
+			input:          []interface{}{"foobarbaz"},
+			expectedOutput: "369972cd3fda2b1e239bf114f4c2c65115b05fee2e4e5b2ae19ce7b5d757c572",
+		},
+		{
+			name:           "hash multiple strings",
+			input:          []interface{}{"foo", "bar"},
+			expectedOutput: "09234807e4af85f17c66b48ee3bca89dffd1f1233659f9f940a2b17b0b8c6bc5",
+		},
+		{
+			name:           "hash reader",
+			input:          []interface{}{strings.NewReader("foobar")},
+			expectedOutput: "09234807e4af85f17c66b48ee3bca89dffd1f1233659f9f940a2b17b0b8c6bc5",
+		},
+		{
+			name:           "hash bytes",
+			input:          []interface{}{[]byte("foobar")},
+			expectedOutput: "09234807e4af85f17c66b48ee3bca89dffd1f1233659f9f940a2b17b0b8c6bc5",
+		},
+		{
+			name:           "hash complex object",
+			input:          []interface{}{struct{ foo map[string]interface{} }{foo: map[string]interface{}{"a": 123}}},
+			expectedOutput: "d0a1b2af1705c1b8495b00145082ef7470384e62ac1c4d9b9cdbbe0476c28f8c",
+		},
+		{
+			name:           "hash multiple different things",
+			input:          []interface{}{"f", strings.NewReader("oo"), []byte("bar")},
+			expectedOutput: "09234807e4af85f17c66b48ee3bca89dffd1f1233659f9f940a2b17b0b8c6bc5",
+		},
+		{
+			name: "marshal error is forwarded",
+			input: []interface{}{map[float64]string{
+				1.: "lol",
+			}},
+			expectedOutput: "",
+			expectedError: &json.UnsupportedTypeError{
+				Type: reflect.MapOf(
+					reflect.TypeOf(1.),
+					reflect.TypeOf("lol"),
+				)},
+		},
+	}
+
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			hash, err := HashToString(tc.input...)
+			require.Equal(t, tc.expectedOutput, hash)
+			require.Equal(t, tc.expectedError, err)
+		})
+	}
+}