Add customization and background information

README.md

@@ -1,17 +1,17 @@
-# libpam
-Patch Debian's PAM to support longer passwords
+# sftpmgr libpam
+Patch PAM on Debian 11 "bullseye" to support longer passwords (increased from <512 to <4096).
 
 ## Usage
 
-1. Download components which are intended to be installed from GitHub Actions, e.g:
+1. Download components from GitHub Actions, e.g:
 
     ```
     wget https://github.com/sftpmgr/libpam/releases/download/UserBuild_2022.06.26_02-09/libpam-modules_1.4.0-9+deb11u1_amd64.deb
     wget https://github.com/sftpmgr/libpam/releases/download/UserBuild_2022.06.26_02-09/libpam-modules-bin_1.4.0-9+deb11u1_amd64.deb
     wget https://github.com/sftpmgr/libpam/releases/download/UserBuild_2022.06.26_02-09/libpam-runtime_1.4.0-9+deb11u1_all.deb
     wget https://github.com/sftpmgr/libpam/releases/download/UserBuild_2022.06.26_02-09/libpam0g_1.4.0-9+deb11u1_amd64.deb
     ```
-2. Install downloaded components:
+2. Install downloaded packages, e.g.:
 
     ```
     sudo dpkg -i libpam-modules_1.4.0-9+deb11u1_amd64.deb
@@ -20,9 +20,11 @@ Patch Debian's PAM to support longer passwords
     sudo dpkg -i libpam0g_1.4.0-9+deb11u1_amd64.deb
     ```
 
-    or
-
-    ```
-    sudo dpkg -i *.deb
-    ```
+## Customization
+
+See `.github/workflows/ci.yaml` - this consists of a very simple change to `PAM_MAX_RESP_SIZE` in `libpam/include/security/_pam_types.h`.
+
+## Background
+
+When using PAM's `pam_exec.so` with `expose_authtok` enabled, the password is truncated to 511 octets. More [discussion here](https://github.com/linux-pam/linux-pam/issues/59).