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Add automatic HTTPS with ACME
642e599466fe4f5066afdc9a24775694a52c9749 · Keenan Nemetz · 15d ago · parent 91e6a33a
server/acme.go +216
| @@ -0,0 +1,216 @@ | |||
| 1 | package server | ||
| 2 | |||
| 3 | import ( | ||
| 4 | "context" | ||
| 5 | "crypto/tls" | ||
| 6 | "errors" | ||
| 7 | "fmt" | ||
| 8 | "net" | ||
| 9 | "net/http" | ||
| 10 | "net/url" | ||
| 11 | "os" | ||
| 12 | "sort" | ||
| 13 | "strings" | ||
| 14 | |||
| 15 | "github.com/rodent-software/vole/forge/config" | ||
| 16 | "github.com/rodent-software/vole/forge/repo" | ||
| 17 | "golang.org/x/crypto/acme" | ||
| 18 | "golang.org/x/crypto/acme/autocert" | ||
| 19 | ) | ||
| 20 | |||
| 21 | // acmeSetup owns the certificates for the HTTPS listener. Certificates are | ||
| 22 | // obtained on demand from an ACME certificate authority and reused from a | ||
| 23 | // directory cache, so a restart does not ask for them again. | ||
| 24 | type acmeSetup struct { | ||
| 25 | manager *autocert.Manager | ||
| 26 | hosts map[string]bool | ||
| 27 | // pages is the site suffix. A host under it is eligible for a certificate | ||
| 28 | // when it names a repository that is publicly readable, which keeps an | ||
| 29 | // arbitrary Host header (or a private repository's name) from asking the | ||
| 30 | // certificate authority for a new name. | ||
| 31 | pages string | ||
| 32 | site func(string) bool | ||
| 33 | httpsPort string | ||
| 34 | } | ||
| 35 | |||
| 36 | // newACME builds the certificate manager when https_addr is set. It returns nil | ||
| 37 | // for an instance that lets a proxy terminate TLS. sitePublic reports whether a | ||
| 38 | // repository is publicly readable, for site hostnames. | ||
| 39 | func newACME(cfg *config.Config, sitePublic func(string) bool) (*acmeSetup, error) { | ||
| 40 | if strings.TrimSpace(cfg.HTTPSAddr) == "" { | ||
| 41 | return nil, nil | ||
| 42 | } | ||
| 43 | |||
| 44 | hosts := make(map[string]bool) | ||
| 45 | for _, raw := range cfg.ACMEDomains { | ||
| 46 | host, err := certificateHost(raw) | ||
| 47 | if err != nil { | ||
| 48 | return nil, fmt.Errorf("acme_domains: %w", err) | ||
| 49 | } | ||
| 50 | hosts[host] = true | ||
| 51 | } | ||
| 52 | if strings.TrimSpace(cfg.PublicURL) != "" { | ||
| 53 | u, err := url.Parse(strings.TrimSpace(cfg.PublicURL)) | ||
| 54 | if err != nil || u.Hostname() == "" { | ||
| 55 | return nil, fmt.Errorf("https_addr requires public_url to name a host: %q", cfg.PublicURL) | ||
| 56 | } | ||
| 57 | if u.Scheme != "https" { | ||
| 58 | return nil, fmt.Errorf("https_addr requires an https public_url, got %q", cfg.PublicURL) | ||
| 59 | } | ||
| 60 | host, err := certificateHost(u.Hostname()) | ||
| 61 | if err != nil { | ||
| 62 | return nil, fmt.Errorf("public_url: %w", err) | ||
| 63 | } | ||
| 64 | hosts[host] = true | ||
| 65 | } | ||
| 66 | if len(hosts) == 0 { | ||
| 67 | return nil, errors.New("https_addr is set but there is no certificate host: set public_url or acme_domains") | ||
| 68 | } | ||
| 69 | |||
| 70 | a := &acmeSetup{ | ||
| 71 | hosts: hosts, | ||
| 72 | site: sitePublic, | ||
