| // Copyright 2015 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 "net/cert/internal/name_constraints.h" |
| |
| #include <limits.h> |
| |
| #include <memory> |
| |
| #include "base/logging.h" |
| #include "base/numerics/clamped_math.h" |
| #include "base/strings/string_util.h" |
| #include "net/cert/internal/cert_errors.h" |
| #include "net/cert/internal/common_cert_errors.h" |
| #include "net/cert/internal/verify_name_match.h" |
| #include "net/der/input.h" |
| #include "net/der/parser.h" |
| #include "net/der/tag.h" |
| #include "starboard/types.h" |
| |
| namespace net { |
| |
| namespace { |
| |
| // The name types of GeneralName that are fully supported in name constraints. |
| // |
| // (The other types will have the minimal checking described by RFC 5280 |
| // section 4.2.1.10: If a name constraints extension that is marked as critical |
| // imposes constraints on a particular name form, and an instance of |
| // that name form appears in the subject field or subjectAltName |
| // extension of a subsequent certificate, then the application MUST |
| // either process the constraint or reject the certificate.) |
| const int kSupportedNameTypes = GENERAL_NAME_DNS_NAME | |
| GENERAL_NAME_DIRECTORY_NAME | |
| GENERAL_NAME_IP_ADDRESS; |
| |
| // Controls wildcard handling of DNSNameMatches. |
| // If WildcardMatchType is WILDCARD_PARTIAL_MATCH "*.bar.com" is considered to |
| // match the constraint "foo.bar.com". If it is WILDCARD_FULL_MATCH, "*.bar.com" |
| // will match "bar.com" but not "foo.bar.com". |
| enum WildcardMatchType { WILDCARD_PARTIAL_MATCH, WILDCARD_FULL_MATCH }; |
| |
| // Returns true if |name| falls in the subtree defined by |dns_constraint|. |
| // RFC 5280 section 4.2.1.10: |
| // DNS name restrictions are expressed as host.example.com. Any DNS |
| // name that can be constructed by simply adding zero or more labels |
| // to the left-hand side of the name satisfies the name constraint. For |
| // example, www.host.example.com would satisfy the constraint but |
| // host1.example.com would not. |
| // |
| // |wildcard_matching| controls handling of wildcard names (|name| starts with |
| // "*."). Wildcard handling is not specified by RFC 5280, but certificate |
| // verification allows it, name constraints must check it similarly. |
| bool DNSNameMatches(base::StringPiece name, |
| base::StringPiece dns_constraint, |
| WildcardMatchType wildcard_matching) { |
| // Everything matches the empty DNS name constraint. |
| if (dns_constraint.empty()) |
| return true; |
| |
| // Normalize absolute DNS names by removing the trailing dot, if any. |
| if (!name.empty() && *name.rbegin() == '.') |
| name.remove_suffix(1); |
| if (!dns_constraint.empty() && *dns_constraint.rbegin() == '.') |
| dns_constraint.remove_suffix(1); |
| |
| // Wildcard partial-match handling ("*.bar.com" matching name constraint |
| // "foo.bar.com"). This only handles the case where the the dnsname and the |
| // constraint match after removing the leftmost label, otherwise it is handled |
| // by falling through to the check of whether the dnsname is fully within or |
| // fully outside of the constraint. |
| if (wildcard_matching == WILDCARD_PARTIAL_MATCH && name.size() > 2 && |
| name[0] == '*' && name[1] == '.') { |
| size_t dns_constraint_dot_pos = dns_constraint.find('.'); |
| if (dns_constraint_dot_pos != std::string::npos) { |
| base::StringPiece dns_constraint_domain( |
| dns_constraint.begin() + dns_constraint_dot_pos + 1, |
| dns_constraint.size() - dns_constraint_dot_pos - 1); |
| base::StringPiece wildcard_domain(name.begin() + 2, name.size() - 2); |
| if (base::EqualsCaseInsensitiveASCII(wildcard_domain, |
| dns_constraint_domain)) { |
| return true; |
| } |
| } |
| } |
| |
| if (!base::EndsWith(name, dns_constraint, |
| base::CompareCase::INSENSITIVE_ASCII)) { |
| return false; |
| } |
| // Exact match. |
| if (name.size() == dns_constraint.size()) |
| return true; |
| // If dNSName constraint starts with a dot, only subdomains should match. |
| // (e.g., "foo.bar.com" matches constraint ".bar.com", but "bar.com" doesn't.) |
