src/extensions/common/csp_validator.cc

   1 // Copyright 2013 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "extensions/common/csp_validator.h"
   6
   7 #include <vector>
   8
   9 #include "base/strings/string_split.h"
  10 #include "base/strings/string_tokenizer.h"
  11 #include "base/strings/string_util.h"
  12 #include "content/public/common/url_constants.h"
  13 #include "extensions/common/constants.h"
  14 #include "net/base/registry_controlled_domains/registry_controlled_domain.h"
  15
  16 namespace extensions {
  17
  18 namespace csp_validator {
  19
  20 namespace {
  21
  22 const char kDefaultSrc[] = "default-src";
  23 const char kScriptSrc[] = "script-src";
  24 const char kObjectSrc[] = "object-src";
  25
  26 const char kSandboxDirectiveName[] = "sandbox";
  27 const char kAllowSameOriginToken[] = "allow-same-origin";
  28 const char kAllowTopNavigation[] = "allow-top-navigation";
  29
  30 struct DirectiveStatus {
  31   explicit DirectiveStatus(const char* name)
  32     : directive_name(name)
  33     , seen_in_policy(false)
  34     , is_secure(false) {
  35   }
  36
  37   const char* directive_name;
  38   bool seen_in_policy;
  39   bool is_secure;
  40 };
  41
  42 // Returns whether |url| starts with |scheme_and_separator| and does not have a
  43 // too permissive wildcard host name. If |should_check_rcd| is true, then the
  44 // Public suffix list is used to exclude wildcard TLDs such as "https://*.org".
  45 bool isNonWildcardTLD(const std::string& url,
  46                       const std::string& scheme_and_separator,
  47                       bool should_check_rcd) {
  48   if (!StartsWithASCII(url, scheme_and_separator, true))
  49     return false;
  50
  51   size_t start_of_host = scheme_and_separator.length();
  52
  53   size_t end_of_host = url.find("/", start_of_host);
  54   if (end_of_host == std::string::npos)
  55     end_of_host = url.size();
  56
  57   // Note: It is sufficient to only compare the first character against '*'
  58   // because the CSP only allows wildcards at the start of a directive, see
  59   // host-source and host-part at http://www.w3.org/TR/CSP2/#source-list-syntax
  60   bool is_wildcard_subdomain = end_of_host > start_of_host + 2 &&
  61       url[start_of_host] == '*' && url[start_of_host + 1] == '.';
  62   if (is_wildcard_subdomain)
  63     start_of_host += 2;
  64
  65   size_t start_of_port = url.rfind(":", end_of_host);
  66   // The ":" check at the end of the following condition is used to avoid
  67   // treating the last part of an IPv6 address as a port.
  68   if (start_of_port > start_of_host && url[start_of_port - 1] != ':') {
  69     bool is_valid_port = false;
  70     // Do a quick sanity check. The following check could mistakenly flag
  71     // ":123456" or ":****" as valid, but that does not matter because the
  72     // relaxing CSP directive will just be ignored by Blink.
  73     for (size_t i = start_of_port + 1; i < end_of_host; ++i) {
  74       is_valid_port = IsAsciiDigit(url[i]) || url[i] == '*';
  75       if (!is_valid_port)
  76         break;
  77     }
  78     if (is_valid_port)
  79       end_of_host = start_of_port;
  80   }
  81
  82   std::string host(url, start_of_host, end_of_host - start_of_host);
  83   // Global wildcards are not allowed.
  84   if (host.empty() || host.find("*") != std::string::npos)
  85     return false;
  86
  87   if (!is_wildcard_subdomain || !should_check_rcd)
  88     return true;
  89
  90   // Allow *.googleapis.com to be whitelisted for backwards-compatibility.
  91   // (crbug.com/409952)
  92   if (host == "googleapis.com")
  93     return true;
  94
  95   // Wildcards on subdomains of a TLD are not allowed.
  96   size_t registry_length = net::registry_controlled_domains::GetRegistryLength(
  97       host,
  98       net::registry_controlled_domains::INCLUDE_UNKNOWN_REGISTRIES,
  99       net::registry_controlled_domains::INCLUDE_PRIVATE_REGISTRIES);
 100   return registry_length != 0;
 101 }
 102
 103 bool HasOnlySecureTokens(base::StringTokenizer& tokenizer,
 104                          Manifest::Type type) {
 105   while (tokenizer.GetNext()) {
 106     std::string source = tokenizer.token();
 107     base::StringToLowerASCII(&source);
 108
 109     // We might need to relax this whitelist over time.