| 73 | httpsPort: listenPort(cfg.HTTPSAddr), | ||
| 74 | } | ||
| 75 | if strings.TrimSpace(cfg.PagesDomain) != "" { | ||
| 76 | domain, err := certificateHost(cfg.PagesDomain) | ||
| 77 | if err != nil { | ||
| 78 | return nil, fmt.Errorf("pages_domain: %w", err) | ||
| 79 | } | ||
| 80 | a.pages = domain | ||
| 81 | } | ||
| 82 | |||
| 83 | cachePath := cfg.ACMECachePath() | ||
| 84 | // The cache holds the ACME account key. Create it up front so a permissions | ||
| 85 | // mistake is a startup error, not a failed handshake the first time somebody | ||
| 86 | // visits. | ||
| 87 | if err := os.MkdirAll(cachePath, 0o700); err != nil { | ||
| 88 | return nil, fmt.Errorf("acme cache %s: %w", cachePath, err) | ||
| 89 | } | ||
| 90 | a.manager = &autocert.Manager{ | ||
| 91 | Prompt: autocert.AcceptTOS, | ||
| 92 | Cache: autocert.DirCache(cachePath), | ||
| 93 | HostPolicy: a.allows, | ||
| 94 | Email: strings.TrimSpace(cfg.ACMEEmail), | ||
| 95 | } | ||
| 96 | if directory := strings.TrimSpace(cfg.ACMEDirectoryURL); directory != "" { | ||
| 97 | u, err := url.Parse(directory) | ||
| 98 | if err != nil || (u.Scheme != "http" && u.Scheme != "https") || u.Host == "" { | ||
| 99 | return nil, fmt.Errorf("acme_directory_url %q is not an http(s) URL", directory) | ||
| 100 | } | ||
| 101 | a.manager.Client = &acme.Client{DirectoryURL: directory} | ||
| 102 | } | ||
| 103 | return a, nil | ||
| 104 | } | ||
| 105 | |||
| 106 | // tlsConfig is suitable for http.Server.ServeTLS. The manager answers | ||
| 107 | // tls-alpn-01 challenges through the same listener that serves the forge. | ||
| 108 | func (a *acmeSetup) tlsConfig() *tls.Config { | ||
| 109 | cfg := a.manager.TLSConfig() | ||
| 110 | cfg.MinVersion = tls.VersionTLS12 | ||
| 111 | return cfg | ||
| 112 | } | ||
| 113 | |||
| 114 | // httpHandler answers ACME HTTP-01 challenges and sends every other request to | ||
| 115 | // the HTTPS listener. Keeping it on a real HTTP listener also makes a blocked | ||
| 116 | // tls-alpn-01 challenge recoverable through HTTP-01. | ||
| 117 | func (a *acmeSetup) httpHandler() http.Handler { | ||
| 118 | return a.manager.HTTPHandler(http.HandlerFunc(a.redirectToHTTPS)) | ||
| 119 | } | ||
| 120 | |||
| 121 | func (a *acmeSetup) redirectToHTTPS(w http.ResponseWriter, r *http.Request) { | ||
| 122 | if r.Method != http.MethodGet && r.Method != http.MethodHead { | ||
| 123 | http.Error(w, "use HTTPS", http.StatusBadRequest) | ||
| 124 | return | ||
| 125 | } | ||
| 126 | host := requestHost(r.Host) | ||
| 127 | if err := a.allows(r.Context(), host); err != nil { | ||
| 128 | http.NotFound(w, r) | ||
| 129 | return | ||
| 130 | } | ||
| 131 | if a.httpsPort != "" && a.httpsPort != "443" { | ||
| 132 | host = net.JoinHostPort(host, a.httpsPort) | ||
| 133 | } | ||
| 134 | http.Redirect(w, r, "https://"+host+r.URL.RequestURI(), http.StatusMovedPermanently) | ||
| 135 | } | ||
| 136 | |||
| 137 | // allows is the autocert HostPolicy. Exact names come from public_url and | ||
| 138 | // acme_domains. Site names are allowed only while the repository they name is | ||
| 139 | // publicly readable. | ||
