SSL: Add an option to disable certificate revocation checks

New tool option --ssl-no-revoke.
New value CURLSSLOPT_NO_REVOKE for CURLOPT_SSL_OPTIONS.

Currently this option applies only to WinSSL where we have automatic
certificate revocation checking by default. According to the
ssl-compared chart there are other backends that have automatic checking
(NSS, wolfSSL and DarwinSSL) so we could possibly accommodate them at
some later point.

Bug: https://github.com/bagder/curl/issues/264
Reported-by: zenden2k <zenden2k@gmail.com>

3 files changed, 37 insertions, 7 deletions

diff --git a/docs/SSL-PROBLEMS b/docs/SSL-PROBLEMS
index 5a56d3da5..45faa241c 100644
--- a/docs/SSL-PROBLEMS
+++ b/docs/SSL-PROBLEMS
@@ -71,3 +71,17 @@ Allow BEAST
   introduced. Exactly as it sounds, it re-introduces the BEAST vulnerability
   but on the other hand it allows curl to connect to that kind of strange
   servers.
+
+Disabling certificate revocation checks
+
+  Some SSL backends may do certificate revocation checks (CRL, OCSP, etc)
+  depending on the OS or build configuration. The --ssl-no-revoke option was
+  introduced in 7.44.0 to disable revocation checking but currently is only
+  supported for WinSSL (the native Windows SSL library), with an exception in
+  the case of Windows' Untrusted Publishers blacklist which it seems can't be
+  bypassed. This option may have broader support to accommodate other SSL
+  backends in the future.
+
+  References:
+
+  http://curl.haxx.se/docs/ssl-compared.html
diff --git a/docs/curl.1 b/docs/curl.1
index afd4e8c35..69ab9781d 100644
--- a/docs/curl.1
+++ b/docs/curl.1
@@ -1545,6 +1545,10 @@ and TLS1.0 protocols known as BEAST.  If this option isn't used, the SSL layer
 may use workarounds known to cause interoperability problems with some older
 SSL implementations. WARNING: this option loosens the SSL security, and by
 using this flag you ask for exactly that.  (Added in 7.25.0)
+.IP "--ssl-no-revoke"
+(WinSSL) This option tells curl to disable certificate revocation checks.
+WARNING: this option loosens the SSL security, and by using this flag you ask
+for exactly that.  (Added in 7.44.0)
 .IP "--socks4 <host[:port]>"
 Use the specified SOCKS4 proxy. If the port number is not specified, it is
 assumed at port 1080. (Added in 7.15.2)
diff --git a/docs/libcurl/opts/CURLOPT_SSL_OPTIONS.3 b/docs/libcurl/opts/CURLOPT_SSL_OPTIONS.3
index 09bcb96cf..0afd2fb6a 100644
--- a/docs/libcurl/opts/CURLOPT_SSL_OPTIONS.3
+++ b/docs/libcurl/opts/CURLOPT_SSL_OPTIONS.3
@@ -30,13 +30,25 @@ CURLcode curl_easy_setopt(CURL *handle, CURLOPT_SSL_OPTIONS, long bitmask);
 .SH DESCRIPTION
 Pass a long with a bitmask to tell libcurl about specific SSL behaviors.
 
-\fICURLSSLOPT_ALLOW_BEAST\fP is the only supported bit and by setting this the
-user will tell libcurl to not attempt to use any workarounds for a security
-flaw in the SSL3 and TLS1.0 protocols.  If this option isn't used or this bit
-is set to 0, the SSL layer libcurl uses may use a work-around for this flaw
-although it might cause interoperability problems with some (older) SSL
-implementations. WARNING: avoiding this work-around lessens the security, and
-by setting this option to 1 you ask for exactly that.
+\fICURLSSLOPT_ALLOW_BEAST\fP tells libcurl to not attempt to use any
+workarounds for a security flaw in the SSL3 and TLS1.0 protocols.  If this
+option isn't used or this bit is set to 0, the SSL layer libcurl uses may use a
+work-around for this flaw although it might cause interoperability problems
+with some (older) SSL implementations. WARNING: avoiding this work-around
+lessens the security, and by setting this option to 1 you ask for exactly that.
+This option is only supported for DarwinSSL, NSS and OpenSSL.
+
+Added in 7.44.0:
+
+\fICURLSSLOPT_NO_REVOKE\fP tells libcurl to disable certificate revocation
+checks for those SSL backends where such behavior is present. \fBCurrently this
+option is only supported for WinSSL (the native Windows SSL library), with an
+exception in the case of Windows' Untrusted Publishers blacklist which it seems
+can't be bypassed.\fP This option may have broader support to accommodate other
+SSL backends in the future.
+http://curl.haxx.se/docs/ssl-compared.html
+
+
 .SH DEFAULT
 0
 .SH PROTOCOLS