add new test to verify ber decoding using real pkcs7

from the wild.

ber_test.go

@@ -3,6 +3,8 @@ package pkcs7
 import (
 	"bytes"
 	"encoding/asn1"
+	"encoding/pem"
+	"fmt"
 	"strings"
 	"testing"
 )
@@ -46,6 +48,7 @@ func TestBer2Der_Negatives(t *testing.T) {
 		{[]byte{0x30, 0x84, 0x80, 0x0, 0x0, 0x0}, "length is negative"},
 		{[]byte{0x30, 0x82, 0x0, 0x1}, "length has leading zero"},
 		{[]byte{0x30, 0x80, 0x1, 0x2, 0x1, 0x2}, "Invalid BER format"},
+		{[]byte{0x30, 0x80, 0x1, 0x2}, "BER tag length is more than available data"},
 		{[]byte{0x30, 0x03, 0x01, 0x02}, "length is more than available data"},
 		{[]byte{0x30}, "end of ber data reached"},
 	}
@@ -96,3 +99,88 @@ func TestBer2Der_NestedMultipleIndefinite(t *testing.T) {
 		t.Errorf("Resulting DER has trailing data: % X", rest)
 	}
 }
+
+func TestVerifyIndefiniteLengthBer(t *testing.T) {
+	decoded := mustDecodePEM([]byte(testPKCS7))
+
+	_, err := ber2der(decoded)
+	if err != nil {
+		t.Errorf("cannot parse indefinite length ber: %v", err)
+	}
+}
+
+func mustDecodePEM(data []byte) []byte {
+	var block *pem.Block
+	block, rest := pem.Decode(data)
+	if len(rest) != 0 {
+		panic(fmt.Errorf("unexpected remaining PEM block during decode"))
+	}
+	return block.Bytes
+}
+
+const testPKCS7 = `
+-----BEGIN PKCS7-----
+MIAGCSqGSIb3DQEHAqCAMIACAQExDzANBglghkgBZQMEAgEFADCABgkqhkiG9w0B
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+-----END PKCS7-----
+`