SSL certificate verify GitHub action (#13697)

* Implement SSL/TLS certificate checking #782

* SSL: Add nimDisableCertificateValidation

Remove NIM_SSL_CERT_VALIDATION env var
tests/untestable/thttpclient_ssl.nim ran successfully on Linux with libssl 1.1.1d

* SSL: update integ test to skip flapping tests

* Revert .travis.yml change

* nimDisableCertificateValidation disable imports

Prevent loading symbols that are not defined on older SSL libs

* SSL: disable verification in net.nim

..when nimDisableCertificateValidation is set

* Update changelog

* Fix peername type

* Add define check for windows

* Disable test on windows

* Add exprimental GitHub action CI for SSL

* Test nimDisableCertificateValidation

tests/stdlib/thttpclient_ssl.nim

@@ -0,0 +1,126 @@
+discard """
+  cmd: "nim $target --threads:on -d:ssl $options $file"
+"""
+
+#            Nim - Basic SSL integration tests
+#        (c) Copyright 2018 Nim contributors
+#
+#    See the file "copying.txt", included in this
+#    distribution, for details about the copyright.
+#
+## Warning: this test performs local networking.
+## Test with:
+## ./bin/nim c -d:ssl -p:. --threads:on -r tests/stdlib/thttpclient_ssl.nim
+
+when not defined(windows):
+  # Disabled on Windows due to old OpenSSL version
+
+  import
+    httpclient,
+    net,
+    openssl,
+    os,
+    strutils,
+    threadpool,
+    times,
+    unittest
+
+  # bogus self-signed certificate
+  const
+    certFile = "tests/stdlib/thttpclient_ssl_cert.pem"
+    keyFile = "tests/stdlib/thttpclient_ssl_key.pem"
+
+  proc log(msg: string) =
+    when defined(ssldebug):
+      echo "    [" & $epochTime() & "] " & msg
+    # FIXME
+    echo "    [" & $epochTime() & "] " & msg
+    discard
+
+  proc runServer(port: Port): bool {.thread.} =
+    ## Run a trivial HTTPS server in a {.thread.}
+    ## Exit after serving one request
+
+    var socket = newSocket()
+    socket.setSockOpt(OptReusePort, true)
+    socket.bindAddr(port)
+
+    var ctx = newContext(certFile=certFile, keyFile=keyFile)
+
+    ##  Handle one connection
+    socket.listen()
+
+    var client: Socket
+    var address = ""
+
+    log "server: ready"
+    socket.acceptAddr(client, address)
+    log "server: incoming connection"
+
+    var ssl: SslPtr = SSL_new(ctx.context)
+    discard SSL_set_fd(ssl, client.getFd())
+    log "server: accepting connection"
+    if SSL_accept(ssl) <= 0:
+      ERR_print_errors_fp(stderr)
+    else:
+      const reply = "HTTP/1.0 200 OK\r\nServer: test\r\nContent-type: text/html\r\nContent-Length: 0\r\n\r\n"
+      log "server: sending reply"
+      discard SSL_write(ssl, reply.cstring, reply.len)
+
+    log "server: receiving a line"
+    let line = client.recvLine()
+    log "server: received $# bytes" % $line.len
+    log "closing"
+    SSL_free(ssl)
+    close(client)
+    close(socket)
+    log "server: exited"
+
+
+  suite "SSL self signed certificate check":
+
+    test "TCP socket":
+      const port = 12347.Port
+      let t = spawn runServer(port)
+      sleep(100)
+      var sock = newSocket()
+      var ctx = newContext()
+      ctx.wrapSocket(sock)
+      try:
+        log "client: connect"
+        sock.connect("127.0.0.1", port)
+        fail()
+      except:
+        let msg = getCurrentExceptionMsg()
+        check(msg.contains("certificate verify failed"))
+
+    test "HttpClient default: no check":
+      const port = 12345.Port
+      let t = spawn runServer(port)
+      sleep(100)
+
+      var client = newHttpClient()
+      try:
+        log "client: connect"
+        discard client.getContent("https://127.0.0.1:12345")
+      except:
+        let msg = getCurrentExceptionMsg()
+        log "client: unexpected exception: " & msg
+        fail()
+
+    test "HttpClient with CVerifyPeer":
+      const port = 12346.Port
+      let t = spawn runServer(port)
+      sleep(100)
+
+      var client = newHttpClient(sslContext=newContext(verifyMode=CVerifyPeer))
+      try:
+        log "client: connect"
+        discard client.getContent("https://127.0.0.1:12346")
+        log "getContent should have raised an exception"
+        fail()
+      except:
+        let msg = getCurrentExceptionMsg()
+        log "client: exception: " & msg
+        # SSL_shutdown:shutdown while in init
+        check(msg.contains("shutdown while in init") or msg.contains("alert number 48"))