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// Copyright (c) 2017, Google Inc.
//
// Permission to use, copy, modify, and/or distribute this software for any
// purpose with or without fee is hereby granted, provided that the above
// copyright notice and this permission notice appear in all copies.
//
// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
// WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
// MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
// SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
// WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
// OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
// CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */
// inject-hash parses an archive containing a file object file. It finds a FIPS
// module inside that object, calculates its hash and replaces the default hash
// value in the object with the calculated value.
package main
import (
"bytes"
"crypto/hmac"
"crypto/sha512"
"debug/elf"
"errors"
"flag"
"fmt"
"io"
"io/ioutil"
"os"
)
func do(outPath, oInput string, arInput string) error {
var objectBytes []byte
if len(arInput) > 0 {
if len(oInput) > 0 {
return fmt.Errorf("-in-archive and -in-object are mutually exclusive")
}
arFile, err := os.Open(arInput)
if err != nil {
return err
}
defer arFile.Close()
ar, err := ParseAR(arFile)
if err != nil {
return err
}
if len(ar) != 1 {
return fmt.Errorf("expected one file in archive, but found %d", len(ar))
}
for _, contents := range ar {
objectBytes = contents
}
} else if len(oInput) > 0 {
var err error
if objectBytes, err = ioutil.ReadFile(oInput); err != nil {
return err
}
} else {
return fmt.Errorf("exactly one of -in-archive or -in-object is required")
}
object, err := elf.NewFile(bytes.NewReader(objectBytes))
if err != nil {
return errors.New("failed to parse object: " + err.Error())
}
// Find the .text section.
var textSection *elf.Section
var textSectionIndex elf.SectionIndex
for i, section := range object.Sections {
if section.Name == ".text" {
textSectionIndex = elf.SectionIndex(i)
textSection = section
break
}
}
if textSection == nil {
return errors.New("failed to find .text section in object")
}
// Find the starting and ending symbols for the module.
var startSeen, endSeen bool
var start, end uint64
symbols, err := object.Symbols()
if err != nil {
return errors.New("failed to parse symbols: " + err.Error())
}
for _, symbol := range symbols {
if symbol.Section != textSectionIndex {
continue
}
switch symbol.Name {
case "BORINGSSL_bcm_text_start":
if startSeen {
return errors.New("duplicate start symbol found")
}
startSeen = true
start = symbol.Value
case "BORINGSSL_bcm_text_end":
if endSeen {
return errors.New("duplicate end symbol found")
}
endSeen = true
end = symbol.Value
default:
continue
}
}
if !startSeen || !endSeen {
return errors.New("could not find module boundaries in object")
}
if max := textSection.Size; start > max || start > end || end > max {
return fmt.Errorf("invalid module boundaries: start: %x, end: %x, max: %x", start, end, max)
}
// Extract the module from the .text section and hash it.
text := textSection.Open()
if _, err := text.Seek(int64(start), 0); err != nil {
return errors.New("failed to seek to module start in .text: " + err.Error())
}
moduleText := make([]byte, end-start)
if _, err := io.ReadFull(text, moduleText); err != nil {
return errors.New("failed to read .text: " + err.Error())
}
var zeroKey [64]byte
mac := hmac.New(sha512.New, zeroKey[:])
mac.Write(moduleText)
calculated := mac.Sum(nil)
// Replace the default hash value in the object with the calculated
// value and write it out.
offset := bytes.Index(objectBytes, uninitHashValue[:])
if offset < 0 {
return errors.New("did not find uninitialised hash value in object file")
}
if bytes.Index(objectBytes[offset+1:], uninitHashValue[:]) >= 0 {
return errors.New("found two occurrences of uninitialised hash value in object file")
}
copy(objectBytes[offset:], calculated)
return ioutil.WriteFile(outPath, objectBytes, 0644)
}
func main() {
arInput := flag.String("in-archive", "", "Path to a .a file")
oInput := flag.String("in-object", "", "Path to a .o file")
outPath := flag.String("o", "", "Path to output object")
flag.Parse()
if err := do(*outPath, *oInput, *arInput); err != nil {
fmt.Fprintf(os.Stderr, "%s\n", err)
os.Exit(1)
}
}
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