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
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--- /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 */
+/* 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 = CS string_copy_malloc(arg); /* PAM frees resp */
+      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 */