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std.Io.net.HostName: implement DNS name expansion

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This commit is contained in:
Andrew Kelley 2025-10-02 20:45:16 -07:00
parent f1a590c876
commit 85a6fea3be
1 changed files with 44 additions and 52 deletions
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96
lib/std/Io/net/HostName.zig
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@ -51,6 +51,7 @@ pub const LookupError = error{
ResolvConfParseFailed, ResolvConfParseFailed,
InvalidDnsARecord, InvalidDnsARecord,
InvalidDnsAAAARecord, InvalidDnsAAAARecord,
InvalidDnsCnameRecord,
NameServerFailure, NameServerFailure,
} || Io.Timestamp.Error || IpAddress.BindError || Io.File.OpenError || Io.File.Reader.Error || Io.Cancelable; } || Io.Timestamp.Error || IpAddress.BindError || Io.File.OpenError || Io.File.Reader.Error || Io.Cancelable;
@ -381,16 +382,8 @@ fn lookupDns(io: Io, lookup_canon_name: []const u8, rc: *const ResolvConf, optio
addresses_len += 1; addresses_len += 1;
}, },
std.posix.RR.CNAME => { std.posix.RR.CNAME => {
_ = &canonical_name; _, canonical_name = expand(record.packet, record.data_off, options.canonical_name_buffer) catch
@panic("TODO"); return error.InvalidDnsCnameRecord;
//var tmp: [256]u8 = undefined;
//// Returns len of compressed name. strlen to get canon name.
//_ = try posix.dn_expand(packet, record.data, &tmp);
//const canon_name = mem.sliceTo(&tmp, 0);
//if (isValidHostName(canon_name)) {
// ctx.canon.items.len = 0;
// try ctx.canon.appendSlice(gpa, canon_name);
//}
}, },
else => continue, else => continue,
}; };
@ -525,51 +518,50 @@ fn writeResolutionQuery(q: *[280]u8, op: u4, dname: []const u8, class: u8, ty: u
return n; return n;
} }
pub const ExpandDomainNameError = error{InvalidDnsPacket}; pub const ExpandError = error{InvalidDnsPacket} || InitError;
pub fn expandDomainName( /// Decompresses a DNS name.
msg: []const u8, ///
comp_dn: []const u8, /// Returns number of bytes consumed from `packet` starting at `i`,
exp_dn: []u8, /// along with the expanded `HostName`.
) ExpandDomainNameError!usize { ///
// This implementation is ported from musl libc. /// Asserts `buffer` is has length at least `max_len`.
// A more idiomatic "ziggy" implementation would be welcome. pub fn expand(noalias packet: []const u8, start_i: usize, noalias dest_buffer: []u8) ExpandError!struct { usize, HostName } {
var p = comp_dn.ptr; const dest = dest_buffer[0..max_len];
var len: usize = std.math.maxInt(usize);
const end = msg.ptr + msg.len; var i = start_i;
if (p == end or exp_dn.len == 0) return error.InvalidDnsPacket; var dest_i: usize = 0;
var dest = exp_dn.ptr; var len: ?usize = null;
const dend = dest + @min(exp_dn.len, 254);
// detect reference loop using an iteration counter // Detect reference loop using an iteration counter.
var i: usize = 0; for (0..packet.len / 2) |_| {
while (i < msg.len) : (i += 2) { if (i >= packet.len) return error.InvalidDnsPacket;
// loop invariants: p<end, dest<dend
if ((p[0] & 0xc0) != 0) { const c = packet[i];
if (p + 1 == end) return error.InvalidDnsPacket; if ((c & 0xc0) != 0) {
const j = @as(usize, p[0] & 0x3f) << 8 | p[1]; if (i + 1 >= packet.len) return error.InvalidDnsPacket;
if (len == std.math.maxInt(usize)) len = @intFromPtr(p) + 2 - @intFromPtr(comp_dn.ptr); const j: usize = (@as(usize, c & 0x3F) << 8) | packet[i + 1];
if (j >= msg.len) return error.InvalidDnsPacket; if (j >= packet.len) return error.InvalidDnsPacket;
p = msg.ptr + j; if (len == null) len = (i + 2) - start_i;
} else if (p[0] != 0) { i = j;
if (dest != exp_dn.ptr) { } else if (c != 0) {
dest[0] = '.'; if (dest_i != 0) {
dest += 1; dest[dest_i] = '.';
} dest_i += 1;
var j = p[0];
p += 1;
if (j >= @intFromPtr(end) - @intFromPtr(p) or j >= @intFromPtr(dend) - @intFromPtr(dest)) {
return error.InvalidDnsPacket;
}
while (j != 0) {
j -= 1;
dest[0] = p[0];
dest += 1;
p += 1;
} }
const label_len: usize = c;
if (i + 1 + label_len > packet.len) return error.InvalidDnsPacket;
if (dest_i + label_len + 1 > dest.len) return error.InvalidDnsPacket;
@memcpy(dest[dest_i..][0..label_len], packet[i + 1 ..][0..label_len]);
dest_i += label_len;
i += 1 + label_len;
} else { } else {
dest[0] = 0; dest[dest_i] = 0;
if (len == std.math.maxInt(usize)) len = @intFromPtr(p) + 1 - @intFromPtr(comp_dn.ptr); dest_i += 1;
return len; return .{
len orelse i - start_i + 1,
try .init(dest[0..dest_i]),
};
} }
} }
return error.InvalidDnsPacket; return error.InvalidDnsPacket;