dirmngr: Add option--user-agent and always use a User-Agent header.

* dirmngr/dirmngr.h (opt): Add user_agent.
* dirmngr/dirmngr.c (oUserAgent): New.
(opts): Add "user-agent".
(parse_rereadable_options): Set option.
* dirmngr/ks-engine-hkp.c (send_request): Send User-Agent.
* dirmngr/ks-engine-http.c (ks_http_fetch): Ditto.
* dirmngr/ocsp.c (do_ocsp_request): Ditto.
--

Note that the http_open_document function is not used by dirmngr.  If
it ever gets used we may want to add a way to configure the http.c
module with a user-agent string, so that it is send by the
send_request function and we do not need to explictly do that in the
caller.

GnuPG-bug-id: 7715

NEWS

@@ -7,6 +7,8 @@ Noteworthy changes in version 2.5.9 (unreleased)
   * gpg: Do not show the non-standard secp256k1 curve in the menu to
     select the curve.  It can however be specified using its name.
 
+  * dirmngr: New option --user-agent and send a default User-Agent of
+    "GnuPG/2.6" for all HTTP requests.  [T7715]
 
   Release-info: https://dev.gnupg.org/T7695
 

dirmngr/dirmngr.c

@@ -161,6 +161,7 @@ enum cmd_and_opt_values {
   oListenBacklog,
   oFakeCRL,
   oCompatibilityFlags,
+  oUserAgent,
   aTest
 };
 
@@ -251,6 +252,7 @@ static gpgrt_opt_t opts[] = {
                 N_("|URL|redirect all HTTP requests to URL")),
   ARGPARSE_s_n (oHonorHTTPProxy, "honor-http-proxy",
                 N_("use system's HTTP proxy setting")),
+  ARGPARSE_s_s (oUserAgent, "user-agent", "@"),
   ARGPARSE_s_s (oLDAPWrapperProgram, "ldap-wrapper-program", "@"),
 
   ARGPARSE_header ("Keyserver", N_("Configuration for OpenPGP servers")),
@@ -695,6 +697,7 @@ parse_rereadable_options (gpgrt_argparse_t *pargs, int reread)
       opt.ocsp_max_period = 90 * 86400;       /* 90 days.  */
       opt.ocsp_current_period = 3 * 60 * 60;  /* 3 hours. */
       opt.max_replies = DEFAULT_MAX_REPLIES;
+      opt.user_agent = "GnuPG/2.6";
       while (opt.ocsp_signer)
         {
           fingerprint_list_t tmp = opt.ocsp_signer->next;
@@ -906,6 +909,15 @@ parse_rereadable_options (gpgrt_argparse_t *pargs, int reread)
         }
       break;
 
+    case oUserAgent:
+      if (strpbrk (pargs->r.ret_str, "\r\n"))
+        ; /* Ignore if the caller tried to insert CR or LF.  */
+      else if (!strcmp (pargs->r.ret_str, "none"))
+        opt.user_agent = "";
+      else
+        opt.user_agent = pargs->r.ret_str;
+      break;
+
     default:
       return 0; /* Not handled. */
     }

dirmngr/dirmngr.h

@@ -160,6 +160,8 @@ struct
 
   strlist_t keyserver;              /* List of default keyservers.  */
 
+  const char *user_agent;           /* The HTTP Use-Agent (never NULL).  */
+
   /* Compatibility flags (COMPAT_FLAG_xxxx).  */
   unsigned int compat_flags;
 } opt;

dirmngr/ks-engine-hkp.c

@@ -1278,6 +1278,8 @@ send_request (ctrl_t ctrl, const char *request, const char *hostportstr,
          we're good with both HTTP 1.0 and 1.1.  */
       es_fputs ("Pragma: no-cache\r\n"
                 "Cache-Control: no-cache\r\n", fp);
+      if (*opt.user_agent)
+        es_fprintf (fp, "User-Agent: %s\r\n", opt.user_agent);
       if (post_cb)
         err = post_cb (post_cb_value, http);
       if (!err)

dirmngr/ks-engine-http.c

@@ -130,6 +130,8 @@ ks_http_fetch (ctrl_t ctrl, const char *url, unsigned int flags,
       if ((flags & KS_HTTP_FETCH_NOCACHE))
         es_fputs ("Pragma: no-cache\r\n"
                   "Cache-Control: no-cache\r\n", fp);
+      if (*opt.user_agent)
+        es_fprintf (fp, "User-Agent: %s\r\n", opt.user_agent);
       http_start_data (http);
       if (es_ferror (fp))
         err = gpg_error_from_syserror ();

dirmngr/ocsp.c

@@ -197,6 +197,9 @@ do_ocsp_request (ctrl_t ctrl, ksba_ocsp_t ocsp,
       return err;
     }
 
+  if (*opt.user_agent)
+    es_fprintf (http_get_write_ptr (http),
+                "User-Agent: %s\r\n", opt.user_agent);
   es_fprintf (http_get_write_ptr (http),
 	      "Content-Type: application/ocsp-request\r\n"
 	      "Content-Length: %lu\r\n",

doc/dirmngr.texi

@@ -429,6 +429,12 @@ ignoring DPs entirely.
 Ignore all OCSP URLs contained in the certificate.  The effect is to
 force the use of the default responder.
 
+@item --user-agent @var{string}
+@opindex user-agent
+Change the default User-Agent for HTTP requests to @var{string}.  If
+@var{string} is empty or has the value ``none'' no User-Agent header
+will be used.
+
 @item --honor-http-proxy
 @opindex honor-http-proxy
 If the environment variable @env{http_proxy} has been set, use its