 110     if (source == "'self'" ||
 111         source == "'none'" ||
 112         source == "http://127.0.0.1" ||
 113         LowerCaseEqualsASCII(source, "blob:") ||
 114         LowerCaseEqualsASCII(source, "filesystem:") ||
 115         LowerCaseEqualsASCII(source, "http://localhost") ||
 116         StartsWithASCII(source, "http://127.0.0.1:", true) ||
 117         StartsWithASCII(source, "http://localhost:", true) ||
 118         isNonWildcardTLD(source, "https://", true) ||
 119         isNonWildcardTLD(source, "chrome://", false) ||
 120         isNonWildcardTLD(source,
 121                          std::string(extensions::kExtensionScheme) +
 122                          url::kStandardSchemeSeparator,
 123                          false) ||
 124         StartsWithASCII(source, "chrome-extension-resource:", true)) {
 125       continue;
 126     }
 127
 128     // crbug.com/146487
 129     if (type == Manifest::TYPE_EXTENSION ||
 130         type == Manifest::TYPE_LEGACY_PACKAGED_APP) {
 131       if (source == "'unsafe-eval'")
 132         continue;
 133     }
 134
 135     return false;
 136   }
 137
 138   return true;  // Empty values default to 'none', which is secure.
 139 }
 140
 141 // Returns true if |directive_name| matches |status.directive_name|.
 142 bool UpdateStatus(const std::string& directive_name,
 143                   base::StringTokenizer& tokenizer,
 144                   DirectiveStatus* status,
 145                   Manifest::Type type) {
 146   if (status->seen_in_policy)
 147     return false;
 148   if (directive_name != status->directive_name)
 149     return false;
 150   status->seen_in_policy = true;
 151   status->is_secure = HasOnlySecureTokens(tokenizer, type);
 152   return true;
 153 }
 154
 155 }  //  namespace
 156
 157 bool ContentSecurityPolicyIsLegal(const std::string& policy) {
 158   // We block these characters to prevent HTTP header injection when
 159   // representing the content security policy as an HTTP header.
 160   const char kBadChars[] = {',', '\r', '\n', '\0'};
 161
 162   return policy.find_first_of(kBadChars, 0, arraysize(kBadChars)) ==
 163       std::string::npos;
 164 }
 165
 166 bool ContentSecurityPolicyIsSecure(const std::string& policy,
 167                                    Manifest::Type type) {
 168   // See http://www.w3.org/TR/CSP/#parse-a-csp-policy for parsing algorithm.
 169   std::vector<std::string> directives;
 170   base::SplitString(policy, ';', &directives);
 171
 172   DirectiveStatus default_src_status(kDefaultSrc);
 173   DirectiveStatus script_src_status(kScriptSrc);
 174   DirectiveStatus object_src_status(kObjectSrc);
 175
 176   for (size_t i = 0; i < directives.size(); ++i) {
 177     std::string& input = directives[i];
 178     base::StringTokenizer tokenizer(input, " \t\r\n");
 179     if (!tokenizer.GetNext())
 180       continue;
 181
 182     std::string directive_name = tokenizer.token();
 183     base::StringToLowerASCII(&directive_name);
 184
 185     if (UpdateStatus(directive_name, tokenizer, &default_src_status, type))
 186       continue;
 187     if (UpdateStatus(directive_name, tokenizer, &script_src_status, type))
 188       continue;
 189     if (UpdateStatus(directive_name, tokenizer, &object_src_status, type))
 190       continue;
 191   }
 192
 193   if (script_src_status.seen_in_policy && !script_src_status.is_secure)
 194     return false;
 195
 196   if (object_src_status.seen_in_policy && !object_src_status.is_secure)
 197     return false;
 198
 199   if (default_src_status.seen_in_policy && !default_src_status.is_secure) {
 200     return script_src_status.seen_in_policy &&
 201            object_src_status.seen_in_policy;
 202   }
 203
 204   return default_src_status.seen_in_policy ||
 205       (script_src_status.seen_in_policy && object_src_status.seen_in_policy);
 206 }
 207
 208 bool ContentSecurityPolicyIsSandboxed(
 209     const std::string& policy, Manifest::Type type) {
 210   // See http://www.w3.org/TR/CSP/#parse-a-csp-policy for parsing algorithm.
 211   std::vector<std::string> directives;
 212   base::SplitString(policy, ';', &directives);
 213
 214   bool seen_sandbox = false;
 215
 216   for (size_t i = 0; i < directives.size(); ++i) {
 217     std::string& input = directives[i];
 218     base::StringTokenizer tokenizer(input, " \t\r\n");
 219     if (!tokenizer.GetNext())
 220       continue;
 221
 222     std::string directive_name = tokenizer.token();
 223     base::StringToLowerASCII(&directive_name);
 224
 225     if (directive_name != kSandboxDirectiveName)
 226       continue;
 227
 228     seen_sandbox = true;
 229
 230     while (tokenizer.GetNext()) {
 231       std::string token = tokenizer.token();
 232       base::StringToLowerASCII(&token);
 233
 234       // The same origin token negates the sandboxing.
 235       if (token == kAllowSameOriginToken)
 236         return false;
 237
 238       // Platform apps don't allow navigation.
 239       if (type == Manifest::TYPE_PLATFORM_APP) {
 240         if (token == kAllowTopNavigation)
 241           return false;
 242       }
 243     }
 244   }
 245
 246   return seen_sandbox;
 247 }
 248
 249 }  // namespace csp_validator
 250
 251 }  // namespace extensions