Allow for configuration policies

Summary:
Implements a rough interface for validating configuration against
arbitrary policy rules. Policies are provided as YAML and passed via the
command line as file paths or remote URIs.

The format of policies is:

    enforcements:
      - path: <path>
        rule: <rule>

Where `<path>` is a YAML-ish path to a config field and `<rule>` is any
expression our config validator understands (expressions built in by the
validator library and custom tags defined in `config.validation.go`).

Example policy:

    enforcements:
      - path: variants.production.base
        rule: oneof=debian:jessie debian:stretch
      - path: variants.production.runs.as
        rule: ne=foo
      - path: variants.production.node.dependencies
        rule: isfalse

Command flag parsing was implemented in `main.go` to support the new
`--policy=uri` flag and improve existing handling of `--version` and the
usage statement.

Test Plan: Run `go test ./...`.

Reviewers: thcipriani, demon, hashar, mmodell, #release-engineering-team

Reviewed By: thcipriani, #release-engineering-team

Tags: #release-engineering-team

Differential Revision: https://phabricator.wikimedia.org/D999

1 files changed, 537 insertions, 0 deletions

diff --git a/vendor/github.com/pborman/getopt/getopt.go b/vendor/github.com/pborman/getopt/getopt.go
new file mode 100644
index 0000000..e3279ab
--- /dev/null
+++ b/vendor/github.com/pborman/getopt/getopt.go
@@ -0,0 +1,537 @@
+// Copyright 2013 Google Inc.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package getopt (v1) provides traditional getopt processing for implementing
+// commands that use traditional command lines.  The standard Go flag package
+// cannot be used to write a program that parses flags the way ls or ssh does,
+// for example.
+//
+// A new version of this package (v2) (whose package name is also getopt) is
+// available as:
+//
+//	"github.com/pborman/getopt/v2"
+//
+// Getopt supports functionality found in both the standard BSD getopt as well
+// as (one of the many versions of) the GNU getopt_long.  Being a Go package,
+// this package makes common usage easy, but still enables more controlled usage
+// if needed.
+//
+// Typical usage:
+//
+//	// Declare the flags to be used
+//	helpFlag := getopt.Bool('?', "display help")
+//      cmdFlag := getopt.StringLong("command", 'c', "", "the command)
+//
+//	func main() {
+//		// Parse the program arguments
+//		getopt.Parse()
+//		// Get the remaining positional parameters
+//		args := getopt.Args()
+//
+// If you don't want the program to exit on error, use getopt.Getopt:
+//
+//		err := getopt.Getopt(nil)
+//		if err != nil {
+//			// code to handle error
+//			fmt.Fprintln(os.Stderr, err)
+//		}
+//
+// Support is provided for both short (-f) and long (--flag) options.  A single
+// option may have both a short and a long name.  Each option may be a flag or a
+// value.  A value takes an argument.
+//
+// Declaring no long names causes this package to process arguments like the
+// traditional BSD getopt.
+//
+// Short flags may be combined into a single parameter.  For example, "-a -b -c"
+// may also be expressed "-abc".  Long flags must stand on their own "--alpha
+// --beta"
+//
+// Values require an argument.  For short options the argument may either be
+// immediately following the short name or as the next argument.  Only one short
+// value may be combined with short flags in a single argument; the short value
+// must be after all short flags.  For example, if f is a flag and v is a value,
+// then:
+//
+//  -vvalue    (sets v to "value")
+//  -v value   (sets v to "value")
+//  -fvvalue   (sets f, and sets v to "value")
+//  -fv value  (sets f, and sets v to "value")
+//  -vf value  (set v to "f" and value is the first parameter)
+//
+// For the long value option val:
+//
+//  --val value (sets val to "value")
+//  --val=value (sets val to "value")
+//  --valvalue  (invalid option "valvalue")
+//
+// Values with an optional value only set the value if the value is part of the
+// same argument.  In any event, the option count is increased and the option is
+// marked as seen.
+//
+//  -v -f          (sets v and f as being seen)
