This new version returns an error when trying to set the
CURLOPT_SSL_VERIFYSTATUS option if the SSL backend doesn't support the
status_request extension. I also updated the CURLOPT_SSL_VERIFYSTATUS manpage to
reflect this.

Backends that may support the extension implement a Curl_X_cert_status_request
function (e.g. Curl_gtls_cert_status_request) and define the macro
curlssl_cert_status_request used by the Curl_ssl_cert_status_request function.
If the macro is not defined, the backend is assumed to not support the
extension, otherwise the function is called.

Cheers
From 34ee2099bb56f0a67e721b70073c077b2c4dca2c Mon Sep 17 00:00:00 2001
From: Alessandro Ghedini <[email protected]>
Date: Mon, 16 Jun 2014 13:20:47 +0200
Subject: [PATCH 1/4] url: add CURLOPT_SSL_VERIFYSTATUS option

This option can be used to enable/disable certificate status verification using
the "Certificate Status Request" TLS extension defined in RFC6066 section 8.

This also adds the CURLE_SSL_INVALIDCERTSTATUS error, to be used when the
certificate status verification fails, and the Curl_ssl_cert_status_request()
function, used to check whether the SSL backend supports the status_request
extension.
---
 docs/libcurl/opts/CURLOPT_SSL_VERIFYSTATUS.3 | 53 ++++++++++++++++++++++++++++
 include/curl/curl.h                          |  4 +++
 lib/url.c                                    | 11 ++++++
 lib/urldata.h                                |  1 +
 lib/vtls/vtls.c                              | 12 +++++++
 lib/vtls/vtls.h                              |  2 ++
 6 files changed, 83 insertions(+)
 create mode 100644 docs/libcurl/opts/CURLOPT_SSL_VERIFYSTATUS.3

diff --git a/docs/libcurl/opts/CURLOPT_SSL_VERIFYSTATUS.3 b/docs/libcurl/opts/CURLOPT_SSL_VERIFYSTATUS.3
new file mode 100644
index 0000000..d5217cb
--- /dev/null
+++ b/docs/libcurl/opts/CURLOPT_SSL_VERIFYSTATUS.3
@@ -0,0 +1,53 @@
+.\" **************************************************************************
+.\" *                                  _   _ ____  _
+.\" *  Project                     ___| | | |  _ \| |
+.\" *                             / __| | | | |_) | |
+.\" *                            | (__| |_| |  _ <| |___
+.\" *                             \___|\___/|_| \_\_____|
+.\" *
+.\" * Copyright (C) 1998 - 2014, Daniel Stenberg, <[email protected]>, et al.
+.\" *
+.\" * This software is licensed as described in the file COPYING, which
+.\" * you should have received as part of this distribution. The terms
+.\" * are also available at http://curl.haxx.se/docs/copyright.html.
+.\" *
+.\" * You may opt to use, copy, modify, merge, publish, distribute and/or sell
+.\" * copies of the Software, and permit persons to whom the Software is
+.\" * furnished to do so, under the terms of the COPYING file.
+.\" *
+.\" * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
+.\" * KIND, either express or implied.
+.\" *
+.\" **************************************************************************
+.\"
+.TH CURLOPT_SSL_VERIFYSTATUS 3 "04 Dec 2014" "libcurl 7.40.0" "curl_easy_setopt options"
+.SH NAME
+CURLOPT_SSL_VERIFYSTATUS \- verify the certificate's status
+.SH SYNOPSIS
+#include <curl/curl.h>
+
+CURLcode curl_easy_setopt(CURL *handle, CURLOPT_SSL_VERIFYSTATUS, long verify);
+.SH DESCRIPTION
+Pass a long as parameter to enable or disable.
+
+This option determines whether libcurl verifies the status of the server cert
+using the "Certificate Status Request" TLS extension (aka. OCSP stapling).
+
+Note that if this option is enabled but the server does not support the TLS
+extension, the verification will fail.
+
+.SH DEFAULT
+0
+.SH PROTOCOLS
+All TLS based protocols: HTTPS, FTPS, IMAPS, POP3, SMTPS etc.
+.SH EXAMPLE
+TODO
+.SH AVAILABILITY
+This is currently only supported by the GnuTLS and NSS TLS backends.
+.SH RETURN VALUE
+Returns CURLE_OK if OCSP stapling is supported by the SSL backend, otherwise
+returns CURLE_NOT_BUILT_IN.
+.SH "SEE ALSO"
+.BR CURLOPT_SSL_VERIFYHOST "(3), "
+.BR CURLOPT_SSL_VERIFYPEER "(3), "
+.BR CURLOPT_CAINFO "(3), "
diff --git a/include/curl/curl.h b/include/curl/curl.h
index 44b1b7e..32fc48b 100644
--- a/include/curl/curl.h
+++ b/include/curl/curl.h
@@ -523,6 +523,7 @@ typedef enum {
                                     session will be queued */
   CURLE_SSL_PINNEDPUBKEYNOTMATCH, /* 90 - specified pinned public key did not
                                      match */
+  CURLE_SSL_INVALIDCERTSTATUS,   /* 91 - invalid certificate status */
   CURL_LAST /* never use! */
 } CURLcode;
 
