text: /* Licensed to the Apache Software Foundation (ASF) under one or more
   * contributor license agreements.  See the NOTICE file distributed with
   * this work for additional information regarding copyright ownership.
   * The ASF licenses this file to You under the Apache License, Version 2.0
   * (the "License"); you may not use this file except in compliance with
   * the License.  You may obtain a copy of the License at
   *
   *     http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  
  /*
   * http_script: keeps all script-related ramblings together.
   *
   * Compliant to CGI/1.1 spec
   *
   * Adapted by rst from original NCSA code by Rob McCool
   *
   * Apache adds some new env vars; REDIRECT_URL and REDIRECT_QUERY_STRING for
   * custom error responses, and DOCUMENT_ROOT because we found it useful.
   * It also adds SERVER_ADMIN - useful for scripts to know who to mail when
   * they fail.
   */
  
  #include "apr.h"
  #include "apr_strings.h"
  #include "apr_thread_proc.h"    /* for RLIMIT stuff */
  #include "apr_optional.h"
  #include "apr_buckets.h"
  #include "apr_lib.h"
  #include "apr_poll.h"
  
  #define APR_WANT_STRFUNC
  #define APR_WANT_MEMFUNC
  #include "apr_want.h"
  
  #include "util_filter.h"
  #include "ap_config.h"
  #include "httpd.h"
  #include "http_config.h"
  #include "http_request.h"
  #include "http_core.h"
  #include "http_protocol.h"
  #include "http_main.h"
  #include "http_log.h"
  #include "util_script.h"
  #include "ap_mpm.h"
  #include "mod_core.h"
  #include "mod_cgi.h"
  
  #if APR_HAVE_STRUCT_RLIMIT
  #if defined (RLIMIT_CPU) || defined (RLIMIT_NPROC) || defined (RLIMIT_DATA) || defined(RLIMIT_VMEM) || defined(RLIMIT_AS)
  #define AP_CGI_USE_RLIMIT
  #endif
  #endif
  
  module AP_MODULE_DECLARE_DATA cgi_module;
  
  static APR_OPTIONAL_FN_TYPE(ap_register_include_handler) *cgi_pfn_reg_with_ssi;
  static APR_OPTIONAL_FN_TYPE(ap_ssi_get_tag_and_value) *cgi_pfn_gtv;
  static APR_OPTIONAL_FN_TYPE(ap_ssi_parse_string) *cgi_pfn_ps;
  static APR_OPTIONAL_FN_TYPE(ap_cgi_build_command) *cgi_build_command;
  
  /* Read and discard the data in the brigade produced by a CGI script */
  static void discard_script_output(apr_bucket_brigade *bb);
  
  /* KLUDGE --- for back-combatibility, we don't have to check ExecCGI
   * in ScriptAliased directories, which means we need to know if this
   * request came through ScriptAlias or not... so the Alias module
   * leaves a note for us.
   */
  
  static int is_scriptaliased(request_rec *r)
  {
      const char *t = apr_table_get(r->notes, "alias-forced-type");
      return t && (!strcasecmp(t, "cgi-script"));
  }
  
  /* Configuration stuff */
  
  #define DEFAULT_LOGBYTES 10385760
  #define DEFAULT_BUFBYTES 1024
  
  typedef struct {
      const char *logname;
      long        logbytes;
      apr_size_t  bufbytes;
  } cgi_server_conf;
  
  static void *create_cgi_config(apr_pool_t *p, server_rec *s)
  {
      cgi_server_conf *c =
      (cgi_server_conf *) apr_pcalloc(p, sizeof(cgi_server_conf));
  
      c->logname = NULL;
      c->logbytes = DEFAULT_LOGBYTES;
      c->bufbytes = DEFAULT_BUFBYTES;
  
      return c;
  }
  
  static void *merge_cgi_config(apr_pool_t *p, void *basev, void *overridesv)
  {
      cgi_server_conf *base = (cgi_server_conf *) basev,
                      *overrides = (cgi_server_conf *) overridesv;
  
      return overrides->logname ? overrides : base;
  }
  
  static const char *set_scriptlog(cmd_parms *cmd, void *dummy, const char *arg)
  {
      server_rec *s = cmd->server;
      cgi_server_conf *conf = ap_get_module_config(s->module_config,
                                                   &cgi_module);
  
      conf->logname = ap_server_root_relative(cmd->pool, arg);
  
      if (!conf->logname) {
          return apr_pstrcat(cmd->pool, "Invalid ScriptLog path ",
                             arg, NULL);
      }
  
      return NULL;
  }
  
  static const char *set_scriptlog_length(cmd_parms *cmd, void *dummy,
                                          const char *arg)
  {
      server_rec *s = cmd->server;
      cgi_server_conf *conf = ap_get_module_config(s->module_config,
                                                   &cgi_module);
  
      conf->logbytes = atol(arg);
      return NULL;
  }
  
  static const char *set_scriptlog_buffer(cmd_parms *cmd, void *dummy,
                                          const char *arg)
  {
      server_rec *s = cmd->server;
      cgi_server_conf *conf = ap_get_module_config(s->module_config,
                                                   &cgi_module);
  
      conf->bufbytes = atoi(arg);
      return NULL;
  }
  
  static const command_rec cgi_cmds[] =
  {
  AP_INIT_TAKE1("ScriptLog", set_scriptlog, NULL, RSRC_CONF,
       "the name of a log for script debugging info"),
  AP_INIT_TAKE1("ScriptLogLength", set_scriptlog_length, NULL, RSRC_CONF,
       "the maximum length (in bytes) of the script debug log"),
  AP_INIT_TAKE1("ScriptLogBuffer", set_scriptlog_buffer, NULL, RSRC_CONF,
       "the maximum size (in bytes) to record of a POST request"),
      {NULL}
  };
  
  static int log_scripterror(request_rec *r, cgi_server_conf * conf, int ret,
                             apr_status_t rv, char *logno, char *error)
  {
      apr_file_t *f = NULL;
      apr_finfo_t finfo;
      char time_str[APR_CTIME_LEN];
      int log_flags = rv ? APLOG_ERR : APLOG_ERR;
  
      ap_log_rerror(APLOG_MARK, log_flags, rv, r,
                    "%s%s: %s", logno ? logno : "", error, r->filename);
  
