cmd/connector-gen: add helper tool for wide app connector configurations

connector-gen can initially generate connector ACL snippets and
advertise-routes flags for Github and AWS based on their public IP /
domain data.

Updates ENG-2425
Signed-off-by: James Tucker <james@tailscale.com>

cmd/connector-gen/README.md

@@ -0,0 +1,15 @@
+# connector-gen
+
+Generate Tailscale app connector configuration details from third party data.
+
+Tailscale app connectors are used to dynamically route traffic for domain names
+via specific nodes on a tailnet. For larger upstream domains this may involve a
+large number of domains or routes, and fully dynamic discovery may be slower or
+involve more manual labor than ideal. This can be accelerated by
+pre-configuration of the associated routes, based on data provided by the
+target providers, which can be used to set precise `autoApprovers` routes, and
+also to pre-populate the subnet routes via `--advertise-routes` avoiding
+frequent routing reconfiguration that may otherwise occur while routes are
+first being discovered and advertised by the connectors.
+
+

cmd/connector-gen/advertise-routes.go

@@ -0,0 +1,22 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+package main
+
+import (
+	"fmt"
+	"strings"
+
+	"go4.org/netipx"
+)
+
+func advertiseRoutes(set *netipx.IPSet) {
+	fmt.Println()
+	prefixes := set.Prefixes()
+	pfxs := make([]string, 0, len(prefixes))
+	for _, pfx := range prefixes {
+		pfxs = append(pfxs, pfx.String())
+	}
+	fmt.Printf("--advertise-routes=%s", strings.Join(pfxs, ","))
+	fmt.Println()
+}

cmd/connector-gen/aws.go

@@ -0,0 +1,68 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+package main
+
+import (
+	"encoding/json"
+	"fmt"
+	"log"
+	"net/http"
+	"net/netip"
+
+	"go4.org/netipx"
+)
+
+// See https://docs.aws.amazon.com/vpc/latest/userguide/aws-ip-ranges.html
+
+type AWSMeta struct {
+	SyncToken  string `json:"syncToken"`
+	CreateDate string `json:"createDate"`
+	Prefixes   []struct {
+		IPPrefix           string `json:"ip_prefix"`
+		Region             string `json:"region"`
+		Service            string `json:"service"`
+		NetworkBorderGroup string `json:"network_border_group"`
+	} `json:"prefixes"`
+	Ipv6Prefixes []struct {
+		Ipv6Prefix         string `json:"ipv6_prefix"`
+		Region             string `json:"region"`
+		Service            string `json:"service"`
+		NetworkBorderGroup string `json:"network_border_group"`
+	} `json:"ipv6_prefixes"`
+}
+
+func aws() {
+	r, err := http.Get("https://ip-ranges.amazonaws.com/ip-ranges.json")
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer r.Body.Close()
+
+	var aws AWSMeta
+	if err := json.NewDecoder(r.Body).Decode(&aws); err != nil {
+		log.Fatal(err)
+	}
+
+	var ips netipx.IPSetBuilder
+
+	for _, prefix := range aws.Prefixes {
+		ips.AddPrefix(netip.MustParsePrefix(prefix.IPPrefix))
+	}
+	for _, prefix := range aws.Ipv6Prefixes {
+		ips.AddPrefix(netip.MustParsePrefix(prefix.Ipv6Prefix))
+	}
+
+	set, err := ips.IPSet()
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	fmt.Println(`"routes": [`)
+	for _, pfx := range set.Prefixes() {
+		fmt.Printf(`"%s": ["tag:connector"],%s`, pfx.String(), "\n")
+	}
+	fmt.Println(`]`)
+
+	advertiseRoutes(set)
+}

cmd/connector-gen/connector-gen.go

@@ -0,0 +1,34 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+// connector-gen is a tool to generate app connector configuration and flags from service provider address data.
+package main
+
+import (
+	"fmt"
+	"os"
+)
+
+func help() {
+	fmt.Fprintf(os.Stderr, "Usage: %s [help|github|aws] [subcommand-arguments]\n", os.Args[0])
+}
+
+func main() {
+	if len(os.Args) < 2 {
+		help()
+		os.Exit(128)
+	}
+
+	switch os.Args[1] {
+	case "help", "-h", "--help":
+		help()
+		os.Exit(0)
+	case "github":
+		github()
+	case "aws":
+		aws()
+	default:
+		help()
+		os.Exit(128)
+	}
+}

