patch for pam authentication in cvs

[Brian Murphy]

Here is a patch to allow cvs to authenticate via pam.
You need a configuration file like this (for linux)
in /etc/pam.d/cvs:

auth            sufficient        pam_ldap.so
account         sufficient        pam_ldap.so

auth            required        pam_unix.so
account         required        pam_unix.so

to authenticate via ldap first and then to try via
the standard unix shadow/passwd method.

I have not tested this but it should also work on
any system supporting PAM (sun, hp, freebsd).

I hope this comes into the standard distribution. If not
I know there are others with the same needs as me who
can use this.

If there are any problems just contact me and I'll be
glad to fix them.

/Brian

Index: config.h.in
===================================================================
RCS file: /cvs/ccvs/config.h.in,v
retrieving revision 1.74
diff -u -r1.74 config.h.in
--- config.h.in 19 Mar 2003 21:13:29 -0000      1.74
+++ config.h.in 11 Apr 2003 13:47:00 -0000
@@ -205,6 +205,9 @@
 
 /* Define to 1 if you have the <ndir.h> header file, and it defines `DIR'. */
 #undef HAVE_NDIR_H
+
+/* Defined if you have pam */
+#undef HAVE_PAM
 
 /* Define to 1 if you have the `putenv' function. */
 #undef HAVE_PUTENV
Index: configure.in
===================================================================
RCS file: /cvs/ccvs/configure.in,v
retrieving revision 1.187
diff -u -r1.187 configure.in
--- configure.in        1 Apr 2003 22:49:26 -0000       1.187
+++ configure.in        11 Apr 2003 13:47:07 -0000
@@ -315,6 +315,11 @@
 dnl begin --with-*
 dnl
 
+AC_CHECK_HEADER(security/pam_appl.h, 
+  AC_DEFINE(HAVE_PAM, 1, [Defined if you have pam])
+)
+AC_CHECK_LIB(pam, pam_start, [LIBS="${LIBS} -lpam"])
+
 dnl
 dnl set $(KRB4) from --with-krb4=value -- WITH_KRB4
 dnl
Index: src/server.c
===================================================================
RCS file: /cvs/ccvs/src/server.c,v
retrieving revision 1.290
diff -u -r1.290 server.c
--- src/server.c        17 Mar 2003 06:32:11 -0000      1.290
+++ src/server.c        11 Apr 2003 13:47:12 -0000
@@ -5548,50 +5548,99 @@
     return retval;
 }
 
+#ifdef HAVE_PAM
 
-/* Return a hosting username if password matches, else NULL. */
-static char *
-check_password (username, password, repository)
-    char *username, *password, *repository;
-{
-    int rc;
-    char *host_user = NULL;
-    char *found_passwd = NULL;
-    struct passwd *pw;
+#include <security/pam_appl.h>
 
-    /* First we see if this user has a password in the CVS-specific
-       password file.  If so, that's enough to authenticate with.  If
-       not, we'll check /etc/passwd. */
+#define PAM_SERVICENAME "cvs"
 
-    rc = check_repository_password (username, password, repository,
-                                   &host_user);
+struct cvs_pam_userinfo {
+    char *username;
+    char *password;
+};
 
-    if (rc == 2)
-       return NULL;
+#if SOLARIS2 == 260
+struct cvs_pam_userinfo *global_userinfo;
+#endif
 
-    if (rc == 1)
-    {
-       /* host_user already set by reference, so just return. */
-       goto handle_return;
-    }
+static int
+cvs_pam_conv(int num_msg,
+        const struct pam_message **msg,
+        struct pam_response **resp,
+        void *appdata_ptr)
+{
+    int i;
+    struct pam_response *response;
+    struct cvs_pam_userinfo *ui = (struct cvs_pam_userinfo *)appdata_ptr;
+
+#if SOLARIS2 == 260
+    if(!ui)
+        ui = global_userinfo;
+#endif
 
-    assert (rc == 0);
+    if (!ui || !ui->username || !ui->password || !msg || !resp)
+        return PAM_CONV_ERR;
 
