implement socks5h proxy support for http method

Socks support is a requested feature in sofar that the internet is
actually believing Acquire::socks::Proxy would exist. It doesn't and
this commit isn't adding it as that isn't how our configuration works,
but it allows Acquire::http::Proxy="socks5h://…". The HTTPS method was
changed already to support socks proxies (all versions) via curl. This
commit implements only SOCKS5 (RFC1928) with no auth or pass&user auth
(RFC1929), but not GSSAPI which is required by the RFC. The 'h' in the
protocol name further indicates that DNS resolution is delegated to the
socks proxy rather than performed locally.

The implementation works and was tested with Tor as socks proxy for
which implementing socks5h only can actually be considered a feature.

Closes: 744934

2 files changed, 32 insertions, 0 deletions

diff --git a/apt-pkg/contrib/fileutl.cc b/apt-pkg/contrib/fileutl.cc
index 342f9830d..a9d51a6bf 100644
--- a/apt-pkg/contrib/fileutl.cc
+++ b/apt-pkg/contrib/fileutl.cc
@@ -2444,6 +2444,37 @@ bool FileFd::Read(void *To,unsigned long long Size,unsigned long long *Actual)
 
    return FileFdError(_("read, still have %llu to read but none left"), Size);
 }
+bool FileFd::Read(int const Fd, void *To, unsigned long long Size, unsigned long long * const Actual)
+{
+   ssize_t Res = 1;
+   errno = 0;
+   if (Actual != nullptr)
+      *Actual = 0;
+   *static_cast<char *>(To) = '\0';
+   while (Res > 0 && Size > 0)
+   {
+      Res = read(Fd, To, Size);
+      if (Res < 0)
+      {
+	 if (errno == EINTR)
+	 {
+	    Res = 1;
+	    errno = 0;
+	    continue;
+	 }
+	 return _error->Errno("read", _("Read error"));
+      }
+      To = static_cast<char *>(To) + Res;
+      Size -= Res;
+      if (Actual != 0)
+	 *Actual += Res;
+   }
+   if (Size == 0)
+      return true;
+   if (Actual != nullptr)
+      return true;
+   return _error->Error(_("read, still have %llu to read but none left"), Size);
+}
 									/*}}}*/
 // FileFd::ReadLine - Read a complete line from the file		/*{{{*/
 // ---------------------------------------------------------------------
diff --git a/apt-pkg/contrib/fileutl.h b/apt-pkg/contrib/fileutl.h
index c13613171..4a1676dc2 100644
--- a/apt-pkg/contrib/fileutl.h
+++ b/apt-pkg/contrib/fileutl.h
@@ -86,6 +86,7 @@ class FileFd
       return Read(To,Size);
    }   
    bool Read(void *To,unsigned long long Size,unsigned long long *Actual = 0);
+   bool static Read(int const Fd, void *To, unsigned long long Size, unsigned long long * const Actual = 0);
    char* ReadLine(char *To, unsigned long long const Size);
    bool Flush();
    bool Write(const void *From,unsigned long long Size);