return native error codes and map them in more detail in apk

fixes #10668

As discussed in #10749, I suggested that we remove FTP support to reduce possible attack surface
as there are no Alpine mirrors which use FTP.

There are also no known mirrors of any other apk-using distribution which use FTP, so I believe
we are safe to remove support for FTP-based mirrors in apk-tools 3.

Signed-off-by: Ariadne Conill <ariadne@dereferenced.org>

Various parsing of numeric strings were not having adequate range
checking causing information leak or potential crash.

CVE-2021-36159
fixes #10749

Co-authored-by: Ariadne Conill <ariadne@dereferenced.org>
Reported-by: Samanta Navarro <ferivoz@riseup.net>

The connection pooling was broken in two ways:

 1. The original URL was always used as the connection pool URL,
    resulting in duplicate connections to the proxy for http URLs
    (each http URL would get separate proxy connection)

 2. The cache_url stored was always the socket level connect URL.
    In case of HTTPS, the lookup was done done with the real URL,
    but the proxy URL was stored as the "cache URL". Thus HTTPS
    CONNECT connections were never re-used.

This fixes the code with following logic:

 1. The cache key url is the real URL when no-proxy, or when HTTPS
    with proxy (the socket is connected to proxy, but logically it
    is connected to the real URL due to HTTP CONNECT request).
    And for HTTP with proxy, it's the proxy URL so same proxy
    connection can be reused for all requests going through it.

 2. fetch_connect() now gets cache key URL separately, and it always
    gets the same value as the fetch_cache_get() calls.

Ariadne Conill authored 4 years ago and Timo Teräs committed 4 years ago

If getservbyname() fails, libfetch will attempt to connect to port 0.

X509_check_host() is introduced in libressl-2.5.0 and openssl-1.0.2
which are not yet universally available. Add support for building
against the older versions.

loosely based on the freebsd implementation, implement https
connection settings to override CA, and use client certificate.

new files supported in /etc/apk/:
  ca.pem   - if exists, it contains CAs acceptable for https
	     (otherwise system wide CAs are used)
  crl.pem  - if ca.pem is used, this is the (optional) CRL for it
  cert.pem - used as client authentication certificate (+ key)
  cert.key - used as client key (can be also inside cert.pem)

ftp://ftp.fu-berlin.de/unix/NetBSD/packages/current-src/pkgsrc/net/libfetch/files

libfetch comes (at least) in netbsd and freebsd flavors which
differing functionality. Alpine and Arch package netbsd one,
but it's not widely packaged across other distributions.

We need NetBSD version as it does not use funopen(3) which is not
supported in musl, and supports connection pooling.

FreeBSD seems to be the orignal and better maintained version
with support for SSL CAs, client certificate authentication,
proxy authentication, and improved http redirect handling.

So this imports NetBSD version, and future commits will pick up
the needed improvements from FreeBSD tree.

Incidentally, this also fixes #7857 and likes for good.