| 1 | package runs |
| 2 | |
| 3 | import ( |
| 4 | "errors" |
| 5 | "strings" |
| 6 | "unicode" |
| 7 | "unicode/utf8" |
| 8 | ) |
| 9 | |
| 10 | // A `run` service credential carries the command prefixes it may run |
| 11 | // (service-runs spec § 1). These are the limits on that list, and the one |
| 12 | // function that decides whether an argv is inside it. The console mints |
| 13 | // with CheckCommandPrefixes, reads a stored list back through it, and gates |
| 14 | // a run's create on CommandGranted. |
| 15 | const ( |
| 16 | MaxCommandPrefixes = 32 |
| 17 | MaxCommandWordBytes = 128 |
| 18 | ) |
| 19 | |
| 20 | var ( |
| 21 | ErrNoCommands = errors.New("runs: no command prefixes") |
| 22 | ErrTooManyCommands = errors.New("runs: more than 32 command prefixes") |
| 23 | ErrEmptyCommand = errors.New("runs: a command prefix has no words") |
| 24 | ErrEmptyCommandWord = errors.New("runs: a command prefix holds an empty word") |
| 25 | ErrCommandWordTooLong = errors.New("runs: a command word over 128 bytes") |
| 26 | ErrCommandWordChars = errors.New("runs: a command word holds a space, a comma or a character that cannot be printed") |
| 27 | ) |
| 28 | |
| 29 | // CheckCommandPrefixes is the shape every stored command list has: at least |
| 30 | // one prefix and at most MaxCommandPrefixes, each with at least one word, |
| 31 | // each word 1 to MaxCommandWordBytes bytes. A zero-word prefix is refused |
| 32 | // because it would match every argv. |
| 33 | // |
| 34 | // A word is also valid UTF-8 made only of printable characters, with no |
| 35 | // whitespace and no comma (validCommandWord). Whitespace and commas are the |
| 36 | // text form's separators, so a word holding one would come back as a |
| 37 | // different grant when a listing is copied into a new mint; a control |
| 38 | // character could hide a prefix in a terminal listing. |
| 39 | func CheckCommandPrefixes(prefixes [][]string) error { |
| 40 | if len(prefixes) == 0 { |
| 41 | return ErrNoCommands |
| 42 | } |
| 43 | if len(prefixes) > MaxCommandPrefixes { |
| 44 | return ErrTooManyCommands |
| 45 | } |
| 46 | for _, p := range prefixes { |
| 47 | if len(p) == 0 { |
| 48 | return ErrEmptyCommand |
| 49 | } |
| 50 | for _, w := range p { |
| 51 | if w == "" { |
| 52 | return ErrEmptyCommandWord |
| 53 | } |
| 54 | if len(w) > MaxCommandWordBytes { |
| 55 | return ErrCommandWordTooLong |
| 56 | } |
| 57 | if !validCommandWord(w) { |
| 58 | return ErrCommandWordChars |
| 59 | } |
| 60 | } |
| 61 | } |
| 62 | return nil |
| 63 | } |
| 64 | |
| 65 | // validCommandWord: valid UTF-8, every rune printable, none a space or a |
| 66 | // comma. U+FFFD is refused too: it is what invalid UTF-8 becomes once a |
| 67 | // JSON decoder has replaced it, so refusing it makes a mangled word fail |
| 68 | // the same way at the API door as at the form. |
| 69 | func validCommandWord(w string) bool { |
| 70 | if !utf8.ValidString(w) { |
| 71 | return false |
| 72 | } |
| 73 | for _, r := range w { |
| 74 | if r == ',' || r == utf8.RuneError || unicode.IsSpace(r) || !unicode.IsPrint(r) { |
| 75 | return false |
| 76 | } |
| 77 | } |
| 78 | return true |
| 79 | } |
| 80 | |
| 81 | // CommandGranted reports whether argv starts with every word of at least one |
| 82 | // prefix, compared word for word and exactly: no globbing, no case folding, |
| 83 | // no substring. It fails closed: a zero-word prefix matches nothing, and so |
| 84 | // does an empty argv. |
| 85 | func CommandGranted(argv []string, prefixes [][]string) bool { |
| 86 | for _, p := range prefixes { |
| 87 | if len(p) == 0 || len(argv) < len(p) { |
| 88 | continue |
| 89 | } |
| 90 | match := true |
| 91 | for i, w := range p { |
| 92 | if argv[i] != w { |
| 93 | match = false |
| 94 | break |
| 95 | } |
| 96 | } |
| 97 | if match { |
| 98 | return true |
| 99 | } |
| 100 | } |
| 101 | return false |
| 102 | } |
| 103 | |
| 104 | // ParseCommandList reads the text form both mint doors take, the CLI's |
| 105 | // --commands flag and the console form's field: prefixes separated by |
| 106 | // commas, a prefix's words by spaces. "import classic,import sync" is two |
| 107 | // prefixes of two words each. An entry with no words is dropped, the way an |
| 108 | // empty rung entry is, so a trailing comma grants nothing rather than |
| 109 | // everything. It returns nil when nothing was named; validation is |
| 110 | // CheckCommandPrefixes's. |
| 111 | func ParseCommandList(s string) [][]string { |
| 112 | var out [][]string |
| 113 | for _, entry := range strings.Split(s, ",") { |
| 114 | if words := strings.Fields(entry); len(words) > 0 { |
| 115 | out = append(out, words) |
| 116 | } |
| 117 | } |
| 118 | return out |
| 119 | } |
| 120 | |
| 121 | // UnreadableCommands is what a listing shows, in place of a command list, |
| 122 | // for a run credential whose stored list cannot be read. The console and the |
| 123 | // CLI both print it. |
| 124 | const UnreadableCommands = "(unreadable — refused at sign-in)" |
| 125 | |
| 126 | // FormatCommandList is a command list for a person to read: |
| 127 | // "import classic, import sync". |
| 128 | func FormatCommandList(prefixes [][]string) string { |
| 129 | parts := make([]string, len(prefixes)) |
| 130 | for i, p := range prefixes { |
| 131 | parts[i] = strings.Join(p, " ") |
| 132 | } |
| 133 | return strings.Join(parts, ", ") |
| 134 | } |
| 135 | |
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