-    if (!system_auth)
-    {
-       /* Note that the message _does_ distinguish between the case in
-          which we check for a system password and the case in which
-          we do not.  It is a real pain to track down why it isn't
-          letting you in if it won't say why, and I am not convinced
-          that the potential information disclosure to an attacker
-          outweighs this.  */
-       printf ("error 0 no such user %s in CVSROOT/passwd\n", username);
+    response = malloc(num_msg * sizeof(struct pam_response));
+    if (!response)
+        return PAM_CONV_ERR;
+    for (i = 0; i < num_msg; i++){
+        response[i].resp_retcode = 0;
+        response[i].resp = 0;
+        switch(msg[i]->msg_style) {
+            case PAM_PROMPT_ECHO_ON:
+                response[i].resp = strdup(ui->username);
+                break;
+            case PAM_PROMPT_ECHO_OFF:
+                response[i].resp = strdup(ui->password);
+                break;
+            default:
+                if(response)
+                    free(response);
+                return PAM_CONV_ERR;
+        }
+    }
+
+    *resp = response;
+    return PAM_SUCCESS;
+}
+
+static int
+check_system_password (username, password)
+    char *username, *password;
+{
+    pam_handle_t *pamh = NULL;
+    int retval;
+    struct cvs_pam_userinfo ui = { username, password };
+    struct pam_conv conv = { cvs_pam_conv, (void *)&ui };
 
-       error_exit ();
-    }
+#if SOLARIS2 == 260
+      global_userinfo = &ui;
+#endif
 
-    /* No cvs password found, so try /etc/passwd. */
+    retval = pam_start(PAM_SERVICENAME, username, &conv, &pamh);
+
+    if (retval == PAM_SUCCESS)
+        retval = pam_authenticate(pamh, 0);
+
+    if (retval == PAM_SUCCESS)
+        retval = pam_acct_mgmt(pamh, 0);
 
+    if (pam_end(pamh,retval) != PAM_SUCCESS) {
+        printf("E Fatal error, aborting.\n
+                pam failed to release authenticator\n");
+        error_exit ();
+    }
+
+    return (retval == PAM_SUCCESS);       /* indicate success */
+}
+#else
+static int
+check_system_password (username, password)
+    char *username, *password;
+{
+    char *found_passwd = NULL;
+    struct passwd *pw;
 #ifdef HAVE_GETSPNAM
     {
        struct spwd *spw;
@@ -5637,32 +5686,74 @@
        /* user exists and has a password */
        if (strcmp (found_passwd, crypt (password, found_passwd)) == 0)
        {
-           host_user = xstrdup (username);
+           return 1;
        }
        else
        {
-           host_user = NULL;
 #ifdef LOG_AUTHPRIV
            syslog (LOG_AUTHPRIV | LOG_NOTICE,
                    "password mismatch for %s: %s vs. %s", username,
                    crypt(password, found_passwd), found_passwd);
 #endif
+            return 0;
        }
-       goto handle_return;
     }
 
     if (password && *password)
+        return 1;
+
+    return 0;
+}
+#endif
+
+/* Return a hosting username if password matches, else NULL. */
+static char *
+check_password (username, password, repository)
+    char *username, *password, *repository;
+{
+    int rc;
+    char *host_user = NULL;
+
+    /* First we see if this user has a password in the CVS-specific
+       password file.  If so, that's enough to authenticate with.  If
+       not, we'll check /etc/passwd. */
+
+    rc = check_repository_password (username, password, repository,
+                                   &host_user);
+
+    if (rc == 2)
+       return NULL;
+
+    if (rc == 1)
     {
-       /* user exists and has no system password, but we got
-          one as parameter */
-       host_user = xstrdup (username);
+       /* host_user already set by reference, so just return. */
        goto handle_return;
     }
 
-    /* user exists but has no password at all */
-    host_user = NULL;
+    assert (rc == 0);
+
+    if (!system_auth)
+    {
+       /* Note that the message _does_ distinguish between the case in
+          which we check for a system password and the case in which
+          we do not.  It is a real pain to track down why it isn't
+          letting you in if it won't say why, and I am not convinced
+          that the potential information disclosure to an attacker
+          outweighs this.  */
+       printf ("error 0 no such user %s in CVSROOT/passwd\n", username);
+
+       error_exit ();
+    }
+
+    /* No cvs password found, so try /etc/passwd. */
+    if ( check_system_password(username, password) )
+        host_user = xstrdup (username);
+    else
+        host_user = NULL;
+
 #ifdef LOG_AUTHPRIV
-    syslog (LOG_AUTHPRIV | LOG_NOTICE,
+    if (!host_user)
+        syslog (LOG_AUTHPRIV | LOG_NOTICE,
            "login refused for %s: user has no password", username);
 #endif