| 140 | func (a *acmeSetup) allows(_ context.Context, host string) error { | ||
| 141 | host = requestHost(host) | ||
| 142 | if a.hosts[host] { | ||
| 143 | return nil | ||
| 144 | } | ||
| 145 | if a.pages != "" { | ||
| 146 | suffix := "." + a.pages | ||
| 147 | if strings.HasSuffix(host, suffix) { | ||
| 148 | name := strings.TrimSuffix(host, suffix) | ||
| 149 | if repo.ValidateName(name) == nil && (a.site == nil || a.site(name)) { | ||
| 150 | return nil | ||
| 151 | } | ||
| 152 | } | ||
| 153 | } | ||
| 154 | return fmt.Errorf("acme: host %q is not configured for automatic certificates", host) | ||
| 155 | } | ||
| 156 | |||
| 157 | // hostNames is the configured certificate set, sorted for a startup log. | ||
| 158 | func (a *acmeSetup) hostNames() []string { | ||
| 159 | out := make([]string, 0, len(a.hosts)) | ||
| 160 | for host := range a.hosts { | ||
| 161 | out = append(out, host) | ||
| 162 | } | ||
| 163 | sort.Strings(out) | ||
| 164 | return out | ||
| 165 | } | ||
| 166 | |||
| 167 | func certificateHost(raw string) (string, error) { | ||
| 168 | host := normalizeHost(raw) | ||
| 169 | if host == "" { | ||
| 170 | return "", errors.New("empty host name") | ||
| 171 | } | ||
| 172 | if strings.Contains(host, "*") { | ||
| 173 | return "", fmt.Errorf("%q: wildcards are not supported; name each host", raw) | ||
| 174 | } | ||
| 175 | if strings.Contains(host, "://") || strings.ContainsAny(host, "/:@ \t") { | ||
| 176 | return "", fmt.Errorf("%q: use a bare host name, not a URL or address", raw) | ||
| 177 | } | ||
| 178 | if net.ParseIP(host) != nil { | ||
| 179 | return "", fmt.Errorf("%q: IP addresses are not supported", raw) | ||
| 180 | } | ||
| 181 | if !strings.Contains(host, ".") { | ||
| 182 | return "", fmt.Errorf("%q: use a fully qualified domain name", raw) | ||
| 183 | } | ||
| 184 | for _, label := range strings.Split(host, ".") { | ||
| 185 | if label == "" || len(label) > 63 || label[0] == '-' || label[len(label)-1] == '-' { | ||
| 186 | return "", fmt.Errorf("%q: invalid DNS name", raw) | ||
| 187 | } | ||
| 188 | for _, r := range label { | ||
| 189 | if (r < 'a' || r > 'z') && (r < '0' || r > '9') && r != '-' { | ||
| 190 | return "", fmt.Errorf("%q: invalid DNS name", raw) | ||
| 191 | } | ||
| 192 | } | ||
| 193 | } | ||
| 194 | return host, nil | ||
| 195 | } | ||
| 196 | |||
| 197 | func normalizeHost(host string) string { | ||
| 198 | return strings.TrimRight(strings.ToLower(strings.TrimSpace(host)), ".") | ||
| 199 | } | ||
| 200 | |||
| 201 | // requestHost drops a port from a Host header without treating an IPv6 literal | ||
| 202 | // as a host and port pair. | ||
| 203 | func requestHost(hostport string) string { | ||
| 204 | if host, _, err := net.SplitHostPort(hostport); err == nil { | ||
| 205 | return normalizeHost(host) | ||
| 206 | } | ||
| 207 | return normalizeHost(hostport) | ||
| 208 | } | ||
| 209 | |||
| 210 | func listenPort(addr string) string { | ||
| 211 | _, port, err := net.SplitHostPort(addr) | ||
| 212 | if err != nil { | ||
| 213 | return "" | ||
| 214 | } | ||
| 215 | return port | ||
| 216 | } | ||