From c15cb6cc7ac68e539dd3969e614be52e9a943ec7 Mon Sep 17 00:00:00 2001
From: Daniel Kirchner <daniel@ekpyron.org>
Date: Thu, 5 Apr 2018 14:25:14 +0200
Subject: [PATCH] Prevent information about file existence outside the allowed
 paths to leak by mimicing boost::filesystem::weakly_canonical.

---
 Changelog.md                  |  1 +
 libdevcore/CommonIO.cpp       | 20 ++++++++++++++++++++
 libdevcore/CommonIO.h         |  5 +++++
 solc/CommandLineInterface.cpp | 14 +++++++-------
 4 files changed, 33 insertions(+), 7 deletions(-)

diff --git a/Changelog.md b/Changelog.md
index d6860bdf9..c2ef7210a 100644
--- a/Changelog.md
+++ b/Changelog.md
@@ -20,6 +20,7 @@ Bugfixes:
  * Code Generator: Bugfix in modifier lookup in libraries.
  * Code Generator: Implement packed encoding of external function types.
  * Code Generator: Treat empty base constructor argument list as not provided.
+ * Commandline interface: Fix error messages for imported files that do not exist.
  * Commandline interface: Support ``--evm-version constantinople`` properly.
  * DocString Parser: Fix error message for empty descriptions.
  * Standard JSON: Support ``constantinople`` as ``evmVersion`` properly.
diff --git a/libdevcore/CommonIO.cpp b/libdevcore/CommonIO.cpp
index 6526baf97..0063a8d46 100644
--- a/libdevcore/CommonIO.cpp
+++ b/libdevcore/CommonIO.cpp
@@ -167,3 +167,23 @@ int dev::readStandardInputChar()
 	DisableConsoleBuffering disableConsoleBuffering;
 	return cin.get();
 }
+
+boost::filesystem::path dev::weaklyCanonicalFilesystemPath(boost::filesystem::path const &_path)
+{
+	if (boost::filesystem::exists(_path))
+		return boost::filesystem::canonical(_path);
+	else
+	{
+		boost::filesystem::path head(_path);
+		boost::filesystem::path tail;
+		for (auto it = --_path.end(); !head.empty(); --it)
+		{
+			if (boost::filesystem::exists(head))
+				break;
+			tail = (*it) / tail;
+			head.remove_filename();
+		}
+		head = boost::filesystem::canonical(head);
+		return head / tail;
+	}
+}
diff --git a/libdevcore/CommonIO.h b/libdevcore/CommonIO.h
index 3ecdb4c38..9ba68e745 100644
--- a/libdevcore/CommonIO.h
+++ b/libdevcore/CommonIO.h
@@ -25,6 +25,7 @@
 
 #include <sstream>
 #include <string>
+#include <boost/filesystem.hpp>
 #include "Common.h"
 
 namespace dev
@@ -57,4 +58,8 @@ std::string toString(_T const& _t)
 	return o.str();
 }
 
+/// Partial implementation of boost::filesystem::weakly_canonical (available in boost>=1.60).
+/// Should be replaced by the boost implementation as soon as support for boost<1.60 can be dropped.
+boost::filesystem::path weaklyCanonicalFilesystemPath(boost::filesystem::path const &_path);
+
 }
diff --git a/solc/CommandLineInterface.cpp b/solc/CommandLineInterface.cpp
index 93203de60..4da394b2f 100644
--- a/solc/CommandLineInterface.cpp
+++ b/solc/CommandLineInterface.cpp
@@ -700,13 +700,7 @@ bool CommandLineInterface::processInput()
 		try
 		{
 			auto path = boost::filesystem::path(_path);
-			if (!boost::filesystem::exists(path))
-				return ReadCallback::Result{false, "File not found."};
-
-			auto canonicalPath = boost::filesystem::canonical(path);
-			if (!boost::filesystem::is_regular_file(canonicalPath))
-				return ReadCallback::Result{false, "Not a valid file."};
-
+			auto canonicalPath = weaklyCanonicalFilesystemPath(path);
 			bool isAllowed = false;
 			for (auto const& allowedDir: m_allowedDirectories)
 			{
@@ -723,6 +717,12 @@ bool CommandLineInterface::processInput()
 			if (!isAllowed)
 				return ReadCallback::Result{false, "File outside of allowed directories."};
 
+			if (!boost::filesystem::exists(canonicalPath))
+				return ReadCallback::Result{false, "File not found."};
+
+			if (!boost::filesystem::is_regular_file(canonicalPath))
+				return ReadCallback::Result{false, "Not a valid file."};
+
 			auto contents = dev::readFileAsString(canonicalPath.string());
 			m_sourceCodes[path.string()] = contents;
 			return ReadCallback::Result{true, contents};