From 7976403b133aa22df3ffc39cd7638fea265200ee Mon Sep 17 00:00:00 2001
From: awgh <awgh@awgh.org>
Date: Fri, 19 Jun 2020 23:33:58 -0700
Subject: [PATCH] Added Exports() which returns an array of Export structs
 describing the exported functions, if there are any.

---
 pe/exports.go | 119 ++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 119 insertions(+)
 create mode 100644 pe/exports.go

diff --git a/pe/exports.go b/pe/exports.go
new file mode 100644
index 0000000..129d340
--- /dev/null
+++ b/pe/exports.go
@@ -0,0 +1,119 @@
+package pe
+
+import (
+	"encoding/binary"
+)
+
+// ExportDirectory - data directory definition for exported functions
+type ExportDirectory struct {
+	ExportFlags       uint32 // reserved, must be zero
+	TimeDateStamp     uint32
+	MajorVersion      uint16
+	MinorVersion      uint16
+	NameRVA           uint32 // pointer to the name of the DLL
+	OrdinalBase       uint32
+	NumberOfFunctions uint32
+	NumberOfNames     uint32 // also Ordinal Table Len
+	AddressTableAddr  uint32 // RVA of EAT, relative to image base
+	NameTableAddr     uint32 // RVA of export name pointer table, relative to image base
+	OrdinalTableAddr  uint32 // address of the ordinal table, relative to iamge base
+
+	DllName string
+}
+
+// Export - describes a single export entry
+type Export struct {
+	Ordinal        uint32
+	Name           string
+	VirtualAddress uint32
+}
+
+// Exports - gets exports
+func (f *File) Exports() ([]Export, error) {
+	pe64 := f.Machine == IMAGE_FILE_MACHINE_AMD64
+
+	// grab the number of data directory entries
+	var ddLength uint32
+	if pe64 {
+		ddLength = f.OptionalHeader.(*OptionalHeader64).NumberOfRvaAndSizes
+	} else {
+		ddLength = f.OptionalHeader.(*OptionalHeader32).NumberOfRvaAndSizes
+	}
+
+	// check that the length of data directory entries is large
+	// enough to include the exports directory.
+	if ddLength < IMAGE_DIRECTORY_ENTRY_EXPORT+1 {
+		return nil, nil
+	}
+
+	// grab the export data directory entry
+	var edd DataDirectory
+	if pe64 {
+		edd = f.OptionalHeader.(*OptionalHeader64).DataDirectory[IMAGE_DIRECTORY_ENTRY_EXPORT]
+	} else {
+		edd = f.OptionalHeader.(*OptionalHeader32).DataDirectory[IMAGE_DIRECTORY_ENTRY_EXPORT]
+	}
+
+	// figure out which section contains the export directory table
+	var ds *Section
+	ds = nil
+	for _, s := range f.Sections {
+		if s.VirtualAddress <= edd.VirtualAddress && edd.VirtualAddress < s.VirtualAddress+s.VirtualSize {
+			ds = s
+			break
+		}
+	}
+
+	// didn't find a section, so no exports were found
+	if ds == nil {
+		return nil, nil
+	}
+
+	d, err := ds.Data()
+	if err != nil {
+		return nil, err
+	}
+
+	exportDirOffset := edd.VirtualAddress - ds.VirtualAddress
+
+	// seek to the virtual address specified in the export data directory
+	dxd := d[exportDirOffset:]
+
+	// deserialize export directory
+	var dt ExportDirectory
+	dt.ExportFlags = binary.LittleEndian.Uint32(dxd[0:4])
+	dt.TimeDateStamp = binary.LittleEndian.Uint32(dxd[4:8])
+	dt.MajorVersion = binary.LittleEndian.Uint16(dxd[8:10])
+	dt.MinorVersion = binary.LittleEndian.Uint16(dxd[10:12])
+	dt.NameRVA = binary.LittleEndian.Uint32(dxd[12:16])
+	dt.OrdinalBase = binary.LittleEndian.Uint32(dxd[16:20])
+	dt.NumberOfFunctions = binary.LittleEndian.Uint32(dxd[20:24])
+	dt.NumberOfNames = binary.LittleEndian.Uint32(dxd[24:28])
+	dt.AddressTableAddr = binary.LittleEndian.Uint32(dxd[28:32])
+	dt.NameTableAddr = binary.LittleEndian.Uint32(dxd[32:36])
+	dt.OrdinalTableAddr = binary.LittleEndian.Uint32(dxd[36:40])
+
+	dt.DllName, _ = getString(d, int(dt.NameRVA-ds.VirtualAddress))
+
+	// seek to address table
+	dna := d[dt.AddressTableAddr-ds.VirtualAddress:]
+	// seek to ordinal table
+	dno := d[dt.OrdinalTableAddr-ds.VirtualAddress:]
+	// seek to names table
+	dnn := d[dt.NameTableAddr-ds.VirtualAddress:]
+
+	var exports []Export
+	var i uint32
+	for i = 0; i < dt.NumberOfFunctions; i++ {
+		var export Export
+		export.Ordinal = dt.OrdinalBase +
+			uint32(binary.LittleEndian.Uint16(dno[i*2:(i*2)+2]))
+
+		nameRVA := uint32(binary.LittleEndian.Uint32(dnn[i*4 : (i*4)+4]))
+		export.Name, _ = getString(d, int(nameRVA-ds.VirtualAddress))
+		export.VirtualAddress =
+			binary.LittleEndian.Uint32(dna[i*4 : (i*4)+4])
+		exports = append(exports, export)
+	}
+	return exports, nil
+}