Add support for -no-CApath and -no-CAfile options

For those command line options that take the verification options
-CApath and -CAfile, if those options are absent then the default path or
file is used instead. It is not currently possible to specify *no* path or
file at all. This change adds the options -no-CApath and -no-CAfile to
specify that the default locations should not be used to all relevant
applications.

Reviewed-by: Andy Polyakov <appro@openssl.org>
diff --git a/apps/s_client.c b/apps/s_client.c
index 65e3bb8..e990a43 100644
--- a/apps/s_client.c
+++ b/apps/s_client.c
@@ -466,8 +466,8 @@
     OPT_SRP_LATEUSER, OPT_SRP_MOREGROUPS, OPT_SSL3,
     OPT_TLS1_2, OPT_TLS1_1, OPT_TLS1, OPT_DTLS, OPT_DTLS1,
     OPT_DTLS1_2, OPT_TIMEOUT, OPT_MTU, OPT_KEYFORM, OPT_PASS,
-    OPT_CERT_CHAIN, OPT_CAPATH, OPT_CHAINCAPATH, OPT_VERIFYCAPATH,
-    OPT_KEY, OPT_RECONNECT, OPT_BUILD_CHAIN, OPT_CAFILE,
+    OPT_CERT_CHAIN, OPT_CAPATH, OPT_NOCAPATH, OPT_CHAINCAPATH, OPT_VERIFYCAPATH,
+    OPT_KEY, OPT_RECONNECT, OPT_BUILD_CHAIN, OPT_CAFILE, OPT_NOCAFILE,
     OPT_CHAINCAFILE, OPT_VERIFYCAFILE, OPT_NEXTPROTONEG, OPT_ALPN,
     OPT_SERVERINFO, OPT_STARTTLS, OPT_SERVERNAME, OPT_JPAKE,
     OPT_USE_SRTP, OPT_KEYMATEXPORT, OPT_KEYMATEXPORTLEN, OPT_SMTPHOST,
@@ -495,6 +495,10 @@
     {"pass", OPT_PASS, 's', "Private key file pass phrase source"},
     {"CApath", OPT_CAPATH, '/', "PEM format directory of CA's"},
     {"CAfile", OPT_CAFILE, '<', "PEM format file of CA's"},
+    {"no-CAfile", OPT_NOCAFILE, '-',
+     "Do not load the default certificates file"},
+    {"no-CApath", OPT_NOCAPATH, '-',
+     "Do not load certificates from the default certificates directory"},
     {"reconnect", OPT_RECONNECT, '-',
      "Drop and re-make the connection with the same Session-ID"},
     {"pause", OPT_PAUSE, '-', "Sleep  after each read and write system call"},
@@ -651,6 +655,7 @@
     struct sockaddr peer;
     struct timeval timeout, *timeoutp;
     fd_set readfds, writefds;
+    int noCApath = 0, noCAfile = 0;
     int build_chain = 0, cbuf_len, cbuf_off, cert_format = FORMAT_PEM;
     int key_format = FORMAT_PEM, crlf = 0, full_log = 1, mbuf_len = 0;
     int prexit = 0;
@@ -991,6 +996,9 @@
         case OPT_CAPATH:
             CApath = opt_arg();
             break;
+        case OPT_NOCAPATH:
+            noCApath = 1;
+            break;
         case OPT_CHAINCAPATH:
             chCApath = opt_arg();
             break;
@@ -1003,6 +1011,9 @@
         case OPT_CAFILE:
             CAfile = opt_arg();
             break;
+        case OPT_NOCAFILE:
+            noCAfile = 1;
+            break;
         case OPT_CHAINCAFILE:
             chCAfile = opt_arg();
             break;
@@ -1267,7 +1278,7 @@
 
     SSL_CTX_set_verify(ctx, verify, verify_callback);
 
-    if (!ctx_set_verify_locations(ctx, CAfile, CApath)) {
+    if (!ctx_set_verify_locations(ctx, CAfile, CApath, noCAfile, noCApath)) {
         ERR_print_errors(bio_err);
         goto end;
     }