This makes comparing host name with dns name from certificate case
insensitive.
I found a few domains (from the
[cloudflare](https://radar.cloudflare.com/domains) list of top domains)
for which tls.Client fails to connect. Error is:
```zig
error: TlsInitializationFailed
Code/zig/lib/std/crypto/Certificate.zig:336:9: 0x1177b1f in verifyHostName (http_get_std)
return error.CertificateHostMismatch;
Code/zig/lib/std/crypto/tls23/handshake_client.zig:461:25: 0x11752bd in parseServerCertificate (http_get_std)
try subject.verifyHostName(opt.host);
```
In its certificate this domains have host names which are not strictly
lower case. This is what checkHostName is comparing:
|host_name | dns_name |
|------------------------------------------------|
|ey.com | EY.COM |
|truist.com | Truist.com |
|wscampanhas.bradesco | WSCAMPANHAS.BRADESCO |
|dell.com | Dell.com |
From
[RFC2818](https://datatracker.ietf.org/doc/html/rfc2818#section-2.4):
> Matching is performed using the matching rules specified by
[RFC2459].
From [RFC2459](https://datatracker.ietf.org/doc/html/rfc2459#section-4.2.1.7):
> When comparing URIs, conforming implementations
> MUST compare the scheme and host without regard to case, but assume
> the remainder of the scheme-specific-part is case sensitive.
Testing with:
```
const std = @import("std");
pub fn main() !void {
var gpa = std.heap.GeneralPurposeAllocator(.{}){};
const allocator = gpa.allocator();
const args = try std.process.argsAlloc(allocator);
defer std.process.argsFree(allocator, args);
if (args.len > 1) {
const domain = args[1];
var client: std.http.Client = .{ .allocator = allocator };
defer client.deinit();
// Add https:// prefix if needed
const url = brk: {
const scheme = "https://";
if (domain.len >= scheme.len and std.mem.eql(u8, domain[0..scheme.len], scheme))
break :brk domain;
var url_buf: [128]u8 = undefined;
break :brk try std.fmt.bufPrint(&url_buf, "https://{s}", .{domain});
};
const uri = try std.Uri.parse(url);
var server_header_buffer: [16 * 1024]u8 = undefined;
var req = try client.open(.GET, uri, .{ .server_header_buffer = &server_header_buffer });
defer req.deinit();
try req.send();
try req.wait();
}
}
```
`$ zig run example/main.zig -- truist.com `
c1e7eb7389