@@ -1622,6 +1623,9 @@ typedef enum {
   /* Path to Unix domain socket */
   CINIT(UNIX_SOCKET_PATH, OBJECTPOINT, 231),
 
+  /* Set if we should verify the certificate status. */
+  CINIT(SSL_VERIFYSTATUS, LONG, 232),
+
   CURLOPT_LASTENTRY /* the last unused */
 } CURLoption;
 
diff --git a/lib/url.c b/lib/url.c
index d3bb5e0..407910c 100644
--- a/lib/url.c
+++ b/lib/url.c
@@ -1997,6 +1997,17 @@ CURLcode Curl_setopt(struct SessionHandle *data, CURLoption option,
 
     data->set.ssl.verifyhost = (0 != arg)?TRUE:FALSE;
     break;
+  case CURLOPT_SSL_VERIFYSTATUS:
+    /*
+     * Enable certificate status verifying.
+     */
+    if(!Curl_ssl_cert_status_request()) {
+      result = CURLE_NOT_BUILT_IN;
+      break;
+    }
+
+    data->set.ssl.verifystatus = (0 != va_arg(param, long))?TRUE:FALSE;
+    break;
   case CURLOPT_SSL_CTX_FUNCTION:
 #ifdef have_curlssl_ssl_ctx
     /*
diff --git a/lib/urldata.h b/lib/urldata.h
index 5f77470..50a745f 100644
--- a/lib/urldata.h
+++ b/lib/urldata.h
@@ -366,6 +366,7 @@ struct ssl_config_data {
 
   bool verifypeer;       /* set TRUE if this is desired */
   bool verifyhost;       /* set TRUE if CN/SAN must match hostname */
+  bool verifystatus;     /* set TRUE if certificate status must be checked */
   char *CApath;          /* certificate dir (doesn't work on windows) */
   char *CAfile;          /* certificate to verify peer against */
   const char *CRLfile;   /* CRL to check certificate revocation */
diff --git a/lib/vtls/vtls.c b/lib/vtls/vtls.c
index a53ff4a..cf1df24 100644
--- a/lib/vtls/vtls.c
+++ b/lib/vtls/vtls.c
@@ -848,4 +848,16 @@ void Curl_ssl_md5sum(unsigned char *tmp, /* input */
 #endif
 }
 
+/*
+ * Check whether the SSL backend supports the status_request extension.
+ */
+bool Curl_ssl_cert_status_request(void)
+{
+#ifdef curlssl_cert_status_request
+  return curlssl_cert_status_request();
+#else
+  return FALSE;
+#endif
+}
+
 #endif /* USE_SSL */
diff --git a/lib/vtls/vtls.h b/lib/vtls/vtls.h
index 19ef1cd..eedf921 100644
--- a/lib/vtls/vtls.h
+++ b/lib/vtls/vtls.h
@@ -116,6 +116,8 @@ void Curl_ssl_md5sum(unsigned char *tmp, /* input */
 CURLcode Curl_pin_peer_pubkey(const char *pinnedpubkey,
                               const unsigned char *pubkey, size_t pubkeylen);
 
+bool Curl_ssl_cert_status_request(void);
+
 #define SSL_SHUTDOWN_TIMEOUT 10000 /* ms */
 
 #else
-- 
2.1.4

From 58097168388887f7ff856bcddbaef30675f38a5e Mon Sep 17 00:00:00 2001
From: Alessandro Ghedini <[email protected]>
Date: Mon, 16 Jun 2014 13:21:02 +0200
Subject: [PATCH 2/4] gtls: add support for the Certificate Status Request TLS
 extension

Also known as "status_request" or OCSP stapling, defined in RFC6066 section 8.

