--- a/build.rs	Tue Jun 24 14:54:47 2025 -0400
+++ b/build.rs	Tue Jun 24 17:08:01 2025 -0400
@@ -14,13 +14,13 @@
             .allowlist_var(".*")
             .allowlist_function("pam_start")
             .allowlist_function("pam_[gs]et_item")
-            .allowlist_function("pam_get_user")
-            .allowlist_function("pam_get_authtok")
+            .allowlist_function("pam_get_(user|authtok)")
             .allowlist_function("pam_end")
             .allowlist_function("pam_strerror")
             .allowlist_function("pam_authenticate")
             .allowlist_function("pam_chauthtok")
             .allowlist_function("pam_acct_mgmt")
+            .allowlist_function("pam_(ge|pu)tenv(list)?")
             .default_macro_constant_type(MacroTypeVariation::Unsigned);
 
         let linux_builder = common_builder

--- a/src/environ.rs	Tue Jun 24 14:54:47 2025 -0400
+++ b/src/environ.rs	Tue Jun 24 17:08:01 2025 -0400
@@ -3,26 +3,31 @@
 //! PAM modules can set environment variables to apply to a user session.
 //! This module manages the interface for doing all of that.
 
+use crate::constants::Result;
 use std::ffi::{OsStr, OsString};
 
 /// A key/value map for environment variables, as [`OsString`]s.
 ///
 /// This is a limited subset of what [`HashMap`](std::collections::HashMap)
 /// can do. Notably, we do *not* support mutable iteration.
-pub trait EnvironMap {
+pub trait EnvironMap<'a> {
     /// Gets the environment variable of the given key.
-    fn get(&self, val: &OsStr) -> Option<&OsStr>;
+    fn get(&self, key: impl AsRef<OsStr>) -> Option<OsString>;
 
     /// Iterates over the key/value pairs of the environment.
-    fn iter(&self) -> impl Iterator<Item = (&OsStr, &OsStr)>;
+    fn iter(&self) -> Result<impl Iterator<Item = (OsString, OsString)>>;
 }
 
-pub trait EnvironMapMut: EnvironMap {
+pub trait EnvironMapMut<'a>: EnvironMap<'a> {
     /// Sets the environment variable with the given key,
     /// returning the old one if present.
-    fn insert(&mut self, key: &OsStr, val: &OsStr) -> Option<OsString>;
+    fn insert(
+        &mut self,
+        key: impl AsRef<OsStr>,
+        val: impl AsRef<OsStr>,
+    ) -> Result<Option<OsString>>;
 
     /// Removes the environment variable from the map, returning its old value
     /// if present.
-    fn remove(&mut self, key: &OsStr) -> Option<OsString>;
+    fn remove(&mut self, key: impl AsRef<OsStr>) -> Result<Option<OsString>>;
 }

--- a/src/handle.rs	Tue Jun 24 14:54:47 2025 -0400
+++ b/src/handle.rs	Tue Jun 24 17:08:01 2025 -0400
@@ -198,8 +198,8 @@
     trait_item!(
         /// Sets the identity of the remote user logging in.
         ///
-        /// This is usually set by the application before making calls
-        /// into a PAM session. (TODO: check this!)
+        /// This may be set by the application before making calls
+        /// into a PAM transaction.
         set = set_remote_user,
         item = "PAM_RUSER"
     );
@@ -220,8 +220,8 @@
     trait_item!(
         /// Sets the location where the user is coming from.
         ///
-        /// This is usually set by the application before making calls
-        /// into a PAM session. (TODO: check this!)
+        /// This may be set by the application before making calls
+        /// into a PAM transaction.
         set = set_remote_host,
         item = "PAM_RHOST",
         see = Self::remote_host

--- a/src/lib.rs	Tue Jun 24 14:54:47 2025 -0400
+++ b/src/lib.rs	Tue Jun 24 17:08:01 2025 -0400
@@ -43,7 +43,7 @@
 pub use crate::{
     constants::{ErrorCode, Flags, Result},
     conv::{BinaryData, Conversation, ConversationAdapter},
-    environ::EnvironMap,
+    environ::{EnvironMap, EnvironMapMut},
     handle::{PamHandleApplication, PamHandleModule, PamShared},
     module::PamModule,
 };

