├── .gitignore ├── LICENSE ├── README.md ├── go.mod ├── go.sum └── shamir.go /.gitignore: -------------------------------------------------------------------------------- 1 | 2 | # Created by https://www.toptal.com/developers/gitignore/api/macos,intellij,go 3 | # Edit at https://www.toptal.com/developers/gitignore?templates=macos,intellij,go 4 | 5 | ### Go ### 6 | # If you prefer the allow list template instead of the deny list, see community template: 7 | # https://github.com/github/gitignore/blob/main/community/Golang/Go.AllowList.gitignore 8 | # 9 | # Binaries for programs and plugins 10 | *.exe 11 | *.exe~ 12 | *.dll 13 | *.so 14 | *.dylib 15 | 16 | # Test binary, built with `go test -c` 17 | *.test 18 | 19 | # Output of the go coverage tool, specifically when used with LiteIDE 20 | *.out 21 | 22 | # Dependency directories (remove the comment below to include it) 23 | # vendor/ 24 | 25 | # Go workspace file 26 | go.work 27 | 28 | ### Go Patch ### 29 | /vendor/ 30 | /Godeps/ 31 | 32 | ### Intellij ### 33 | # Covers JetBrains IDEs: IntelliJ, RubyMine, PhpStorm, AppCode, PyCharm, CLion, Android Studio, WebStorm and Rider 34 | # Reference: https://intellij-support.jetbrains.com/hc/en-us/articles/206544839 35 | 36 | # User-specific stuff 37 | .idea/**/workspace.xml 38 | .idea/**/tasks.xml 39 | .idea/**/usage.statistics.xml 40 | .idea/**/dictionaries 41 | .idea/**/shelf 42 | 43 | # AWS User-specific 44 | .idea/**/aws.xml 45 | 46 | # Generated files 47 | .idea/**/contentModel.xml 48 | 49 | # Sensitive or high-churn files 50 | .idea/**/dataSources/ 51 | .idea/**/dataSources.ids 52 | .idea/**/dataSources.local.xml 53 | .idea/**/sqlDataSources.xml 54 | .idea/**/dynamic.xml 55 | .idea/**/uiDesigner.xml 56 | .idea/**/dbnavigator.xml 57 | 58 | # Gradle 59 | .idea/**/gradle.xml 60 | .idea/**/libraries 61 | 62 | # Gradle and Maven with auto-import 63 | # When using Gradle or Maven with auto-import, you should exclude module files, 64 | # since they will be recreated, and may cause churn. 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We also recommend that a 185 | file or class name and description of purpose be included on the 186 | same "printed page" as the copyright notice for easier 187 | identification within third-party archives. 188 | 189 | Copyright [yyyy] [name of copyright owner] 190 | 191 | Licensed under the Apache License, Version 2.0 (the "License"); 192 | you may not use this file except in compliance with the License. 193 | You may obtain a copy of the License at 194 | 195 | http://www.apache.org/licenses/LICENSE-2.0 196 | 197 | Unless required by applicable law or agreed to in writing, software 198 | distributed under the License is distributed on an "AS IS" BASIS, 199 | WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 200 | See the License for the specific language governing permissions and 201 | limitations under the License. 202 | -------------------------------------------------------------------------------- /README.md: -------------------------------------------------------------------------------- 1 | # Shamir 2 | 3 | [![standard-readme compliant](https://img.shields.io/badge/readme%20style-standard-brightgreen.svg?style=flat-square)](https://github.com/RichardLitt/standard-readme) 4 | 5 | A CLI frontend for [Hashicorp Vault's](https://www.vaultproject.io/) [Shamir's Secret Sharing](https://en.wikipedia.org/wiki/Shamir%27s_Secret_Sharing) [implementation](https://github.com/hashicorp/vault/tree/main/shamir). This allows you to split a secret into `x` shares, and then combine them back into a single secret using any `y` of those shares with `y <= x`. 