1 files changed, 120 insertions, 0 deletions
diff --git a/src/util/fipstools/fipscommon/ar.go b/src/util/fipstools/fipscommon/ar.go
new file mode 100644
index 00000000..85b378d6
--- /dev/null
+++ b/src/util/fipstools/fipscommon/ar.go
@@ -0,0 +1,120 @@
+// 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. */
+
+// ar.go contains functions for parsing .a archive files.
+
+package fipscommon
+
+import (
+	"bytes"
+	"errors"
+	"io"
+	"strconv"
+	"strings"
+)
+
+// ParseAR parses an archive file from r and returns a map from filename to
+// contents, or else an error.
+func ParseAR(r io.Reader) (map[string][]byte, error) {
+	// See https://en.wikipedia.org/wiki/Ar_(Unix)#File_format_details
+	const expectedMagic = "!<arch>\n"
+	var magic [len(expectedMagic)]byte
+	if _, err := io.ReadFull(r, magic[:]); err != nil {
+		return nil, err
+	}
+	if string(magic[:]) != expectedMagic {
+		return nil, errors.New("ar: not an archive file")
+	}
+
+	const filenameTableName = "//"
+	const symbolTableName = "/"
+	var longFilenameTable []byte
+	ret := make(map[string][]byte)
+
+	for {
+		var header [60]byte
+		if _, err := io.ReadFull(r, header[:]); err != nil {
+			if err == io.EOF {
+				break
+			}
+			return nil, errors.New("ar: error reading file header: " + err.Error())
+		}
+
+		name := strings.TrimRight(string(header[:16]), " ")
+		sizeStr := strings.TrimRight(string(header[48:58]), "\x00 ")
+		size, err := strconv.ParseUint(sizeStr, 10, 64)
+		if err != nil {
+			return nil, errors.New("ar: failed to parse file size: " + err.Error())
+		}
+
+		// File contents are padded to a multiple of two bytes
+		storedSize := size
+		if storedSize%2 == 1 {
+			storedSize++
+		}
+
+		contents := make([]byte, storedSize)
+		if _, err := io.ReadFull(r, contents); err != nil {
+			return nil, errors.New("ar: error reading file contents: " + err.Error())
+		}
+		contents = contents[:size]
+
+		switch {
+		case name == filenameTableName:
+			if longFilenameTable != nil {
+				return nil, errors.New("ar: two filename tables found")
+			}
+			longFilenameTable = contents
+			continue
+
+		case name == symbolTableName:
+			continue
+
+		case len(name) > 1 && name[0] == '/':
+			if longFilenameTable == nil {
+				return nil, errors.New("ar: long filename reference found before filename table")
+			}
+
+			// A long filename is stored as "/" followed by a
+			// base-10 offset in the filename table.
+			offset, err := strconv.ParseUint(name[1:], 10, 64)
+			if err != nil {
+				return nil, errors.New("ar: failed to parse filename offset: " + err.Error())
+			}
+			if offset > uint64((^uint(0))>>1) {
+				return nil, errors.New("ar: filename offset overflow")
+			}
+
+			if int(offset) > len(longFilenameTable) {
+				return nil, errors.New("ar: filename offset out of bounds")
+			}
+
+			filename := longFilenameTable[offset:]
+			if i := bytes.IndexByte(filename, '/'); i < 0 {
+				return nil, errors.New("ar: unterminated filename in table")
+			} else {
+				filename = filename[:i]
+			}
+
+			name = string(filename)
+
+		default:
+			name = strings.TrimRight(name, "/")
+		}
+
+		ret[name] = contents
+	}
+
+	return ret, nil
+}