--- a/src/libpam/answer.rs	Tue Jun 24 14:54:47 2025 -0400
+++ b/src/libpam/answer.rs	Tue Jun 24 17:08:01 2025 -0400
@@ -9,6 +9,7 @@
 use std::ops::{Deref, DerefMut};
 use std::ptr::NonNull;
 use std::{iter, mem, ptr, slice};
+use std::mem::ManuallyDrop;
 
 /// The corridor via which the answer to Messages navigate through PAM.
 #[derive(Debug)]
@@ -48,9 +49,7 @@
     /// This object is consumed and the `Answer` pointer now owns its data.
     /// It can be recreated with [`Self::from_c_heap`].
     pub fn into_ptr(self) -> NonNull<Answer> {
-        let ret = self.base;
-        mem::forget(self);
-        ret
+        ManuallyDrop::new(self).base
     }
 
     /// Takes ownership of a list of answers allocated on the C heap.

--- a/src/libpam/conversation.rs	Tue Jun 24 14:54:47 2025 -0400
+++ b/src/libpam/conversation.rs	Tue Jun 24 17:08:01 2025 -0400
@@ -55,7 +55,7 @@
             conv.communicate(&borrowed?);
 
             // Send our answers back.
-            let owned = Answers::build(messages).map_err(|_| ErrorCode::ConversationError)?;
+            let owned = Answers::build(messages)?;
             *answers_ptr = owned.into_ptr().as_ptr();
             Ok(())
         };

--- a/src/libpam/environ.rs	Tue Jun 24 14:54:47 2025 -0400
+++ b/src/libpam/environ.rs	Tue Jun 24 17:08:01 2025 -0400
@@ -1,12 +1,13 @@
 #![allow(unused_variables)] // for now
-use crate::environ::EnvironMapMut;
+use crate::constants::{ErrorCode, Result};
+use crate::environ::{EnvironMap, EnvironMapMut};
 use crate::libpam::memory::CHeapString;
-use crate::{EnvironMap, LibPamHandle};
-use std::ffi::{c_char, OsStr, OsString};
-use std::os::unix::ffi::OsStrExt;
+use crate::libpam::{memory, pam_ffi, LibPamHandle};
+use std::ffi::{c_char, CStr, CString, OsStr, OsString};
+use std::marker::PhantomData;
+use std::os::unix::ffi::{OsStrExt, OsStringExt};
+use std::ptr;
 use std::ptr::NonNull;
-use std::{iter, ptr};
-use crate::libpam::memory;
 
 pub struct LibPamEnviron<'a> {
     source: &'a LibPamHandle,
@@ -16,6 +17,58 @@
     source: &'a mut LibPamHandle,
 }
 
