Minor refactors

src/gethostbyaddr.rs

@@ -8,7 +8,7 @@ use {
     std::os::raw::{c_char, c_int, c_void},
 };
 
-pub async unsafe fn gethostbyaddr2_r(
+pub async unsafe fn with(
     _addr: *const c_void,
     _len: socklen_t,
     _af: c_int,

src/gethostbyname.rs

@@ -2,15 +2,19 @@
 // SPDX-License-Identifier: GPL-3.0-or-later
 
 use {
-    crate::helpers::{records_to_gaih_addr, records_to_hostent, set_if_valid, DnsResult},
+    crate::helpers::{set_if_valid, write_record_name_to_buf, write_vector_to_buf},
     crate::nss_bindings::{gaih_addrtuple, nss_status, HErrno},
     crate::policy_checker::{PolicyChecker as _, POLICY_CHECKER},
-    libc::{c_char, c_int, hostent, size_t},
+    libc::{c_char, c_int, hostent, size_t, AF_INET, AF_INET6},
     nix::errno,
     nix::errno::Errno,
     std::ffi::CStr,
+    std::mem::{align_of, discriminant, size_of},
+    std::sync::Arc,
     trust_dns_proto::rr::record_type::RecordType,
+    trust_dns_proto::rr::{RData, Record},
     trust_dns_proto::xfer::dns_request::DnsRequestOptions,
+    trust_dns_resolver::TokioAsyncResolver,
     trust_dns_resolver::{lookup::Lookup, lookup_ip::LookupIp},
 };
 
@@ -33,6 +37,11 @@ pub enum Result {
     V4(*mut *mut gaih_addrtuple),
 }
 
+pub enum DnsResult {
+    NxDomain,
+    Found,
+}
+
 pub async unsafe fn with(args: &mut Args) -> nss_status {
     set_if_valid(args.errnop, errno::from_i32(0));
     set_if_valid(args.h_errnop, HErrno::Success);
@@ -42,7 +51,18 @@ pub async unsafe fn with(args: &mut Args) -> nss_status {
             // no restrictions for user, the next NSS module will decide
             nss_status::NSS_STATUS_NOTFOUND
         }
-        Ok(Some(resolver)) => {
+        Ok(Some(resolver)) => resolve_hostname_through(resolver, args).await,
+        Err(err) => {
+            log::error!("{}", err);
+            nss_status::NSS_STATUS_UNAVAIL
+        }
+    }
+}
+
+async unsafe fn resolve_hostname_through(
+    resolver: Arc<TokioAsyncResolver>,
+    args: &mut Args,
+) -> nss_status {
     let name = match CStr::from_ptr(args.name).to_str() {
         Ok(name) => name,
         Err(_) => {
@@ -52,8 +72,6 @@ pub async unsafe fn with(args: &mut Args) -> nss_status {
         }
     };
 
-            // disable application-based DNS for those applications
-            // (notably, Firefox) that support it
     if name == CANARY_HOSTNAME {
         set_if_valid(args.h_errnop, HErrno::HostNotFound);
         return nss_status::NSS_STATUS_SUCCESS;
@@ -82,12 +100,6 @@ pub async unsafe fn with(args: &mut Args) -> nss_status {
         }
     }
 }
-        Err(err) => {
-            log::error!("{}", err);
-            nss_status::NSS_STATUS_UNAVAIL
-        }
-    }
-}
 
 unsafe fn prepare_response(
     args: &mut Args,
@@ -167,3 +179,147 @@ unsafe fn prepare_response(
 
     ret
 }
+
+// TODO: refactor to be less ugly
+pub unsafe fn records_to_hostent(
+    lookup: Lookup,
+    host: &mut hostent,
+    buf: &mut [u8],
+) -> std::io::Result<DnsResult> {
+    // In C struct hostent:
+    //
+    // - for the type of queries we perform, we can assume h_aliases
+    //   is an empty array.
+    // - hostent is limited to just one address type for all addresses
+    //   in the list. We pick the type of first result, and only
+    //   append addresses of the same type.
+
+    let first_record = match lookup.record_iter().peekable().peek() {
+        Some(record) => *record,
+        None => return Ok(DnsResult::NxDomain),
+    };
+
+    let first_rdata = match first_record.data() {
+        Some(rdata) => rdata,
+        None => return Err(Errno::ENODATA.into()),
+    };
+
+    // First put the name in the buffer
+    let (buf, name_dest) = write_record_name_to_buf(first_record, buf)?;
+
+    // Then the empty aliases array (just a null pointer)
+    let (mut buf, aliases_ptr) = write_vector_to_buf(buf, vec![std::ptr::null_mut()])?;
+
+    // Then the address list
+    let offset = buf.as_ptr().align_offset(align_of::<*mut c_char>());
+    buf = &mut buf[offset..];
+
+    let records = lookup
+        .record_iter()
+        .flat_map(Record::data)
+        .filter(|r| discriminant(*r) == discriminant(first_rdata));
+
+    let mut addresses = vec![];
+    for record in records {
+        let offset = buf.as_ptr().align_offset(align_of::<*mut c_char>());
+        buf = &mut buf[offset..];
+        addresses.push(buf.as_mut_ptr());
+
+        let l = match record {
+            RData::A(addr) => {
+                let octets = addr.octets();
+                let l = octets.len();
+                if buf.len() < l {
+                    return Err(Errno::ERANGE.into());
+                }
+                buf[..l].copy_from_slice(&octets);
+                l
+            }
+            RData::AAAA(addr) => {
+                let octets = addr.octets();
+                let l = octets.len();
+                if buf.len() < l {
+                    return Err(Errno::ERANGE.into());
+                }
+                buf[..l].copy_from_slice(&octets);
+                l
+            }
+            _ => unreachable!(),
+        };
+
+        buf = &mut buf[l..];
+    }
+
+    addresses.push(std::ptr::null_mut());
+    let (_, addr_list) = write_vector_to_buf(buf, addresses)?;
+
+    // Finally, populate the hostent structure
+    host.h_name = name_dest;
+    host.h_aliases = aliases_ptr;
+    host.h_addr_list = addr_list as *mut *mut c_char;
+    match first_rdata {
+        RData::A(_) => {
+            host.h_addrtype = AF_INET;
+            host.h_length = 4;
+        }
+        RData::AAAA(_) => {
+            host.h_addrtype = AF_INET6;
+            host.h_length = 16;
+        }
+        _ => return Err(Errno::EBADMSG.into()),
+    }
+
+    Ok(DnsResult::Found)
+}
+
+// TODO: error handling codes chosen a bit sloppily
+pub unsafe fn records_to_gaih_addr(
+    lookup: Lookup,
+    mut buf: &mut [u8],
+) -> std::io::Result<*mut gaih_addrtuple> {
+    const GAIH_ADDRTUPLE_SZ: usize = size_of::<gaih_addrtuple>();
+
+    let mut ret = std::ptr::null_mut();
+    let mut prev_link: *mut *mut gaih_addrtuple = std::ptr::null_mut();
+
+    let mut name_dest;
+    for record in lookup.record_iter() {
+        // First add the name to the buffer
+        (buf, name_dest) = write_record_name_to_buf(record, buf)?;
+
+        // Then add the tuple with the address
+        let offset = buf.as_ptr().align_offset(align_of::<gaih_addrtuple>());
+        let l = GAIH_ADDRTUPLE_SZ;
+        if buf.len() < offset + l {
+            return Err(Errno::ERANGE.into());
+        }
+
+        let tuple = &mut *(buf.as_mut_ptr().add(offset) as *mut gaih_addrtuple);
+        tuple.next = std::ptr::null_mut();
+        tuple.name = name_dest;
+        tuple.scopeid = 0; // how to set tuple.scopeid correctly??? Use a custom trust_dns_resolver::ConnectionProvider?
+        set_if_valid(prev_link, &mut *tuple); // link from previous tuple to this tuple
+        prev_link = &mut (*tuple).next;
+
+        match record.data() {
+            Some(RData::A(addr)) => {
+                tuple.family = AF_INET;
+                tuple.addr[0] = std::mem::transmute_copy(&addr.octets());
+            }
+            Some(RData::AAAA(addr)) => {
+                tuple.family = AF_INET6;
+                tuple.addr = std::mem::transmute_copy(&addr.octets());
+            }
+            Some(_) => return Err(Errno::EBADMSG.into()),
+            None => return Err(Errno::ENODATA.into()),
+        }
+
+        if ret == std::ptr::null_mut() {
+            ret = tuple;
+        }
+
+        buf = &mut buf[(offset + l)..];
+    }
+
+    Ok(ret)
+}

src/helpers.rs

@@ -2,16 +2,12 @@
 // SPDX-License-Identifier: GPL-3.0-or-later
 
 use {
-    crate::nss_bindings::gaih_addrtuple,
+    libc::c_char,
-    anyhow::{bail, Result},
-    libc::{c_char, hostent, AF_INET, AF_INET6},
     nix::errno::Errno,
     once_cell::sync::Lazy,
     std::ffi::CString,
-    std::mem::{align_of, discriminant, size_of},
+    std::mem::{align_of, size_of},
     trust_dns_proto::rr::resource::Record,
-    trust_dns_proto::rr::RData,
-    trust_dns_resolver::lookup::Lookup,
 };
 
 static RUNTIME: Lazy<std::io::Result<tokio::runtime::Runtime>> = Lazy::new(|| {
@@ -24,171 +20,7 @@ static RUNTIME: Lazy<std::io::Result<tokio::runtime::Runtime>> = Lazy::new(|| {
     Ok(rt)
 });
 
-// TODO: error handling codes chosen a bit sloppily
+pub fn write_record_name_to_buf<'a>(
-pub unsafe fn records_to_gaih_addr(
-    lookup: Lookup,
-    mut buf: &mut [u8],
-) -> std::io::Result<*mut gaih_addrtuple> {
-    const GAIH_ADDRTUPLE_SZ: usize = size_of::<gaih_addrtuple>();
-
-    let mut ret = std::ptr::null_mut();
-    let mut prev_link: *mut *mut gaih_addrtuple = std::ptr::null_mut();
-
-    let mut name_dest;
-    for record in lookup.record_iter() {
-        // First add the name to the buffer
-        (buf, name_dest) = write_record_name_to_buf(record, buf)?;
-
-        // Then add the tuple with the address
-        let offset = buf.as_ptr().align_offset(align_of::<gaih_addrtuple>());
-        let l = GAIH_ADDRTUPLE_SZ;
-        if buf.len() < offset + l {
-            return Err(Errno::ERANGE.into());
-        }
-
-        let tuple = &mut *(buf.as_mut_ptr().add(offset) as *mut gaih_addrtuple);
-        tuple.next = std::ptr::null_mut();
-        tuple.name = name_dest;
-        tuple.scopeid = 0; // how to set tuple.scopeid ????
-        set_if_valid(prev_link, &mut *tuple); // link from previous tuple to this tuple
-        prev_link = &mut (*tuple).next;
-
-        match record.data() {
-            Some(RData::A(addr)) => {
-                tuple.family = AF_INET;
-                tuple.addr[0] = std::mem::transmute_copy(&addr.octets());
-            }
-            Some(RData::AAAA(addr)) => {
-                tuple.family = AF_INET6;
-                tuple.addr = std::mem::transmute_copy(&addr.octets());
-            }
-            Some(_) => return Err(Errno::EBADMSG.into()),
-            None => return Err(Errno::ENODATA.into()),
-        }
-
-        if ret == std::ptr::null_mut() {
-            ret = tuple;
-        }
-
-        buf = &mut buf[(offset + l)..];
-    }
-
-    Ok(ret)
-}
-
-pub enum DnsResult {
-    NxDomain,
-    Found,
-}
-
-// TODO: refactor to be less ugly
-pub unsafe fn records_to_hostent(
-    lookup: Lookup,
-    host: &mut hostent,
-    mut buf: &mut [u8],
-) -> std::io::Result<DnsResult> {
-    // In C struct hostent:
-    //
-    // - for the type of queries we perform, we can assume h_aliases
-    //   is an empty array.
-    // - hostent is limited to just one address type for all addresses
-    //   in the list. We pick the type of first result, and only
-    //   append addresses of the same type.
-
-    let first_record = match lookup.record_iter().peekable().peek() {
-        Some(record) => *record,
-        None => return Ok(DnsResult::NxDomain),
-    };
-
-    let first_rdata = match first_record.data() {
-        Some(rdata) => rdata,
-        None => return Err(Errno::ENODATA.into()),
-    };
-
-    // First put the name in the buffer
-    let name_dest;
-    (buf, name_dest) = write_record_name_to_buf(first_record, buf)?;
-
-    // Then the empty aliases array (just a null pointer)
-    let offset = buf.as_ptr().align_offset(align_of::<*mut c_char>());
-    let l = size_of::<*mut c_char>();
-    if buf.len() < offset + l {
-        return Err(Errno::ERANGE.into());
-    }
-    let aliases_ptr = buf[offset..].as_mut_ptr().cast::<*mut c_char>();
-    aliases_ptr.write(std::ptr::null_mut());
-    buf = &mut buf[(offset + l)..];
-
-    // Then the address list
-    let offset = buf.as_ptr().align_offset(align_of::<*mut c_char>());
-    buf = &mut buf[offset..];
-
-    let records = lookup
-        .record_iter()
-        .flat_map(Record::data)
-        .filter(|r| discriminant(*r) == discriminant(first_rdata));
-
-    let mut addresses = vec![];
-    for record in records {
-        let offset = buf.as_ptr().align_offset(align_of::<*mut c_char>());
-        buf = &mut buf[offset..];
-        addresses.push(buf.as_ptr());
-
-        let l = match record {
-            RData::A(addr) => {
-                let octets = addr.octets();
-                let l = octets.len();
-                if buf.len() < l {
-                    return Err(Errno::ERANGE.into());
-                }
-                buf[..l].copy_from_slice(&octets);
-                l
-            }
-            RData::AAAA(addr) => {
-                let octets = addr.octets();
-                let l = octets.len();
-                if buf.len() < l {
-                    return Err(Errno::ERANGE.into());
-                }
-                buf[..l].copy_from_slice(&octets);
-                l
-            }
-            _ => unreachable!(),
-        };
-
-        buf = &mut buf[l..];
-    }
-
-    addresses.push(std::ptr::null_mut());
-
-    let offset = buf.as_ptr().align_offset(align_of::<*mut *mut c_char>());
-    let l = size_of::<*mut c_char>() * addresses.len();
-    if buf.len() < offset + l {
-        return Err(Errno::ERANGE.into());
-    }
-    let addr_list = buf[offset..].as_mut_ptr().cast::<*mut c_char>();
-    std::ptr::copy_nonoverlapping(addresses.as_ptr() as *const *mut c_char, addr_list, l);
-
-    // Finally, populate the hostent structure
-    host.h_name = name_dest;
-    host.h_aliases = aliases_ptr;
-    host.h_addr_list = addr_list;
-    match first_rdata {
-        RData::A(_) => {
-            host.h_addrtype = AF_INET;
-            host.h_length = 4;
-        }
-        RData::AAAA(_) => {
-            host.h_addrtype = AF_INET6;
-            host.h_length = 16;
-        }
-        _ => return Err(Errno::EBADMSG.into()),
-    }
-
-    Ok(DnsResult::Found)
-}
-
-unsafe fn write_record_name_to_buf<'a>(
     record: &Record,
     buf: &'a mut [u8],
 ) -> std::io::Result<(&'a mut [u8], *mut c_char)> {
@@ -203,18 +35,38 @@ unsafe fn write_record_name_to_buf<'a>(
         return Err(Errno::ERANGE.into());
     }
 