+//  -vvalue -f     (sets v to "value" and sets f)
+//  --val -f       (sets v and f as being seen)
+//  --val=value -f (sets v to "value" and sets f)
+//
+// There is no convience function defined for making the value optional.  The
+// SetOptional method must be called on the actual Option.
+//
+//  v := String("val", 'v', "", "the optional v")
+//  Lookup("v").SetOptional()
+//
+//  var s string
+//  StringVar(&s, "val", 'v', "the optional v).SetOptional()
+//
+// Parsing continues until the first non-option or "--" is encountered.
+//
+// The short name "-" can be used, but it either is specified as "-" or as part
+// of a group of options, for example "-f-".  If there are no long options
+// specified then "--f" could also be used.  If "-" is not declared as an option
+// then the single "-" will also terminate the option processing but unlike
+// "--", the "-" will be part of the remaining arguments.
+//
+// Normally the parsing is performed by calling the Parse function.  If it is
+// important to see the order of the options then the Getopt function should be
+// used.  The standard Parse function does the equivalent of:
+//
+// func Parse() {
+//	if err := getopt.Getopt(os.Args, nil); err != nil {
+//		fmt.Fprintln(os.Stderr, err)
+//		s.usage()
+//		os.Exit(1)
+//	}
+//
+// When calling Getopt it is the responsibility of the caller to print any
+// errors.
+//
+// Normally the default option set, CommandLine, is used.  Other option sets may
+// be created with New.
+//
+// After parsing, the sets Args will contain the non-option arguments.  If an
+// error is encountered then Args will begin with argument that caused the
+// error.
+//
+// It is valid to call a set's Parse a second time to amend the current set of
+// flags or values.  As an example:
+//
+//  var a = getopt.Bool('a', "", "The a flag")
+//  var b = getopt.Bool('b', "", "The a flag")
+//  var cmd = ""
+//
+//  var opts = getopt.CommandLine
+//
+//  opts.Parse(os.Args)
+//  if opts.NArgs() > 0 {
+//      cmd = opts.Arg(0)
+//      opts.Parse(opts.Args())
+//  }
+//
+// If called with set to { "prog", "-a", "cmd", "-b", "arg" } then both and and
+// b would be set, cmd would be set to "cmd", and opts.Args() would return {
+// "arg" }.
+//
+// Unless an option type explicitly prohibits it, an option may appear more than
+// once in the arguments.  The last value provided to the option is the value.
+//
+// SYNTAX
+//
+// For each option type there are an unfortunately large number of ways, 8, to
+// initialize the option.  This number is derived from three attributes:
+//
+//  1)  Short or Long name
+//  2)  Normal vs Var
+//  3)  Command Line vs Option Set
+//
+// The first two variations provide 4 signature:
+//
+//  Option(name rune, [value type,]  helpvalue... string)
+//  OptionLong(name string, short rune, [value type,]  helpvalue... string)
+//  OptionVar(p *type, name rune, helpvalue... string)
+//  OptionVarLong(p *type, name string, short rune, helpvalue... string)
+//
+// Foo can actually be expressed in terms of FooLong:
+//
+//  func Foo(name rune, value type, helpvalue... string) *type {
+//      return FooLong("", name, value, helpvalue...)
+//  }
+//
+// Normally Foo is used, unless long options are needed.  Setting short to 0
+// creates only a long option.
+//
+// The difference bentween Foo and FooVar is that you pass a pointer, p, to the
+// location of the value to FooVar.  The default value is simply *p.  The
+// initial value of *p is the defaut value of the option.
+//
+// Foo is actually a wrapper around FooVar:
+//
+//  func Foo(name rune, value type, helpvalue... string) *type {
+//      p := value
+//      FooVar(&p, name, helpvalue... string)
+//      return &p
+//  }
+//
+//
+// The third variation provides a top-level function and a method on a Set:
+//
+//  func Option(...)
+//  func (s *Set) Option(...)
+//
+// The top-level function is simply:
+//
+//  func Option(...) *type {
+//      return CommandLine.Option(...) {
+//  }
+//
+// To simplfy documentation, typically only the main top-level function is fully
+// documented.  The others will have documentation when there is something
+// special about them.