+impl LibPamHandle {
+    fn environ_get(&self, key: &OsStr) -> Option<OsString> {
+        let key = CString::new(key.as_bytes()).ok()?;
+        // SAFETY: We are a valid handle and are calling with a good key.
+        unsafe {
+            copy_env(pam_ffi::pam_getenv(
+                (self as *const LibPamHandle).cast_mut(),
+                key.as_ptr(),
+            ))
+        }
+    }
+
+    fn environ_set(&mut self, key: &OsStr, value: Option<&OsStr>) -> Result<Option<OsString>> {
+        let old = self.environ_get(key);
+        let total_len = key.len() + value.map(OsStr::len).unwrap_or_default() + 2;
+        let mut result = Vec::with_capacity(total_len);
+        result.extend(key.as_bytes());
+        if let Some(value) = value {
+            result.push(b'=');
+            result.extend(value.as_bytes());
+        }
+        let put = CString::new(result).map_err(|_| ErrorCode::ConversationError)?;
+        // SAFETY: This is a valid handle and a valid environment string.
+        ErrorCode::result_from(unsafe { pam_ffi::pam_putenv(self, put.as_ptr()) })?;
+        Ok(old)
+    }
+
+    fn environ_iter(&self) -> Result<impl Iterator<Item = (OsString, OsString)>> {
+        // SAFETY: This is a valid PAM handle.
+        unsafe {
+            NonNull::new(pam_ffi::pam_getenvlist(
+                (self as *const LibPamHandle).cast_mut(),
+            ))
+            .map(|ptr| EnvList::from_ptr(ptr.cast()))
+            .ok_or(ErrorCode::BufferError)
+        }
+    }
+}
+
+/// Copies the data of the given C string pointer to an OsString,
+/// or None if src is null.
+unsafe fn copy_env(src: *const c_char) -> Option<OsString> {
+    let val = match NonNull::new(src.cast_mut()) {
+        None => return None,
+        Some(ptr) => ptr.as_ptr(),
+    };
+    // SAFETY: We were just returned this string from PAM.
+    // We have to trust it.
+    let c_str = unsafe { CStr::from_ptr(val) };
+    Some(OsString::from_vec(c_str.to_bytes().to_vec()))
+}
+
 impl<'a> LibPamEnviron<'a> {
     pub fn new(source: &'a LibPamHandle) -> Self {
         Self { source }
@@ -26,83 +79,94 @@
     pub fn new(source: &'a mut LibPamHandle) -> Self {
         Self { source }
     }
+}
 
-    fn immut(&self) -> LibPamEnviron {
-        LibPamEnviron {
-            source: self.source,
+impl EnvironMap<'_> for LibPamEnviron<'_> {
+    fn get(&self, key: impl AsRef<OsStr>) -> Option<OsString> {
+        self.source.environ_get(key.as_ref())
+    }
+
+    fn iter(&self) -> Result<impl Iterator<Item = (OsString, OsString)>> {
+        self.source.environ_iter()
+    }
+}
+
+impl EnvironMap<'_> for LibPamEnvironMut<'_> {
+    fn get(&self, key: impl AsRef<OsStr>) -> Option<OsString> {
+        self.source.environ_get(key.as_ref())
+    }
+
+    fn iter(&self) -> Result<impl Iterator<Item = (OsString, OsString)>> {
+        self.source.environ_iter()
+    }
+}
+
+impl EnvironMapMut<'_> for LibPamEnvironMut<'_> {
+    fn insert(
+        &mut self,
+        key: impl AsRef<OsStr>,
+        val: impl AsRef<OsStr>,
+    ) -> Result<Option<OsString>> {
+        self.source.environ_set(key.as_ref(), Some(val.as_ref()))
+    }
+
+    fn remove(&mut self, key: impl AsRef<OsStr>) -> Result<Option<OsString>> {
+        self.source.environ_set(key.as_ref(), None)
+    }
+}
+
+struct EnvList<'a> {
+    /// Pointer to the start of the environment variable list.
+    ///
+    /// This can't be a `CHeapBox` because it's not just a single
+    /// `Option<EnvVar>`.
+    start: NonNull<Option<EnvVar>>,
+    /// The environment variable we're about to iterate into.
+    current: NonNull<Option<EnvVar>>,
+    _owner: PhantomData<&'a LibPamHandle>,
+}
+
+impl EnvList<'_> {
+    unsafe fn from_ptr(ptr: NonNull<*mut c_char>) -> Self {
+        Self {
+            start: ptr.cast(),
+            current: ptr.cast(),
+            _owner: Default::default(),
+        }
+    }
+}
+impl Iterator for EnvList<'_> {
+    type Item = (OsString, OsString);
+
+    fn next(&mut self) -> Option<Self::Item> {
+        // SAFETY: We were given a pointer to a valid environment list,
+        // and we only ever advance it to the exact end of the list.
+        match unsafe { self.current.as_mut() } {
+            None => None,
+            Some(item) => {
+                let ret = item.as_kv();
+                // SAFETY: We know we're still pointing to a valid pointer,
+                // and advancing it one more is allowed.
+                unsafe {
+                    self.current = self.current.add(1);
+                    ptr::drop_in_place(item as *mut EnvVar);
+                }
+                Some(ret)
+            }
         }
     }
 }
 
