Merge pull request #4793 from ethereum/emptyRemappings

Disallow remappings with empty prefix.

10 files changed, 82 insertions, 43 deletions

diff --git a/Changelog.md b/Changelog.md
index b2f9bf05..56e00003 100644
--- a/Changelog.md
+++ b/Changelog.md
@@ -16,6 +16,7 @@ Breaking Changes:
  * Commandline interface: Remove obsolete ``--formal`` option.
  * Commandline interface: Rename the ``--julia`` option to ``--yul``.
  * Commandline interface: Require ``-`` if standard input is used as source.
+ * Compiler interface: Disallow remappings with empty prefix.
  * Control Flow Analyzer: Turn warning about returning uninitialized storage pointers into an error.
  * General: ``continue`` in a ``do...while`` loop jumps to the condition (it used to jump to the loop body). Warning: this may silently change the semantics of existing code.
  * General: Disallow declaring empty structs.
diff --git a/docs/layout-of-source-files.rst b/docs/layout-of-source-files.rst
index 46ef3d57..4bacd704 100644
--- a/docs/layout-of-source-files.rst
+++ b/docs/layout-of-source-files.rst
@@ -100,11 +100,10 @@ When the compiler is invoked, it is not only possible to specify how to
 discover the first element of a path, but it is possible to specify path prefix
 remappings so that e.g. ``github.com/ethereum/dapp-bin/library`` is remapped to
 ``/usr/local/dapp-bin/library`` and the compiler will read the files from there.
-If multiple remappings can be applied, the one with the longest key is tried first. This
-allows for a "fallback-remapping" with e.g. ``""`` maps to
-``"/usr/local/include/solidity"``. Furthermore, these remappings can
-depend on the context, which allows you to configure packages to
-import e.g. different versions of a library of the same name.
+If multiple remappings can be applied, the one with the longest key is tried first.
+An empty prefix is not allowed. Furthermore, these remappings can depend on the context,
+which allows you to configure packages to import e.g. different versions of a library
+of the same name.
 
 **solc**:
 
@@ -148,7 +147,7 @@ Note that solc only allows you to include files from certain directories:
 They have to be in the directory (or subdirectory) of one of the explicitly
 specified source files or in the directory (or subdirectory) of a remapping
 target. If you want to allow direct absolute includes, just add the
-remapping ``=/``.
+remapping ``/=/``.
 
 If there are multiple remappings that lead to a valid file, the remapping
 with the longest common prefix is chosen.
diff --git a/docs/using-the-compiler.rst b/docs/using-the-compiler.rst
index 1d7cb97b..b286e1a3 100644
--- a/docs/using-the-compiler.rst
+++ b/docs/using-the-compiler.rst
@@ -23,14 +23,15 @@ it is also possible to provide path redirects using ``prefix=path`` in the follo
 
 ::
 
-    solc github.com/ethereum/dapp-bin/=/usr/local/lib/dapp-bin/ =/usr/local/lib/fallback file.sol
+    solc github.com/ethereum/dapp-bin/=/usr/local/lib/dapp-bin/ file.sol
 
 This essentially instructs the compiler to search for anything starting with
-``github.com/ethereum/dapp-bin/`` under ``/usr/local/lib/dapp-bin`` and if it does not
-find the file there, it will look at ``/usr/local/lib/fallback`` (the empty prefix
-always matches). ``solc`` will not read files from the filesystem that lie outside of
+``github.com/ethereum/dapp-bin/`` under ``/usr/local/lib/dapp-bin``.
+``solc`` will not read files from the filesystem that lie outside of
 the remapping targets and outside of the directories where explicitly specified source
-files reside, so things like ``import "/etc/passwd";`` only work if you add ``=/`` as a remapping.
+files reside, so things like ``import "/etc/passwd";`` only work if you add ``/=/`` as a remapping.
+
+An empty remapping prefix is not allowed.
 
