From 2aea9e3b2d6d9a3ad1f5e3c76e7e0d99c0872122 Mon Sep 17 00:00:00 2001
From: Jack Lloyd <jack@randombit.net>
Date: Thu, 9 Nov 2017 12:19:28 -0500
Subject: Add UCS-2 and UCS-4 to UTF-8 conversion functions

Crosschecked by fuzzing and comparing with iconv

Needed in #1250
---
 src/lib/utils/charset.cpp | 81 +++++++++++++++++++++++++++++++++++++++++++++++
 src/lib/utils/charset.h   | 16 ++++++++++
 2 files changed, 97 insertions(+)

(limited to 'src/lib/utils')

diff --git a/src/lib/utils/charset.cpp b/src/lib/utils/charset.cpp
index 546e4e74d..dadee8f78 100644
--- a/src/lib/utils/charset.cpp
+++ b/src/lib/utils/charset.cpp
@@ -7,10 +7,91 @@
 
 #include <botan/charset.h>
 #include <botan/exceptn.h>
+#include <botan/loadstor.h>
 #include <cctype>
 
 namespace Botan {
 
+namespace {
+
+void append_utf8_for(std::string& s, uint32_t c)
+   {
+   if(c >= 0xD800 && c < 0xE000)
+      throw Decoding_Error("Invalid Unicode character");
+
+   if(c <= 0x7F)
+      {
+      const uint8_t b0 = static_cast<uint8_t>(c);
+      s.push_back(static_cast<char>(b0));
+      }
+   else if(c <= 0x7FF)
+      {
+      const uint8_t b0 = 0xC0 | static_cast<uint8_t>(c >> 6);
+      const uint8_t b1 = 0x80 | static_cast<uint8_t>(c & 0x3F);
+      s.push_back(static_cast<char>(b0));
+      s.push_back(static_cast<char>(b1));
+      }
+   else if(c <= 0xFFFF)
+      {
+      const uint8_t b0 = 0xE0 | static_cast<uint8_t>(c >> 12);
+      const uint8_t b1 = 0x80 | static_cast<uint8_t>((c >> 6) & 0x3F);
+      const uint8_t b2 = 0x80 | static_cast<uint8_t>(c & 0x3F);
+      s.push_back(static_cast<char>(b0));
+      s.push_back(static_cast<char>(b1));
+      s.push_back(static_cast<char>(b2));
+      }
+   else if(c <= 0x10FFFF)
+      {
+      const uint8_t b0 = 0xF0 | static_cast<uint8_t>(c >> 18);
+      const uint8_t b1 = 0x80 | static_cast<uint8_t>((c >> 12) & 0x3F);
+      const uint8_t b2 = 0x80 | static_cast<uint8_t>((c >> 6) & 0x3F);
+      const uint8_t b3 = 0x80 | static_cast<uint8_t>(c & 0x3F);
+      s.push_back(static_cast<char>(b0));
+      s.push_back(static_cast<char>(b1));
+      s.push_back(static_cast<char>(b2));
+      s.push_back(static_cast<char>(b3));
+      }
+   else
+      throw Decoding_Error("Invalid Unicode character");
+
+   }
+
+}
+
+std::string ucs2_to_utf8(const uint8_t ucs2[], size_t len)
+   {
+   if(len % 2 != 0)
+      throw Decoding_Error("Invalid length for UCS-2 string");
+
+   const size_t chars = len / 2;
+
+   std::string s;
+   for(size_t i = 0; i != chars; ++i)
+      {
+      const uint16_t c = load_be<uint16_t>(ucs2, i);
+      append_utf8_for(s, c);
+      }
+
+   return s;
+   }
+
+std::string ucs4_to_utf8(const uint8_t ucs4[], size_t len)
+   {
+   if(len % 4 != 0)
+      throw Decoding_Error("Invalid length for UCS-4 string");
+
+   const size_t chars = len / 4;
+
+   std::string s;
+   for(size_t i = 0; i != chars; ++i)
+      {
+      const uint32_t c = load_be<uint32_t>(ucs4, i);
+      append_utf8_for(s, c);
+      }
+
+   return s;
+   }
+
 namespace Charset {
 
 namespace {
diff --git a/src/lib/utils/charset.h b/src/lib/utils/charset.h
index 528ab908b..3f2ff9912 100644
--- a/src/lib/utils/charset.h
+++ b/src/lib/utils/charset.h
@@ -23,6 +23,22 @@ enum Character_Set {
    LATIN1_CHARSET
 };
 
+/**
+* Convert a sequence of UCS-2 (big endian) characters to a UTF-8 string
+* This is used for ASN.1 BMPString type
+* @param ucs2 the sequence of UCS-2 characters
+* @param len length of ucs2 in bytes, must be a multiple of 2
+*/
+std::string BOTAN_UNSTABLE_API ucs2_to_utf8(const uint8_t ucs2[], size_t len);
+
+/**
+* Convert a sequence of UCS-4 (big endian) characters to a UTF-8 string
+* This is used for ASN.1 UniversalString type
+* @param ucs4 the sequence of UCS-4 characters
+* @param len length of ucs4 in bytes, must be a multiple of 4
+*/
+std::string BOTAN_UNSTABLE_API ucs4_to_utf8(const uint8_t ucs4[], size_t len);
+
 namespace Charset {
 
 /*
-- 
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