DRYer

tools/cmd/ssh/askpass.go

@@ -72,7 +72,10 @@ func RunSSHAskpass() {
 			break
 		}
 	}
-	data = shm.ReadWithSize(data_shm, 1)
+	data, err = shm.ReadWithSize(data_shm, 1)
+	if err != nil {
+		fatal(fmt.Errorf("Failed to read from SHM file with error: %w", err))
+	}
 	response := ""
 	if is_confirm {
 		var ok bool

tools/cmd/ssh/main.go

@@ -65,11 +65,7 @@ func get_destination(hostname string) (username, hostname_for_match string) {
 }
 
 func read_data_from_shared_memory(shm_name string) ([]byte, error) {
-	data, err := shm.ReadWithSizeAndUnlink(shm_name, func(f *os.File) error {
+	data, err := shm.ReadWithSizeAndUnlink(shm_name, func(s fs.FileInfo) error {
-		s, err := f.Stat()
-		if err != nil {
-			return fmt.Errorf("Failed to stat SHM file with error: %w", err)
-		}
 		if stat, ok := s.Sys().(unix.Stat_t); ok {
 			if os.Getuid() != int(stat.Uid) || os.Getgid() != int(stat.Gid) {
 				return fmt.Errorf("Incorrect owner on SHM file")

tools/utils/shm/shm.go

@@ -104,43 +104,58 @@ func truncate_or_unlink(ans *os.File, size uint64) (err error) {
 	return
 }
 
-func read_till_buf_full(f *os.File, buf []byte) ([]byte, error) {
+const NUM_BYTES_FOR_SIZE = 4
-	p := buf
-	for len(p) > 0 {
-		n, err := f.Read(p)
-		p = p[n:]
-		if err != nil {
-			if len(p) == 0 && errors.Is(err, io.EOF) {
-				err = nil
-			}
-			err = fmt.Errorf("Failed to read from SHM file with error: %w", err)
-			return buf[:len(buf)-len(p)], err
-		}
-	}
-	return buf, nil
-}
-
-func read_with_size(f *os.File) ([]byte, error) {
-	szbuf := []byte{0, 0, 0, 0}
-	szbuf, err := read_till_buf_full(f, szbuf)
-	if err != nil {
-		return nil, err
-	}
-	size := int(binary.BigEndian.Uint32(szbuf))
-	return read_till_buf_full(f, make([]byte, size))
-}
 
 func WriteWithSize(self MMap, b []byte, at int) error {
-	szbuf := []byte{0, 0, 0, 0}
+	if len(self.Slice()) < at+len(b)+NUM_BYTES_FOR_SIZE {
-	binary.BigEndian.PutUint32(szbuf, uint32(len(b)))
+		return io.ErrShortBuffer
-	copy(self.Slice()[at:], szbuf)
+	}
-	copy(self.Slice()[at+4:], b)
+	binary.BigEndian.PutUint32(self.Slice()[at:], uint32(len(b)))
+	copy(self.Slice()[at+NUM_BYTES_FOR_SIZE:], b)
 	return nil
 }
 
-func ReadWithSize(self MMap, at int) []byte {
+func ReadWithSize(self MMap, at int) ([]byte, error) {
-	size := int(binary.BigEndian.Uint32(self.Slice()[at : at+4]))
+	s := self.Slice()[at:]
-	return self.Slice()[at+4 : at+4+size]
+	if len(s) < NUM_BYTES_FOR_SIZE {
+		return nil, io.ErrShortBuffer
+	}
+	size := int(binary.BigEndian.Uint32(self.Slice()[at : at+NUM_BYTES_FOR_SIZE]))
+	s = s[NUM_BYTES_FOR_SIZE:]
+	if len(s) < size {
+		return nil, io.ErrShortBuffer
+	}
+	return s[:size], nil
+}
+
+func ReadWithSizeAndUnlink(name string, file_callback ...func(fs.FileInfo) error) ([]byte, error) {
+	mmap, err := Open(name, 0)
+	if err != nil {
+		return nil, err
+	}
+	if len(file_callback) > 0 {
+		s, err := mmap.Stat()
+		if err != nil {
+			return nil, fmt.Errorf("Failed to stat SHM file with error: %w", err)
+		}
+		for _, f := range file_callback {
+			err = f(s)
+			if err != nil {
+				return nil, err
+			}
+		}
+	}
+	defer func() {
+		mmap.Close()
+		mmap.Unlink()
+	}()
+	slice, err := ReadWithSize(mmap, 0)
+	if err != nil {
+		return nil, err
+	}
+	ans := make([]byte, len(slice))
+	copy(ans, slice)
+	return ans, nil
 }
 
 func test_integration_with_python(args []string) (rc int, err error) {
@@ -161,7 +176,7 @@ func test_integration_with_python(args []string) (rc int, err error) {
 		if err != nil {
 			return 1, err
 		}
-		mmap, err := CreateTemp("shmtest-", uint64(len(data)+4))
+		mmap, err := CreateTemp("shmtest-", uint64(len(data)+NUM_BYTES_FOR_SIZE))
 		if err != nil {
 			return 1, err
 		}

tools/utils/shm/shm_fs.go

@@ -142,21 +142,13 @@ func Open(name string, size uint64) (MMap, error) {
 	if err != nil {
 		return nil, err
 	}
+	if size == 0 {
+		s, err := ans.Stat()
+		if err != nil {
+			ans.Close()
+			return nil, fmt.Errorf("Failed to stat SHM file with error: %w", err)
+		}
+		size = uint64(s.Size())
+	}
 	return file_mmap(ans, size, READ, false, name)
 }
-
-func ReadWithSizeAndUnlink(name string, file_callback ...func(*os.File) error) ([]byte, error) {
-	f, err := open(name)
-	if err != nil {
-		return nil, err
-	}
-	defer f.Close()
-	defer os.Remove(f.Name())
-	for _, cb := range file_callback {
-		err = cb(f)
-		if err != nil {
-			return nil, err
-		}
-	}
-	return read_with_size(f)
-}

tools/utils/shm/shm_syscall.go

@@ -4,7 +4,6 @@
 package shm
 
 import (
-	"encoding/binary"
 	"errors"
 	"fmt"
 	"io/fs"
@@ -159,23 +158,13 @@ func Open(name string, size uint64) (MMap, error) {
 	if err != nil {
 		return nil, err
 	}
+	if size == 0 {
+		s, err := ans.Stat()
+		if err != nil {
+			ans.Close()
+			return nil, fmt.Errorf("Failed to stat SHM file with error: %w", err)
+		}
+		size = uint64(s.Size())
+	}
 	return syscall_mmap(ans, size, READ, false)
 }
-
-func ReadWithSizeAndUnlink(name string, file_callback ...func(*os.File) error) ([]byte, error) {
-	mmap, err := Open(name, 4)
-	if err != nil {
-		return nil, err
-	}
-	size := uint64(binary.BigEndian.Uint32(mmap.Slice()))
-	mmap.Close()
-	mmap, err = Open(name, 4+size)
-	if err != nil {
-		return nil, err
-	}
-	ans := make([]byte, size)
-	copy(ans, mmap.Slice()[4:])
-	mmap.Close()
-	mmap.Unlink()
-	return ans, nil
-}