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Simplify putDomainName and add length checks

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This commit is contained in:
dmiller 2026-08-14 17:16:20 +00:00
parent 5de629e3dd
commit 9b62481a67
1 changed files with 26 additions and 16 deletions
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42
libnetutil/massdns.cc
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@ -1852,28 +1852,38 @@ size_t DNS::Factory::putUnsignedShort(u16 num, u8 *buf, size_t offset, size_t ma
size_t DNS::Factory::putDomainName(const std::string &name, u8 *buf, size_t offset, size_t maxlen)
{
size_t ret=0;
if( !( buf && (maxlen > (offset + name.length() + 1))) ) return ret;
assert(buf != NULL);
if (offset >= maxlen || name.length() >= maxlen - offset)
return 0;
std::string namew = name + ".";
std::string accumulator;
for (std::string::const_iterator c=namew.begin(); c != namew.end(); ++c)
u8 *out = buf + offset;
size_t label_start = ret;
u8 label_len = 0;
out[ret++] = 0; // placeholder for label length
for (std::string::const_iterator c=name.begin(); c != name.end(); ++c)
{
if (ret >= DNS_NAME_MAX_LENGTH)
return 0;
if((*c)=='.')
{
u8 length = accumulator.length();
*(buf+offset+ret) = length;
ret += 1;
memcpy(buf+offset+ret, accumulator.c_str(), length);
ret += length;
accumulator.clear();
out[label_start] = label_len;
label_len = 0;
label_start = ret;
out[ret++] = 0; // placeholder for label length
}
else {
if (label_len >= DNS_LABEL_MAX_LENGTH)
return 0;
out[ret++] = *c;
label_len++;
}
else
accumulator += (*c);
}
*(buf+offset+ret) = 0;
ret += 1;
if (label_len > 0)
{
out[label_start] = label_len;
out[ret++] = 0; // Empty label terminates name
}
return ret;
}