This requires GnuTLS 3.1.3 or higher to build, however it's recommended to use
at least GnuTLS 3.3.11 since previous versions had a bug that caused the OCSP
response verfication to fail even on valid responses.
---
 lib/vtls/gtls.c | 44 ++++++++++++++++++++++++++++++++++++++++++++
 lib/vtls/gtls.h |  3 +++
 2 files changed, 47 insertions(+)

diff --git a/lib/vtls/gtls.c b/lib/vtls/gtls.c
index 5d4e48a..27ca691 100644
--- a/lib/vtls/gtls.c
+++ b/lib/vtls/gtls.c
@@ -98,6 +98,14 @@ static bool gtls_inited = FALSE;
 #      define HAS_ALPN
 #    endif
 #  endif
+
+#  if (GNUTLS_VERSION_NUMBER >= 0x03020d)
+#    define HAS_OCSP
+#  endif
+#endif
+
+#ifdef HAS_OCSP
+# include <gnutls/ocsp.h>
 #endif
 
 /*
@@ -663,6 +671,16 @@ gtls_connect_step1(struct connectdata *conn,
   /* lowat must be set to zero when using custom push and pull functions. */
   gnutls_transport_set_lowat(session, 0);
 
+#ifdef HAS_OCSP
+  if(data->set.ssl.verifystatus) {
+    rc = gnutls_ocsp_status_request_enable_client(session, NULL, 0, NULL);
+    if(rc != GNUTLS_E_SUCCESS) {
+      failf(data, "gnutls_ocsp_status_request_enable_client() failed: %d", rc);
+      return CURLE_SSL_CONNECT_ERROR;
+    }
+  }
+#endif
+
   /* This might be a reconnect, so we check for a session ID in the cache
      to speed up things */
 
@@ -822,6 +840,23 @@ gtls_connect_step3(struct connectdata *conn,
   else
     infof(data, "\t server certificate verification SKIPPED\n");
 
+#ifdef HAS_OCSP
+  if(data->set.ssl.verifystatus) {
+    if(gnutls_ocsp_status_request_is_checked(session, 0) == 0) {
+      if(verify_status & GNUTLS_CERT_REVOKED)
+        failf(data, "SSL server certificate was REVOKED\n");
+      else
+        failf(data, "SSL server certificate status verification FAILED");
+
+      return CURLE_SSL_INVALIDCERTSTATUS;
+    }
+    else
+      infof(data, "SSL server certificate status verification OK\n");
+  }
+  else
+    infof(data, "SSL server certificate status verification SKIPPED\n");
+#endif
+
   /* initialize an X.509 certificate structure. */
   gnutls_x509_crt_init(&x509_cert);
 
@@ -1392,4 +1427,13 @@ void Curl_gtls_md5sum(unsigned char *tmp, /* input */
 #endif
 }
 
+bool Curl_gtls_cert_status_request(void)
+{
+#ifdef HAS_OCSP
+  return TRUE;
+#else
+  return FALSE;
+#endif
+}
+
 #endif /* USE_GNUTLS */
diff --git a/lib/vtls/gtls.h b/lib/vtls/gtls.h
index 12460be..d02a366 100644
--- a/lib/vtls/gtls.h
+++ b/lib/vtls/gtls.h
@@ -53,6 +53,8 @@ void Curl_gtls_md5sum(unsigned char *tmp, /* input */
                       unsigned char *md5sum, /* output */
                       size_t md5len);
 
+bool Curl_gtls_cert_status_request(void);
+
 /* API setup for GnuTLS */
 #define curlssl_init Curl_gtls_init
 #define curlssl_cleanup Curl_gtls_cleanup
@@ -70,6 +72,7 @@ void Curl_gtls_md5sum(unsigned char *tmp, /* input */
 #define curlssl_data_pending(x,y) ((void)x, (void)y, 0)
 #define curlssl_random(x,y,z) Curl_gtls_random(x,y,z)
 #define curlssl_md5sum(a,b,c,d) Curl_gtls_md5sum(a,b,c,d)
+#define curlssl_cert_status_request() Curl_gtls_cert_status_request()
 #define CURL_SSL_BACKEND CURLSSLBACKEND_GNUTLS
 
