| // Copyright 2018 The Chromium OS 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 "shill/dns_util.h" |
| |
| #include <errno.h> |
| #include <limits.h> |
| #include <netinet/in.h> |
| |
| #include <cstring> |
| |
| #include <base/metrics/field_trial.h> |
| #include <base/metrics/histogram_macros.h> |
| #include <base/strings/string_number_conversions.h> |
| #include <base/strings/string_split.h> |
| |
| namespace { |
| |
| // RFC 1035, section 2.3.4: labels 63 octets or less. |
| // Section 3.1: Each label is represented as a one octet length field followed |
| // by that number of octets. |
| const int kMaxLabelLength = 63; |
| |
| // RFC 1035, section 3.1: To simplify implementations, the total length of |
| // a domain name (i.e., label octets and label length octets) is restricted |
| // to 255 octets or less. |
| const int kMaxNameLength = 255; |
| |
| } // namespace |
| |
| namespace shill { |
| |
| // Based on DJB's public domain code. |
| bool DNSDomainFromDot(const base::StringPiece& dotted, std::string* out) { |
| const char* buf = dotted.data(); |
| size_t n = dotted.size(); |
| char label[kMaxLabelLength]; |
| size_t labellen = 0; /* <= sizeof label */ |
| char name[kMaxNameLength]; |
| size_t namelen = 0; /* <= sizeof name */ |
| char ch; |
| |
| for (;;) { |
| if (!n) |
| break; |
| ch = *buf++; |
| --n; |
| if (ch == '.') { |
| // Don't allow empty labels per http://crbug.com/456391. |
| if (!labellen) |
| return false; |
| if (namelen + labellen + 1 > sizeof name) |
| return false; |
| name[namelen++] = static_cast<char>(labellen); |
| memcpy(name + namelen, label, labellen); |
| namelen += labellen; |
| labellen = 0; |
| continue; |
| } |
| if (labellen >= sizeof label) |
| return false; |
| if (!IsValidHostLabelCharacter(ch, labellen == 0)) { |
| return false; |
| } |
| label[labellen++] = ch; |
| } |
| |
| // Allow empty label at end of name to disable suffix search. |
| if (labellen) { |
| if (namelen + labellen + 1 > sizeof name) |
| return false; |
| name[namelen++] = static_cast<char>(labellen); |
| memcpy(name + namelen, label, labellen); |
| namelen += labellen; |
| labellen = 0; |
| } |
| |
| if (namelen + 1 > sizeof name) |
| return false; |
| if (namelen == 0) // Empty names e.g. "", "." are not valid. |
| return false; |
| name[namelen++] = 0; // This is the root label (of length 0). |
| |
| *out = std::string(name, namelen); |
| return true; |
| } |
| |
| bool IsValidDNSDomain(const base::StringPiece& dotted) { |
| std::string dns_formatted; |
| return DNSDomainFromDot(dotted, &dns_formatted); |
| } |
| |
| bool IsValidHostLabelCharacter(char c, bool is_first_char) { |
| return (c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z') || |
| (c >= '0' && c <= '9') || (!is_first_char && c == '-') || c == '_'; |
| } |
| |
| } // namespace shill |