6 | 7 | ```shell 8 | $ shamir split secret.txt # default: split into 5 shares where you need any 3 to restore the secret (numbers configurable) 9 | ``` 10 | 11 | ```shell 12 | $ shamir restore shares.txt # shares.txt should contain at least 3 newline separated shares from above 13 | ``` 14 | 15 | ## Table of Contents 16 | 17 | - [Table of Contents](#table-of-contents) 18 | - [Background](#background) 19 | - [Install](#install) 20 | - [Usage](#usage) 21 | - [Split](#split) 22 | - [Restore](#restore) 23 | - [Related Efforts](#related-efforts) 24 | - [Maintainers](#maintainers) 25 | - [Contributing](#contributing) 26 | - [License](#license) 27 | 28 | ## Background 29 | 30 | Extra care needs to be taken when dealing with secrets. Therefore, this tiny tool is designed to be: 31 | 32 | - **credible** - It uses [Hashicorp Vault's](https://github.com/hashicorp/vault/tree/main/shamir) Shamir's Secret Sharing implementation. 33 | - **minimal** - It only uses Go's standard library besides the above dependency. 34 | - **approachable** - The 131 [LoC](https://de.wikipedia.org/wiki/Lines_of_Code) should be quick and easy to audit yourself. 35 | 36 | Further it's: 37 | 38 | - **configurable** - You can configure the number of shares and the number of shares needed to restore the secret. 39 | - **composable** - You can pipe [stdin](https://en.wikipedia.org/wiki/Standard_streams) to it and use it in scripts. 40 | 41 | > *Write programs that do one thing and do it well.* - [Douglas McIlroy](https://en.wikipedia.org/wiki/Douglas_McIlroy) 42 | 43 | ## Install 44 | 45 | When you are dealing with secrets I would recommend compiling the code yourself instead of relying on a binary distribution: 46 | 47 | ```shell 48 | go install github.com/dennis-tra/shamir@latest 49 | ``` 50 | 51 | Make sure the `$GOPATH/bin` is in your `PATH` variable to access the installed `shamir` executable. 52 | 53 | ## Usage 54 | 55 | ### Split 56 | 57 | Let's imagine you have confidential data in a file called `secret.txt`. You could then run any of the following commands: 58 | 59 | ```shell 60 | $ shamir split secret.txt 61 | $ shamir split -shares 10 -threshold 5 secret.txt 62 | $ cat secret.txt | shamir split 63 | ``` 64 | 65 | The CLI exposes the following options: 66 | 67 | - `-shares` - The number of shares to split the secret into. 68 | - `-threshold` - The number of shares needed to restore the secret. 69 | 70 | Example: 71 | 72 | ```shell 73 | $ echo "My very secret secret." | shamir split -shares 4 -threshold 3 74 | gU3GKbSg3CpSHtC+04y8OH9mtIdiq2tm 75 | GXmZfZhoqRAgzGO+fULXEXfDusDJuCcX 76 | ByQs4+phvdU2zXzMjYvjA+7qLLTke8Uk 77 | 9dV1XA0pJV2RDzLYh6qwKzjxJ+iBrd9W 78 | ``` 79 | 80 | Each line corresponds to one share of which you need any three to restore the original message. 81 | 82 | To create separate files for each share, pipe `shamir` to the unix `split` command: 83 | 84 | ```shell 85 | $ echo "My very secret secret." | shamir split -shares 4 -threshold 3 | split -l 1 - share_ 86 | ``` 87 | 88 | `-l 1` means to split after each line, `-` means to use stdin and `share_` is the prefix for the files. The above command will create 4 files named `share_aa`, `share_ab`, `share_ac` and `share_ad`. 89 | 90 | ### Restore 91 | 92 | Let's imagine you have a file called `shares.txt` which contains more than `threshold` shares of your secret **separated by newlines**. You could then run any of the following commands: 93 | 94 | ```shell 95 | $ shamir restore shares.txt 96 | $ cat shares.txt | shamir restore 97 | ``` 98 | 99 | Example: 100 | 101 | ```shell 102 | $ echo "9dV1XA0pJV2RDzLYh6qwKzjxJ+iBrd9W\nByQs4+phvdU2zXzMjYvjA+7qLLTke8Uk" | shamir restore # not enough shares 103 | VL_��n�!�m5��Π8 104 | $ echo "9dV1XA0pJV2RDzLYh6qwKzjxJ+iBrd9W\nByQs4+phvdU2zXzMjYvjA+7qLLTke8Uk\ngU3GKbSg3CpSHtC+04y8OH9mtIdiq2tm" | shamir restore 105 | My very secret secret. 106 | ``` 107 | 108 | Note the `\n` characters in the `echo` command to separate the shares from above. Share ordering is not relevant. 109 | 110 | ## Related Efforts 111 | 112 | - [kinvolk/go-shamir](https://github.com/kinvolk/go-shamir) - A small CLI tool for Shamir's Secret Sharing written in Go, using Vault's Shamir implementation 113 | 114 | ## Maintainers 115 | 116 | [@dennis-tra](https://github.com/dennis-tra). 