 If there are multiple matches due to remappings, the one with the longest common prefix is selected.
 
diff --git a/libsolidity/interface/CompilerStack.cpp b/libsolidity/interface/CompilerStack.cpp
index 836e30d2..e800b278 100644
--- a/libsolidity/interface/CompilerStack.cpp
+++ b/libsolidity/interface/CompilerStack.cpp
@@ -58,22 +58,31 @@ using namespace std;
 using namespace dev;
 using namespace dev::solidity;
 
-void CompilerStack::setRemappings(vector<string> const& _remappings)
+boost::optional<CompilerStack::Remapping> CompilerStack::parseRemapping(string const& _remapping)
+{
+	auto eq = find(_remapping.begin(), _remapping.end(), '=');
+	if (eq == _remapping.end())
+		return {};
+
+	auto colon = find(_remapping.begin(), eq, ':');
+
+	Remapping r;
+
+	r.context = colon == eq ? string() : string(_remapping.begin(), colon);
+	r.prefix = colon == eq ? string(_remapping.begin(), eq) : string(colon + 1, eq);
+	r.target = string(eq + 1, _remapping.end());
+
+	if (r.prefix.empty())
+		return {};
+
+	return r;
+}
+
+void CompilerStack::setRemappings(vector<Remapping> const& _remappings)
 {
-	vector<Remapping> remappings;
 	for (auto const& remapping: _remappings)
-	{
-		auto eq = find(remapping.begin(), remapping.end(), '=');
-		if (eq == remapping.end())
-			continue; // ignore
-		auto colon = find(remapping.begin(), eq, ':');
-		Remapping r;
-		r.context = colon == eq ? string() : string(remapping.begin(), colon);
-		r.prefix = colon == eq ? string(remapping.begin(), eq) : string(colon + 1, eq);
-		r.target = string(eq + 1, remapping.end());
-		remappings.push_back(r);
-	}
-	swap(m_remappings, remappings);
+		solAssert(!remapping.prefix.empty(), "");
+	m_remappings = _remappings;
 }
 
 void CompilerStack::setEVMVersion(EVMVersion _version)
diff --git a/libsolidity/interface/CompilerStack.h b/libsolidity/interface/CompilerStack.h
index 2234a8c9..9a15fbf0 100644
--- a/libsolidity/interface/CompilerStack.h
+++ b/libsolidity/interface/CompilerStack.h
@@ -84,6 +84,13 @@ public:
 		CompilationSuccessful
 	};
 
+	struct Remapping
+	{
+		std::string context;
+		std::string prefix;
+		std::string target;
+	};
+
 	/// Creates a new compiler stack.
 	/// @param _readFile callback to used to read files for import statements. Must return
 	/// and must not emit exceptions.
@@ -103,8 +110,11 @@ public:
 	/// All settings, with the exception of remappings, are reset.
 	void reset(bool _keepSources = false);
 
-	/// Sets path remappings in the format "context:prefix=target"
-	void setRemappings(std::vector<std::string> const& _remappings);
+	// Parses a remapping of the format "context:prefix=target".
+	static boost::optional<Remapping> parseRemapping(std::string const& _remapping);
+
+	/// Sets path remappings.
+	void setRemappings(std::vector<Remapping> const& _remappings);
 
 	/// Sets library addresses. Addresses are cleared iff @a _libraries is missing.
 	/// Will not take effect before running compile.
@@ -319,13 +329,6 @@ private:
 		FunctionDefinition const& _function
 	) const;
 
-	struct Remapping
-	{
-		std::string context;
-		std::string prefix;
-		std::string target;
-	};
-
 	ReadCallback::Callback m_readFile;
 	ReadCallback::Callback m_smtQuery;
 	bool m_optimize = false;
diff --git a/libsolidity/interface/StandardCompiler.cpp b/libsolidity/interface/StandardCompiler.cpp
index 58b84163..c1996777 100644
--- a/libsolidity/interface/StandardCompiler.cpp
+++ b/libsolidity/interface/StandardCompiler.cpp
@@ -326,9 +326,14 @@ Json::Value StandardCompiler::compileInternal(Json::Value const& _input)
 		m_compilerStack.setEVMVersion(*version);
 	}
 