-impl EnvironMap for LibPamEnviron<'_> {
-    fn get(&self, val: &OsStr) -> Option<&OsStr> {
-        todo!()
-    }
-
-    fn iter(&self) -> impl Iterator<Item = (&OsStr, &OsStr)> {
-        iter::from_fn(|| todo!())
-    }
-}
-
-impl EnvironMap for LibPamEnvironMut<'_> {
-    fn get(&self, val: &OsStr) -> Option<&OsStr> {
-        todo!()
-    }
-
-    fn iter(&self) -> impl Iterator<Item = (&OsStr, &OsStr)> {
-        iter::from_fn(|| todo!())
-    }
-}
-
-impl EnvironMapMut for LibPamEnvironMut<'_> {
-    fn insert(&mut self, key: &OsStr, val: &OsStr) -> Option<OsString> {
-        todo!()
-    }
-
-    fn remove(&mut self, key: &OsStr) -> Option<OsString> {
-        todo!()
-    }
-}
-
-struct EnvList {
-    /// Pointer to the start of the environment variable list.
-    ///
-    /// This can't be a `CHeapBox` because it's not just a single
-    /// `Option<EnvVar>`.
-    vars: NonNull<Option<EnvVar>>,
-}
-
-impl EnvList {
-    unsafe fn from_ptr(ptr: NonNull<*mut c_char>) -> Self {
-        Self{vars: ptr.cast()}
-    }
-
-    fn iter(&self) -> impl Iterator<Item = (&OsStr, &OsStr)> {
-        let mut current = self.vars;
-        iter::from_fn(move || {
-            match unsafe {current.as_ref()} {
-                None => None,
-                Some(item) => {
-                    let ret = item.as_kv();
-                    current = unsafe {current.add(1) };
-                    Some(ret)
-                }
+impl Drop for EnvList<'_> {
+    fn drop(&mut self) {
+        // SAFETY: We own self.start, and we know that self.current points to
+        // either an item we haven't used, or to the None end.
+        unsafe {
+            while let Some(var_ref) = self.current.as_mut() {
+                ptr::drop_in_place(var_ref as *mut EnvVar);
+                self.current = self.current.add(1);
             }
-        })
-    }
-}
-
-impl Drop for EnvList {
-    fn drop(&mut self) {
-        // SAFETY: We own this pointer, and we know it's valid environment data
-        // from PAM.
-        unsafe {
-            let mut var = self.vars;
-            while let Some(var_ref) = var.as_mut() {
-                ptr::drop_in_place(var_ref as *mut EnvVar);
-                var = var.add(1);
-            }
-            memory::free(self.vars.as_ptr())
+            memory::free(self.start.as_ptr())
         }
     }
 }
@@ -110,27 +174,30 @@
 struct EnvVar(CHeapString);
 
 impl EnvVar {
-    fn as_kv(&self) -> (&OsStr, &OsStr) {
+    fn as_kv(&self) -> (OsString, OsString) {
         let bytes = self.0.to_bytes();
         let mut split = bytes.splitn(2, |&b| b == b'=');
         (
-            OsStr::from_bytes(split.next().unwrap_or_default()),
-            OsStr::from_bytes(split.next().unwrap_or_default()),
+            OsString::from_vec(split.next().unwrap_or_default().into()),
+            OsString::from_vec(split.next().unwrap_or_default().into()),
         )
     }
 }
 
 #[cfg(test)]
 mod tests {
-    use crate::libpam::memory::CHeapBox;
     use super::*;
 
