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// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "chrome/common/extensions/csp_validator.h"
#include "base/string_split.h"
#include "base/string_util.h"
#include "base/strings/string_tokenizer.h"
namespace extensions {
namespace csp_validator {
namespace {
const char kDefaultSrc[] = "default-src";
const char kScriptSrc[] = "script-src";
const char kObjectSrc[] = "object-src";
const char kSandboxDirectiveName[] = "sandbox";
const char kAllowSameOriginToken[] = "allow-same-origin";
const char kAllowTopNavigation[] = "allow-top-navigation";
const char kAllowPopups[] = "allow-popups";
struct DirectiveStatus {
explicit DirectiveStatus(const char* name)
: directive_name(name)
, seen_in_policy(false)
, is_secure(false) {
}
const char* directive_name;
bool seen_in_policy;
bool is_secure;
};
bool HasOnlySecureTokens(base::StringTokenizer& tokenizer,
Manifest::Type type) {
while (tokenizer.GetNext()) {
std::string source = tokenizer.token();
StringToLowerASCII(&source);
// Don't alow whitelisting of all hosts. This boils down to:
// 1. Maximum of 2 '*' characters.
// 2. Each '*' is either followed by a '.' or preceded by a ':'
int wildcards = 0;
size_t length = source.length();
for (size_t i = 0; i < length; ++i) {
if (source[i] == L'*') {
wildcards++;
if (wildcards > 2)
return false;
bool isWildcardPort = i > 0 && source[i - 1] == L':';
bool isWildcardSubdomain = i + 1 < length && source[i + 1] == L'.';
if (!isWildcardPort && !isWildcardSubdomain)
return false;
}
}
// We might need to relax this whitelist over time.
if (source == "'self'" ||
source == "'none'" ||
source == "http://127.0.0.1" ||
LowerCaseEqualsASCII(source, "blob:") ||
LowerCaseEqualsASCII(source, "filesystem:") ||
LowerCaseEqualsASCII(source, "http://localhost") ||
StartsWithASCII(source, "http://127.0.0.1:", false) ||
StartsWithASCII(source, "http://localhost:", false) ||
StartsWithASCII(source, "https://", true) ||
StartsWithASCII(source, "chrome://", true) ||
StartsWithASCII(source, "chrome-extension://", true) ||
StartsWithASCII(source, "chrome-extension-resource:", true)) {
continue;
}
// crbug.com/146487
if (type == Manifest::TYPE_EXTENSION ||
type == Manifest::TYPE_LEGACY_PACKAGED_APP) {
if (source == "'unsafe-eval'")
continue;
}
return false;
}
return true; // Empty values default to 'none', which is secure.
}
// Returns true if |directive_name| matches |status.directive_name|.
bool UpdateStatus(const std::string& directive_name,
base::StringTokenizer& tokenizer,
DirectiveStatus* status,
Manifest::Type type) {
if (status->seen_in_policy)
return false;
if (directive_name != status->directive_name)
return false;
status->seen_in_policy = true;
status->is_secure = HasOnlySecureTokens(tokenizer, type);
return true;
}
} // namespace
bool ContentSecurityPolicyIsLegal(const std::string& policy) {
// We block these characters to prevent HTTP header injection when
// representing the content security policy as an HTTP header.
const char kBadChars[] = {',', '\r', '\n', '\0'};
return policy.find_first_of(kBadChars, 0, arraysize(kBadChars)) ==
std::string::npos;
}
bool ContentSecurityPolicyIsSecure(const std::string& policy,
Manifest::Type type) {
// See http://www.w3.org/TR/CSP/#parse-a-csp-policy for parsing algorithm.
std::vector<std::string> directives;
base::SplitString(policy, ';', &directives);
DirectiveStatus default_src_status(kDefaultSrc);
DirectiveStatus script_src_status(kScriptSrc);
DirectiveStatus object_src_status(kObjectSrc);
for (size_t i = 0; i < directives.size(); ++i) {
std::string& input = directives[i];
base::StringTokenizer tokenizer(input, " \t\r\n");
if (!tokenizer.GetNext())
continue;
std::string directive_name = tokenizer.token();
StringToLowerASCII(&directive_name);
if (UpdateStatus(directive_name, tokenizer, &default_src_status, type))
continue;
if (UpdateStatus(directive_name, tokenizer, &script_src_status, type))
continue;
if (UpdateStatus(directive_name, tokenizer, &object_src_status, type))
continue;
}
if (script_src_status.seen_in_policy && !script_src_status.is_secure)
return false;
if (object_src_status.seen_in_policy && !object_src_status.is_secure)
return false;
if (default_src_status.seen_in_policy && !default_src_status.is_secure) {
return script_src_status.seen_in_policy &&
object_src_status.seen_in_policy;
}
return default_src_status.seen_in_policy ||
(script_src_status.seen_in_policy && object_src_status.seen_in_policy);
}
bool ContentSecurityPolicyIsSandboxed(
const std::string& policy, Manifest::Type type) {
// See http://www.w3.org/TR/CSP/#parse-a-csp-policy for parsing algorithm.
std::vector<std::string> directives;
base::SplitString(policy, ';', &directives);
bool seen_sandbox = false;
for (size_t i = 0; i < directives.size(); ++i) {
std::string& input = directives[i];
base::StringTokenizer tokenizer(input, " \t\r\n");
if (!tokenizer.GetNext())
continue;
std::string directive_name = tokenizer.token();
StringToLowerASCII(&directive_name);
if (directive_name != kSandboxDirectiveName)
continue;
seen_sandbox = true;
while (tokenizer.GetNext()) {
std::string token = tokenizer.token();
StringToLowerASCII(&token);
// The same origin token negates the sandboxing.
if (token == kAllowSameOriginToken)
return false;
// Platform apps don't allow navigation.
if (type == Manifest::TYPE_PLATFORM_APP) {
if (token == kAllowTopNavigation)
return false;
}
}
}
return seen_sandbox;
}
} // csp_validator
} // extensions
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