-	vector<string> remappings;
+	vector<CompilerStack::Remapping> remappings;
 	for (auto const& remapping: settings.get("remappings", Json::Value()))
-		remappings.push_back(remapping.asString());
+	{
+		if (auto r = CompilerStack::parseRemapping(remapping.asString()))
+			remappings.emplace_back(std::move(*r));
+		else
+			return formatFatalError("JSONError", "Invalid remapping: \"" + remapping.asString() + "\"");
+	}
 	m_compilerStack.setRemappings(remappings);
 
 	Json::Value optimizerSettings = settings.get("optimizer", Json::Value());
diff --git a/solc/CommandLineInterface.cpp b/solc/CommandLineInterface.cpp
index 429bd637..f7d1c748 100644
--- a/solc/CommandLineInterface.cpp
+++ b/solc/CommandLineInterface.cpp
@@ -392,7 +392,18 @@ bool CommandLineInterface::readInputFilesAndConfigureRemappings()
 		{
 			auto eq = find(path.begin(), path.end(), '=');
 			if (eq != path.end())
-				path = string(eq + 1, path.end());
+			{
+				if (auto r = CompilerStack::parseRemapping(path))
+				{
+					m_remappings.emplace_back(std::move(*r));
+					path = string(eq + 1, path.end());
+				}
+				else
+				{
+					cerr << "Invalid remapping: \"" << path << "\"." << endl;
+					return false;
+				}
+			}
 			else if (path == "-")
 				addStdin = true;
 			else
@@ -808,7 +819,7 @@ bool CommandLineInterface::processInput()
 		if (m_args.count(g_argMetadataLiteral) > 0)
 			m_compiler->useMetadataLiteralSources(true);
 		if (m_args.count(g_argInputFile))
-			m_compiler->setRemappings(m_args[g_argInputFile].as<vector<string>>());
+			m_compiler->setRemappings(m_remappings);
 		for (auto const& sourceCode: m_sourceCodes)
 			m_compiler->addSource(sourceCode.first, sourceCode.second);
 		if (m_args.count(g_argLibraries))
diff --git a/solc/CommandLineInterface.h b/solc/CommandLineInterface.h
index 45ec1eb5..010dce34 100644
--- a/solc/CommandLineInterface.h
+++ b/solc/CommandLineInterface.h
@@ -97,6 +97,8 @@ private:
 	boost::program_options::variables_map m_args;
 	/// map of input files to source code strings
 	std::map<std::string, std::string> m_sourceCodes;
+	/// list of remappings
+	std::vector<dev::solidity::CompilerStack::Remapping> m_remappings;
 	/// list of allowed directories to read files from
 	std::vector<boost::filesystem::path> m_allowedDirectories;
 	/// map of library names to addresses
diff --git a/test/cmdlineTests.sh b/test/cmdlineTests.sh
index 7256386d..a260da34 100755
--- a/test/cmdlineTests.sh
+++ b/test/cmdlineTests.sh
@@ -144,6 +144,10 @@ test_solc_file_input_failures "file_not_found.sol" "" "" "\"file_not_found.sol\"
 printTask "Testing passing files that are not files..."
 test_solc_file_input_failures "." "" "" "\".\" is not a valid file."
 
