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 "extensions/common/error_utils.h"
  15 #include "extensions/common/install_warning.h"
  16 #include "extensions/common/manifest_constants.h"
  17 #include "net/base/registry_controlled_domains/registry_controlled_domain.h"
  18
  19 namespace extensions {
  20
  21 namespace csp_validator {
  22
  23 namespace {
  24
  25 const char kDefaultSrc[] = "default-src";
  26 const char kScriptSrc[] = "script-src";
  27 const char kObjectSrc[] = "object-src";
  28 const char kPluginTypes[] = "plugin-types";
  29
  30 const char kObjectSrcDefaultDirective[] = "object-src 'self';";
  31 const char kScriptSrcDefaultDirective[] =
  32     "script-src 'self' chrome-extension-resource:;";
  33
  34 const char kSandboxDirectiveName[] = "sandbox";
  35 const char kAllowSameOriginToken[] = "allow-same-origin";
  36 const char kAllowTopNavigation[] = "allow-top-navigation";
  37
  38 // This is the list of plugin types which are fully sandboxed and are safe to
  39 // load up in an extension, regardless of the URL they are navigated to.
  40 const char* const kSandboxedPluginTypes[] = {
  41   "application/pdf",
  42   "application/x-google-chrome-pdf",
  43   "application/x-pnacl"
  44 };
  45
  46 struct DirectiveStatus {
  47   explicit DirectiveStatus(const char* name)
  48       : directive_name(name), seen_in_policy(false) {}
  49
  50   const char* directive_name;
  51   bool seen_in_policy;
  52 };
  53
  54 // Returns whether |url| starts with |scheme_and_separator| and does not have a
  55 // too permissive wildcard host name. If |should_check_rcd| is true, then the
  56 // Public suffix list is used to exclude wildcard TLDs such as "https://*.org".
  57 bool isNonWildcardTLD(const std::string& url,
  58                       const std::string& scheme_and_separator,
  59                       bool should_check_rcd) {
  60   if (!StartsWithASCII(url, scheme_and_separator, true))
  61     return false;
  62
  63   size_t start_of_host = scheme_and_separator.length();
  64
  65   size_t end_of_host = url.find("/", start_of_host);
  66   if (end_of_host == std::string::npos)
  67     end_of_host = url.size();
  68
  69   // Note: It is sufficient to only compare the first character against '*'
  70   // because the CSP only allows wildcards at the start of a directive, see
  71   // host-source and host-part at http://www.w3.org/TR/CSP2/#source-list-syntax
  72   bool is_wildcard_subdomain = end_of_host > start_of_host + 2 &&
  73       url[start_of_host] == '*' && url[start_of_host + 1] == '.';
  74   if (is_wildcard_subdomain)
  75     start_of_host += 2;
  76
  77   size_t start_of_port = url.rfind(":", end_of_host);
  78   // The ":" check at the end of the following condition is used to avoid
  79   // treating the last part of an IPv6 address as a port.
  80   if (start_of_port > start_of_host && url[start_of_port - 1] != ':') {
  81     bool is_valid_port = false;
  82     // Do a quick sanity check. The following check could mistakenly flag
  83     // ":123456" or ":****" as valid, but that does not matter because the
  84     // relaxing CSP directive will just be ignored by Blink.
  85     for (size_t i = start_of_port + 1; i < end_of_host; ++i) {
  86       is_valid_port = IsAsciiDigit(url[i]) || url[i] == '*';
  87       if (!is_valid_port)
  88         break;
  89     }
  90     if (is_valid_port)
  91       end_of_host = start_of_port;
  92   }
  93
  94   std::string host(url, start_of_host, end_of_host - start_of_host);
  95   // Global wildcards are not allowed.
  96   if (host.empty() || host.find("*") != std::string::npos)
  97     return false;
  98
  99   if (!is_wildcard_subdomain || !should_check_rcd)
 100     return true;
 101
 102   // Allow *.googleapis.com to be whitelisted for backwards-compatibility.
 103   // (crbug.com/409952)
 104   if (host == "googleapis.com")
 105     return true;
 106
 107   // Wildcards on subdomains of a TLD are not allowed.
 108   size_t registry_length = net::registry_controlled_domains::GetRegistryLength(
 109       host,
 110       net::registry_controlled_domains::INCLUDE_UNKNOWN_REGISTRIES,
 111       net::registry_controlled_domains::INCLUDE_PRIVATE_REGISTRIES);
 112   return registry_length != 0;
 113 }
 114
 115 InstallWarning CSPInstallWarning(const std::string& csp_warning) {
 116   return InstallWarning(csp_warning, manifest_keys::kContentSecurityPolicy);
 117 }
 118
 119 void GetSecureDirectiveValues(const std::string& directive_name,
 120                               base::StringTokenizer* tokenizer,
 121                               int options,
 122                               std::vector<std::string>* sane_csp_parts,
 123                               std::vector<InstallWarning>* warnings) {
 124   sane_csp_parts->push_back(directive_name);
 125   while (tokenizer->GetNext()) {
 126     std::string source = tokenizer->token();
 127     base::StringToLowerASCII(&source);
 128     bool is_secure_csp_token = false;
 129
 130     // We might need to relax this whitelist over time.
