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 (!base::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 = base::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'" || source == "'none'" ||
 132         source == "http://127.0.0.1" ||
 133         base::LowerCaseEqualsASCII(source, "blob:") ||
 134         base::LowerCaseEqualsASCII(source, "filesystem:") ||
 135         base::LowerCaseEqualsASCII(source, "http://localhost") ||
 136         base::StartsWithASCII(source, "http://127.0.0.1:", true) ||
 137         base::StartsWithASCII(source, "http://localhost:", true) ||
 138         isNonWildcardTLD(source, "https://", true) ||
 139         isNonWildcardTLD(source, "chrome://", false) ||
 140         isNonWildcardTLD(source, std::string(extensions::kExtensionScheme) +
 141                                      url::kStandardSchemeSeparator,
 142                          false) ||
 143         base::StartsWithASCII(source, "chrome-extension-resource:", true)) {
 144       is_secure_csp_token = true;
 145     } else if ((options & OPTIONS_ALLOW_UNSAFE_EVAL) &&
 146                source == "'unsafe-eval'") {
 147       is_secure_csp_token = true;
 148     }
 149
 150     if (is_secure_csp_token) {
 151       sane_csp_parts->push_back(source);
 152     } else if (warnings) {
 153       warnings->push_back(CSPInstallWarning(ErrorUtils::FormatErrorMessage(
 154           manifest_errors::kInvalidCSPInsecureValue, source, directive_name)));
 155     }
 156   }
 157   // End of CSP directive that was started at the beginning of this method. If
 158   // none of the values are secure, the policy will be empty and default to
 159   // 'none', which is secure.
 160   sane_csp_parts->back().push_back(';');
 161 }
 162
 163 // Returns true if |directive_name| matches |status.directive_name|.
 164 bool UpdateStatus(const std::string& directive_name,
 165                   base::StringTokenizer* tokenizer,
 166                   DirectiveStatus* status,
 167                   int options,
 168                   std::vector<std::string>* sane_csp_parts,
 169                   std::vector<InstallWarning>* warnings) {
 170   if (directive_name != status->directive_name)
 171     return false;
 172
 173   if (!status->seen_in_policy) {
 174     status->seen_in_policy = true;
 175     GetSecureDirectiveValues(directive_name, tokenizer, options, sane_csp_parts,
 176                              warnings);
 177   } else {
 178     // Don't show any errors for duplicate CSP directives, because it will be
 179     // ignored by the CSP parser (http://www.w3.org/TR/CSP2/#policy-parsing).
 180     GetSecureDirectiveValues(directive_name, tokenizer, options, sane_csp_parts,
 181                              NULL);
 182   }
 183   return true;
 184 }
 185
 186 // Returns true if the |plugin_type| is one of the fully sandboxed plugin types.
 187 bool PluginTypeAllowed(const std::string& plugin_type) {
 188   for (size_t i = 0; i < arraysize(kSandboxedPluginTypes); ++i) {
 189     if (plugin_type == kSandboxedPluginTypes[i])
 190       return true;
 191   }
 192   return false;
 193 }
 194
 195 // Returns true if the policy is allowed to contain an insecure object-src
 196 // directive. This requires OPTIONS_ALLOW_INSECURE_OBJECT_SRC to be specified
 197 // as an option and the plugin-types that can be loaded must be restricted to
 198 // the set specified in kSandboxedPluginTypes.
 199 bool AllowedToHaveInsecureObjectSrc(
 200     int options,
 201     const std::vector<std::string>& directives) {
 202   if (!(options & OPTIONS_ALLOW_INSECURE_OBJECT_SRC))
 203     return false;
 204
 205   for (size_t i = 0; i < directives.size(); ++i) {
 206     const std::string& input = directives[i];
 207     base::StringTokenizer tokenizer(input, " \t\r\n");
 208     if (!tokenizer.GetNext())
 209       continue;
 210     if (!base::LowerCaseEqualsASCII(tokenizer.token(), kPluginTypes))
 211       continue;
 212     while (tokenizer.GetNext()) {
 213       if (!PluginTypeAllowed(tokenizer.token()))
 214         return false;
 215     }
 216     // All listed plugin types are whitelisted.
 217     return true;
 218   }
 219   // plugin-types not specified.
 220   return false;
 221 }
 222
 223 }  //  namespace
 224
 225 bool ContentSecurityPolicyIsLegal(const std::string& policy) {
 226   // We block these characters to prevent HTTP header injection when
 227   // representing the content security policy as an HTTP header.
