From 5e7ee8f33e088c9e2db7005abc5eb39a4afd9cd9 Mon Sep 17 00:00:00 2001
From: Randy Heit <rheit@zdoom.fake>
Date: Tue, 4 Jun 2013 02:06:40 +0000
Subject: [PATCH] - Addded support for multi-line values in INI files, so you
 can't maliciously inject stray   newline characters into the config file
 using ACS's SetCVarString.

SVN r4326 (trunk)
---
 src/configfile.cpp | 109 ++++++++++++++++++++++++++++++++++++++++++++-
 src/configfile.h   |   2 +
 2 files changed, 109 insertions(+), 2 deletions(-)

diff --git a/src/configfile.cpp b/src/configfile.cpp
index fcbed42c3..b8e37d91c 100644
--- a/src/configfile.cpp
+++ b/src/configfile.cpp
@@ -38,9 +38,12 @@
 
 #include "doomtype.h"
 #include "configfile.h"
+#include "m_random.h"
 
 #define READBUFFERSIZE	256
 
+static FRandom pr_endtag;
+
 //====================================================================
 //
 // FConfigFile Constructor
@@ -679,13 +682,68 @@ bool FConfigFile::ReadConfig (void *file)
 					whiteprobe++;
 				}
 				*(whiteprobe - 1) = 0;
-				NewConfigEntry (section, start, whiteprobe);
+				// Check for multi-line value
+				if (whiteprobe[0] == '<' && whiteprobe[1] == '<' && whiteprobe[2] == '<' && whiteprobe[3] != '\0')
+				{
+					ReadMultiLineValue (file, section, start, whiteprobe + 3);
+				}
+				else
+				{
+					NewConfigEntry (section, start, whiteprobe);
+				}
 			}
 		}
 	}
 	return true;
 }
 
+//====================================================================
+//
+// FConfigFile :: ReadMultiLineValue
+//
+// Reads a multi-line value, with format as follows:
+//
+//    key=<<<ENDTAG
+//    ... blah blah blah ...
+//    >>>ENDTAG
+//
+// The final ENDTAG must be on a line all by itself.
+//
+//====================================================================
+
+FConfigFile::FConfigEntry *FConfigFile::ReadMultiLineValue(void *file, FConfigSection *section, const char *key, const char *endtag)
+{
+	char readbuf[READBUFFERSIZE];
+	FString value;
+	size_t endlen = strlen(endtag);
+
+	// Keep on reading lines until we reach a line that matches >>>endtag
+	while (ReadLine(readbuf, READBUFFERSIZE, file) != NULL)
+	{
+		// Does the start of this line match the endtag?
+		if (readbuf[0] == '>' && readbuf[1] == '>' && readbuf[2] == '>' &&
+			strncmp(readbuf + 3, endtag, endlen) == 0)
+		{ // Is there nothing but line break characters after the match?
+			size_t i;
+			for (i = endlen + 3; readbuf[i] != '\0'; ++i)
+			{
+				if (readbuf[i] != '\n' && readbuf[i] != '\r')
+				{ // Not a line break character
+					break;
+				}
+			}
+			if (readbuf[i] == '\0')
+			{ // We're done; strip the previous line's line breaks, since it's not part of the value.
+				value.StripRight("\n\r");
+			}
+			break;
+		}
+		// Append this line to the value.
+		value << readbuf;
+	}
+	return NewConfigEntry(section, key, value);
+}
+
 //====================================================================
 //
 // FConfigFile :: ReadLine
@@ -732,7 +790,16 @@ bool FConfigFile::WriteConfigFile () const
 		fprintf (file, "[%s]\n", section->Name);
 		while (entry != NULL)
 		{
-			fprintf (file, "%s=%s\n", entry->Key, entry->Value);
+			if (strpbrk(entry->Value, "\r\n") == NULL)
+			{ // Single-line value
+				fprintf (file, "%s=%s\n", entry->Key, entry->Value);
+			}
+			else
+			{ // Multi-line value
+				const char *endtag = GenerateEndTag(entry->Value);
+				fprintf (file, "%s=<<<%s\n%s\n>>>%s\n", entry->Key,
+					endtag, entry->Value, endtag);
+			}
 			entry = entry->Next;
 		}
 		section = section->Next;
@@ -742,6 +809,44 @@ bool FConfigFile::WriteConfigFile () const
 	return true;
 }
 
+//====================================================================
+//
+// FConfigFile :: GenerateEndTag
+//
+// Generates a terminator sequence for multi-line values that does
+// not appear anywhere in the value.
+//
+//====================================================================
+
+const char *FConfigFile::GenerateEndTag(const char *value)
+{
+	static const char Base64Table[] =
+		"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789._";
+	static char EndTag[25] = "EOV-";
+
+	// Try different 20-character sequences until we find one that
+	// isn't in the value. We create the sequences by generating two
+	// 64-bit random numbers and Base64 encoding the first 15 bytes
+	// from them.
+	union { QWORD rand_num[2]; BYTE rand_bytes[16]; };
+	do
+	{
+		rand_num[0] = pr_endtag.GenRand64();
+		rand_num[1] = pr_endtag.GenRand64();
+
+		for (int i = 0; i < 5; ++i)
+		{
+			DWORD three_bytes = (rand_bytes[i*3] << 16) | (rand_bytes[i*3+1] << 8) | (rand_bytes[i*3+2]);
+			EndTag[4+i*4  ] = Base64Table[rand_bytes[i*3] >> 2];
+			EndTag[4+i*4+1] = Base64Table[((rand_bytes[i*3] & 3) << 4) | (rand_bytes[i*3+1] >> 4)];
+			EndTag[4+i*4+2] = Base64Table[((rand_bytes[i*3+1] & 15) << 2) | (rand_bytes[i*3+2] >> 6)];
+			EndTag[4+i*4+3] = Base64Table[rand_bytes[i*3+2] & 63];
+		}
+	}
+	while (strstr(value, EndTag) != NULL);
+	return EndTag;
+}
+
 //====================================================================
 //
 // FConfigFile :: WriteCommentHeader
diff --git a/src/configfile.h b/src/configfile.h
index b704dd359..25c366f01 100644
--- a/src/configfile.h
+++ b/src/configfile.h
@@ -78,6 +78,7 @@ protected:
 
 	virtual char *ReadLine (char *string, int n, void *file) const;
 	bool ReadConfig (void *file);
+	static const char *GenerateEndTag(const char *value);
 
 	bool OkayToWrite;
 	bool FileExisted;
@@ -110,6 +111,7 @@ private:
 	FConfigEntry *FindEntry (FConfigSection *section, const char *key) const;
 	FConfigSection *NewConfigSection (const char *name);
 	FConfigEntry *NewConfigEntry (FConfigSection *section, const char *key, const char *value);
+	FConfigEntry *ReadMultiLineValue (void *file, FConfigSection *section, const char *key, const char *terminator);
 	void SetSectionNote (FConfigSection *section, const char *note);
 
 public: