--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/libpam/response.rs	Fri Jun 06 22:35:08 2025 -0400
@@ -0,0 +1,317 @@
+//! Types used when dealing with PAM conversations.
+
+use crate::conv::BinaryData;
+use crate::libpam::memory;
+use crate::libpam::memory::{CBinaryData, Immovable, NulError, TooBigError};
+use crate::Response;
+use std::ffi::{c_int, c_void, CStr};
+use std::ops::{Deref, DerefMut};
+use std::result::Result as StdResult;
+use std::str::Utf8Error;
+use std::{iter, mem, ptr, slice};
+
+#[repr(transparent)]
+#[derive(Debug)]
+pub struct RawTextResponse(RawResponse);
+
+impl RawTextResponse {
+    /// Interprets the provided `RawResponse` as a text response.
+    ///
+    /// # Safety
+    ///
+    /// It's up to you to provide a response that is a `RawTextResponse`.
+    pub unsafe fn upcast(from: &mut RawResponse) -> &mut Self {
+        // SAFETY: We're provided a valid reference.
+        &mut *(from as *mut RawResponse).cast::<Self>()
+    }
+
+    /// Fills in the provided `RawResponse` with the given text.
+    ///
+    /// You are responsible for calling [`free`](Self::free_contents)
+    /// on the pointer you get back when you're done with it.
+    pub fn fill(dest: &mut RawResponse, text: impl AsRef<str>) -> StdResult<&mut Self, NulError> {
+        dest.data = memory::malloc_str(text)?.cast();
+        // SAFETY: We just filled this in so we know it's a text response.
+        Ok(unsafe { Self::upcast(dest) })
+    }
+
+    /// Gets the string stored in this response.
+    pub fn contents(&self) -> StdResult<&str, Utf8Error> {
+        if self.0.data.is_null() {
+            Ok("")
+        } else {
+            // SAFETY: This data is either passed from PAM (so we are forced to
+            // trust it) or was created by us in TextResponseInner::alloc.
+            // In either case, it's going to be a valid null-terminated string.
+            unsafe { CStr::from_ptr(self.0.data.cast()) }.to_str()
+        }
+    }
+
+    /// Releases memory owned by this response.
+    pub fn free_contents(&mut self) {
+        // SAFETY: We know we own this data.
+        // After we're done, it will be null.
+        unsafe {
+            memory::zero_c_string(self.0.data);
+            libc::free(self.0.data);
+            self.0.data = ptr::null_mut()
+        }
+    }
+}
+
+/// A [`RawResponse`] with [`CBinaryData`] in it.
+#[repr(transparent)]
+#[derive(Debug)]
+pub struct RawBinaryResponse(RawResponse);
+
+impl RawBinaryResponse {
+    /// Interprets the provided `RawResponse` as a binary response.
+    ///
+    /// # Safety
+    ///
+    /// It's up to you to provide a response that is a `RawBinaryResponse`.
+    pub unsafe fn upcast(from: &mut RawResponse) -> &mut Self {
+        // SAFETY: We're provided a valid reference.
+        &mut *(from as *mut RawResponse).cast::<Self>()
+    }
+
+    /// Fills in a `RawResponse` with the provided binary data.
+    ///
+    /// The `data_type` is a tag you can use for whatever.
+    /// It is passed through PAM unchanged.
+    ///
+    /// The referenced data is copied to the C heap. We do not take ownership.
+    /// You are responsible for calling [`free`](Self::free_contents)
+    /// on the pointer you get back when you're done with it.
+    pub fn fill<'a>(
+        dest: &'a mut RawResponse,
+        data: &[u8],
+        data_type: u8,
+    ) -> StdResult<&'a mut Self, TooBigError> {
+        dest.data = CBinaryData::alloc(data, data_type)?.cast();
+        // SAFETY: We just filled this in, so we know it's binary.
+        Ok(unsafe { Self::upcast(dest) })
+    }
+
+    /// Gets the binary data in this response.
+    pub fn data(&self) -> &[u8] {
+        self.contents().map(CBinaryData::contents).unwrap_or(&[])
+    }
+
+    /// Gets the `data_type` tag that was embedded with the message.
+    pub fn data_type(&self) -> u8 {
+        self.contents().map(CBinaryData::data_type).unwrap_or(0)
+    }
+
+    fn contents(&self) -> Option<&CBinaryData> {
+        // SAFETY: This was either something we got from PAM (in which case
+        // we trust it), or something that was created with
+        // BinaryResponseInner::alloc. In both cases, it points to valid data.
+        unsafe { self.0.data.cast::<CBinaryData>().as_ref() }
+    }
+
+    pub fn to_owned(&self) -> BinaryData {
+        BinaryData::new(self.data().into(), self.data_type())
+    }
+
+    /// Releases memory owned by this response.
+    pub fn free_contents(&mut self) {
+        // SAFETY: We know that our data pointer is either valid or null.
+        // Once we're done, it's null and the response is safe.
+        unsafe {
+            let data_ref = self.0.data.cast::<CBinaryData>().as_mut();
+            if let Some(d) = data_ref {
+                d.zero_contents()
+            }
+            libc::free(self.0.data);
+            self.0.data = ptr::null_mut()
+        }
+    }
+}
+
+/// Generic version of response data.
+///
+/// This has the same structure as [`RawBinaryResponse`]
+/// and [`RawTextResponse`].
+#[repr(C)]
+#[derive(Debug)]
+pub struct RawResponse {
+    /// Pointer to the data returned in a response.
+    /// For most responses, this will be a [`CStr`], but for responses to
+    /// [`MessageStyle::BinaryPrompt`]s, this will be [`CBinaryData`]
+    /// (a Linux-PAM extension).
+    data: *mut c_void,
+    /// Unused.
+    return_code: c_int,
+    _marker: Immovable,
+}
+
+/// A contiguous block of responses.
+#[derive(Debug)]
+pub struct OwnedResponses {
+    base: *mut RawResponse,
+    count: usize,
+}
+
+impl OwnedResponses {
+    /// Allocates an owned list of responses on the C heap.
+    fn alloc(count: usize) -> Self {
+        OwnedResponses {
+            // SAFETY: We are doing allocation here.
+            base: unsafe { libc::calloc(count, size_of::<RawResponse>()) }.cast(),
+            count,
+        }
+    }
+
+    pub fn build(value: &[Response]) -> StdResult<Self, FillError> {
+        let mut outputs = OwnedResponses::alloc(value.len());
+        // If we fail in here after allocating OwnedResponses,
+        // we still free all memory, even though we don't zero it first.
+        // This is an acceptable level of risk.
+        for (input, output) in iter::zip(value.iter(), outputs.iter_mut()) {
+            match input {
+                Response::NoResponse => {
+                    RawTextResponse::fill(output, "")?;
+                }
+                Response::Text(data) => {
+                    RawTextResponse::fill(output, data)?;
+                }
+                Response::MaskedText(data) => {
+                    RawTextResponse::fill(output, data.unsecure())?;
+                }
+                Response::Binary(data) => {
+                    RawBinaryResponse::fill(output, data.data(), data.data_type())?;
+                }
+            }
+        }
+        Ok(outputs)
+    }
+
+    /// Converts this into a `*RawResponse` for passing to PAM.
+    ///
+    /// The pointer "owns" its own data (i.e., this will not be dropped).
+    pub fn into_ptr(self) -> *mut RawResponse {
+        let ret = self.base;
+        mem::forget(self);
+        ret
+    }
+
+    /// Takes ownership of a list of responses allocated on the C heap.
+    ///
+    /// # Safety
+    ///
+    /// It's up to you to make sure you pass a valid pointer.
+    pub unsafe fn from_c_heap(base: *mut RawResponse, count: usize) -> Self {
+        OwnedResponses { base, count }
+    }
+}
+
+#[derive(Debug, thiserror::Error)]
+#[error("error converting responses: {0}")]
+pub enum FillError {
+    NulError(#[from] NulError),
+    TooBigError(#[from] TooBigError),
+}
+
+impl Deref for OwnedResponses {
+    type Target = [RawResponse];
+    fn deref(&self) -> &Self::Target {
+        // SAFETY: This is the memory we manage ourselves.
+        unsafe { slice::from_raw_parts(self.base, self.count) }
+    }
+}
+
+impl DerefMut for OwnedResponses {
+    fn deref_mut(&mut self) -> &mut Self::Target {
+        // SAFETY: This is the memory we manage ourselves.
+        unsafe { slice::from_raw_parts_mut(self.base, self.count) }
+    }
+}
+
+impl Drop for OwnedResponses {
+    fn drop(&mut self) {
+        // SAFETY: We allocated this ourselves, or it was provided to us by PAM.
+        unsafe {
+            for resp in self.iter_mut() {
+                libc::free(resp.data)
+            }
+            libc::free(self.base.cast())
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::{BinaryData, OwnedResponses, RawBinaryResponse, RawTextResponse, Response};
+
+    #[test]
+    fn test_round_trip() {
+        let responses = [
+            Response::Binary(BinaryData::new(vec![1, 2, 3], 99)),
+            Response::Text("whats going on".to_owned()),
+            Response::MaskedText("well then".into()),
+            Response::NoResponse,
+            Response::Text("bogus".to_owned()),
+        ];
+        let sent = OwnedResponses::build(&responses).unwrap();
+        let heap_resps = sent.into_ptr();
+        let mut received = unsafe { OwnedResponses::from_c_heap(heap_resps, 5) };
+
+        let assert_text = |want, raw| {
+            let up = unsafe { RawTextResponse::upcast(raw) };
+            assert_eq!(want, up.contents().unwrap());
+            up.free_contents();
+            assert_eq!("", up.contents().unwrap());
+        };
+        let assert_bin = |want_data: &[u8], want_type, raw| {
+            let up = unsafe { RawBinaryResponse::upcast(raw) };
+            assert_eq!(want_data, up.data());
+            assert_eq!(want_type, up.data_type());
+            up.free_contents();
+            let empty: [u8; 0] = [];
+            assert_eq!(&empty, up.data());
+            assert_eq!(0, up.data_type());
+        };
+        if let [zero, one, two, three, four] = &mut received[..] {
+            assert_bin(&[1, 2, 3], 99, zero);
+            assert_text("whats going on", one);
+            assert_text("well then", two);
+            assert_text("", three);
+            assert_text("bogus", four);
+        } else {
+            panic!("wrong size!")
+        }
+    }
+
+    #[test]
+    fn test_text_response() {
+        let mut responses = OwnedResponses::alloc(2);
+        let text = RawTextResponse::fill(&mut responses[0], "hello").unwrap();
+        let data = text.contents().expect("valid");
+        assert_eq!("hello", data);
+        text.free_contents();
+        text.free_contents();
+        RawTextResponse::fill(&mut responses[1], "hell\0").expect_err("should error; contains nul");
+    }
+
+    #[test]
+    fn test_binary_response() {
+        let mut responses = OwnedResponses::alloc(1);
+        let real_data = [1, 2, 3, 4, 5, 6, 7, 8];
+        let resp = RawBinaryResponse::fill(&mut responses[0], &real_data, 7)
+            .expect("alloc should succeed");
+        let data = resp.data();
+        assert_eq!(&real_data, data);
+        assert_eq!(7, resp.data_type());
+        resp.free_contents();
+        resp.free_contents();
+    }
+
+    #[test]
+    #[ignore]
+    fn test_binary_response_too_big() {
+        let big_data: Vec<u8> = vec![0xFFu8; 10_000_000_000];
+        let mut responses = OwnedResponses::alloc(1);
+        RawBinaryResponse::fill(&mut responses[0], &big_data, 0).expect_err("this is too big!");
+    }
+}