Fixes aws#642. Issue with spacing in headers for s3 v4 signing

private/signer/v4/v4.go

@@ -337,7 +337,7 @@ func (v4 *signer) buildCanonicalHeaders(r rule, header http.Header) {
 		}
 	}
 
-	v4.canonicalHeaders = strings.Join(headerValues, "\n")
+	v4.canonicalHeaders = strings.Join(stripExcessSpaces(headerValues), "\n")
 }
 
 func (v4 *signer) buildCanonicalString() {
@@ -443,3 +443,23 @@ func makeSha256Reader(reader io.ReadSeeker) []byte {
 	io.Copy(hash, reader)
 	return hash.Sum(nil)
 }
+
+func stripExcessSpaces(headerVals []string) []string {
+	vals := make([]string, len(headerVals))
+	for i, str := range headerVals {
+		stripped := ""
+		found := false
+		str = strings.TrimSpace(str)
+		for _, c := range str {
+			if !found && c == ' ' {
+				stripped += string(c)
+				found = true
+			} else if c != ' ' {
+				stripped += string(c)
+				found = false
+			}
+		}
+		vals[i] = stripped
+	}
+	return vals
+}

private/signer/v4/v4_test.go

@@ -290,6 +290,35 @@ func TestResignRequestExpiredRequest(t *testing.T) {
 	assert.NotEqual(t, querySig, r.HTTPRequest.Header.Get("Authorization"))
 }
 
+func TestStripExcessHeaders(t *testing.T) {
+	vals := []string{
+		"123",
+		"1 2 3",
+		"  1 2 3",
+		"1  2 3",
+		"1  23",
+		"1  2  3",
+		"1  2  ",
+		" 1  2  ",
+	}
+
+	expected := []string{
+		"123",
+		"1 2 3",
+		"1 2 3",
+		"1 2 3",
+		"1 23",
+		"1 2 3",
+		"1 2",
+		"1 2",
+	}
+
+	newVals := stripExcessSpaces(vals)
+	for i := 0; i < len(newVals); i++ {
+		assert.Equal(t, newVals[i], expected[i])
+	}
+}
+
 func BenchmarkPresignRequest(b *testing.B) {
 	signer := buildSigner("dynamodb", "us-east-1", time.Now(), 300*time.Second, "{}")
 	for i := 0; i < b.N; i++ {