 131     if (source == "'self'" ||
 132         source == "'none'" ||
 133         source == "http://127.0.0.1" ||
 134         LowerCaseEqualsASCII(source, "blob:") ||
 135         LowerCaseEqualsASCII(source, "filesystem:") ||
 136         LowerCaseEqualsASCII(source, "http://localhost") ||
 137         StartsWithASCII(source, "http://127.0.0.1:", true) ||
 138         StartsWithASCII(source, "http://localhost:", true) ||
 139         isNonWildcardTLD(source, "https://", true) ||
 140         isNonWildcardTLD(source, "chrome://", false) ||
 141         isNonWildcardTLD(source,
 142                          std::string(extensions::kExtensionScheme) +
 143                          url::kStandardSchemeSeparator,
 144                          false) ||
 145         StartsWithASCII(source, "chrome-extension-resource:", true)) {
 146       is_secure_csp_token = true;
 147     } else if ((options & OPTIONS_ALLOW_UNSAFE_EVAL) &&
 148                source == "'unsafe-eval'") {
 149       is_secure_csp_token = true;
 150     }
 151
 152     if (is_secure_csp_token) {
 153       sane_csp_parts->push_back(source);
 154     } else if (warnings) {
 155       warnings->push_back(CSPInstallWarning(ErrorUtils::FormatErrorMessage(
 156           manifest_errors::kInvalidCSPInsecureValue, source, directive_name)));
 157     }
 158   }
 159   // End of CSP directive that was started at the beginning of this method. If
 160   // none of the values are secure, the policy will be empty and default to
 161   // 'none', which is secure.
 162   sane_csp_parts->back().push_back(';');
 163 }
 164
 165 // Returns true if |directive_name| matches |status.directive_name|.
 166 bool UpdateStatus(const std::string& directive_name,
 167                   base::StringTokenizer* tokenizer,
 168                   DirectiveStatus* status,
 169                   int options,
 170                   std::vector<std::string>* sane_csp_parts,
 171                   std::vector<InstallWarning>* warnings) {
 172   if (directive_name != status->directive_name)
 173     return false;
 174
 175   if (!status->seen_in_policy) {
 176     status->seen_in_policy = true;
 177     GetSecureDirectiveValues(directive_name, tokenizer, options, sane_csp_parts,
 178                              warnings);
 179   } else {
 180     // Don't show any errors for duplicate CSP directives, because it will be
 181     // ignored by the CSP parser (http://www.w3.org/TR/CSP2/#policy-parsing).
 182     GetSecureDirectiveValues(directive_name, tokenizer, options, sane_csp_parts,
 183                              NULL);
 184   }
 185   return true;
 186 }
 187
 188 // Returns true if the |plugin_type| is one of the fully sandboxed plugin types.
 189 bool PluginTypeAllowed(const std::string& plugin_type) {
 190   for (size_t i = 0; i < arraysize(kSandboxedPluginTypes); ++i) {
 191     if (plugin_type == kSandboxedPluginTypes[i])
 192       return true;
 193   }
 194   return false;
 195 }
 196
 197 // Returns true if the policy is allowed to contain an insecure object-src
 198 // directive. This requires OPTIONS_ALLOW_INSECURE_OBJECT_SRC to be specified
 199 // as an option and the plugin-types that can be loaded must be restricted to
 200 // the set specified in kSandboxedPluginTypes.
 201 bool AllowedToHaveInsecureObjectSrc(
 202     int options,
 203     const std::vector<std::string>& directives) {
 204   if (!(options & OPTIONS_ALLOW_INSECURE_OBJECT_SRC))
 205     return false;
 206
 207   for (size_t i = 0; i < directives.size(); ++i) {
 208     const std::string& input = directives[i];
 209     base::StringTokenizer tokenizer(input, " \t\r\n");
 210     if (!tokenizer.GetNext())
 211       continue;
 212     if (!LowerCaseEqualsASCII(tokenizer.token(), kPluginTypes))
 213       continue;
 214     while (tokenizer.GetNext()) {
 215       if (!PluginTypeAllowed(tokenizer.token()))
 216         return false;
 217     }
 218     // All listed plugin types are whitelisted.
 219     return true;
 220   }
 221   // plugin-types not specified.
 222   return false;
 223 }
 224
 225 }  //  namespace
 226
 227 bool ContentSecurityPolicyIsLegal(const std::string& policy) {
 228   // We block these characters to prevent HTTP header injection when
 229   // representing the content security policy as an HTTP header.
