http: improve AWS HTTP v4 Signature auth

- Add support services without region and service prefixes in
the URL endpoint (ex. Min.IO, GCP, Yandex Cloud, Mail.Ru Cloud Solutions, etc)
by providing region and service parameters via aws-sigv4 option.
- Add [:region[:service]] suffix to aws-sigv4 option;
- Fix memory allocation errors.
- Refactor memory management.
- Use Curl_http_method instead() STRING_CUSTOMREQUEST.
- Refactor canonical headers generating.
- Remove repeated sha256_to_hex() usage.
- Add some docs fixes.
- Add some codestyle fixes.
- Add overloaded strndup() for debug - curl_dbg_strndup().
- Update tests.

Closes #6524

src/tool_cfgable.c

@@ -169,7 +169,7 @@ static void free_config_fields(struct OperationConfig *config)
   Curl_safefree(config->ftp_account);
   Curl_safefree(config->ftp_alternative_to_user);
 
-  Curl_safefree(config->aws_sigv4_provider);
+  Curl_safefree(config->aws_sigv4);
 }
 
 void config_free(struct OperationConfig *config)

src/tool_cfgable.h

@@ -284,7 +284,7 @@ struct OperationConfig {
                                      0 is valid. default: CURL_HET_DEFAULT. */
   bool haproxy_protocol;          /* whether to send HAProxy protocol v1 */
   bool disallow_username_in_url;  /* disallow usernames in URLs */
-  char *aws_sigv4_provider;
+  char *aws_sigv4;
   struct GlobalConfig *global;
   struct OperationConfig *prev;
   struct OperationConfig *next;   /* Always last in the struct */

src/tool_getparam.c

@@ -113,7 +113,7 @@ static const struct LongShort aliases[]= {
   {"*t", "proxy-ntlm",               ARG_BOOL},
   {"*u", "crlf",                     ARG_BOOL},
   {"*v", "stderr",                   ARG_FILENAME},
-  {"*V", "aws-sigv4",             ARG_STRING},
+  {"*V", "aws-sigv4",                ARG_STRING},
   {"*w", "interface",                ARG_STRING},
   {"*x", "krb",                      ARG_STRING},
   {"*x", "krb4",                     ARG_STRING},
@@ -806,8 +806,9 @@ ParameterError getparameter(const char *flag, /* f or -long-flag */
 
       case 'V': /* --aws-sigv4 */
         config->authtype |= CURLAUTH_AWS_SIGV4;
-        GetStr(&config->aws_sigv4_provider, nextarg);
+        GetStr(&config->aws_sigv4, nextarg);
         break;
+
       case 'v': /* --stderr */
         if(strcmp(nextarg, "-")) {
           FILE *newfile = fopen(nextarg, FOPEN_WRITETEXT);

src/tool_help.c

@@ -133,7 +133,7 @@ static const struct helptxt helptext[] = {
   {"-a, --append",
    "Append to target file when uploading",
    CURLHELP_FTP | CURLHELP_SFTP},
-  {"    --aws-sigv4 <provider1[:provider2]>",
+  {"    --aws-sigv4 <provider1[:provider2[:region[:service]]]>",
    "Use AWS V4 signature authentication",
    CURLHELP_AUTH | CURLHELP_HTTP},
   {"    --basic",

src/tool_operate.c

@@ -1662,7 +1662,7 @@ static CURLcode single_transfer(struct GlobalConfig *global,
           my_setopt_str(curl, CURLOPT_PROXY_SSLKEYTYPE,
                         config->proxy_key_type);
           my_setopt_str(curl, CURLOPT_AWS_SIGV4,
-                        config->aws_sigv4_provider);
+                        config->aws_sigv4);
 
           if(config->insecure_ok) {
             my_setopt(curl, CURLOPT_SSL_VERIFYPEER, 0L);