      /* XXX Very expensive mainline case! Open, then getfileinfo! */
      if (!conf->logname ||
          ((apr_stat(&finfo, conf->logname,
                     APR_FINFO_SIZE, r->pool) == APR_SUCCESS) &&
           (finfo.size > conf->logbytes)) ||
          (apr_file_open(&f, conf->logname,
                         APR_APPEND|APR_WRITE|APR_CREATE, APR_OS_DEFAULT,
                         r->pool) != APR_SUCCESS)) {
          return ret;
      }
  
      /* "%% [Wed Jun 19 10:53:21 1996] GET /cgi-bin/printenv HTTP/1.0" */
      apr_ctime(time_str, apr_time_now());
      apr_file_printf(f, "%%%% [%s] %s %s%s%s %s\n", time_str, r->method, r->uri,
                      r->args ? "?" : "", r->args ? r->args : "", r->protocol);
      /* "%% 500 /usr/local/apache/cgi-bin */
      apr_file_printf(f, "%%%% %d %s\n", ret, r->filename);
  
      apr_file_printf(f, "%%error\n%s\n", error);
  
      apr_file_close(f);
      return ret;
  }
  
  /* Soak up stderr from a script and redirect it to the error log.
   */
  static apr_status_t log_script_err(request_rec *r, apr_file_t *script_err)
  {
      char argsbuffer[HUGE_STRING_LEN];
      char *newline;
      apr_status_t rv;
      cgi_server_conf *conf = ap_get_module_config(r->server->module_config, &cgi_module);
  
      while ((rv = apr_file_gets(argsbuffer, HUGE_STRING_LEN,
                                 script_err)) == APR_SUCCESS) {
          newline = strchr(argsbuffer, '\n');
          if (newline) {
              *newline = '\0';
          }
          log_scripterror(r, conf, r->status, 0, APLOGNO(01215), argsbuffer);
      }
  
      return rv;
  }
  
  static int log_script(request_rec *r, cgi_server_conf * conf, int ret,
                        char *dbuf, const char *sbuf, apr_bucket_brigade *bb,
                        apr_file_t *script_err)
  {
      const apr_array_header_t *hdrs_arr = apr_table_elts(r->headers_in);
      const apr_table_entry_t *hdrs = (const apr_table_entry_t *) hdrs_arr->elts;
      char argsbuffer[HUGE_STRING_LEN];
      apr_file_t *f = NULL;
      apr_bucket *e;
      const char *buf;
      apr_size_t len;
      apr_status_t rv;
      int first;
      int i;
      apr_finfo_t finfo;
      char time_str[APR_CTIME_LEN];
  
      /* XXX Very expensive mainline case! Open, then getfileinfo! */
      if (!conf->logname ||
          ((apr_stat(&finfo, conf->logname,
                     APR_FINFO_SIZE, r->pool) == APR_SUCCESS) &&
           (finfo.size > conf->logbytes)) ||
          (apr_file_open(&f, conf->logname,
                         APR_APPEND|APR_WRITE|APR_CREATE, APR_OS_DEFAULT,
                         r->pool) != APR_SUCCESS)) {
          /* Soak up script output */
          discard_script_output(bb);
          log_script_err(r, script_err);
          return ret;
      }
  
      /* "%% [Wed Jun 19 10:53:21 1996] GET /cgi-bin/printenv HTTP/1.0" */
      apr_ctime(time_str, apr_time_now());
      apr_file_printf(f, "%%%% [%s] %s %s%s%s %s\n", time_str, r->method, r->uri,
                      r->args ? "?" : "", r->args ? r->args : "", r->protocol);
      /* "%% 500 /usr/local/apache/cgi-bin" */
      apr_file_printf(f, "%%%% %d %s\n", ret, r->filename);
  
      apr_file_puts("%request\n", f);
      for (i = 0; i < hdrs_arr->nelts; ++i) {
          if (!hdrs[i].key)
              continue;
          apr_file_printf(f, "%s: %s\n", hdrs[i].key, hdrs[i].val);
      }
      if ((r->method_number == M_POST || r->method_number == M_PUT) &&
          *dbuf) {
          apr_file_printf(f, "\n%s\n", dbuf);
      }
  
      apr_file_puts("%response\n", f);
      hdrs_arr = apr_table_elts(r->err_headers_out);
      hdrs = (const apr_table_entry_t *) hdrs_arr->elts;
  
      for (i = 0; i < hdrs_arr->nelts; ++i) {
          if (!hdrs[i].key)
              continue;
          apr_file_printf(f, "%s: %s\n", hdrs[i].key, hdrs[i].val);
      }
  
      if (sbuf && *sbuf)
          apr_file_printf(f, "%s\n", sbuf);
  
      first = 1;
      for (e = APR_BRIGADE_FIRST(bb);
           e != APR_BRIGADE_SENTINEL(bb);
           e = APR_BUCKET_NEXT(e))
      {
          if (APR_BUCKET_IS_EOS(e)) {
              break;
          }
          rv = apr_bucket_read(e, &buf, &len, APR_BLOCK_READ);
          if (rv != APR_SUCCESS || (len == 0)) {
              break;
          }
          if (first) {
              apr_file_puts("%stdout\n", f);
              first = 0;
          }
          apr_file_write(f, buf, &len);
          apr_file_puts("\n", f);
      }
  
      if (apr_file_gets(argsbuffer, HUGE_STRING_LEN, script_err) == APR_SUCCESS) {
          apr_file_puts("%stderr\n", f);
          apr_file_puts(argsbuffer, f);
          while (apr_file_gets(argsbuffer, HUGE_STRING_LEN,
                               script_err) == APR_SUCCESS) {
              apr_file_puts(argsbuffer, f);
          }
          apr_file_puts("\n", f);
      }
  
