From a02d0fa6328b2fa06e99dba7db3ad65174b93c2f Mon Sep 17 00:00:00 2001
From: Pieter Lexis <pieter.lexis@powerdns.com>
Date: Tue, 6 Apr 2021 23:44:51 +0200
Subject: [PATCH] Add function to make a bytestring from hex

---
 pdns/misc.cc         | 15 +++++++++++++++
 pdns/misc.hh         |  2 ++
 pdns/test-misc_hh.cc |  7 +++++++
 3 files changed, 24 insertions(+)

diff --git a/pdns/misc.cc b/pdns/misc.cc
index ad3a2f4506..494e49849f 100644
--- a/pdns/misc.cc
+++ b/pdns/misc.cc
@@ -577,6 +577,21 @@ string makeHexDump(const string& str)
   return ret;
 }
 
+string makeBytesFromHex(const string &in) {
+  if (in.size() % 2 != 0) {
+    throw std::range_error("odd number of bytes in hex string");
+  }
+  string ret;
+  unsigned int num;
+  for (size_t i = 0; i < in.size(); i+=2) {
+    string numStr = in.substr(i, 2);
+    num = 0;
+    sscanf(numStr.c_str(), "%02x", &num);
+    ret.push_back((uint8_t)num);
+  }
+  return ret;
+}
+
 void normalizeTV(struct timeval& tv)
 {
   if(tv.tv_usec > 1000000) {
diff --git a/pdns/misc.hh b/pdns/misc.hh
index 6307293f55..d2a1ac2767 100644
--- a/pdns/misc.hh
+++ b/pdns/misc.hh
@@ -304,6 +304,8 @@ inline void unixDie(const string &why)
 }
 
 string makeHexDump(const string& str);
+//! Convert the hexstring in to a byte string
+string makeBytesFromHex(const string &in);
 
 void normalizeTV(struct timeval& tv);
 const struct timeval operator+(const struct timeval& lhs, const struct timeval& rhs);
diff --git a/pdns/test-misc_hh.cc b/pdns/test-misc_hh.cc
index bc10168df2..0f591bcfd7 100644
--- a/pdns/test-misc_hh.cc
+++ b/pdns/test-misc_hh.cc
@@ -391,4 +391,11 @@ BOOST_AUTO_TEST_CASE(test_parseSVCBValueList)
   BOOST_CHECK_EQUAL(out[0], "foobar123 blabla bla,baz quux456");
 }
 
+BOOST_AUTO_TEST_CASE(test_makeBytesFromHex) {
+  string out = makeBytesFromHex("1234567890abcdef");
+  BOOST_CHECK_EQUAL(out, "\x12\x34\x56\x78\x90\xab\xcd\xef");
+
+  BOOST_CHECK_THROW(makeBytesFromHex("123"), std::range_error);
+}
+
 BOOST_AUTO_TEST_SUITE_END()
-- 
2.47.2