+//
+// VALUEHELP
+//
+// All non-flag options are created with a "valuehelp" as the last parameter.
+// Valuehelp should be 0, 1, or 2 strings.  The first string, if provided, is
+// the usage message for the option.  If the second string, if provided, is the
+// name to use for the value when displaying the usage.  If not provided the
+// term "value" is assumed.
+//
+// The usage message for the option created with
+//
+//  StringLong("option", 'o', "defval", "a string of letters")
+//
+// is
+//
+//  -o, -option=value
+//
+//  StringLong("option", 'o', "defval", "a string of letters", "string")
+//
+// is
+//
+//  -o, -option=string
+package getopt
+
+import (
+	"fmt"
+	"io"
+	"os"
+	"path"
+	"sort"
+	"strings"
+)
+
+// stderr allows tests to capture output to standard error.
+var stderr io.Writer = os.Stderr
+
+// exit allows tests to capture an os.Exit call
+var exit = os.Exit
+
+// DisplayWidth is used to determine where to split usage long lines.
+var DisplayWidth = 80
+
+// HelpColumn is the maximum column position that help strings start to display
+// at.  If the option usage is too long then the help string will be displayed
+// on the next line.  For example:
+//
+//   -a   this is the a flag
+//   -u, --under=location
+//        the u flag's usage is quite long
+var HelpColumn = 20
+
+// PrintUsage prints the usage of the program to w.
+func (s *Set) PrintUsage(w io.Writer) {
+	sort.Sort(s.options)
+	flags := ""
+
+	// Build up the list of short flag names and also compute
+	// how to display the option in the longer help listing.
+	// We also keep track of the longest option usage string
+	// that is no more than HelpColumn-3 bytes (at which point
+	// we use two lines to display the help).  The three
+	// is for the leading space and the two spaces before the
+	// help string.
+	for _, opt := range s.options {
+		if opt.name == "" {
+			opt.name = "value"
+		}
+		if opt.uname == "" {
+			opt.uname = opt.usageName()
+		}
+		if opt.flag && opt.short != 0 && opt.short != '-' {
+			flags += string(opt.short)
+		}
+	}
+
+	var opts []string
+
+	// The short option - is special
+	if s.shortOptions['-'] != nil {
+		opts = append(opts, "-")
+	}
+
+	// If we have a bundle of flags, add them to the list
+	if flags != "" {
+		opts = append(opts, "-"+flags)
+	}
+
+	// Now append all the long options and options that require
+	// values.
+	for _, opt := range s.options {
+		if opt.flag {
+			if opt.short != 0 {
+				continue
+			}
+			flags = "--" + opt.long
+		} else if opt.short != 0 {
+			flags = "-" + string(opt.short) + " " + opt.name
+		} else {
+			flags = "--" + string(opt.long) + " " + opt.name
+		}
+		opts = append(opts, flags)
+	}
+	flags = strings.Join(opts, "] [")
+	if flags != "" {
+		flags = " [" + flags + "]"
+	}
+	if s.parameters != "" {
+		flags += " " + s.parameters
+	}
+	fmt.Fprintf(w, "Usage: %s%s\n", s.program, flags)
+	s.PrintOptions(w)
+}
+
+// PrintOptions prints the list of options in s to w.
+func (s *Set) PrintOptions(w io.Writer) {
+	sort.Sort(s.options)
+	max := 4
+	for _, opt := range s.options {
+		if opt.name == "" {
+			opt.name = "value"
+		}
+		if opt.uname == "" {
+			opt.uname = opt.usageName()
+		}
+		if max < len(opt.uname) && len(opt.uname) <= HelpColumn-3 {
+			max = len(opt.uname)
+		}
+	}
+	// Now print one or more usage lines per option.
+	for _, opt := range s.options {
+		if opt.uname != "" {
+			opt.help = strings.TrimSpace(opt.help)
+			if len(opt.help) == 0 {
+				fmt.Fprintf(w, " %s\n", opt.uname)
+				continue
+			}
+			help := strings.Split(opt.help, "\n")
+			// If they did not put in newlines then we will insert
+			// them to keep the help messages from wrapping.
+			if len(help) == 1 {
+				help = breakup(help[0], DisplayWidth-HelpColumn)
+			}
+			if len(opt.uname) <= max {
+				fmt.Fprintf(w, " %-*s  %s\n", max, opt.uname, help[0])
+				help = help[1:]
+			} else {
+				fmt.Fprintf(w, " %s\n", opt.uname)
+			}
+			for _, s := range help {
+				fmt.Fprintf(w, " %-*s  %s\n", max, " ", s)
+			}
+		}
+	}
+}
+
+// breakup breaks s up into strings no longer than max bytes.
+func breakup(s string, max int) []string {
+	var a []string
+
+	for {
+		// strip leading spaces