| // RFC 5280 is ambiguous, but this matches the behavior of other platforms. |
| if (!dns_constraint.empty() && dns_constraint[0] == '.') |
| dns_constraint.remove_prefix(1); |
| // Subtree match. |
| if (name.size() > dns_constraint.size() && |
| name[name.size() - dns_constraint.size() - 1] == '.') { |
| return true; |
| } |
| // Trailing text matches, but not in a subtree (e.g., "foobar.com" is not a |
| // match for "bar.com"). |
| return false; |
| } |
| |
| // Parses a GeneralSubtrees |value| and store the contents in |subtrees|. |
| // The individual values stored into |subtrees| are not validated by this |
| // function. |
| // NOTE: |subtrees| is not pre-initialized by the function(it is expected to be |
| // a default initialized object), and it will be modified regardless of the |
| // return value. |
| WARN_UNUSED_RESULT bool ParseGeneralSubtrees(const der::Input& value, |
| GeneralNames* subtrees, |
| CertErrors* errors) { |
| DCHECK(errors); |
| |
| // GeneralSubtrees ::= SEQUENCE SIZE (1..MAX) OF GeneralSubtree |
| // |
| // GeneralSubtree ::= SEQUENCE { |
| // base GeneralName, |
| // minimum [0] BaseDistance DEFAULT 0, |
| // maximum [1] BaseDistance OPTIONAL } |
| // |
| // BaseDistance ::= INTEGER (0..MAX) |
| der::Parser sequence_parser(value); |
| // The GeneralSubtrees sequence should have at least 1 element. |
| if (!sequence_parser.HasMore()) |
| return false; |
| while (sequence_parser.HasMore()) { |
| der::Parser subtree_sequence; |
| if (!sequence_parser.ReadSequence(&subtree_sequence)) |
| return false; |
| |
| der::Input raw_general_name; |
| if (!subtree_sequence.ReadRawTLV(&raw_general_name)) |
| return false; |
| |
| if (!ParseGeneralName( |
| raw_general_name, |
| GeneralNames::IP_ADDRESS_AND_NETMASK, subtrees, errors)) { |
| errors->AddError(kFailedParsingGeneralName); |
| return false; |
| } |
| |
| // RFC 5280 section 4.2.1.10: |
| // Within this profile, the minimum and maximum fields are not used with any |
| // name forms, thus, the minimum MUST be zero, and maximum MUST be absent. |
| // However, if an application encounters a critical name constraints |
| // extension that specifies other values for minimum or maximum for a name |
| // form that appears in a subsequent certificate, the application MUST |
| // either process these fields or reject the certificate. |
| |
| // Note that technically failing here isn't required: rather only need to |
| // fail if a name of this type actually appears in a subsequent cert and |
| // this extension was marked critical. However the minimum and maximum |
| // fields appear uncommon enough that implementing that isn't useful. |
| if (subtree_sequence.HasMore()) |
| return false; |
| } |
| return true; |
| } |
| |
| } // namespace |
| |
| NameConstraints::~NameConstraints() = default; |
| |
| // static |
| std::unique_ptr<NameConstraints> NameConstraints::Create( |
| const der::Input& extension_value, |
| bool is_critical, |
| CertErrors* errors) { |
| DCHECK(errors); |
| |
| std::unique_ptr<NameConstraints> name_constraints(new NameConstraints()); |
| if (!name_constraints->Parse(extension_value, is_critical, errors)) |
| return nullptr; |
| return name_constraints; |
| } |
| |
| bool NameConstraints::Parse(const der::Input& extension_value, |
| bool is_critical, |
| CertErrors* errors) { |
| DCHECK(errors); |
| |
| der::Parser extension_parser(extension_value); |
| der::Parser sequence_parser; |
| |
| // NameConstraints ::= SEQUENCE { |
| // permittedSubtrees [0] GeneralSubtrees OPTIONAL, |
| // excludedSubtrees [1] GeneralSubtrees OPTIONAL } |
| if (!extension_parser.ReadSequence(&sequence_parser)) |
| return false; |
| if (extension_parser.HasMore()) |
| return false; |
| |
| bool had_permitted_subtrees = false; |
| der::Input permitted_subtrees_value; |
| if (!sequence_parser.ReadOptionalTag(der::ContextSpecificConstructed(0), |
| &permitted_subtrees_value, |
| &had_permitted_subtrees)) { |
| return false; |
| } |
| if (had_permitted_subtrees && |
| !ParseGeneralSubtrees(permitted_subtrees_value, &permitted_subtrees_, |
| errors)) { |
| return false; |
| } |
| constrained_name_types_ |= |
