hsts: add support for Strict-Transport-Security

- enable in the build (configure)
- header parsing
- host name lookup
- unit tests for the above
- CI build
- CURL_VERSION_HSTS bit
- curl_version_info support
- curl -V output
- curl-config --features
- CURLOPT_HSTS_CTRL
- man page for CURLOPT_HSTS_CTRL
- curl --hsts (sets CURLOPT_HSTS_CTRL and works with --libcurl)
- man page for --hsts
- save cache to disk
- load cache from disk
- CURLOPT_HSTS
- man page for CURLOPT_HSTS
- added docs/HSTS.md
- fixed --version docs
- adjusted curl_easy_duphandle

Closes #5896

src/tool_cfgable.c

@@ -54,6 +54,7 @@ static void free_config_fields(struct OperationConfig *config)
   Curl_safefree(config->egd_file);
   Curl_safefree(config->useragent);
   Curl_safefree(config->altsvc);
+  Curl_safefree(config->hsts);
   Curl_safefree(config->cookie);
   Curl_safefree(config->cookiejar);
   Curl_safefree(config->cookiefile);

src/tool_cfgable.h

@@ -58,6 +58,7 @@ struct OperationConfig {
   char *cookiejar;          /* write to this file */
   char *cookiefile;         /* read from this file */
   char *altsvc;             /* alt-svc cache file name */
+  char *hsts;               /* HSTS cache file name */
   bool cookiesession;       /* new session? */
   bool encoding;            /* Accept-Encoding please */
   bool tr_encoding;         /* Transfer-Encoding please */

src/tool_getparam.c

@@ -219,6 +219,7 @@ static const struct LongShort aliases[]= {
   {"A",  "user-agent",               ARG_STRING},
   {"b",  "cookie",                   ARG_STRING},
   {"ba", "alt-svc",                  ARG_STRING},
+  {"bb", "hsts",                     ARG_STRING},
   {"B",  "use-ascii",                ARG_BOOL},
   {"c",  "cookie-jar",               ARG_STRING},
   {"C",  "continue-at",              ARG_STRING},
@@ -1291,6 +1292,12 @@ ParameterError getparameter(const char *flag, /* f or -long-flag */
         else
           return PARAM_LIBCURL_DOESNT_SUPPORT;
         break;
+      case 'b': /* --hsts */
+        if(curlinfo->features & CURL_VERSION_HSTS)
+          GetStr(&config->hsts, nextarg);
+        else
+          return PARAM_LIBCURL_DOESNT_SUPPORT;
+        break;
       default:  /* --cookie string coming up: */
         if(nextarg[0] == '@') {
           nextarg++;

src/tool_help.c

@@ -328,6 +328,9 @@ static const struct helptxt helptext[] = {
   {"    --hostpubmd5 <md5>",
    "Acceptable MD5 hash of the host public key",
    CURLHELP_SFTP | CURLHELP_SCP},
+  {"    --hsts <file name>",
+   "Enable HSTS with this cache file",
+   CURLHELP_HTTP},
   {"    --http0.9",
    "Allow HTTP 0.9 responses",
    CURLHELP_HTTP},
@@ -862,6 +865,7 @@ static const struct feat feats[] = {
   {"MultiSSL",       CURL_VERSION_MULTI_SSL},
   {"PSL",            CURL_VERSION_PSL},
   {"alt-svc",        CURL_VERSION_ALTSVC},
+  {"HSTS",           CURL_VERSION_HSTS},
 };
 
 static void print_category(curlhelp_t category)

src/tool_operate.c

@@ -2072,6 +2072,9 @@ static CURLcode single_transfer(struct GlobalConfig *global,
         if(config->altsvc)
           my_setopt_str(curl, CURLOPT_ALTSVC, config->altsvc);
 
+        if(config->hsts)
+          my_setopt_bitmask(curl, CURLOPT_HSTS_CTRL, CURLHSTS_ENABLE);
+
 #ifdef USE_METALINK
         if(!metalink && config->use_metalink) {
           outs->metalink_parser = metalink_parser_context_new();

src/tool_setopt.c

@@ -62,6 +62,11 @@ const struct NameValue setopt_nv_CURL_SOCKS_PROXY[] = {
   NVEND,
 };
 
+const struct NameValueUnsigned setopt_nv_CURLHSTS[] = {
+  NV(CURLHSTS_ENABLE),
+  NVEND,
+};
+
 const struct NameValueUnsigned setopt_nv_CURLAUTH[] = {
   NV(CURLAUTH_ANY),             /* combination */
   NV(CURLAUTH_ANYSAFE),         /* combination */

src/tool_setopt.h

@@ -64,8 +64,10 @@ extern const struct NameValueUnsigned setopt_nv_CURLSSLOPT[];
 extern const struct NameValue setopt_nv_CURL_NETRC[];
 extern const struct NameValue setopt_nv_CURLPROTO[];
 extern const struct NameValueUnsigned setopt_nv_CURLAUTH[];
+extern const struct NameValueUnsigned setopt_nv_CURLHSTS[];
 
 /* Map options to NameValue sets */
+#define setopt_nv_CURLOPT_HSTS_CTRL setopt_nv_CURLHSTS
 #define setopt_nv_CURLOPT_HTTP_VERSION setopt_nv_CURL_HTTP_VERSION
 #define setopt_nv_CURLOPT_HTTPAUTH setopt_nv_CURLAUTH
 #define setopt_nv_CURLOPT_SSLVERSION setopt_nv_CURL_SSLVERSION