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/untestable/thttpclient_ssl_env_var.nim

@@ -0,0 +1,74 @@
+#
+#            Nim - SSL integration tests
+#        (c) Copyright 2017 Nim contributors
+#
+#    See the file "copying.txt", included in this
+#    distribution, for details about the copyright.
+#
+## Warning: this test performs external networking.
+## Compile with:
+## ./bin/nim c -d:ssl -p:. tests/untestable/thttpclient_ssl_env_var.nim
+##
+## Test with:
+##  SSL_CERT_FILE=BogusInexistentFileName tests/untestable/thttpclient_ssl_env_var
+##  SSL_CERT_DIR=BogusInexistentDirName tests/untestable/thttpclient_ssl_env_var
+
+import httpclient, unittest, ospaths
+from net import newSocket, newContext, wrapSocket, connect, close, Port,
+  CVerifyPeerUseEnvVars
+from strutils import contains
+
+const
+  expired = "https://expired.badssl.com/"
+  good = "https://google.com/"
+
+
+suite "SSL certificate check":
+
+  test "httpclient with inexistent file":
+    if existsEnv("SSL_CERT_FILE"):
+      var ctx = newContext(verifyMode=CVerifyPeerUseEnvVars)
+      var client = newHttpClient(sslContext=ctx)
+      checkpoint("Client created")
+      check client.getContent("https://google.com").contains("doctype")
+      checkpoint("Google ok")
+      try:
+        let a = $client.getContent(good)
+        echo "Connection should have failed"
+        fail()
+      except:
+        echo getCurrentExceptionMsg()
+        check getCurrentExceptionMsg().contains("certificate verify failed")
+
+    elif existsEnv("SSL_CERT_DIR"):
+      try:
+        var ctx = newContext(verifyMode=CVerifyPeerUseEnvVars)
+        var client = newHttpClient(sslContext=ctx)
+        echo "Should have raised 'No SSL/TLS CA certificates found.'"
+        fail()
+      except:
+        check getCurrentExceptionMsg() ==
+          "No SSL/TLS CA certificates found."
+
+  test "net socket with inexistent file":
+    if existsEnv("SSL_CERT_FILE"):
+      var sock = newSocket()
+      var ctx = newContext(verifyMode=CVerifyPeerUseEnvVars)
+      ctx.wrapSocket(sock)
+      checkpoint("Socket created")
+      try:
+        sock.connect("expired.badssl.com", 443.Port)
+        fail()
+      except:
+        sock.close
+        check getCurrentExceptionMsg().contains("certificate verify failed")
+
+    elif existsEnv("SSL_CERT_DIR"):
+      var sock = newSocket()
+      checkpoint("Socket created")
+      try:
+        var ctx = newContext(verifyMode=CVerifyPeerUseEnvVars) # raises here
+        fail()
+      except:
+        check getCurrentExceptionMsg() ==
+          "No SSL/TLS CA certificates found."