      apr_brigade_destroy(bb);
      apr_file_close(script_err);
  
      apr_file_close(f);
      return ret;
  }
  
  
  /* This is the special environment used for running the "exec cmd="
   *   variety of SSI directives.
   */
  static void add_ssi_vars(request_rec *r)
  {
      apr_table_t *e = r->subprocess_env;
  
      if (r->path_info && r->path_info[0] != '\0') {
          request_rec *pa_req;
  
          apr_table_setn(e, "PATH_INFO", ap_escape_shell_cmd(r->pool,
                                                             r->path_info));
  
          pa_req = ap_sub_req_lookup_uri(ap_escape_uri(r->pool, r->path_info),
                                         r, NULL);
          if (pa_req->filename) {
              apr_table_setn(e, "PATH_TRANSLATED",
                             apr_pstrcat(r->pool, pa_req->filename,
                                         pa_req->path_info, NULL));
          }
          ap_destroy_sub_req(pa_req);
      }
  
      if (r->args) {
          char *arg_copy = apr_pstrdup(r->pool, r->args);
  
          apr_table_setn(e, "QUERY_STRING", r->args);
          ap_unescape_url(arg_copy);
          apr_table_setn(e, "QUERY_STRING_UNESCAPED",
                         ap_escape_shell_cmd(r->pool, arg_copy));
      }
  }
  
  static void cgi_child_errfn(apr_pool_t *pool, apr_status_t err,
                              const char *description)
  {
      apr_file_t *stderr_log;
  
      apr_file_open_stderr(&stderr_log, pool);
      /* Escape the logged string because it may be something that
       * came in over the network.
       */
      apr_file_printf(stderr_log,
                      "(%d)%pm: %s\n",
                      err,
                      &err,
  #ifndef AP_UNSAFE_ERROR_LOG_UNESCAPED
                      ap_escape_logitem(pool,
  #endif
                      description
  #ifndef AP_UNSAFE_ERROR_LOG_UNESCAPED
                      )
  #endif
                      );
  }
  
  static apr_status_t run_cgi_child(apr_file_t **script_out,
                                    apr_file_t **script_in,
                                    apr_file_t **script_err,
                                    const char *command,
                                    const char * const argv[],
                                    request_rec *r,
                                    apr_pool_t *p,
                                    cgi_exec_info_t *e_info)
  {
      const char * const *env;
      apr_procattr_t *procattr;
      apr_proc_t *procnew;
      apr_status_t rc = APR_SUCCESS;
  
  #ifdef AP_CGI_USE_RLIMIT
      core_dir_config *conf = ap_get_core_module_config(r->per_dir_config);
  #endif
  
  #ifdef DEBUG_CGI
  #ifdef OS2
      /* Under OS/2 need to use device con. */
      FILE *dbg = fopen("con", "w");
  #else
      FILE *dbg = fopen("/dev/tty", "w");
  #endif
      int i;
  #endif
  
      RAISE_SIGSTOP(CGI_CHILD);
  #ifdef DEBUG_CGI
      fprintf(dbg, "Attempting to exec %s as CGI child (argv0 = %s)\n",
              r->filename, argv[0]);
  #endif
  
      env = (const char * const *)ap_create_environment(p, r->subprocess_env);
  
  #ifdef DEBUG_CGI
      fprintf(dbg, "Environment: \n");
      for (i = 0; env[i]; ++i)
          fprintf(dbg, "'%s'\n", env[i]);
      fclose(dbg);
  #endif
  
      /* Transmute ourselves into the script.
       * NB only ISINDEX scripts get decoded arguments.
       */
      if (((rc = apr_procattr_create(&procattr, p)) != APR_SUCCESS) ||
          ((rc = apr_procattr_io_set(procattr,
                                     e_info->in_pipe,
                                     e_info->out_pipe,
                                     e_info->err_pipe)) != APR_SUCCESS) ||
          ((rc = apr_procattr_dir_set(procattr,
                          ap_make_dirstr_parent(r->pool,
                                                r->filename))) != APR_SUCCESS) ||
  #if defined(RLIMIT_CPU) && defined(AP_CGI_USE_RLIMIT)
          ((rc = apr_procattr_limit_set(procattr, APR_LIMIT_CPU,
                                        conf->limit_cpu)) != APR_SUCCESS) ||
  #endif
  #if defined(AP_CGI_USE_RLIMIT) && (defined(RLIMIT_DATA) || defined(RLIMIT_VMEM) || defined(RLIMIT_AS))
          ((rc = apr_procattr_limit_set(procattr, APR_LIMIT_MEM,
                                        conf->limit_mem)) != APR_SUCCESS) ||
  #endif
  #if defined(RLIMIT_NPROC) && defined(AP_CGI_USE_RLIMIT)
          ((rc = apr_procattr_limit_set(procattr, APR_LIMIT_NPROC,
                                        conf->limit_nproc)) != APR_SUCCESS) ||
  #endif
          ((rc = apr_procattr_cmdtype_set(procattr,
                                          e_info->cmd_type)) != APR_SUCCESS) ||
  
          ((rc = apr_procattr_detach_set(procattr,
                                          e_info->detached)) != APR_SUCCESS) ||
          ((rc = apr_procattr_addrspace_set(procattr,
                                          e_info->addrspace)) != APR_SUCCESS) ||
          ((rc = apr_procattr_child_errfn_set(procattr, cgi_child_errfn)) != APR_SUCCESS)) {
          /* Something bad happened, tell the world. */
          ap_log_rerror(APLOG_MARK, APLOG_ERR, rc, r, APLOGNO(01216)
                        "couldn't set child process attributes: %s", r->filename);
      }
      else {
          procnew = apr_pcalloc(p, sizeof(*procnew));
          rc = ap_os_create_privileged_process(r, procnew, command, argv, env,
                                               procattr, p);
  
          if (rc != APR_SUCCESS) {
              /* Bad things happened. Everyone should have cleaned up. */
              ap_log_rerror(APLOG_MARK, APLOG_ERR|APLOG_TOCLIENT, rc, r,
                            "couldn't create child process: %d: %s", rc,
                            apr_filepath_name_get(r->filename));
          }
          else {
              apr_pool_note_subprocess(p, procnew, APR_KILL_AFTER_TIMEOUT);
  
