From ffaf0de82a17f7783acc06f43fe5bcdd548705bc Mon Sep 17 00:00:00 2001
From: Piotr Osiewicz <24362066+osiewicz@users.noreply.github.com>
Date: Sat, 20 Nov 2021 06:17:29 +0100
Subject: [PATCH] read/coff: add support for extended relocations (#399)

---
 src/read/coff/section.rs | 20 ++++++++++++++++++--
 testfiles                |  2 +-
 tests/coff.rs            | 23 +++++++++++++++++++++++
 tests/integration.rs     |  1 +
 4 files changed, 43 insertions(+), 3 deletions(-)
 create mode 100644 tests/coff.rs

diff --git a/src/read/coff/section.rs b/src/read/coff/section.rs
index 48c1529b..cb2edec9 100644
--- a/src/read/coff/section.rs
+++ b/src/read/coff/section.rs
@@ -470,8 +470,24 @@ impl pe::ImageSectionHeader {
         &self,
         data: R,
     ) -> read::Result<&'data [pe::ImageRelocation]> {
-        let pointer = self.pointer_to_relocations.get(LE).into();
-        let number = self.number_of_relocations.get(LE).into();
+        let mut pointer = self.pointer_to_relocations.get(LE).into();
+        let mut number: usize = self.number_of_relocations.get(LE).into();
+        if number == core::u16::MAX.into()
+            && self.characteristics.get(LE) & pe::IMAGE_SCN_LNK_NRELOC_OVFL != 0
+        {
+            // Extended relocations. Read first relocation (which contains extended count) & adjust
+            // relocations pointer.
+            let extended_relocation_info = data
+                .read_at::<pe::ImageRelocation>(pointer)
+                .read_error("Invalid COFF relocation offset or number")?;
+            number = extended_relocation_info.virtual_address.get(LE) as usize;
+            if number == 0 {
+                return Err(Error("Invalid COFF relocation number"));
+            }
+            pointer += core::mem::size_of::<pe::ImageRelocation>() as u64;
+            // Extended relocation info does not contribute to the count of sections.
+            number -= 1;
+        }
         data.read_slice_at(pointer, number)
             .read_error("Invalid COFF relocation offset or number")
     }
diff --git a/testfiles b/testfiles
index 26f9fc09..fd4ed2a6 160000
--- a/testfiles
+++ b/testfiles
@@ -1 +1 @@
-Subproject commit 26f9fc09c3eec709dd88b4f4675da59ab2d9dff2
+Subproject commit fd4ed2a6230c80a1b6e216ad0504905f987ce200
diff --git a/tests/coff.rs b/tests/coff.rs
new file mode 100644
index 00000000..3e61ec28
--- /dev/null
+++ b/tests/coff.rs
@@ -0,0 +1,23 @@
+use object::{pe, read, Object, ObjectSection};
+use std::fs;
+use std::path::PathBuf;
+
+#[cfg(feature = "coff")]
+#[test]
+fn coff_extended_relocations() {
+    let path_to_obj: PathBuf = ["testfiles", "coff", "relocs_overflow.o"].iter().collect();
+    let contents = fs::read(&path_to_obj).expect("Could not read relocs_overflow.o");
+    let file =
+        read::coff::CoffFile::parse(&contents[..]).expect("Could not parse relocs_overflow.o");
+    let code_section = file
+        .section_by_name(".text")
+        .expect("Could not find .text section in relocs_overflow.o");
+    match code_section.flags() {
+        object::SectionFlags::Coff { characteristics } => {
+            assert!(characteristics & pe::IMAGE_SCN_LNK_NRELOC_OVFL != 0)
+        }
+        _ => panic!("Invalid section flags flavour."),
+    };
+    let relocations = code_section.relocations().collect::<Vec<_>>();
+    assert_eq!(relocations.len(), 65536);
+}
diff --git a/tests/integration.rs b/tests/integration.rs
index ee859f2c..e31e50f0 100644
--- a/tests/integration.rs
+++ b/tests/integration.rs
@@ -1 +1,2 @@
+mod coff;
 mod round_trip;