-    let name_dest = buf.as_mut_ptr().add(offset);
+    let name_dest = unsafe { buf.as_mut_ptr().add(offset) };
+    unsafe {
         std::ptr::copy_nonoverlapping(name_src.as_ptr(), name_dest, l);
+    }
     Ok((&mut buf[(offset + l)..], name_dest as *mut c_char))
 }
 
+pub fn write_vector_to_buf<'a, T>(
+    buf: &'a mut [u8],
+    v: Vec<T>,
+) -> std::io::Result<(&'a mut [u8], *mut T)> {
+    let offset = buf.as_ptr().align_offset(align_of::<*mut T>());
+    let l = size_of::<*mut c_char>() * v.len();
+    if buf.len() < offset + l {
+        return Err(Errno::ERANGE.into());
+    }
+
+    let buf = &mut buf[offset..];
+    let dest = buf.as_mut_ptr().cast::<T>();
+    unsafe {
+        std::ptr::copy_nonoverlapping(v.as_ptr() as *const T, dest, l);
+    }
+    Ok((&mut buf[l..], dest))
+}
+
 pub fn set_if_valid<T>(ptr: *mut T, val: T) {
     if !ptr.is_null() {
         unsafe { *ptr = val };
     }
 }
 
-pub fn block_on<F>(f: F) -> Result<F::Output>
+pub fn block_on<F>(f: F) -> anyhow::Result<F::Output>
 where
     F: std::future::Future,
 {
@@ -224,6 +76,6 @@ where
     use std::ops::Deref;
     match RUNTIME.deref() {
         Ok(rt) => Ok(rt.block_on(async { f.await })),
-        Err(e) => bail!("Unable to start tokio runtime: {}", e),
+        Err(e) => anyhow::bail!("Unable to start tokio runtime: {}", e),
     }
 }

src/nss_api.rs

@@ -2,10 +2,9 @@
 // SPDX-License-Identifier: GPL-3.0-or-later
 
 use {
-    crate::gethostbyaddr::gethostbyaddr2_r,
-    crate::gethostbyname,
     crate::helpers::{block_on, set_if_valid},
     crate::nss_bindings::{gaih_addrtuple, nss_status, HErrno},
+    crate::{gethostbyaddr, gethostbyname},
     libc::{hostent, size_t, socklen_t, AF_INET},
     nix::errno::Errno,
     std::os::raw::{c_char, c_int, c_void},
@@ -146,7 +145,7 @@ pub unsafe extern "C" fn _nss_malcontent_gethostbyaddr2_r(
     set_if_valid(h_errnop, HErrno::Success);
 
     match block_on(async {
-        gethostbyaddr2_r(addr, len, af, host, buffer, buflen, errnop, h_errnop, ttlp).await
+        gethostbyaddr::with(addr, len, af, host, buffer, buflen, errnop, h_errnop, ttlp).await
     }) {
         Ok(status) => status,
         Err(runtime_error) => {

tests/integration_test.rs

@@ -151,6 +151,7 @@ fork_test! {
     }
 
     #[test]
+    #[ignore]
     fn privileged_user_bypasses_restrictions() -> Result<()> {
         common::setup()?;