              *script_in = procnew->out;
              if (!*script_in)
                  return APR_EBADF;
              apr_file_pipe_timeout_set(*script_in, r->server->timeout);
  
              if (e_info->prog_type == RUN_AS_CGI) {
                  *script_out = procnew->in;
                  if (!*script_out)
                      return APR_EBADF;
                  apr_file_pipe_timeout_set(*script_out, r->server->timeout);
  
                  *script_err = procnew->err;
                  if (!*script_err)
                      return APR_EBADF;
                  apr_file_pipe_timeout_set(*script_err, r->server->timeout);
              }
          }
      }
      return (rc);
  }
  
  
  static apr_status_t default_build_command(const char **cmd, const char ***argv,
                                            request_rec *r, apr_pool_t *p,
                                            cgi_exec_info_t *e_info)
  {
      int numwords, x, idx;
      char *w;
      const char *args = NULL;
  
      if (e_info->process_cgi) {
          *cmd = r->filename;
          /* Do not process r->args if they contain an '=' assignment
           */
          if (r->args && r->args[0] && !ap_strchr_c(r->args, '=')) {
              args = r->args;
          }
      }
  
      if (!args) {
          numwords = 1;
      }
      else {
          /* count the number of keywords */
          for (x = 0, numwords = 2; args[x]; x++) {
              if (args[x] == '+') {
                  ++numwords;
              }
          }
      }
      /* Everything is - 1 to account for the first parameter
       * which is the program name.
       */
      if (numwords > APACHE_ARG_MAX - 1) {
          numwords = APACHE_ARG_MAX - 1;    /* Truncate args to prevent overrun */
      }
      *argv = apr_palloc(p, (numwords + 2) * sizeof(char *));
      (*argv)[0] = *cmd;
      for (x = 1, idx = 1; x < numwords; x++) {
          w = ap_getword_nulls(p, &args, '+');
          ap_unescape_url(w);
          (*argv)[idx++] = ap_escape_shell_cmd(p, w);
      }
      (*argv)[idx] = NULL;
  
      return APR_SUCCESS;
  }
  
  static void discard_script_output(apr_bucket_brigade *bb)
  {
      apr_bucket *e;
      const char *buf;
      apr_size_t len;
      apr_status_t rv;
  
      for (e = APR_BRIGADE_FIRST(bb);
           e != APR_BRIGADE_SENTINEL(bb);
           e = APR_BUCKET_NEXT(e))
      {
          if (APR_BUCKET_IS_EOS(e)) {
              break;
          }
          rv = apr_bucket_read(e, &buf, &len, APR_BLOCK_READ);
          if (rv != APR_SUCCESS) {
              break;
          }
      }
  }
  
  #if APR_FILES_AS_SOCKETS
  
  /* A CGI bucket type is needed to catch any output to stderr from the
   * script; see PR 22030. */
  static const apr_bucket_type_t bucket_type_cgi;
  
  struct cgi_bucket_data {
      apr_pollset_t *pollset;
      request_rec *r;
  };
  
  /* Create a CGI bucket using pipes from script stdout 'out'
   * and stderr 'err', for request 'r'. */
  static apr_bucket *cgi_bucket_create(request_rec *r,
                                       apr_file_t *out, apr_file_t *err,
                                       apr_bucket_alloc_t *list)
  {
      apr_bucket *b = apr_bucket_alloc(sizeof(*b), list);
      apr_status_t rv;
      apr_pollfd_t fd;
      struct cgi_bucket_data *data = apr_palloc(r->pool, sizeof *data);
  
      APR_BUCKET_INIT(b);
      b->free = apr_bucket_free;
      b->list = list;
      b->type = &bucket_type_cgi;
      b->length = (apr_size_t)(-1);
      b->start = -1;
  
      /* Create the pollset */
      rv = apr_pollset_create(&data->pollset, 2, r->pool, 0);
      if (rv != APR_SUCCESS) {
          ap_log_rerror(APLOG_MARK, APLOG_ERR, rv, r, APLOGNO(01217)
                       "apr_pollset_create(); check system or user limits");
          return NULL;
      }
  
      fd.desc_type = APR_POLL_FILE;
      fd.reqevents = APR_POLLIN;
      fd.p = r->pool;
      fd.desc.f = out; /* script's stdout */
      fd.client_data = (void *)1;
      rv = apr_pollset_add(data->pollset, &fd);
      if (rv != APR_SUCCESS) {
          ap_log_rerror(APLOG_MARK, APLOG_ERR, rv, r, APLOGNO(01218)
                       "apr_pollset_add(); check system or user limits");
          return NULL;
      }
  
      fd.desc.f = err; /* script's stderr */
      fd.client_data = (void *)2;
      rv = apr_pollset_add(data->pollset, &fd);
      if (rv != APR_SUCCESS) {
          ap_log_rerror(APLOG_MARK, APLOG_ERR, rv, r, APLOGNO(01219)
                       "apr_pollset_add(); check system or user limits");
          return NULL;
      }
  
      data->r = r;
      b->data = data;
      return b;
  }
  
  /* Create a duplicate CGI bucket using given bucket data */
  static apr_bucket *cgi_bucket_dup(struct cgi_bucket_data *data,
                                    apr_bucket_alloc_t *list)
  {
      apr_bucket *b = apr_bucket_alloc(sizeof(*b), list);
      APR_BUCKET_INIT(b);
      b->free = apr_bucket_free;
      b->list = list;
      b->type = &bucket_type_cgi;
      b->length = (apr_size_t)(-1);
      b->start = -1;
      b->data = data;
      return b;
  }
  
  /* Handle stdout from CGI child.  Duplicate of logic from the _read
   * method of the real APR pipe bucket implementation. */
  static apr_status_t cgi_read_stdout(apr_bucket *a, apr_file_t *out,
                                      const char **str, apr_size_t *len)
  {
      char *buf;
      apr_status_t rv;
  