| permitted_subtrees_.present_name_types & |
| (is_critical ? GENERAL_NAME_ALL_TYPES : kSupportedNameTypes); |
| |
| bool had_excluded_subtrees = false; |
| der::Input excluded_subtrees_value; |
| if (!sequence_parser.ReadOptionalTag(der::ContextSpecificConstructed(1), |
| &excluded_subtrees_value, |
| &had_excluded_subtrees)) { |
| return false; |
| } |
| if (had_excluded_subtrees && |
| !ParseGeneralSubtrees(excluded_subtrees_value, &excluded_subtrees_, |
| errors)) { |
| return false; |
| } |
| constrained_name_types_ |= |
| excluded_subtrees_.present_name_types & |
| (is_critical ? GENERAL_NAME_ALL_TYPES : kSupportedNameTypes); |
| |
| // RFC 5280 section 4.2.1.10: |
| // Conforming CAs MUST NOT issue certificates where name constraints is an |
| // empty sequence. That is, either the permittedSubtrees field or the |
| // excludedSubtrees MUST be present. |
| if (!had_permitted_subtrees && !had_excluded_subtrees) |
| return false; |
| |
| if (sequence_parser.HasMore()) |
| return false; |
| |
| return true; |
| } |
| |
| void NameConstraints::IsPermittedCert(const der::Input& subject_rdn_sequence, |
| const GeneralNames* subject_alt_names, |
| CertErrors* errors) const { |
| // Checking NameConstraints is O(number_of_names * number_of_constraints). |
| // Impose a hard limit to mitigate the use of name constraints as a DoS |
| // mechanism. |
| const size_t kMaxChecks = 1048576; // 1 << 20 |
| base::ClampedNumeric<size_t> check_count = 0; |
| |
| if (subject_alt_names) { |
| check_count += |
| base::ClampMul(subject_alt_names->dns_names.size(), |
| base::ClampAdd(excluded_subtrees_.dns_names.size(), |
| permitted_subtrees_.dns_names.size())); |
| check_count += base::ClampMul( |
| subject_alt_names->directory_names.size(), |
| base::ClampAdd(excluded_subtrees_.directory_names.size(), |
| permitted_subtrees_.directory_names.size())); |
| check_count += base::ClampMul( |
| subject_alt_names->ip_addresses.size(), |
| base::ClampAdd(excluded_subtrees_.ip_address_ranges.size(), |
| permitted_subtrees_.ip_address_ranges.size())); |
| } |
| |
| if (!(subject_alt_names && subject_rdn_sequence.Length() == 0)) { |
| check_count += base::ClampAdd(excluded_subtrees_.directory_names.size(), |
| permitted_subtrees_.directory_names.size()); |
| } |
| |
| if (check_count > kMaxChecks) { |
| errors->AddError(cert_errors::kTooManyNameConstraintChecks); |
| return; |
| } |
| |
| // Subject Alternative Name handling: |
| // |
| // RFC 5280 section 4.2.1.6: |
| // id-ce-subjectAltName OBJECT IDENTIFIER ::= { id-ce 17 } |
| // |
| // SubjectAltName ::= GeneralNames |
| // |
| // GeneralNames ::= SEQUENCE SIZE (1..MAX) OF GeneralName |
| |
| if (subject_alt_names) { |
| // Check unsupported name types: |
| // constrained_name_types() for the unsupported types will only be true if |
| // that type of name was present in a name constraint that was marked |
| // critical. |
| // |
| // RFC 5280 section 4.2.1.10: |
| // If a name constraints extension that is marked as critical |
| // imposes constraints on a particular name form, and an instance of |
| // that name form appears in the subject field or subjectAltName |
| // extension of a subsequent certificate, then the application MUST |
| // either process the constraint or reject the certificate. |
| if (constrained_name_types() & subject_alt_names->present_name_types & |
| ~kSupportedNameTypes) { |
| errors->AddError(cert_errors::kNotPermittedByNameConstraints); |
| return; |
| } |
| |
| // Check supported name types: |
| for (const auto& dns_name : subject_alt_names->dns_names) { |
| if (!IsPermittedDNSName(dns_name)) { |
| errors->AddError(cert_errors::kNotPermittedByNameConstraints); |
| return; |
| } |
| } |
| |
| for (const auto& directory_name : subject_alt_names->directory_names) { |
| if (!IsPermittedDirectoryName(directory_name)) { |
| errors->AddError(cert_errors::kNotPermittedByNameConstraints); |
| return; |
| } |
| } |
| |
| for (const auto& ip_address : subject_alt_names->ip_addresses) { |
| if (!IsPermittedIP(ip_address)) { |
| errors->AddError(cert_errors::kNotPermittedByNameConstraints); |
