X-Git-Url: https://ruderich.org/simon/gitweb/?a=blobdiff_plain;f=file.go;fp=file.go;h=b48d0751ae3bad521ea36dd39ec2327a6ec5168c;hb=92afde4e875a96e1ab865e29b9f0d11b08d7db1c;hp=0000000000000000000000000000000000000000;hpb=748846b9a65726fd19d43b45a4db68ef4c2e77f4;p=nsscash%2Fnsscash.git

diff --git a/file.go b/file.go
new file mode 100644
index 0000000..b48d075
--- /dev/null
+++ b/file.go
@@ -0,0 +1,152 @@
+// Download and write files atomically to the file system
+
+// Copyright (C) 2019  Simon Ruderich
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+package main
+
+import (
+	"bytes"
+	"fmt"
+	"io/ioutil"
+	"log"
+	"net/http"
+	"os"
+	"path/filepath"
+	"syscall"
+
+	"github.com/pkg/errors"
+)
+
+func handleFiles(cfg *Config, state *State) error {
+	for i, f := range cfg.Files {
+		err := fetchFile(&cfg.Files[i], state)
+		if err != nil {
+			return errors.Wrapf(err, "%q (%s)", f.Url, f.Type)
+		}
+	}
+
+	for i, f := range cfg.Files {
+		// No update required
+		if f.body == nil {
+			continue
+		}
+
+		err := deployFile(&cfg.Files[i])
+		if err != nil {
+			return errors.Wrapf(err, "%q (%s)", f.Url, f.Type)
+		}
+	}
+
+	return nil
+}
+
+func fetchFile(file *File, state *State) error {
+	t := state.LastModified[file.Url]
+	status, body, err := fetchIfModified(file.Url, &t)
+	if err != nil {
+		return err
+	}
+	if status == http.StatusNotModified {
+		log.Printf("%q -> %q: not modified", file.Url, file.Path)
+		return nil
+	}
+	if status != http.StatusOK {
+		return fmt.Errorf("status code %v", status)
+	}
+	state.LastModified[file.Url] = t
+
+	if file.Type == FileTypePlain {
+		if len(body) == 0 {
+			return fmt.Errorf("refusing to use empty response")
+		}
+		file.body = body
+
+	} else if file.Type == FileTypePasswd {
+		pws, err := ParsePasswds(bytes.NewReader(body))
+		if err != nil {
+			return err
+		}
+		// Safety check: having no users can be very dangerous, don't
+		// permit it
+		if len(pws) == 0 {
+			return fmt.Errorf("refusing to use empty passwd file")
+		}
+
+		var x bytes.Buffer
+		err = SerializePasswds(&x, pws)
+		if err != nil {
+			return err
+		}
+		file.body = x.Bytes()
+
+	} else {
+		return fmt.Errorf("unsupported file type %v", file.Type)
+	}
+	return nil
+}
+
+func deployFile(file *File) error {
+	log.Printf("%q -> %q: updating file", file.Url, file.Path)
+
+	// Safety check
+	if len(file.body) == 0 {
+		return fmt.Errorf("refusing to write empty file")
+	}
+
+	// Write the file in an atomic fashion by creating a temporary file
+	// and renaming it over the target file
+
+	dir := filepath.Dir(file.Path)
+	name := filepath.Base(file.Path)
+
+	f, err := ioutil.TempFile(dir, "tmp-"+name+"-")
+	if err != nil {
+		return err
+	}
+	defer os.Remove(f.Name())
+	defer f.Close()
+
+	// Apply permissions/user/group from the target file
+	stat, err := os.Stat(file.Path)
+	if err != nil {
+		// We do not create the path if it doesn't exist, because we
+		// do not know the proper permissions
+		return errors.Wrapf(err, "file.path %q must exist", file.Path)
+	}
+	err = f.Chmod(stat.Mode())
+	if err != nil {
+		return err
+	}
+	// TODO: support more systems
+	sys, ok := stat.Sys().(*syscall.Stat_t)
+	if !ok {
+		return fmt.Errorf("unsupported FileInfo.Sys()")
+	}
+	err = f.Chown(int(sys.Uid), int(sys.Gid))
+	if err != nil {
+		return err
+	}
+
+	_, err = f.Write(file.body)
+	if err != nil {
+		return err
+	}
+	err = f.Sync()
+	if err != nil {
+		return err
+	}
+	return os.Rename(f.Name(), file.Path)
+}