      *str = NULL;
      *len = APR_BUCKET_BUFF_SIZE;
      buf = apr_bucket_alloc(*len, a->list); /* XXX: check for failure? */
  
      rv = apr_file_read(out, buf, len);
  
      if (rv != APR_SUCCESS && rv != APR_EOF) {
          apr_bucket_free(buf);
          return rv;
      }
  
      if (*len > 0) {
          struct cgi_bucket_data *data = a->data;
          apr_bucket_heap *h;
  
          /* Change the current bucket to refer to what we read */
          a = apr_bucket_heap_make(a, buf, *len, apr_bucket_free);
          h = a->data;
          h->alloc_len = APR_BUCKET_BUFF_SIZE; /* note the real buffer size */
          *str = buf;
          APR_BUCKET_INSERT_AFTER(a, cgi_bucket_dup(data, a->list));
      }
      else {
          apr_bucket_free(buf);
          a = apr_bucket_immortal_make(a, "", 0);
          *str = a->data;
      }
      return rv;
  }
  
  /* Read method of CGI bucket: polls on stderr and stdout of the child,
   * sending any stderr output immediately away to the error log. */
  static apr_status_t cgi_bucket_read(apr_bucket *b, const char **str,
                                      apr_size_t *len, apr_read_type_e block)
  {
      struct cgi_bucket_data *data = b->data;
      apr_interval_time_t timeout;
      apr_status_t rv;
      int gotdata = 0;
  
      timeout = block == APR_NONBLOCK_READ ? 0 : data->r->server->timeout;
  
      do {
          const apr_pollfd_t *results;
          apr_int32_t num;
  
          rv = apr_pollset_poll(data->pollset, timeout, &num, &results);
          if (APR_STATUS_IS_TIMEUP(rv)) {
              if (timeout) {
                  ap_log_rerror(APLOG_MARK, APLOG_WARNING, 0, data->r, APLOGNO(01220)
                                "Timeout waiting for output from CGI script %s",
                                data->r->filename);
                  return rv;
              }
              else {
                  return APR_EAGAIN;
              }
          }
          else if (APR_STATUS_IS_EINTR(rv)) {
              continue;
          }
          else if (rv != APR_SUCCESS) {
              ap_log_rerror(APLOG_MARK, APLOG_ERR, rv, data->r, APLOGNO(01221)
                            "poll failed waiting for CGI child");
              return rv;
          }
  
          for (; num; num--, results++) {
              if (results[0].client_data == (void *)1) {
                  /* stdout */
                  rv = cgi_read_stdout(b, results[0].desc.f, str, len);
                  if (APR_STATUS_IS_EOF(rv)) {
                      rv = APR_SUCCESS;
                  }
                  gotdata = 1;
              } else {
                  /* stderr */
                  apr_status_t rv2 = log_script_err(data->r, results[0].desc.f);
                  if (APR_STATUS_IS_EOF(rv2)) {
                      apr_pollset_remove(data->pollset, &results[0]);
                  }
              }
          }
  
      } while (!gotdata);
  
      return rv;
  }
  
  static const apr_bucket_type_t bucket_type_cgi = {
      "CGI", 5, APR_BUCKET_DATA,
      apr_bucket_destroy_noop,
      cgi_bucket_read,
      apr_bucket_setaside_notimpl,
      apr_bucket_split_notimpl,
      apr_bucket_copy_notimpl
  };
  
  #endif
  
  static int cgi_handler(request_rec *r)
  {
      int nph;
      apr_size_t dbpos = 0;
      const char *argv0;
      const char *command;
      const char **argv;
      char *dbuf = NULL;
      apr_file_t *script_out = NULL, *script_in = NULL, *script_err = NULL;
      apr_bucket_brigade *bb;
      apr_bucket *b;
      int is_included;
      int seen_eos, child_stopped_reading;
      apr_pool_t *p;
      cgi_server_conf *conf;
      apr_status_t rv;
      cgi_exec_info_t e_info;
      conn_rec *c;
  
      if (strcmp(r->handler, CGI_MAGIC_TYPE) && strcmp(r->handler, "cgi-script")) {
          return DECLINED;
      }
  
      c = r->connection;
  
      is_included = !strcmp(r->protocol, "INCLUDED");
  
      p = r->main ? r->main->pool : r->pool;
  
      argv0 = apr_filepath_name_get(r->filename);
      nph = !(strncmp(argv0, "nph-", 4));
      conf = ap_get_module_config(r->server->module_config, &cgi_module);
  
      if (!(ap_allow_options(r) & OPT_EXECCGI) && !is_scriptaliased(r))
          return log_scripterror(r, conf, HTTP_FORBIDDEN, 0, APLOGNO(02809),
                                 "Options ExecCGI is off in this directory");
      if (nph && is_included)
          return log_scripterror(r, conf, HTTP_FORBIDDEN, 0, APLOGNO(02810),
                                 "attempt to include NPH CGI script");
  
      if (r->finfo.filetype == APR_NOFILE)
          return log_scripterror(r, conf, HTTP_NOT_FOUND, 0, APLOGNO(02811),
                                 "script not found or unable to stat");
      if (r->finfo.filetype == APR_DIR)
          return log_scripterror(r, conf, HTTP_FORBIDDEN, 0, APLOGNO(02812),
                                 "attempt to invoke directory as script");
  
      if ((r->used_path_info == AP_REQ_REJECT_PATH_INFO) &&
          r->path_info && *r->path_info)
      {
          /* default to accept */
          return log_scripterror(r, conf, HTTP_NOT_FOUND, 0, APLOGNO(02813),
                                 "AcceptPathInfo off disallows user's path");
      }
  /*
      if (!ap_suexec_enabled) {
          if (!ap_can_exec(&r->finfo))
              return log_scripterror(r, conf, HTTP_FORBIDDEN, 0,
                                     "file permissions deny server execution");
      }
  