| return; |
| } |
| } |
| } |
| |
| // Subject handling: |
| |
| // RFC 5280 section 4.2.1.10: |
| // Legacy implementations exist where an electronic mail address is embedded |
| // in the subject distinguished name in an attribute of type emailAddress |
| // (Section 4.1.2.6). When constraints are imposed on the rfc822Name name |
| // form, but the certificate does not include a subject alternative name, the |
| // rfc822Name constraint MUST be applied to the attribute of type emailAddress |
| // in the subject distinguished name. |
| if (!subject_alt_names && |
| (constrained_name_types() & GENERAL_NAME_RFC822_NAME)) { |
| bool contained_email_address = false; |
| if (!NameContainsEmailAddress(subject_rdn_sequence, |
| &contained_email_address)) { |
| errors->AddError(cert_errors::kNotPermittedByNameConstraints); |
| return; |
| } |
| if (contained_email_address) { |
| errors->AddError(cert_errors::kNotPermittedByNameConstraints); |
| return; |
| } |
| } |
| |
| // RFC 5280 4.1.2.6: |
| // If subject naming information is present only in the subjectAltName |
| // extension (e.g., a key bound only to an email address or URI), then the |
| // subject name MUST be an empty sequence and the subjectAltName extension |
| // MUST be critical. |
| // This code assumes that criticality condition is checked by the caller, and |
| // therefore only needs to avoid the IsPermittedDirectoryName check against an |
| // empty subject in such a case. |
| if (subject_alt_names && subject_rdn_sequence.Length() == 0) |
| return; |
| |
| if (!IsPermittedDirectoryName(subject_rdn_sequence)) { |
| errors->AddError(cert_errors::kNotPermittedByNameConstraints); |
| return; |
| } |
| } |
| |
| bool NameConstraints::IsPermittedDNSName(base::StringPiece name) const { |
| for (const auto& excluded_name : excluded_subtrees_.dns_names) { |
| // When matching wildcard hosts against excluded subtrees, consider it a |
| // match if the constraint would match any expansion of the wildcard. Eg, |
| // *.bar.com should match a constraint of foo.bar.com. |
| if (DNSNameMatches(name, excluded_name, WILDCARD_PARTIAL_MATCH)) |
| return false; |
| } |
| |
| // If permitted subtrees are not constrained, any name that is not excluded is |
| // allowed. |
| if (!(permitted_subtrees_.present_name_types & GENERAL_NAME_DNS_NAME)) |
| return true; |
| |
| for (const auto& permitted_name : permitted_subtrees_.dns_names) { |
| // When matching wildcard hosts against permitted subtrees, consider it a |
| // match only if the constraint would match all expansions of the wildcard. |
| // Eg, *.bar.com should match a constraint of bar.com, but not foo.bar.com. |
| if (DNSNameMatches(name, permitted_name, WILDCARD_FULL_MATCH)) |
| return true; |
| } |
| |
| return false; |
| } |
| |
| bool NameConstraints::IsPermittedDirectoryName( |
| const der::Input& name_rdn_sequence) const { |
| for (const auto& excluded_name : excluded_subtrees_.directory_names) { |
| if (VerifyNameInSubtree(name_rdn_sequence, excluded_name)) |
| return false; |
| } |
| |
| // If permitted subtrees are not constrained, any name that is not excluded is |
| // allowed. |
| if (!(permitted_subtrees_.present_name_types & GENERAL_NAME_DIRECTORY_NAME)) |
| return true; |
| |
| for (const auto& permitted_name : permitted_subtrees_.directory_names) { |
| if (VerifyNameInSubtree(name_rdn_sequence, permitted_name)) |
| return true; |
| } |
| |
| return false; |
| } |
| |
| bool NameConstraints::IsPermittedIP(const IPAddress& ip) const { |
| for (const auto& excluded_ip : excluded_subtrees_.ip_address_ranges) { |
| if (IPAddressMatchesPrefix(ip, excluded_ip.first, excluded_ip.second)) |
| return false; |
| } |
| |
| // If permitted subtrees are not constrained, any name that is not excluded is |
| // allowed. |
| if (!(permitted_subtrees_.present_name_types & GENERAL_NAME_IP_ADDRESS)) |
| return true; |
| |
| for (const auto& permitted_ip : permitted_subtrees_.ip_address_ranges) { |
| if (IPAddressMatchesPrefix(ip, permitted_ip.first, permitted_ip.second)) |
| return true; |
| } |
| |
| return false; |
| } |
| |
| } // namespace net |
