csp_validator.cc revision 03b57e008b61dfcb1fbad3aea950ae0e001748b0 
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
16namespace extensions {
17
18namespace csp_validator {
19
20namespace {
21
22const char kDefaultSrc[] = "default-src";
23const char kScriptSrc[] = "script-src";
24const char kObjectSrc[] = "object-src";
25
26const char kSandboxDirectiveName[] = "sandbox";
27const char kAllowSameOriginToken[] = "allow-same-origin";
28const char kAllowTopNavigation[] = "allow-top-navigation";
29
30struct 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".
45bool 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  // Wildcards on subdomains of a TLD are not allowed.
91  size_t registry_length = net::registry_controlled_domains::GetRegistryLength(
92      host,
93      net::registry_controlled_domains::INCLUDE_UNKNOWN_REGISTRIES,
94      net::registry_controlled_domains::INCLUDE_PRIVATE_REGISTRIES);
95  return registry_length != 0;
96}
97
98bool HasOnlySecureTokens(base::StringTokenizer& tokenizer,
99                         Manifest::Type type) {
100  while (tokenizer.GetNext()) {
101    std::string source = tokenizer.token();
102    base::StringToLowerASCII(&source);
103
104    // We might need to relax this whitelist over time.
105    if (source == "'self'" ||
106        source == "'none'" ||
107        source == "http://127.0.0.1" ||
108        LowerCaseEqualsASCII(source, "blob:") ||
109        LowerCaseEqualsASCII(source, "filesystem:") ||
110        LowerCaseEqualsASCII(source, "http://localhost") ||
111        StartsWithASCII(source, "http://127.0.0.1:", true) ||
112        StartsWithASCII(source, "http://localhost:", true) ||
113        isNonWildcardTLD(source, "https://", true) ||
114        isNonWildcardTLD(source, "chrome://", false) ||
115        isNonWildcardTLD(source,
116                         std::string(extensions::kExtensionScheme) +
117                         url::kStandardSchemeSeparator,
118                         false) ||
119        StartsWithASCII(source, "chrome-extension-resource:", true)) {
120      continue;
121    }
122
123    // crbug.com/146487
124    if (type == Manifest::TYPE_EXTENSION ||
125        type == Manifest::TYPE_LEGACY_PACKAGED_APP) {
126      if (source == "'unsafe-eval'")
127        continue;
128    }
129
130    return false;
131  }
132
133  return true;  // Empty values default to 'none', which is secure.
134}
135
136// Returns true if |directive_name| matches |status.directive_name|.
137bool UpdateStatus(const std::string& directive_name,
138                  base::StringTokenizer& tokenizer,
139                  DirectiveStatus* status,
140                  Manifest::Type type) {
141  if (status->seen_in_policy)
142    return false;
143  if (directive_name != status->directive_name)
144    return false;
145  status->seen_in_policy = true;
146  status->is_secure = HasOnlySecureTokens(tokenizer, type);
147  return true;
148}
149
150}  //  namespace
151
152bool ContentSecurityPolicyIsLegal(const std::string& policy) {
153  // We block these characters to prevent HTTP header injection when
154  // representing the content security policy as an HTTP header.
155  const char kBadChars[] = {',', '\r', '\n', '\0'};
156
157  return policy.find_first_of(kBadChars, 0, arraysize(kBadChars)) ==
158      std::string::npos;
159}
160
161bool ContentSecurityPolicyIsSecure(const std::string& policy,
162                                   Manifest::Type type) {
163  // See http://www.w3.org/TR/CSP/#parse-a-csp-policy for parsing algorithm.
164  std::vector<std::string> directives;
165  base::SplitString(policy, ';', &directives);
166
167  DirectiveStatus default_src_status(kDefaultSrc);
168  DirectiveStatus script_src_status(kScriptSrc);
169  DirectiveStatus object_src_status(kObjectSrc);
170
171  for (size_t i = 0; i < directives.size(); ++i) {
172    std::string& input = directives[i];
173    base::StringTokenizer tokenizer(input, " \t\r\n");
174    if (!tokenizer.GetNext())
175      continue;
176
177    std::string directive_name = tokenizer.token();
178    base::StringToLowerASCII(&directive_name);
179
180    if (UpdateStatus(directive_name, tokenizer, &default_src_status, type))
181      continue;
182    if (UpdateStatus(directive_name, tokenizer, &script_src_status, type))
183      continue;
184    if (UpdateStatus(directive_name, tokenizer, &object_src_status, type))
185      continue;
186  }
187
188  if (script_src_status.seen_in_policy && !script_src_status.is_secure)
189    return false;
190
191  if (object_src_status.seen_in_policy && !object_src_status.is_secure)
192    return false;
193
194  if (default_src_status.seen_in_policy && !default_src_status.is_secure) {
195    return script_src_status.seen_in_policy &&
196           object_src_status.seen_in_policy;
197  }
198
199  return default_src_status.seen_in_policy ||
200      (script_src_status.seen_in_policy && object_src_status.seen_in_policy);
201}
202
203bool ContentSecurityPolicyIsSandboxed(
204    const std::string& policy, Manifest::Type type) {
205  // See http://www.w3.org/TR/CSP/#parse-a-csp-policy for parsing algorithm.
206  std::vector<std::string> directives;
207  base::SplitString(policy, ';', &directives);
208
209  bool seen_sandbox = false;
210
211  for (size_t i = 0; i < directives.size(); ++i) {
212    std::string& input = directives[i];
213    base::StringTokenizer tokenizer(input, " \t\r\n");
214    if (!tokenizer.GetNext())
215      continue;
216
217    std::string directive_name = tokenizer.token();
218    base::StringToLowerASCII(&directive_name);
219
220    if (directive_name != kSandboxDirectiveName)
221      continue;
222
223    seen_sandbox = true;
224
225    while (tokenizer.GetNext()) {
226      std::string token = tokenizer.token();
227      base::StringToLowerASCII(&token);
228
229      // The same origin token negates the sandboxing.
230      if (token == kAllowSameOriginToken)
231        return false;
232
233      // Platform apps don't allow navigation.
234      if (type == Manifest::TYPE_PLATFORM_APP) {
235        if (token == kAllowTopNavigation)
236          return false;
237      }
238    }
239  }
240
241  return seen_sandbox;
242}
243
244}  // namespace csp_validator
245
246}  // namespace extensions
247