+    fn os(text: &str) -> OsString {
+        OsString::from_vec(text.into())
+    }
+
     #[test]
     fn test_split_kv() {
         fn test(input: &str, key: &str, value: &str) {
             let data = CHeapString::new(input).unwrap();
-            let key = OsStr::from_bytes(key.as_bytes());
-            let value = OsStr::from_bytes(value.as_bytes());
+            let key = os(key);
+            let value = os(value);
 
             assert_eq!(EnvVar(data).as_kv(), (key, value));
         }
@@ -141,26 +208,46 @@
         test("", "", "");
     }
 
+    fn env_list(strings: &[&'static str]) -> EnvList<'static> {
+        let ptrs: NonNull<Option<CHeapString>> = memory::calloc(strings.len() + 1).unwrap();
+        unsafe {
+            for (idx, &text) in strings.iter().enumerate() {
+                ptr::write(
+                    ptrs.add(idx).as_ptr(),
+                    Some(CHeapString::new(text).unwrap()),
+                )
+            }
+            ptr::write(ptrs.add(strings.len()).as_ptr(), None);
+            EnvList::from_ptr(ptrs.cast())
+        }
+    }
+
     #[test]
     fn test_iter() {
-        let bx = CHeapBox::new([
-            Some("ONE=two"),
-            Some("BIRDS=birds=birds"),
-            Some("me"),
-            Some("you="),
-            None,
-        ].map(|txt| txt.map(|txt| CHeapString::new(txt).unwrap()))).unwrap();
-        let env_ptr = CHeapBox::into_ptr(bx);
+        let envs = env_list(&["ONE=two", "BIRDS=birds=birds", "me", "you="]);
+        let result: Vec<_> = envs.collect();
+        assert_eq!(
+            vec![
+                (os("ONE"), os("two")),
+                (os("BIRDS"), os("birds=birds")),
+                (os("me"), os("")),
+                (os("you"), os("")),
+            ],
+            result
+        );
+    }
 
-        let envs = unsafe {EnvList::from_ptr(env_ptr.cast())};
-        let bytes = |data: &'static str| OsStr::from_bytes(data.as_ref());
-        let result: Vec<_> = envs.iter().collect();
-        assert_eq!(vec![
-            (bytes("ONE"), bytes("two")),
-            (bytes("BIRDS"), bytes("birds=birds")),
-            (bytes("me"), bytes("")),
-            (bytes("you"), bytes("")),
-        ],
-        result);
+    #[test]
+    fn test_iter_partial() {
+        let mut envs = env_list(&[
+            "iterating=this",
+            "also=here",
+            "but not=this one",
+            "or even=the last",
+        ]);
+
+        assert_eq!(Some((os("iterating"), os("this"))), envs.next());
+        assert_eq!(Some((os("also"), os("here"))), envs.next());
+        // let envs drop
     }
 }

--- a/src/libpam/memory.rs	Tue Jun 24 14:54:47 2025 -0400
+++ b/src/libpam/memory.rs	Tue Jun 24 17:08:01 2025 -0400
@@ -6,7 +6,7 @@
 use std::ffi::{c_char, CStr, CString};
 use std::fmt::{Display, Formatter, Result as FmtResult};
 use std::marker::{PhantomData, PhantomPinned};
-use std::mem::offset_of;
+use std::mem::{offset_of, ManuallyDrop};
 use std::ops::{Deref, DerefMut};
 use std::ptr::NonNull;
 use std::result::Result as StdResult;
@@ -96,9 +96,7 @@
 
     /// Converts this CBox into a raw pointer.
     pub fn into_ptr(this: Self) -> NonNull<T> {
-        let ret = this.0;
-        mem::forget(this);
-        ret
+        ManuallyDrop::new(this).0
     }
 
     /// Gets a pointer from this but doesn't convert this into a raw pointer.
@@ -177,9 +175,8 @@
     ///
     /// You are responsible for freeing it later.
     pub fn into_ptr(self) -> NonNull<c_char> {
-        let ptr = CHeapBox::as_ptr(&self.0);
-        mem::forget(self);
-        ptr
+        let this = ManuallyDrop::new(self);
+        CHeapBox::as_ptr(&this.0)
     }
 
     /// Converts this into a dumb box. It will no longer be zeroed upon drop.