 230   const char kBadChars[] = {',', '\r', '\n', '\0'};
 231
 232   return policy.find_first_of(kBadChars, 0, arraysize(kBadChars)) ==
 233       std::string::npos;
 234 }
 235
 236 std::string SanitizeContentSecurityPolicy(
 237     const std::string& policy,
 238     int options,
 239     std::vector<InstallWarning>* warnings) {
 240   // See http://www.w3.org/TR/CSP/#parse-a-csp-policy for parsing algorithm.
 241   std::vector<std::string> directives;
 242   base::SplitString(policy, ';', &directives);
 243
 244   DirectiveStatus default_src_status(kDefaultSrc);
 245   DirectiveStatus script_src_status(kScriptSrc);
 246   DirectiveStatus object_src_status(kObjectSrc);
 247
 248   bool allow_insecure_object_src =
 249       AllowedToHaveInsecureObjectSrc(options, directives);
 250
 251   std::vector<std::string> sane_csp_parts;
 252   std::vector<InstallWarning> default_src_csp_warnings;
 253   for (size_t i = 0; i < directives.size(); ++i) {
 254     std::string& input = directives[i];
 255     base::StringTokenizer tokenizer(input, " \t\r\n");
 256     if (!tokenizer.GetNext())
 257       continue;
 258
 259     std::string directive_name = tokenizer.token();
 260     base::StringToLowerASCII(&directive_name);
 261
 262     if (UpdateStatus(directive_name, &tokenizer, &default_src_status, options,
 263                      &sane_csp_parts, &default_src_csp_warnings))
 264       continue;
 265     if (UpdateStatus(directive_name, &tokenizer, &script_src_status, options,
 266                      &sane_csp_parts, warnings))
 267       continue;
 268     if (!allow_insecure_object_src &&
 269         UpdateStatus(directive_name, &tokenizer, &object_src_status, options,
 270                      &sane_csp_parts, warnings))
 271       continue;
 272
 273     // Pass the other CSP directives as-is without further validation.
 274     sane_csp_parts.push_back(input + ";");
 275   }
 276
 277   if (default_src_status.seen_in_policy) {
 278     if (!script_src_status.seen_in_policy ||
 279         !object_src_status.seen_in_policy) {
 280       // Insecure values in default-src are only relevant if either script-src
 281       // or object-src is omitted.
 282       if (warnings)
 283         warnings->insert(warnings->end(),
 284                          default_src_csp_warnings.begin(),
 285                          default_src_csp_warnings.end());
 286     }
 287   } else {
 288     if (!script_src_status.seen_in_policy) {
 289       sane_csp_parts.push_back(kScriptSrcDefaultDirective);
 290       if (warnings)
 291         warnings->push_back(CSPInstallWarning(ErrorUtils::FormatErrorMessage(
 292             manifest_errors::kInvalidCSPMissingSecureSrc, kScriptSrc)));
 293     }
 294     if (!object_src_status.seen_in_policy && !allow_insecure_object_src) {
 295       sane_csp_parts.push_back(kObjectSrcDefaultDirective);
 296       if (warnings)
 297         warnings->push_back(CSPInstallWarning(ErrorUtils::FormatErrorMessage(
 298             manifest_errors::kInvalidCSPMissingSecureSrc, kObjectSrc)));
 299     }
 300   }
 301
 302   return JoinString(sane_csp_parts, ' ');
 303 }
 304
 305 bool ContentSecurityPolicyIsSandboxed(
 306     const std::string& policy, Manifest::Type type) {
 307   // See http://www.w3.org/TR/CSP/#parse-a-csp-policy for parsing algorithm.
 308   std::vector<std::string> directives;
 309   base::SplitString(policy, ';', &directives);
 310
 311   bool seen_sandbox = false;
 312
 313   for (size_t i = 0; i < directives.size(); ++i) {
 314     std::string& input = directives[i];
 315     base::StringTokenizer tokenizer(input, " \t\r\n");
 316     if (!tokenizer.GetNext())
 317       continue;
 318
 319     std::string directive_name = tokenizer.token();
 320     base::StringToLowerASCII(&directive_name);
 321
 322     if (directive_name != kSandboxDirectiveName)
 323       continue;
 324
 325     seen_sandbox = true;
 326
 327     while (tokenizer.GetNext()) {
 328       std::string token = tokenizer.token();
 329       base::StringToLowerASCII(&token);
 330
 331       // The same origin token negates the sandboxing.
 332       if (token == kAllowSameOriginToken)
 333         return false;
 334
 335       // Platform apps don't allow navigation.
 336       if (type == Manifest::TYPE_PLATFORM_APP) {
 337         if (token == kAllowTopNavigation)
 338           return false;
 339       }
 340     }
 341   }
 342
 343   return seen_sandbox;
 344 }
 345
 346 }  // namespace csp_validator
 347
 348 }  // namespace extensions