 228   const char kBadChars[] = {',', '\r', '\n', '\0'};
 229
 230   return policy.find_first_of(kBadChars, 0, arraysize(kBadChars)) ==
 231       std::string::npos;
 232 }
 233
 234 std::string SanitizeContentSecurityPolicy(
 235     const std::string& policy,
 236     int options,
 237     std::vector<InstallWarning>* warnings) {
 238   // See http://www.w3.org/TR/CSP/#parse-a-csp-policy for parsing algorithm.
 239   std::vector<std::string> directives;
 240   base::SplitString(policy, ';', &directives);
 241
 242   DirectiveStatus default_src_status(kDefaultSrc);
 243   DirectiveStatus script_src_status(kScriptSrc);
 244   DirectiveStatus object_src_status(kObjectSrc);
 245
 246   bool allow_insecure_object_src =
 247       AllowedToHaveInsecureObjectSrc(options, directives);
 248
 249   std::vector<std::string> sane_csp_parts;
 250   std::vector<InstallWarning> default_src_csp_warnings;
 251   for (size_t i = 0; i < directives.size(); ++i) {
 252     std::string& input = directives[i];
 253     base::StringTokenizer tokenizer(input, " \t\r\n");
 254     if (!tokenizer.GetNext())
 255       continue;
 256
 257     std::string directive_name = tokenizer.token();
 258     base::StringToLowerASCII(&directive_name);
 259
 260     if (UpdateStatus(directive_name, &tokenizer, &default_src_status, options,
 261                      &sane_csp_parts, &default_src_csp_warnings))
 262       continue;
 263     if (UpdateStatus(directive_name, &tokenizer, &script_src_status, options,
 264                      &sane_csp_parts, warnings))
 265       continue;
 266     if (!allow_insecure_object_src &&
 267         UpdateStatus(directive_name, &tokenizer, &object_src_status, options,
 268                      &sane_csp_parts, warnings))
 269       continue;
 270
 271     // Pass the other CSP directives as-is without further validation.
 272     sane_csp_parts.push_back(input + ";");
 273   }
 274
 275   if (default_src_status.seen_in_policy) {
 276     if (!script_src_status.seen_in_policy ||
 277         !object_src_status.seen_in_policy) {
 278       // Insecure values in default-src are only relevant if either script-src
 279       // or object-src is omitted.
 280       if (warnings)
 281         warnings->insert(warnings->end(),
 282                          default_src_csp_warnings.begin(),
 283                          default_src_csp_warnings.end());
 284     }
 285   } else {
 286     if (!script_src_status.seen_in_policy) {
 287       sane_csp_parts.push_back(kScriptSrcDefaultDirective);
 288       if (warnings)
 289         warnings->push_back(CSPInstallWarning(ErrorUtils::FormatErrorMessage(
 290             manifest_errors::kInvalidCSPMissingSecureSrc, kScriptSrc)));
 291     }
 292     if (!object_src_status.seen_in_policy && !allow_insecure_object_src) {
 293       sane_csp_parts.push_back(kObjectSrcDefaultDirective);
 294       if (warnings)
 295         warnings->push_back(CSPInstallWarning(ErrorUtils::FormatErrorMessage(
 296             manifest_errors::kInvalidCSPMissingSecureSrc, kObjectSrc)));
 297     }
 298   }
 299
 300   return JoinString(sane_csp_parts, ' ');
 301 }
 302
 303 bool ContentSecurityPolicyIsSandboxed(
 304     const std::string& policy, Manifest::Type type) {
 305   // See http://www.w3.org/TR/CSP/#parse-a-csp-policy for parsing algorithm.
 306   std::vector<std::string> directives;
 307   base::SplitString(policy, ';', &directives);
 308
 309   bool seen_sandbox = false;
 310
 311   for (size_t i = 0; i < directives.size(); ++i) {
 312     std::string& input = directives[i];
 313     base::StringTokenizer tokenizer(input, " \t\r\n");
 314     if (!tokenizer.GetNext())
 315       continue;
 316
 317     std::string directive_name = tokenizer.token();
 318     base::StringToLowerASCII(&directive_name);
 319
 320     if (directive_name != kSandboxDirectiveName)
 321       continue;
 322
 323     seen_sandbox = true;
 324
 325     while (tokenizer.GetNext()) {
 326       std::string token = tokenizer.token();
 327       base::StringToLowerASCII(&token);
 328
 329       // The same origin token negates the sandboxing.
 330       if (token == kAllowSameOriginToken)
 331         return false;
 332
 333       // Platform apps don't allow navigation.
 334       if (type == Manifest::TYPE_PLATFORM_APP) {
 335         if (token == kAllowTopNavigation)
 336           return false;
 337       }
 338     }
 339   }
 340
 341   return seen_sandbox;
 342 }
 343
 344 }  // namespace csp_validator
 345
 346 }  // namespace extensions