 #endif /* USE_GNUTLS */
-- 
2.1.4

From 38fb2cd0e2b60d8ab34f08564fec1a83d5e782c8 Mon Sep 17 00:00:00 2001
From: Alessandro Ghedini <[email protected]>
Date: Tue, 24 Jun 2014 23:25:59 +0200
Subject: [PATCH 3/4] nss: add support for the Certificate Status Request TLS
 extension

Also known as "status_request" or OCSP stapling, defined in RFC6066 section 8.

This requires NSS 3.15 or higher.
---
 lib/vtls/nss.c  | 45 +++++++++++++++++++++++++++++++++++++++++++++
 lib/vtls/nssg.h |  3 +++
 2 files changed, 48 insertions(+)

diff --git a/lib/vtls/nss.c b/lib/vtls/nss.c
index 37fe480..0dff268 100644
--- a/lib/vtls/nss.c
+++ b/lib/vtls/nss.c
@@ -639,6 +639,34 @@ static SECStatus nss_auth_cert_hook(void *arg, PRFileDesc *fd, PRBool checksig,
                                     PRBool isServer)
 {
   struct connectdata *conn = (struct connectdata *)arg;
+
+#ifdef SSL_ENABLE_OCSP_STAPLING
+  if(conn->data->set.ssl.verifystatus) {
+    SECStatus cacheResult;
+
+    const SECItemArray *csa = SSL_PeerStapledOCSPResponses(fd);
+    if(!csa) {
+      failf(conn->data, "Invalid OCSP response");
+      return SECFailure;
+    }
+
+    if(csa->len == 0) {
+      failf(conn->data, "No OCSP response received");
+      return SECFailure;
+    }
+
+    cacheResult = CERT_CacheOCSPResponseFromSideChannel(
+      CERT_GetDefaultCertDB(), SSL_PeerCertificate(fd),
+      PR_Now(), &csa->items[0], arg
+    );
+
+    if(cacheResult != SECSuccess) {
+      failf(conn->data, "Invalid OCSP response");
+      return cacheResult;
+    }
+  }
+#endif
+
   if(!conn->data->set.ssl.verifypeer) {
     infof(conn->data, "skipping SSL peer certificate verification\n");
     return SECSuccess;
@@ -1620,6 +1648,14 @@ static CURLcode nss_setup_connect(struct connectdata *conn, int sockindex)
     SSL_SetPKCS11PinArg(connssl->handle, data->set.str[STRING_KEY_PASSWD]);
   }
 
+#ifdef SSL_ENABLE_OCSP_STAPLING
+  if(data->set.ssl.verifystatus) {
+    if(SSL_OptionSet(connssl->handle, SSL_ENABLE_OCSP_STAPLING, PR_TRUE)
+        != SECSuccess)
+      goto error;
+  }
+#endif
+
 #ifdef USE_NGHTTP2
   if(data->set.httpversion == CURL_HTTP_VERSION_2_0) {
 #ifdef SSL_ENABLE_NPN
@@ -1908,4 +1944,13 @@ void Curl_nss_md5sum(unsigned char *tmp, /* input */
   PK11_DestroyContext(MD5pw, PR_TRUE);
 }
 
+bool Curl_nss_cert_status_request(void)
+{
+#ifdef SSL_ENABLE_OCSP_STAPLING
+  return TRUE;
+#else
+  return FALSE;
+#endif
+}
+
 #endif /* USE_NSS */
diff --git a/lib/vtls/nssg.h b/lib/vtls/nssg.h
index 74840e8..963ce4a 100644
--- a/lib/vtls/nssg.h
+++ b/lib/vtls/nssg.h
@@ -60,6 +60,8 @@ void Curl_nss_md5sum(unsigned char *tmp, /* input */
                      unsigned char *md5sum, /* output */
                      size_t md5len);
 
+bool Curl_nss_cert_status_request(void);
+
 /* this backend supports the CAPATH option */
 #define have_curlssl_ca_path 1
 
