Add File Shred command

cmd/sansshell-server/default-policy.rego

@@ -114,3 +114,11 @@ allow {
 allow {
     input.method = "/Network.Network/TCPCheck"
 }
+
+allow {
+    input.type = "LocalFile.ShredRequest"
+    input.message.filename = "/tmp/hello.txt"
+    input.message.force = true
+    input.message.zero = true
+    input.message.remove = true
+}

services/localfile/README.md

@@ -130,3 +130,28 @@ Examples:
 # Set file mode of `/opt/hello` to 644
 sanssh --target $TARGET file chmod --mode=644 /opt/hello
 ```
+
+### sanssh file shred
+Shred file using `/usr/bin/shred` (`/opt/homebrew/bin/shred` on Mac OS) utility.
+Notice: this function is reliant on the presence of `shred` utility on the target system.
+Note that this utility is only effective on Hard Drives, it will not provide same level of security on Solid State Drives.
+
+
+```bash
+sanssh <sanssh-args> file shred [-z] [-f] [-u] [--remove] <file-path>
+```
+Where:
+- `<sanssh-args>` common sanssh arguments
+- `<file-path>` is the absolute path to the file on remote machine.
+- `-z` - add a final zero-ing pass to shred
+- `-f` - force permissions change on the target file if required
+- `-u` - remove the file after shredding
+- `--remove` - alias for `-u`
+
+Examples:
+```bash
+# Perform basic shredding of the file
+sanssh --targets $TARGET file shred /tmp/hello.txt
+# Shred, add zero-ing pass and remove file after, with file permissions change if required
+sanssh --targets $TARGET file shred -f -u -z /tmp/hello.txt
+```

services/localfile/client/client.go

@@ -67,6 +67,7 @@ func (*fileCmd) GetSubpackage(f *flag.FlagSet) *subcommands.Commander {
 	c.Register(&sumCmd{}, "")
 	c.Register(&tailCmd{}, "")
 	c.Register(&mkdirCmd{}, "")
+	c.Register(&shredCmd{}, "")
 	return c
 }
 

services/localfile/client/shred.go

@@ -0,0 +1,81 @@
+/* Copyright (c) 2019 Snowflake Inc. All rights reserved.
+
+   Licensed under the Apache License, Version 2.0 (the
+   "License"); you may not use this file except in compliance
+   with the License.  You may obtain a copy of the License at
+
+     http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing,
+   software distributed under the License is distributed on an
+   "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+   KIND, either express or implied.  See the License for the
+   specific language governing permissions and limitations
+   under the License.
+*/
+
+package client
+
+import (
+	"context"
+	"flag"
+	"fmt"
+	pb "github.com/Snowflake-Labs/sansshell/services/localfile"
+	"github.com/Snowflake-Labs/sansshell/services/util"
+	"github.com/google/subcommands"
+	"os"
+)
+
+type shredCmd struct {
+	force  bool
+	zero   bool
+	remove bool
+}
+
+func (*shredCmd) Name() string     { return "shred" }
+func (*shredCmd) Synopsis() string { return "Shred a file" }
+func (*shredCmd) Usage() string {
+	return `shred <path-to-file>`
+}
+
+func (p *shredCmd) SetFlags(f *flag.FlagSet) {
+	f.BoolVar(&p.force, "f", false, "force permissions change in case current permissions are insufficient")
+	f.BoolVar(&p.remove, "u", false, "remove file after shredding - same as --remove")
+	f.BoolVar(&p.zero, "z", false, "add a zeroing pass after shredding to mask the shredding")
+	f.BoolVar(&p.remove, "remove", false, "remove file after shredding - same as -u")
+}
+
+func (p *shredCmd) Execute(ctx context.Context, f *flag.FlagSet, args ...interface{}) subcommands.ExitStatus {
+	state := args[0].(*util.ExecuteState)
+	if f.NArg() != 1 {
+		fmt.Fprintln(os.Stderr, "please specify a filename to shred")
+		return subcommands.ExitUsageError
+	}
+
+	req := &pb.ShredRequest{
+		Filename: f.Arg(0),
+		Force:    p.force,
+		Zero:     p.zero,
+		Remove:   p.remove,
+	}
+
+	client := pb.NewLocalFileClientProxy(state.Conn)
+	respChan, err := client.ShredOneMany(ctx, req)
+
+	if err != nil {
+		// Emit this to every error file as it's not specific to a given target.
+		for _, e := range state.Err {
+			fmt.Fprintf(e, "All targets - shred error: %v\n", err)
+		}
+		return subcommands.ExitFailure
+	}
+
+	retCode := subcommands.ExitSuccess
+	for r := range respChan {
+		if r.Error != nil {
+			fmt.Fprintf(state.Err[r.Index], "shred error: %v\n", r.Error)
+			retCode = subcommands.ExitFailure
+		}
+	}
+	return retCode
+}

services/localfile/localfile.proto

@@ -74,6 +74,9 @@ service LocalFile {
 
   // Set data value to a file of specified type by provided key
   rpc DataSet(DataSetRequest) returns (google.protobuf.Empty) {}
+
+  // Perform Shred on a single file
+  rpc Shred(ShredRequest) returns (google.protobuf.Empty) {}
 }
 
 // ReadActionRequest indicates the type of read we're performing.
@@ -316,3 +319,15 @@ message DataSetRequest {
   string value = 4;
   DataSetValueType value_type = 5;
 }
+
+// ShredRequest is a request to perform Shred operation on a specific file
+message ShredRequest {
+  // absolute path to the file to be shredded
+  string filename = 1;
+  // force permissions change if necessary
+  bool force = 2;
+  // add final zero-ing pass to mask presence of shredding
+  bool zero = 3;
+  // remove file after shredding
+  bool remove = 4;
+}