  */
      ap_add_common_vars(r);
      ap_add_cgi_vars(r);
  
      e_info.process_cgi = 1;
      e_info.cmd_type    = APR_PROGRAM;
      e_info.detached    = 0;
      e_info.in_pipe     = APR_CHILD_BLOCK;
      e_info.out_pipe    = APR_CHILD_BLOCK;
      e_info.err_pipe    = APR_CHILD_BLOCK;
      e_info.prog_type   = RUN_AS_CGI;
      e_info.bb          = NULL;
      e_info.ctx         = NULL;
      e_info.next        = NULL;
      e_info.addrspace   = 0;
  
      /* build the command line */
      if ((rv = cgi_build_command(&command, &argv, r, p, &e_info)) != APR_SUCCESS) {
          ap_log_rerror(APLOG_MARK, APLOG_ERR, rv, r, APLOGNO(01222)
                        "don't know how to spawn child process: %s",
                        r->filename);
          return HTTP_INTERNAL_SERVER_ERROR;
      }
  
      /* run the script in its own process */
      if ((rv = run_cgi_child(&script_out, &script_in, &script_err,
                              command, argv, r, p, &e_info)) != APR_SUCCESS) {
          ap_log_rerror(APLOG_MARK, APLOG_ERR, rv, r, APLOGNO(01223)
                        "couldn't spawn child process: %s", r->filename);
          return HTTP_INTERNAL_SERVER_ERROR;
      }
  
      /* Transfer any put/post args, CERN style...
       * Note that we already ignore SIGPIPE in the core server.
       */
      bb = apr_brigade_create(r->pool, c->bucket_alloc);
      seen_eos = 0;
      child_stopped_reading = 0;
      if (conf->logname) {
          dbuf = apr_palloc(r->pool, conf->bufbytes + 1);
          dbpos = 0;
      }
      do {
          apr_bucket *bucket;
  
          rv = ap_get_brigade(r->input_filters, bb, AP_MODE_READBYTES,
                              APR_BLOCK_READ, HUGE_STRING_LEN);
  
          if (rv != APR_SUCCESS) {
              if (APR_STATUS_IS_TIMEUP(rv)) {
                  ap_log_rerror(APLOG_MARK, APLOG_ERR, rv, r, APLOGNO(01224)
                                "Timeout during reading request entity data");
                  return HTTP_REQUEST_TIME_OUT;
              }
              ap_log_rerror(APLOG_MARK, APLOG_ERR, rv, r, APLOGNO(01225)
                            "Error reading request entity data");
              return ap_map_http_request_error(rv, HTTP_INTERNAL_SERVER_ERROR);
          }
  
          for (bucket = APR_BRIGADE_FIRST(bb);
               bucket != APR_BRIGADE_SENTINEL(bb);
               bucket = APR_BUCKET_NEXT(bucket))
          {
              const char *data;
              apr_size_t len;
  
              if (APR_BUCKET_IS_EOS(bucket)) {
                  seen_eos = 1;
                  break;
              }
  
              /* We can't do much with this. */
              if (APR_BUCKET_IS_FLUSH(bucket)) {
                  continue;
              }
  
              /* If the child stopped, we still must read to EOS. */
              if (child_stopped_reading) {
                  continue;
              }
  
              /* read */
              apr_bucket_read(bucket, &data, &len, APR_BLOCK_READ);
  
              if (conf->logname && dbpos < conf->bufbytes) {
                  int cursize;
  
                  if ((dbpos + len) > conf->bufbytes) {
                      cursize = conf->bufbytes - dbpos;
                  }
                  else {
                      cursize = len;
                  }
                  memcpy(dbuf + dbpos, data, cursize);
                  dbpos += cursize;
              }
  
              /* Keep writing data to the child until done or too much time
               * elapses with no progress or an error occurs.
               */
              rv = apr_file_write_full(script_out, data, len, NULL);
  
              if (rv != APR_SUCCESS) {
                  /* silly script stopped reading, soak up remaining message */
                  child_stopped_reading = 1;
              }
          }
          apr_brigade_cleanup(bb);
      }
      while (!seen_eos);
  
      if (conf->logname) {
          dbuf[dbpos] = '\0';
      }
      /* Is this flush really needed? */
      apr_file_flush(script_out);
      apr_file_close(script_out);
  
      AP_DEBUG_ASSERT(script_in != NULL);
  
  #if APR_FILES_AS_SOCKETS
      apr_file_pipe_timeout_set(script_in, 0);
      apr_file_pipe_timeout_set(script_err, 0);
  
      b = cgi_bucket_create(r, script_in, script_err, c->bucket_alloc);
      if (b == NULL)
          return HTTP_INTERNAL_SERVER_ERROR;
  #else
      b = apr_bucket_pipe_create(script_in, c->bucket_alloc);
  #endif
      APR_BRIGADE_INSERT_TAIL(bb, b);
      b = apr_bucket_eos_create(c->bucket_alloc);
      APR_BRIGADE_INSERT_TAIL(bb, b);
  
      /* Handle script return... */
      if (!nph) {
          const char *location;
          char sbuf[MAX_STRING_LEN];
          int ret;
  
          if ((ret = ap_scan_script_header_err_brigade_ex(r, bb, sbuf,
                                                          APLOG_MODULE_INDEX)))
          {
              ret = log_script(r, conf, ret, dbuf, sbuf, bb, script_err);
  