+		for len(s) > 0 && s[0] == ' ' {
+			s = s[1:]
+		}
+		// If the option is no longer than the max just return it
+		if len(s) <= max {
+			if len(s) != 0 {
+				a = append(a, s)
+			}
+			return a
+		}
+		x := max
+		for s[x] != ' ' {
+			// the first word is too long?!
+			if x == 0 {
+				x = max
+				for x < len(s) && s[x] != ' ' {
+					x++
+				}
+				if x == len(s) {
+					x--
+				}
+				break
+			}
+			x--
+		}
+		for s[x] == ' ' {
+			x--
+		}
+		a = append(a, s[:x+1])
+		s = s[x+1:]
+	}
+	panic("unreachable")
+}
+
+// Parse uses Getopt to parse args using the options set for s.  The first
+// element of args is used to assign the program for s if it is not yet set.  On
+// error, Parse displays the error message as well as a usage message on
+// standard error and then exits the program.
+func (s *Set) Parse(args []string) {
+	if err := s.Getopt(args, nil); err != nil {
+		fmt.Fprintln(stderr, err)
+		s.usage()
+		exit(1)
+	}
+}
+
+// Parse uses Getopt to parse args using the options set for s.  The first
+// element of args is used to assign the program for s if it is not yet set.
+// Getop calls fn, if not nil, for each option parsed.
+//
+// Getopt returns nil when all options have been processed (a non-option
+// argument was encountered, "--" was encountered, or fn returned false).
+//
+// On error getopt returns a refernce to an InvalidOption (which implements
+// the error interface).
+func (s *Set) Getopt(args []string, fn func(Option) bool) (err error) {
+	s.State = InProgress
+	defer func() {
+		if s.State == InProgress {
+			switch {
+			case err != nil:
+				s.State = Failure
+			case len(s.args) == 0:
+				s.State = EndOfArguments
+			default:
+				s.State = Unknown
+			}
+		}
+	}()
+	if fn == nil {
+		fn = func(Option) bool { return true }
+	}
+	if len(args) == 0 {
+		return nil
+	}
+
+	if s.program == "" {
+		s.program = path.Base(args[0])
+	}
+	args = args[1:]
+Parsing:
+	for len(args) > 0 {
+		arg := args[0]
+		s.args = args
+		args = args[1:]
+
+		// end of options?
+		if arg == "" || arg[0] != '-' {
+			s.State = EndOfOptions
+			return nil
+		}
+
+		if arg == "-" {
+			goto ShortParsing
+		}
+
+		// explicitly request end of options?
+		if arg == "--" {
+			s.args = args
+			s.State = DashDash
+			return nil
+		}
+
+		// Long option processing
+		if len(s.longOptions) > 0 && arg[1] == '-' {
+			e := strings.IndexRune(arg, '=')
+			var value string
+			if e > 0 {
+				value = arg[e+1:]
+				arg = arg[:e]
+			}
+			opt := s.longOptions[arg[2:]]
+			// If we are processing long options then --f is -f
+			// if f is not defined as a long option.
+			// This lets you say --f=false
+			if opt == nil && len(arg[2:]) == 1 {
+				opt = s.shortOptions[rune(arg[2])]
+			}
+			if opt == nil {
+				return unknownOption(arg[2:])
+			}
+			opt.isLong = true
+			// If we require an option and did not have an =
+			// then use the next argument as an option.
+			if !opt.flag && e < 0 && !opt.optional {
+				if len(args) == 0 {
+					return missingArg(opt)
+				}
+				value = args[0]
+				args = args[1:]
+			}
+			opt.count++
+
+			if err := opt.value.Set(value, opt); err != nil {
+				return setError(opt, value, err)
+			}
+
+			if !fn(opt) {
+				s.State = Terminated
+				return nil
+			}
+			continue Parsing
+		}
+
+		// Short option processing
+		arg = arg[1:] // strip -
+	ShortParsing:
+		for i, c := range arg {
+			opt := s.shortOptions[c]
+			if opt == nil {
+				// In traditional getopt, if - is not registered
+				// as an option, a lone - is treated as
+				// if there were a -- in front of it.
+				if arg == "-" {
+					s.State = Dash
+					return nil
+				}
+				return unknownOption(c)
+			}
+			opt.isLong = false
+			opt.count++
+			var value string
+			if !opt.flag {
+				value = arg[1+i:]
+				if value == "" && !opt.optional {
+					if len(args) == 0 {
+						return missingArg(opt)
+					}
+					value = args[0]
+					args = args[1:]
+				}
+			}
+			if err := opt.value.Set(value, opt); err != nil {
+				return setError(opt, value, err)
+			}
+			if !fn(opt) {
+				s.State = Terminated
+				return nil
+			}
+			if !opt.flag {
+				continue Parsing
+			}
+		}
+	}
+	s.args = []string{}
+	return nil
+}