117 | 118 | ## Contributing 119 | 120 | Feel free to dive in! [Open an issue](https://github.com/RichardLitt/standard-readme/issues/new) or submit PRs. 121 | 122 | ## License 123 | 124 | [Apache 2.0](LICENSE) © Dennis Trautwein -------------------------------------------------------------------------------- /go.mod: -------------------------------------------------------------------------------- 1 | module github.com/dennis-tra/shamir 2 | 3 | go 1.18 4 | 5 | require github.com/hashicorp/vault v1.10.3 6 | -------------------------------------------------------------------------------- /go.sum: -------------------------------------------------------------------------------- 1 | github.com/hashicorp/vault v1.10.3 h1:QOgzDNyzbS/14rWTxuU4SDAsd4KXor/VK1C+T97QHLs= 2 | github.com/hashicorp/vault v1.10.3/go.mod h1:BgV2co9MLBBgjiz8By6PHe2hnYQRPDXzQD3zNoqpXF4= 3 | -------------------------------------------------------------------------------- /shamir.go: -------------------------------------------------------------------------------- 1 | package main 2 | 3 | import ( 4 | "encoding/base64" 5 | "flag" 6 | "fmt" 7 | "io" 8 | "io/ioutil" 9 | "os" 10 | "strings" 11 | 12 | "github.com/hashicorp/vault/shamir" 13 | ) 14 | 15 | func main() { 16 | splitCmd := flag.NewFlagSet("split", flag.ExitOnError) 17 | shares := splitCmd.Int("shares", 5, "Number of shares to split into") 18 | threshold := splitCmd.Int("threshold", 3, "Number of shares needed to restore") 19 | 20 | restoreCmd := flag.NewFlagSet("restore", flag.ExitOnError) 21 | 22 | if len(os.Args) < 2 { 23 | fmt.Println("expected 'split' or 'restore' subcommands") 24 | os.Exit(1) 25 | } 26 | 27 | var err error 28 | switch os.Args[1] { 29 | case "split": 30 | err = splitCmd.Parse(os.Args[2:]) 31 | if err != nil { 32 | break 33 | } 34 | err = split(splitCmd.Arg(0), *shares, *threshold) 35 | case "restore": 36 | err = restoreCmd.Parse(os.Args[2:]) 37 | if err != nil { 38 | break 39 | } 40 | err = restore(restoreCmd.Arg(0)) 41 | default: 42 | err = fmt.Errorf("expected 'split' or 'restore' subcommands") 43 | } 44 | 45 | if err != nil { 46 | fmt.Println(err) 47 | os.Exit(1) 48 | } 49 | } 50 | 51 | func split(filename string, shares int, threshold int) error { 52 | src, err := source(filename) 53 | if err != nil { 54 | return err 55 | } 56 | defer src.Close() 57 | 58 | secret, err := ioutil.ReadAll(src) 59 | if err != nil { 60 | return err 61 | } 62 | 63 | byteShares, err := shamir.Split(secret, shares, threshold) 64 | if err != nil { 65 | return err 66 | } 67 | 68 | for _, byteShare := range byteShares { 69 | fmt.Println(base64.StdEncoding.EncodeToString(byteShare)) 70 | } 71 | 72 | return nil 73 | } 74 | 75 | func restore(filename string) error { 76 | src, err := source(filename) 77 | if err != nil { 78 | return err 79 | } 80 | defer src.Close() 81 | 82 | data, err := ioutil.ReadAll(src) 83 | if err != nil { 84 | return err 85 | } 86 | strShares := strings.Split(string(data), "\n") 87 | 88 | byteShares := [][]byte{} 89 | for _, strShare := range strShares { 90 | if strShare == "" { 91 | continue 92 | } 93 | 94 | byteShare, err := base64.StdEncoding.DecodeString(strShare) 95 | if err != nil { 96 | return err 97 | } 98 | 99 | byteShares = append(byteShares, byteShare) 100 | } 101 | 102 | secret, err := shamir.Combine(byteShares) 103 | if err != nil { 104 | return err 105 | } 106 | 107 | fmt.Println(string(secret)) 108 | 109 | return nil 110 | } 111 | 112 | func source(filename string) (io.ReadCloser, error) { 113 | if filename == "" { 114 | stat, err := os.Stdin.Stat() 115 | if err != nil { 116 | return nil, fmt.Errorf("you have an error in stdin: %w", err) 117 | } 118 | 119 | if (stat.Mode() & os.ModeNamedPipe) == 0 { 120 | return nil, fmt.Errorf("nothing to read from stdin") 121 | } 122 | 123 | return os.Stdin, nil 124 | } 125 | 126 | f, err := os.Open(filename) 127 | if err != nil { 128 | return nil, fmt.Errorf("error opening file %q: %w", filename, err) 129 | } 130 | return f, nil 131 | } 132 | --------------------------------------------------------------------------------