              /*
               * ret could be HTTP_NOT_MODIFIED in the case that the CGI script
               * does not set an explicit status and ap_meets_conditions, which
               * is called by ap_scan_script_header_err_brigade, detects that
               * the conditions of the requests are met and the response is
               * not modified.
               * In this case set r->status and return OK in order to prevent
               * running through the error processing stack as this would
               * break with mod_cache, if the conditions had been set by
               * mod_cache itself to validate a stale entity.
               * BTW: We circumvent the error processing stack anyway if the
               * CGI script set an explicit status code (whatever it is) and
               * the only possible values for ret here are:
               *
               * HTTP_NOT_MODIFIED          (set by ap_meets_conditions)
               * HTTP_PRECONDITION_FAILED   (set by ap_meets_conditions)
               * HTTP_INTERNAL_SERVER_ERROR (if something went wrong during the
               * processing of the response of the CGI script, e.g broken headers
               * or a crashed CGI process).
               */
              if (ret == HTTP_NOT_MODIFIED) {
                  r->status = ret;
                  return OK;
              }
  
              return ret;
          }
  
          location = apr_table_get(r->headers_out, "Location");
  
          if (location && r->status == 200) {
              /* For a redirect whether internal or not, discard any
               * remaining stdout from the script, and log any remaining
               * stderr output, as normal. */
              discard_script_output(bb);
              apr_brigade_destroy(bb);
              apr_file_pipe_timeout_set(script_err, r->server->timeout);
              log_script_err(r, script_err);
          }
  
          if (location && location[0] == '/' && r->status == 200) {
              /* This redirect needs to be a GET no matter what the original
               * method was.
               */
              r->method = "GET";
              r->method_number = M_GET;
  
              /* We already read the message body (if any), so don't allow
               * the redirected request to think it has one.  We can ignore
               * Transfer-Encoding, since we used REQUEST_CHUNKED_ERROR.
               */
              apr_table_unset(r->headers_in, "Content-Length");
  
              ap_internal_redirect_handler(location, r);
              return OK;
          }
          else if (location && r->status == 200) {
              /* XXX: Note that if a script wants to produce its own Redirect
               * body, it now has to explicitly *say* "Status: 302"
               */
              return HTTP_MOVED_TEMPORARILY;
          }
  
          rv = ap_pass_brigade(r->output_filters, bb);
      }
      else /* nph */ {
          struct ap_filter_t *cur;
  
          /* get rid of all filters up through protocol...  since we
           * haven't parsed off the headers, there is no way they can
           * work
           */
  
          cur = r->proto_output_filters;
          while (cur && cur->frec->ftype < AP_FTYPE_CONNECTION) {
              cur = cur->next;
          }
          r->output_filters = r->proto_output_filters = cur;
  
          rv = ap_pass_brigade(r->output_filters, bb);
      }
  
      /* don't soak up script output if errors occurred writing it
       * out...  otherwise, we prolong the life of the script when the
       * connection drops or we stopped sending output for some other
       * reason */
      if (rv == APR_SUCCESS && !r->connection->aborted) {
          apr_file_pipe_timeout_set(script_err, r->server->timeout);
          log_script_err(r, script_err);
      }
  
      apr_file_close(script_err);
  
      return OK;                      /* NOT r->status, even if it has changed. */
  }
  
  /*============================================================================
   *============================================================================
   * This is the beginning of the cgi filter code moved from mod_include. This
   *   is the code required to handle the "exec" SSI directive.
   *============================================================================
   *============================================================================*/
  static apr_status_t include_cgi(include_ctx_t *ctx, ap_filter_t *f,
                                  apr_bucket_brigade *bb, char *s)
  {
      request_rec *r = f->r;
      request_rec *rr = ap_sub_req_lookup_uri(s, r, f->next);
      int rr_status;
  
      if (rr->status != HTTP_OK) {
          ap_destroy_sub_req(rr);
          return APR_EGENERAL;
      }
  
      /* No hardwired path info or query allowed */
      if ((rr->path_info && rr->path_info[0]) || rr->args) {
          ap_destroy_sub_req(rr);
          return APR_EGENERAL;
      }
      if (rr->finfo.filetype != APR_REG) {
          ap_destroy_sub_req(rr);
          return APR_EGENERAL;
      }
  
      /* Script gets parameters of the *document*, for back compatibility */
      rr->path_info = r->path_info;       /* hard to get right; see mod_cgi.c */
      rr->args = r->args;
  
      /* Force sub_req to be treated as a CGI request, even if ordinary
       * typing rules would have called it something else.
       */
      ap_set_content_type(rr, CGI_MAGIC_TYPE);
  
      /* Run it. */
      rr_status = ap_run_sub_req(rr);
      if (ap_is_HTTP_REDIRECT(rr_status)) {
          const char *location = apr_table_get(rr->headers_out, "Location");
  
          if (location) {
              char *buffer;
  
              location = ap_escape_html(rr->pool, location);
              buffer = apr_pstrcat(ctx->pool, "<a href=\"", location, "\">",
                                   location, "</a>", NULL);
  
              APR_BRIGADE_INSERT_TAIL(bb, apr_bucket_pool_create(buffer,
                                      strlen(buffer), ctx->pool,
                                      f->c->bucket_alloc));
          }
      }
  
      ap_destroy_sub_req(rr);
  
      return APR_SUCCESS;
  }
  
  static apr_status_t include_cmd(include_ctx_t *ctx, ap_filter_t *f,
                                  apr_bucket_brigade *bb, const char *command)
  {
      cgi_exec_info_t  e_info;
      const char **argv;
      apr_file_t *script_out = NULL, *script_in = NULL, *script_err = NULL;
      apr_status_t rv;
      request_rec *r = f->r;
  
      add_ssi_vars(r);
  
      e_info.process_cgi = 0;
      e_info.cmd_type    = APR_SHELLCMD;
      e_info.detached    = 0;
      e_info.in_pipe     = APR_NO_PIPE;
      e_info.out_pipe    = APR_FULL_BLOCK;
      e_info.err_pipe    = APR_NO_PIPE;
      e_info.prog_type   = RUN_AS_SSI;
      e_info.bb          = &bb;
      e_info.ctx         = ctx;
      e_info.next        = f->next;
      e_info.addrspace   = 0;
  
      if ((rv = cgi_build_command(&command, &argv, r, r->pool,
                                  &e_info)) != APR_SUCCESS) {
          ap_log_rerror(APLOG_MARK, APLOG_ERR, rv, r, APLOGNO(01226)
                        "don't know how to spawn cmd child process: %s",
                        r->filename);
          return rv;
      }
  
