Using pam_python in a script running with mod_python
- by markys
Hi !
I would like to develop a web interface to allow users of a Linux system to do certain tasks related to their account. I decided to write the backend of the site using Python and mod_python on Apache. To authenticate the users, I thought I could use python_pam to query the PAM service. I adapted the example bundled with the module and got this:
# out is the output stream used to print debug
def auth(username, password, out):
def pam_conv(aut, query_list, user_data):
out.write("Query list: " + str(query_list) + "\n")
# List to store the responses to the different queries
resp = []
for item in query_list:
query, qtype = item
# If PAM asks for an input, give the password
if qtype == PAM.PAM_PROMPT_ECHO_ON or qtype == PAM.PAM_PROMPT_ECHO_OFF:
resp.append((str(password), 0))
elif qtype == PAM.PAM_PROMPT_ERROR_MSG or qtype == PAM.PAM_PROMPT_TEXT_INFO:
resp.append(('', 0))
out.write("Our response: " + str(resp) + "\n")
return resp
# If username of password is undefined, fail
if username is None or password is None:
return False
service = 'login'
pam_ = PAM.pam()
pam_.start(service)
# Set the username
pam_.set_item(PAM.PAM_USER, str(username))
# Set the conversation callback
pam_.set_item(PAM.PAM_CONV, pam_conv)
try:
pam_.authenticate()
pam_.acct_mgmt()
except PAM.error, resp:
out.write("Error: " + str(resp) + "\n")
return False
except:
return False
# If we get here, the authentication worked
return True
My problem is that this function does not behave the same wether I use it in a simple script or through mod_python. To illustrate this, I wrote these simple cases:
my_username = "markys"
my_good_password = "lalala"
my_bad_password = "lololo"
def handler(req):
req.content_type = "text/plain"
req.write("1- " + str(auth(my_username,my_good_password,req) + "\n"))
req.write("2- " + str(auth(my_username,my_bad_password,req) + "\n"))
return apache.OK
if __name__ == "__main__":
print "1- " + str(auth(my_username,my_good_password,sys.__stdout__))
print "2- " + str(auth(my_username,my_bad_password,sys.__stdout__))
The result from the script is :
Query list: [('Password: ', 1)]
Our response: [('lalala', 0)]
1- True
Query list: [('Password: ', 1)]
Our response: [('lololo', 0)]
Error: ('Authentication failure', 7)
2- False
but the result from mod_python is :
Query list: [('Password: ', 1)]
Our response: [('lalala', 0)]
Error: ('Authentication failure', 7)
1- False
Query list: [('Password: ', 1)]
Our response: [('lololo', 0)]
Error: ('Authentication failure', 7)
2- False
I don't understand why the auth function does not return the same value given the same inputs. Any idea where I got this wrong ? Here is the original script, if that could help you.
Thanks a lot !
