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// Copyright (c) 2011 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/base/dns_util.h"
#include <cstring>
namespace net {
// Based on DJB's public domain code.
bool DNSDomainFromDot(const base::StringPiece& dotted, std::string* out) {
const char* buf = dotted.data();
unsigned n = dotted.size();
char label[63];
unsigned int labellen = 0; /* <= sizeof label */
char name[255];
unsigned int namelen = 0; /* <= sizeof name */
char ch;
for (;;) {
if (!n)
break;
ch = *buf++;
--n;
if (ch == '.') {
if (labellen) {
if (namelen + labellen + 1 > sizeof name)
return false;
name[namelen++] = labellen;
memcpy(name + namelen, label, labellen);
namelen += labellen;
labellen = 0;
}
continue;
}
if (labellen >= sizeof label)
return false;
label[labellen++] = ch;
}
if (labellen) {
if (namelen + labellen + 1 > sizeof name)
return false;
name[namelen++] = labellen;
memcpy(name + namelen, label, labellen);
namelen += labellen;
labellen = 0;
}
if (namelen + 1 > sizeof name)
return false;
name[namelen++] = 0; // This is the root label (of length 0).
*out = std::string(name, namelen);
return true;
}
std::string DNSDomainToString(const base::StringPiece& domain) {
std::string ret;
for (unsigned i = 0; i < domain.size() && domain[i]; i += domain[i] + 1) {
#if CHAR_MIN < 0
if (domain[i] < 0)
return "";
#endif
if (domain[i] > 63)
return "";
if (i)
ret += ".";
if (static_cast<unsigned>(domain[i]) + i + 1 > domain.size())
return "";
domain.substr(i + 1, domain[i]).AppendToString(&ret);
}
return ret;
}
bool IsSTD3ASCIIValidCharacter(char c) {
if (c <= 0x2c)
return false;
if (c >= 0x7b)
return false;
if (c >= 0x2e && c <= 0x2f)
return false;
if (c >= 0x3a && c <= 0x40)
return false;
if (c >= 0x5b && c <= 0x60)
return false;
return true;
}
std::string TrimEndingDot(const base::StringPiece& host) {
base::StringPiece host_trimmed = host;
size_t len = host_trimmed.length();
if (len > 1 && host_trimmed[len - 1] == '.') {
host_trimmed.remove_suffix(1);
}
return host_trimmed.as_string();
}
bool DnsResponseBuffer::U8(uint8* v) {
if (len_ < 1)
return false;
*v = *p_;
p_++;
len_--;
return true;
}
bool DnsResponseBuffer::U16(uint16* v) {
if (len_ < 2)
return false;
*v = static_cast<uint16>(p_[0]) << 8 |
static_cast<uint16>(p_[1]);
p_ += 2;
len_ -= 2;
return true;
}
bool DnsResponseBuffer::U32(uint32* v) {
if (len_ < 4)
return false;
*v = static_cast<uint32>(p_[0]) << 24 |
static_cast<uint32>(p_[1]) << 16 |
static_cast<uint32>(p_[2]) << 8 |
static_cast<uint32>(p_[3]);
p_ += 4;
len_ -= 4;
return true;
}
bool DnsResponseBuffer::Skip(unsigned n) {
if (len_ < n)
return false;
p_ += n;
len_ -= n;
return true;
}
bool DnsResponseBuffer::Block(base::StringPiece* out, unsigned len) {
if (len_ < len)
return false;
*out = base::StringPiece(reinterpret_cast<const char*>(p_), len);
p_ += len;
len_ -= len;
return true;
}
// DNSName parses a (possibly compressed) DNS name from the packet. If |name|
// is not NULL, then the name is written into it. See RFC 1035 section 4.1.4.
bool DnsResponseBuffer::DNSName(std::string* name) {
unsigned jumps = 0;
const uint8* p = p_;
unsigned len = len_;
if (name)
name->clear();
for (;;) {
if (len < 1)
return false;
uint8 d = *p;
p++;
len--;
// The two couple of bits of the length give the type of the length. It's
// either a direct length or a pointer to the remainder of the name.
if ((d & 0xc0) == 0xc0) {
// This limit matches the depth limit in djbdns.
if (jumps > 100)
return false;
if (len < 1)
return false;
uint16 offset = static_cast<uint16>(d) << 8 |
static_cast<uint16>(p[0]);
offset &= 0x3ff;
p++;
len--;
if (jumps == 0) {
p_ = p;
len_ = len;
}
jumps++;
if (offset >= packet_len_)
return false;
p = &packet_[offset];
len = packet_len_ - offset;
} else if ((d & 0xc0) == 0) {
uint8 label_len = d;
if (len < label_len)
return false;
if (name && label_len) {
if (!name->empty())
name->append(".");
name->append(reinterpret_cast<const char*>(p), label_len);
}
p += label_len;
len -= label_len;
if (jumps == 0) {
p_ = p;
len_ = len;
}
if (label_len == 0)
break;
} else {
return false;
}
}
return true;
}
} // namespace net
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