@@ -86,6 +88,7 @@ void Curl_nss_md5sum(unsigned char *tmp, /* input */
 #define curlssl_data_pending(x,y) ((void)x, (void)y, 0)
 #define curlssl_random(x,y,z) Curl_nss_random(x,y,z)
 #define curlssl_md5sum(a,b,c,d) Curl_nss_md5sum(a,b,c,d)
+#define curlssl_cert_status_request() Curl_nss_cert_status_request()
 #define CURL_SSL_BACKEND CURLSSLBACKEND_NSS
 
 #endif /* USE_NSS */
-- 
2.1.4

From 731aaedce7f9aea243c6c2ec3644c9a3c19af8d7 Mon Sep 17 00:00:00 2001
From: Alessandro Ghedini <[email protected]>
Date: Mon, 16 Jun 2014 20:47:26 +0200
Subject: [PATCH 4/4] curl: add --cert-status option

This enables the CURLOPT_SSL_VERIFYSTATUS functionality.
---
 docs/curl.1         | 10 ++++++++++
 src/tool_cfgable.h  |  1 +
 src/tool_getparam.c |  5 +++++
 src/tool_operate.c  |  3 +++
 4 files changed, 19 insertions(+)

diff --git a/docs/curl.1 b/docs/curl.1
index 0b9971c..aa4ceb9 100644
--- a/docs/curl.1
+++ b/docs/curl.1
@@ -552,6 +552,16 @@ This is currently only implemented in the OpenSSL, GnuTLS and GSKit backends.
 
 If this option is used several times, the last one will be used.
 (Added in 7.39.0)
+.IP "--cert-status"
+(SSL) Tells curl to verify the status of the server certificate by using the
+Certificate Status Request (aka. OCSP stapling) TLS extension.
+
+If this option is enabled and the server sends an invalid (e.g. expired)
+response, if the response suggests that the server certificate has been revoked,
+or no response at all is received, the verification fails.
+
+This is currently only implemented in the GnuTLS and NSS backends.
+(Added in 7.40.0)
 .IP "-f, --fail"
 (HTTP) Fail silently (no output at all) on server errors. This is mostly done
 to better enable scripts etc to better deal with failed attempts. In normal
diff --git a/src/tool_cfgable.h b/src/tool_cfgable.h
index cf8d563..4008cd0 100644
--- a/src/tool_cfgable.h
+++ b/src/tool_cfgable.h
@@ -126,6 +126,7 @@ struct OperationConfig {
   bool globoff;
   bool use_httpget;
   bool insecure_ok;         /* set TRUE to allow insecure SSL connects */
+  bool verifystatus;
   bool create_dirs;
   bool ftp_create_dirs;
   bool ftp_skip_ip;
diff --git a/src/tool_getparam.c b/src/tool_getparam.c
index 3932ccb..ee198c3 100644
--- a/src/tool_getparam.c
+++ b/src/tool_getparam.c
@@ -217,6 +217,7 @@ static const struct LongShort aliases[]= {
   {"En", "ssl-allow-beast",          FALSE},
   {"Eo", "login-options",            TRUE},
   {"Ep", "pinnedpubkey",             TRUE},
+  {"Eq", "cert-status",              FALSE},
   {"f",  "fail",                     FALSE},
   {"F",  "form",                     TRUE},
   {"Fs", "form-string",              TRUE},
@@ -1363,6 +1364,10 @@ ParameterError getparameter(char *flag,    /* f or -long-flag */
         GetStr(&config->pinnedpubkey, nextarg);
         break;
 
+      case 'q': /* --cert-status */
+        config->verifystatus = TRUE;
+        break;
+
       default: /* certificate file */
       {
         char *certname, *passphrase;
diff --git a/src/tool_operate.c b/src/tool_operate.c
index a21bbca..04fd59b 100644
--- a/src/tool_operate.c
+++ b/src/tool_operate.c
@@ -1038,6 +1038,9 @@ static CURLcode operate_do(struct GlobalConfig *global,
             /* libcurl default is strict verifyhost -> 2L   */
             /* my_setopt(curl, CURLOPT_SSL_VERIFYHOST, 2L); */
           }
+
+          if(config->verifystatus)
+            my_setopt(curl, CURLOPT_SSL_VERIFYSTATUS, 1L);
         }
 
         if(built_in_protos & (CURLPROTO_SCP|CURLPROTO_SFTP)) {
-- 
2.1.4

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