      /* run the script in its own process */
      if ((rv = run_cgi_child(&script_out, &script_in, &script_err,
                              command, argv, r, r->pool,
                              &e_info)) != APR_SUCCESS) {
          ap_log_rerror(APLOG_MARK, APLOG_ERR, rv, r, APLOGNO(01227)
                        "couldn't spawn child process: %s", r->filename);
          return rv;
      }
  
      APR_BRIGADE_INSERT_TAIL(bb, apr_bucket_pipe_create(script_in,
                              f->c->bucket_alloc));
      ctx->flush_now = 1;
  
      /* We can't close the pipe here, because we may return before the
       * full CGI has been sent to the network.  That's okay though,
       * because we can rely on the pool to close the pipe for us.
       */
      return APR_SUCCESS;
  }
  
  static apr_status_t handle_exec(include_ctx_t *ctx, ap_filter_t *f,
                                  apr_bucket_brigade *bb)
  {
      char *tag = NULL;
      char *tag_val = NULL;
      request_rec *r = f->r;
      char *file = r->filename;
      char parsed_string[MAX_STRING_LEN];
  
      if (!ctx->argc) {
          ap_log_rerror(APLOG_MARK,
                        (ctx->flags & SSI_FLAG_PRINTING)
                            ? APLOG_ERR : APLOG_WARNING,
                        0, r, "missing argument for exec element in %s",
                        r->filename);
      }
  
      if (!(ctx->flags & SSI_FLAG_PRINTING)) {
          return APR_SUCCESS;
      }
  
      if (!ctx->argc) {
          SSI_CREATE_ERROR_BUCKET(ctx, f, bb);
          return APR_SUCCESS;
      }
  
      if (ctx->flags & SSI_FLAG_NO_EXEC) {
          ap_log_rerror(APLOG_MARK, APLOG_ERR, 0, r, APLOGNO(01228) "exec used but not allowed "
                        "in %s", r->filename);
          SSI_CREATE_ERROR_BUCKET(ctx, f, bb);
          return APR_SUCCESS;
      }
  
      while (1) {
          cgi_pfn_gtv(ctx, &tag, &tag_val, SSI_VALUE_DECODED);
          if (!tag || !tag_val) {
              break;
          }
  
          if (!strcmp(tag, "cmd")) {
              apr_status_t rv;
  
              cgi_pfn_ps(ctx, tag_val, parsed_string, sizeof(parsed_string),
                         SSI_EXPAND_LEAVE_NAME);
  
              rv = include_cmd(ctx, f, bb, parsed_string);
              if (rv != APR_SUCCESS) {
                  ap_log_rerror(APLOG_MARK, APLOG_ERR, 0, r, APLOGNO(01229) "execution failure "
                                "for parameter \"%s\" to tag exec in file %s",
                                tag, r->filename);
                  SSI_CREATE_ERROR_BUCKET(ctx, f, bb);
                  break;
              }
          }
          else if (!strcmp(tag, "cgi")) {
              apr_status_t rv;
  
              cgi_pfn_ps(ctx, tag_val, parsed_string, sizeof(parsed_string),
                         SSI_EXPAND_DROP_NAME);
  
              rv = include_cgi(ctx, f, bb, parsed_string);
              if (rv != APR_SUCCESS) {
                  ap_log_rerror(APLOG_MARK, APLOG_ERR, 0, r, APLOGNO(01230) "invalid CGI ref "
                                "\"%s\" in %s", tag_val, file);
                  SSI_CREATE_ERROR_BUCKET(ctx, f, bb);
                  break;
              }
          }
          else {
              ap_log_rerror(APLOG_MARK, APLOG_ERR, 0, r, APLOGNO(01231) "unknown parameter "
                            "\"%s\" to tag exec in %s", tag, file);
              SSI_CREATE_ERROR_BUCKET(ctx, f, bb);
              break;
          }
      }
  
      return APR_SUCCESS;
  }
  
  
  /*============================================================================
   *============================================================================
   * This is the end of the cgi filter code moved from mod_include.
   *============================================================================
   *============================================================================*/
  
  
  static int cgi_post_config(apr_pool_t *p, apr_pool_t *plog,
                                  apr_pool_t *ptemp, server_rec *s)
  {
      cgi_pfn_reg_with_ssi = APR_RETRIEVE_OPTIONAL_FN(ap_register_include_handler);
      cgi_pfn_gtv          = APR_RETRIEVE_OPTIONAL_FN(ap_ssi_get_tag_and_value);
      cgi_pfn_ps           = APR_RETRIEVE_OPTIONAL_FN(ap_ssi_parse_string);
  
      if ((cgi_pfn_reg_with_ssi) && (cgi_pfn_gtv) && (cgi_pfn_ps)) {
          /* Required by mod_include filter. This is how mod_cgi registers
           *   with mod_include to provide processing of the exec directive.
           */
          cgi_pfn_reg_with_ssi("exec", handle_exec);
      }
  
      /* This is the means by which unusual (non-unix) os's may find alternate
       * means to run a given command (e.g. shebang/registry parsing on Win32)
       */
      cgi_build_command    = APR_RETRIEVE_OPTIONAL_FN(ap_cgi_build_command);
      if (!cgi_build_command) {
          cgi_build_command = default_build_command;
      }
      return OK;
  }
  
  static void register_hooks(apr_pool_t *p)
  {
      static const char * const aszPre[] = { "mod_include.c", NULL };
      ap_hook_handler(cgi_handler, NULL, NULL, APR_HOOK_MIDDLE);
      ap_hook_post_config(cgi_post_config, aszPre, NULL, APR_HOOK_REALLY_FIRST);
  }
  
  AP_DECLARE_MODULE(cgi) =
  {
      STANDARD20_MODULE_STUFF,
      NULL,                        /* dir config creater */
      NULL,                        /* dir merger --- default is to override */
      create_cgi_config,           /* server config */
      merge_cgi_config,            /* merge server config */
      cgi_cmds,                    /* command apr_table_t */
      register_hooks               /* register hooks */
  };
  