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Diffstat (limited to 'src/auths/call_pam.c')
| -rw-r--r-- | src/auths/call_pam.c | 204 |
1 files changed, 204 insertions, 0 deletions
diff --git a/src/auths/call_pam.c b/src/auths/call_pam.c new file mode 100644 index 0000000..80f80f1 --- /dev/null +++ b/src/auths/call_pam.c @@ -0,0 +1,204 @@ +/************************************************* +* Exim - an Internet mail transport agent * +*************************************************/ + +/* Copyright (c) University of Cambridge 1995 - 2018 */ +/* Copyright (c) The Exim Maintainers 2020 - 2021 */ +/* See the file NOTICE for conditions of use and distribution. */ + +#include "../exim.h" + +/* This module contains functions that call the PAM authentication mechanism +defined by Sun for Solaris and also available for Linux and other OS. + +We can't just compile this code and allow the library mechanism to omit the +functions if they are not wanted, because we need to have the PAM headers +available for compiling. Therefore, compile these functions only if SUPPORT_PAM +is defined. However, some compilers don't like compiling empty modules, so keep +them happy with a dummy when skipping the rest. Make it reference itself to +stop picky compilers complaining that it is unused, and put in a dummy argument +to stop even pickier compilers complaining about infinite loops. +Then use a mutually-recursive pair as gcc is just getting stupid. */ + +#ifndef SUPPORT_PAM +static void dummy(int x); +static void dummy2(int x) { dummy(x-1); } +static void dummy(int x) { dummy2(x-1); } +#else /* SUPPORT_PAM */ + +#ifdef PAM_H_IN_PAM +#include <pam/pam_appl.h> +#else +#include <security/pam_appl.h> +#endif + +/* According to the specification, it should be possible to have an application +data pointer passed to the conversation function. However, I was unable to get +this to work on Solaris 2.6, so static variables are used instead. */ + +static int pam_conv_had_error; +static const uschar *pam_args; +static BOOL pam_arg_ended; + + + +/************************************************* +* PAM conversation function * +*************************************************/ + +/* This function is passed to the PAM authentication function, and it calls it +back when it wants data from the client. The string list is in pam_args. When +we reach the end, we pass back an empty string once. If this function is called +again, it will give an error response. This is protection against something +crazy happening. + +Arguments: + num_msg number of messages associated with the call + msg points to an array of length num_msg of pam_message structures + resp set to point to the response block, which has to be got by + this function + appdata_ptr the application data pointer - not used because in Solaris + 2.6 it always arrived in pam_converse() as NULL + +Returns: a PAM return code +*/ + +static int +pam_converse (int num_msg, PAM_CONVERSE_ARG2_TYPE **msg, + struct pam_response **resp, void *appdata_ptr) +{ +int sep = 0; +struct pam_response *reply; + +/* It seems that PAM frees reply[] */ + +if ( pam_arg_ended + || !(reply = malloc(sizeof(struct pam_response) * num_msg))) + return PAM_CONV_ERR; + +for (int i = 0; i < num_msg; i++) + { + uschar *arg; + switch (msg[i]->msg_style) + { + case PAM_PROMPT_ECHO_ON: + case PAM_PROMPT_ECHO_OFF: + if (!(arg = string_nextinlist(&pam_args, &sep, NULL, 0))) + { + arg = US""; + pam_arg_ended = TRUE; + } + reply[i].resp = strdup(CCS arg); /* Use libc malloc, PAM frees resp directly*/ + reply[i].resp_retcode = PAM_SUCCESS; + break; + + case PAM_TEXT_INFO: /* Just acknowledge messages */ + case PAM_ERROR_MSG: + reply[i].resp_retcode = PAM_SUCCESS; + reply[i].resp = NULL; + break; + + default: /* Must be an error of some sort... */ + free(reply); + pam_conv_had_error = TRUE; + return PAM_CONV_ERR; + } + } + +*resp = reply; +return PAM_SUCCESS; +} + + + +/************************************************* +* Perform PAM authentication * +*************************************************/ + +/* This function calls the PAM authentication mechanism, passing over one or +more data strings. + +Arguments: + s a colon-separated list of strings + errptr where to point an error message + +Returns: OK if authentication succeeded + FAIL if authentication failed + ERROR some other error condition +*/ + +int +auth_call_pam(const uschar *s, uschar **errptr) +{ +pam_handle_t *pamh = NULL; +struct pam_conv pamc; +int pam_error; +int sep = 0; +uschar *user; + +/* Set up the input data structure: the address of the conversation function, +and a pointer to application data, which we don't use because I couldn't get it +to work under Solaris 2.6 - it always arrived in pam_converse() as NULL. */ + +pamc.conv = pam_converse; +pamc.appdata_ptr = NULL; + +/* Initialize the static data - the current input data, the error flag, and the +flag for data end. */ + +pam_args = s; +pam_conv_had_error = FALSE; +pam_arg_ended = FALSE; + +/* The first string in the list is the user. If this is an empty string, we +fail. PAM doesn't support authentication with an empty user (it prompts for it, +causing a potential mis-interpretation). */ + +user = string_nextinlist(&pam_args, &sep, NULL, 0); +if (user == NULL || user[0] == 0) return FAIL; + +/* Start off PAM interaction */ + +DEBUG(D_auth) + debug_printf("Running PAM authentication for user \"%s\"\n", user); + +pam_error = pam_start ("exim", CS user, &pamc, &pamh); + +/* Do the authentication - the pam_authenticate() will call pam_converse() to +get the data it wants. After successful authentication we call pam_acct_mgmt() +to apply any other restrictions (e.g. only some times of day). */ + +if (pam_error == PAM_SUCCESS) + { + pam_error = pam_authenticate (pamh, PAM_SILENT); + if (pam_error == PAM_SUCCESS && !pam_conv_had_error) + pam_error = pam_acct_mgmt (pamh, PAM_SILENT); + } + +/* Finish the PAM interaction - this causes it to clean up store etc. Unclear +what should be passed as the second argument. */ + +pam_end(pamh, PAM_SUCCESS); + +/* Sort out the return code. If not success, set the error message. */ + +if (pam_error == PAM_SUCCESS) + { + DEBUG(D_auth) debug_printf("PAM success\n"); + return OK; + } + +*errptr = US pam_strerror(pamh, pam_error); +DEBUG(D_auth) debug_printf("PAM error: %s\n", *errptr); + +if (pam_error == PAM_USER_UNKNOWN || + pam_error == PAM_AUTH_ERR || + pam_error == PAM_ACCT_EXPIRED) + return FAIL; + +return ERROR; +} + +#endif /* SUPPORT_PAM */ + +/* End of call_pam.c */ |