+printTask "Testing passing empty remappings..."
+test_solc_file_input_failures "${0}" "=/some/remapping/target" "" "Invalid remapping: \"=/some/remapping/target\"."
+test_solc_file_input_failures "${0}" "ctx:=/some/remapping/target" "" "Invalid remapping: \"ctx:=/some/remapping/target\"."
+
 printTask "Compiling various other contracts and libraries..."
 (
 cd "$REPO_ROOT"/test/compilationTests/
diff --git a/test/libsolidity/Imports.cpp b/test/libsolidity/Imports.cpp
index df31ac40..dc33d577 100644
--- a/test/libsolidity/Imports.cpp
+++ b/test/libsolidity/Imports.cpp
@@ -167,7 +167,7 @@ BOOST_AUTO_TEST_CASE(name_clash_in_import)
 BOOST_AUTO_TEST_CASE(remappings)
 {
 	CompilerStack c;
-	c.setRemappings(vector<string>{"s=s_1.4.6", "t=Tee"});
+	c.setRemappings(vector<CompilerStack::Remapping>{{"", "s", "s_1.4.6"},{"", "t", "Tee"}});
 	c.addSource("a", "import \"s/s.sol\"; contract A is S {} pragma solidity >=0.0;");
 	c.addSource("b", "import \"t/tee.sol\"; contract A is Tee {} pragma solidity >=0.0;");
 	c.addSource("s_1.4.6/s.sol", "contract S {} pragma solidity >=0.0;");
@@ -179,7 +179,7 @@ BOOST_AUTO_TEST_CASE(remappings)
 BOOST_AUTO_TEST_CASE(context_dependent_remappings)
 {
 	CompilerStack c;
-	c.setRemappings(vector<string>{"a:s=s_1.4.6", "b:s=s_1.4.7"});
+	c.setRemappings(vector<CompilerStack::Remapping>{{"a", "s", "s_1.4.6"}, {"b", "s", "s_1.4.7"}});
 	c.addSource("a/a.sol", "import \"s/s.sol\"; contract A is SSix {} pragma solidity >=0.0;");
 	c.addSource("b/b.sol", "import \"s/s.sol\"; contract B is SSeven {} pragma solidity >=0.0;");
 	c.addSource("s_1.4.6/s.sol", "contract SSix {} pragma solidity >=0.0;");
@@ -200,7 +200,11 @@ BOOST_AUTO_TEST_CASE(filename_with_period)
 BOOST_AUTO_TEST_CASE(context_dependent_remappings_ensure_default_and_module_preserved)
 {
 	CompilerStack c;
-	c.setRemappings(vector<string>{"foo=vendor/foo_2.0.0", "vendor/bar:foo=vendor/foo_1.0.0", "bar=vendor/bar"});
+	c.setRemappings(vector<CompilerStack::Remapping>{
+		{"", "foo", "vendor/foo_2.0.0"},
+		{"vendor/bar", "foo", "vendor/foo_1.0.0"},
+		{"", "bar", "vendor/bar"}
+	});
 	c.addSource("main.sol", "import \"foo/foo.sol\"; import {Bar} from \"bar/bar.sol\"; contract Main is Foo2, Bar {} pragma solidity >=0.0;");
 	c.addSource("vendor/bar/bar.sol", "import \"foo/foo.sol\"; contract Bar {Foo1 foo;} pragma solidity >=0.0;");
 	c.addSource("vendor/foo_1.0.0/foo.sol", "contract Foo1 {} pragma solidity >=0.0;");
@@ -212,7 +216,7 @@ BOOST_AUTO_TEST_CASE(context_dependent_remappings_ensure_default_and_module_pres
 BOOST_AUTO_TEST_CASE(context_dependent_remappings_order_independent)
 {
 	CompilerStack c;
-	c.setRemappings(vector<string>{"a:x/y/z=d", "a/b:x=e"});
+	c.setRemappings(vector<CompilerStack::Remapping>{{"a", "x/y/z", "d"}, {"a/b", "x", "e"}});
 	c.addSource("a/main.sol", "import \"x/y/z/z.sol\"; contract Main is D {} pragma solidity >=0.0;");
 	c.addSource("a/b/main.sol", "import \"x/y/z/z.sol\"; contract Main is E {} pragma solidity >=0.0;");
 	c.addSource("d/z.sol", "contract D {} pragma solidity >=0.0;");
@@ -220,7 +224,7 @@ BOOST_AUTO_TEST_CASE(context_dependent_remappings_order_independent)
 	c.setEVMVersion(dev::test::Options::get().evmVersion());
 	BOOST_CHECK(c.compile());
 	CompilerStack d;
-	d.setRemappings(vector<string>{"a/b:x=e", "a:x/y/z=d"});
+	d.setRemappings(vector<CompilerStack::Remapping>{{"a/b", "x", "e"}, {"a", "x/y/z", "d"}});
 	d.addSource("a/main.sol", "import \"x/y/z/z.sol\"; contract Main is D {} pragma solidity >=0.0;");
 	d.addSource("a/b/main.sol", "import \"x/y/z/z.sol\"; contract Main is E {} pragma solidity >=0.0;");
 	d.addSource("d/z.sol", "contract D {} pragma solidity >=0.0;");