Expose list of completed auth methods to PAM

bz#2408; ok dtucker@

2 files changed, 46 insertions, 6 deletions

diff --git a/auth-pam.c b/auth-pam.c
index 9574d9ac7..de29c04c9 100644
--- a/auth-pam.c
+++ b/auth-pam.c
@@ -926,6 +926,27 @@ finish_pam(void)
         sshpam_cleanup();
 }
 
+static void
+expose_authinfo(const char *caller)
+{
+        char *auth_info;
+
+        /*
+         * Expose authentication information to PAM.
+         * The enviornment variable is versioned. Please increment the
+         * version suffix if the format of session_info changes.
+         */
+        if (sshpam_authctxt->session_info == NULL)
+                auth_info = xstrdup("");
+        else if ((auth_info = sshbuf_dup_string(
+            sshpam_authctxt->session_info)) == NULL)
+                fatal("%s: sshbuf_dup_string failed", __func__);
+
+        debug2("%s: auth information in SSH_AUTH_INFO_0", caller);
+        do_pam_putenv("SSH_AUTH_INFO_0", auth_info);
+        free(auth_info);
+}
+
 u_int
 do_pam_account(void)
 {
@@ -933,6 +954,8 @@ do_pam_account(void)
         if (sshpam_account_status != -1)
                 return (sshpam_account_status);
 
+        expose_authinfo(__func__);
+
         sshpam_err = pam_acct_mgmt(sshpam_handle, 0);
         debug3("PAM: %s pam_acct_mgmt = %d (%s)", __func__, sshpam_err,
             pam_strerror(sshpam_handle, sshpam_err));
@@ -1057,6 +1080,9 @@ void
 do_pam_session(void)
 {
         debug3("PAM: opening session");
+
+        expose_authinfo(__func__);
+
         sshpam_err = pam_set_item(sshpam_handle, PAM_CONV,
             (const void *)&store_conv);
         if (sshpam_err != PAM_SUCCESS)
diff --git a/session.c b/session.c
index a2588e74b..698eaa879 100644
--- a/session.c
+++ b/session.c
@@ -984,8 +984,9 @@ read_etc_default_login(char ***env, u_int *envsize, uid_t uid)
 }
 #endif /* HAVE_ETC_DEFAULT_LOGIN */
 
-void
-copy_environment(char **source, char ***env, u_int *envsize)
+static void
+copy_environment_blacklist(char **source, char ***env, u_int *envsize,
+    const char *blacklist)
 {
         char *var_name, *var_val;
         int i;
@@ -1001,13 +1002,22 @@ copy_environment(char **source, char ***env, u_int *envsize)
                 }
                 *var_val++ = '\0';
 
-                debug3("Copy environment: %s=%s", var_name, var_val);
-                child_set_env(env, envsize, var_name, var_val);
+                if (blacklist == NULL ||
+                    match_pattern_list(var_name, blacklist, 0) != 1) {
+                        debug3("Copy environment: %s=%s", var_name, var_val);
+                        child_set_env(env, envsize, var_name, var_val);
+                }
 
                 free(var_name);
         }
 }
 
+void
+copy_environment(char **source, char ***env, u_int *envsize)
+{
+        copy_environment_blacklist(source, env, envsize, NULL);
+}
+
 static char **
 do_setup_env(Session *s, const char *shell)
 {
@@ -1169,12 +1179,16 @@ do_setup_env(Session *s, const char *shell)
         if (options.use_pam) {
                 char **p;
 
+                /*
+                 * Don't allow SSH_AUTH_INFO variables posted to PAM to leak
+                 * back into the environment.
+                 */
                 p = fetch_pam_child_environment();
-                copy_environment(p, &env, &envsize);
+                copy_environment_blacklist(p, &env, &envsize, "SSH_AUTH_INFO*");
                 free_pam_environment(p);
 
                 p = fetch_pam_environment();
-                copy_environment(p, &env, &envsize);
+                copy_environment_blacklist(p, &env, &envsize, "SSH_AUTH_INFO*");
                 free_pam_environment(p);
         }
 #endif /* USE_PAM */