WebgateDownload

import requests;

url = "https://echo.epa.gov/files/echodownloads/npdes_biosolids_downloads.zip";
target = r"npdes_biosolids_downloads.zip";

print("\nQuerying " + str(url) + "...\n"); 
step1 = requests.get(
    url
   ,allow_redirects=False
);

if step1.status_code == 302:

   print("Encountered initial webgate redirect...\n");
   location = step1.headers['Location'];
   print("Redirecting to " + str(location) + "\n");
   
   cookie1 = None;
   cookie2 = None;
   for k,v in step1.cookies.iteritems():
      if k == 'OAMAuthnHintCookie':
         print("Found cookie1 " + str(k) + ':' + str(v) + "\n");
         cookie1 = k;
      elif k[0:31] == 'OAMRequestContext_echo.epa.gov:':
         print("Found cookie2 " + str(k) + ':' + str(v) + "\n");
         cookie2 = k;

   if cookie1 is None:
      raise Exception('Unable to obtain OAMAuthnHintCookie cookie');
      
   if cookie2 is None:
      raise Exception('Unable to obtain OAMRequestContext cookie');
  
   step2 = requests.get(
       location
      ,cookies=step1.cookies
      ,allow_redirects=False
   );
   
   if step2.status_code != 302:
      raise Exception('No redirection returned from second step.');
      
   location = step2.headers['Location'];
   print("Redirecting to " + str(location) + "\n");
   
   cookie3 = None;
   for k,v in step2.cookies.iteritems():
      if k == 'OAM_ID':
         print("Found cookie3 " + str(k) + ':' + str(v) + "\n");
         cookie3 = k;
   
   print("Redirecting back to original request at " + str(url) + "\n");
   resp = requests.get(
       url
      ,cookies=requests.cookies.merge_cookies(step1.cookies,step2.cookies)
      ,allow_redirects=False
   );
   
   if resp.status_code != 200:
      raise Exception('Webgate authentication failed with code ' + str(response.status) + '.');

elif step1.status_code == 200:
   print("Webgate already authenticated.\n");
   resp = step1;
   
else:
   raise Exception('error in download, code ' + str(step1.status_code));
   
print("Writing payload to file...\n");
open(target,'wb').write(resp.content);
print("Download complete.\n");