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implement CNAME expansion

master
Andrew Kelley 2019-10-29 14:03:39 -04:00
parent 67058b9b70
commit 9ade31faaf
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GPG Key ID: 7C5F548F728501A9
3 changed files with 63 additions and 5 deletions
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8
lib/std/c.zig
View File

@ -191,3 +191,11 @@ pub extern "c" fn getnameinfo(
pub extern "c" fn gai_strerror(errcode: c_int) [*]const u8;
pub extern "c" fn poll(fds: [*]pollfd, nfds: nfds_t, timeout: c_int) c_int;
pub extern "c" fn dn_expand(
msg: [*]const u8,
eomorig: [*]const u8,
comp_dn: [*]const u8,
exp_dn: [*]u8,
length: c_int,
) c_int;

12
lib/std/net.zig
View File

@ -1017,7 +1017,6 @@ fn dnsParse(
}
fn dnsParseCallback(ctx: dpc_ctx, rr: u8, data: []const u8, packet: []const u8) !void {
var tmp: [256]u8 = undefined;
switch (rr) {
os.RR_A => {
if (data.len != 4) return error.InvalidDnsARecord;
@ -1038,10 +1037,13 @@ fn dnsParseCallback(ctx: dpc_ctx, rr: u8, data: []const u8, packet: []const u8)
mem.copy(u8, &new_addr.addr, data);
},
os.RR_CNAME => {
@panic("TODO dn_expand");
//if (__dn_expand(packet, (const unsigned char *)packet + 512,
// data, tmp, sizeof tmp) > 0 && is_valid_hostname(tmp))
// strcpy(ctx->canon, tmp);
var tmp: [256]u8 = undefined;
// Returns len of compressed name. strlen to get canon name.
_ = try os.dn_expand(packet, data, &tmp);
const canon_name = mem.toSliceConst(u8, &tmp);
if (isValidHostName(canon_name)) {
try ctx.canon.replaceContents(canon_name);
}
},
else => return,
}

48
lib/std/os.zig
View File

@ -3076,3 +3076,51 @@ pub fn recvfrom(
}
}
}
pub const DnExpandError = error{InvalidDnsPacket};
pub fn dn_expand(
msg: []const u8,
comp_dn: []const u8,
exp_dn: []u8,
) DnExpandError!usize {
var p = comp_dn.ptr;
var len: usize = std.math.maxInt(usize);
const end = msg.ptr + msg.len;
if (p == end or exp_dn.len == 0) return error.InvalidDnsPacket;
var dest = exp_dn.ptr;
const dend = dest + std.math.min(exp_dn.len, 254);
// detect reference loop using an iteration counter
var i: usize = 0;
while (i < msg.len) : (i += 2) {
// loop invariants: p<end, dest<dend
if ((p[0] & 0xc0) != 0) {
if (p + 1 == end) return error.InvalidDnsPacket;
var j = ((p[0] & usize(0x3f)) << 8) | p[1];
if (len == std.math.maxInt(usize)) len = @ptrToInt(p) + 2 - @ptrToInt(comp_dn.ptr);
if (j >= msg.len) return error.InvalidDnsPacket;
p = msg.ptr + j;
} else if (p[0] != 0) {
if (dest != exp_dn.ptr) {
dest.* = '.';
dest += 1;
}
var j = p[0];
p += 1;
if (j >= @ptrToInt(end) - @ptrToInt(p) or j >= @ptrToInt(dend) - @ptrToInt(dest)) {
return error.InvalidDnsPacket;
}
while (j != 0) {
j -= 1;
dest.* = p[0];
dest += 1;
p += 1;
}
} else {
dest.* = 0;
if (len == std.math.maxInt(usize)) len = @ptrToInt(p) + 1 - @ptrToInt(comp_dn.ptr);
return len;
}
}
return error.InvalidDnsPacket;
}