cmd/connector-gen/github.go

@@ -0,0 +1,116 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+package main
+
+import (
+	"encoding/json"
+	"fmt"
+	"log"
+	"net/http"
+	"net/netip"
+	"slices"
+	"strings"
+
+	"go4.org/netipx"
+)
+
+// See https://docs.github.com/en/authentication/keeping-your-account-and-data-secure/about-githubs-ip-addresses
+
+type GithubMeta struct {
+	VerifiablePasswordAuthentication bool `json:"verifiable_password_authentication"`
+	SSHKeyFingerprints               struct {
+		Sha256Ecdsa   string `json:"SHA256_ECDSA"`
+		Sha256Ed25519 string `json:"SHA256_ED25519"`
+		Sha256Rsa     string `json:"SHA256_RSA"`
+	} `json:"ssh_key_fingerprints"`
+	SSHKeys                  []string `json:"ssh_keys"`
+	Hooks                    []string `json:"hooks"`
+	Web                      []string `json:"web"`
+	API                      []string `json:"api"`
+	Git                      []string `json:"git"`
+	GithubEnterpriseImporter []string `json:"github_enterprise_importer"`
+	Packages                 []string `json:"packages"`
+	Pages                    []string `json:"pages"`
+	Importer                 []string `json:"importer"`
+	Actions                  []string `json:"actions"`
+	Dependabot               []string `json:"dependabot"`
+	Domains                  struct {
+		Website    []string `json:"website"`
+		Codespaces []string `json:"codespaces"`
+		Copilot    []string `json:"copilot"`
+		Packages   []string `json:"packages"`
+	} `json:"domains"`
+}
+
+func github() {
+	r, err := http.Get("https://api.github.com/meta")
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	var ghm GithubMeta
+
+	if err := json.NewDecoder(r.Body).Decode(&ghm); err != nil {
+		log.Fatal(err)
+	}
+	r.Body.Close()
+
+	var ips netipx.IPSetBuilder
+
+	var lists []string
+	lists = append(lists, ghm.Hooks...)
+	lists = append(lists, ghm.Web...)
+	lists = append(lists, ghm.API...)
+	lists = append(lists, ghm.Git...)
+	lists = append(lists, ghm.GithubEnterpriseImporter...)
+	lists = append(lists, ghm.Packages...)
+	lists = append(lists, ghm.Pages...)
+	lists = append(lists, ghm.Importer...)
+	lists = append(lists, ghm.Actions...)
+	lists = append(lists, ghm.Dependabot...)
+
+	for _, s := range lists {
+		ips.AddPrefix(netip.MustParsePrefix(s))
+	}
+
+	set, err := ips.IPSet()
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	fmt.Println(`"routes": [`)
+	for _, pfx := range set.Prefixes() {
+		fmt.Printf(`"%s": ["tag:connector"],%s`, pfx.String(), "\n")
+	}
+	fmt.Println(`]`)
+
+	fmt.Println()
+
+	var domains []string
+	domains = append(domains, ghm.Domains.Website...)
+	domains = append(domains, ghm.Domains.Codespaces...)
+	domains = append(domains, ghm.Domains.Copilot...)
+	domains = append(domains, ghm.Domains.Packages...)
+	slices.Sort(domains)
+	domains = slices.Compact(domains)
+
+	var bareDomains []string
+	for _, domain := range domains {
+		trimmed := strings.TrimPrefix(domain, "*.")
+		if trimmed != domain {
+			bareDomains = append(bareDomains, trimmed)
+		}
+	}
+	domains = append(domains, bareDomains...)
+	slices.Sort(domains)
+	domains = slices.Compact(domains)
+
+	fmt.Println(`"domains": [`)
+	for _, domain := range domains {
+		fmt.Printf(`"%s",%s`, domain, "\n")
+	}
+	fmt.Println(`]`)
+
+	advertiseRoutes(set)
+}