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LibDNS: Make DNS packet parsing fallible

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Previously, a DNS packet containing an invalid name would be returned
with an empty name. With this change, an error is returned if any error
is encountered during parsing.
This commit is contained in:
Tim Ledbetter 2023-11-13 22:36:34 +00:00 • committed by Andreas Kling
parent 95d62822bf
commit 1793f51bc6
8 changed files with 29 additions and 40 deletions
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12
Userland/Libraries/LibDNS/Name.cpp
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@ -21,15 +21,15 @@ Name::Name(DeprecatedString const& name)
m_name = name;
}
Name Name::parse(ReadonlyBytes data, size_t& offset, size_t recursion_level)
ErrorOr<Name> Name::parse(ReadonlyBytes data, size_t& offset, size_t recursion_level)
{
if (recursion_level > 4)
return {};
return Name {};
StringBuilder builder;
while (true) {
if (offset >= data.size())
return {};
return Error::from_string_literal("Unexpected EOF when parsing name");
u8 b = data[offset++];
if (b == '\0') {
// This terminates the name.
@ -37,15 +37,15 @@ Name Name::parse(ReadonlyBytes data, size_t& offset, size_t recursion_level)
} else if ((b & 0xc0) == 0xc0) {
// The two bytes tell us the offset when to continue from.
if (offset >= data.size())
return {};
return Error::from_string_literal("Unexpected EOF when parsing name");
size_t dummy = (b & 0x3f) << 8 | data[offset++];
auto rest_of_name = parse(data, dummy, recursion_level + 1);
auto rest_of_name = TRY(parse(data, dummy, recursion_level + 1));
builder.append(rest_of_name.as_string());
return builder.to_deprecated_string();
} else {
// This is the length of a part.
if (offset + b >= data.size())
return {};
return Error::from_string_literal("Unexpected EOF when parsing name");
builder.append({ data.offset_pointer(offset), b });
builder.append('.');
offset += b;