Initial commit: Null DRM Official

Capture, decrypt, and restream toolkit with compiled-in app modules
(RTE, TG4, BBC), on-device MITM proxy, streamd control plane, and www.
BBC module.yaml is published (clear streams); other module values stay local.

apps/modules/rte/mpd.go

@@ -0,0 +1,146 @@
+package rte
+
+import (
+	"fmt"
+	"regexp"
+	"strings"
+	"sync"
+
+	"drmdecryption/mpd"
+)
+
+func init() {
+	mpd.Register(Name, func() mpd.Rewriter { return NewRewriter() })
+}
+
+var reBaseURL = regexp.MustCompile(`(?i)<BaseURL[^>]*>([^<]+)</BaseURL>`)
+
+// Rewriter turns an ad-stitched upstream MPD into a synthetic manifest on the
+// origin encoder's own segment grid, so a downloader keeps pulling live segments
+// after the upstream session expires. All origins and KIDs come from config.
+type Rewriter struct {
+	cfg Config
+
+	mu           sync.Mutex
+	fallbackCh   string
+	fallbackBase string
+}
+
+// NewRewriter loads the module config and returns a rewriter. A config error is
+// deferred to Rewrite so registry lookup never fails at startup.
+func NewRewriter() *Rewriter {
+	cfg, _, err := loadConfig()
+	if err != nil {
+		return &Rewriter{cfg: Config{}.withDefaults()}
+	}
+	return &Rewriter{cfg: cfg}
+}
+
+// NewRewriterWith builds a rewriter from an already-loaded config.
+func NewRewriterWith(cfg Config) *Rewriter {
+	return &Rewriter{cfg: cfg}
+}
+
+func (r *Rewriter) Name() string { return Name }
+
+// Prime records a channel/origin learned elsewhere (e.g. from the KID).
+func (r *Rewriter) Prime(channel, originBase string) {
+	r.mu.Lock()
+	defer r.mu.Unlock()
+	if channel != "" {
+		r.fallbackCh = channel
+	}
+	if originBase != "" {
+		r.fallbackBase = originBase
+	}
+}
+
+// ResolveKID maps a KID back to its encoder channel and origin.
+func (r *Rewriter) ResolveKID(kidHex string) (channel, originBase string, ok bool) {
+	for ch, kid := range r.cfg.KIDs {
+		if mpd.KIDHex(kid) == kidHex {
+			return ch, r.cfg.Origins[ch], true
+		}
+	}
+	return "", "", false
+}
+
+// Rewrite produces the synthetic MPD. upstreamXML may be empty (expired session):
+// the KID fallback then supplies the channel and origin.
+func (r *Rewriter) Rewrite(upstreamXML []byte, kidHint string) ([]byte, error) {
+	r.mu.Lock()
+	fbCh, fbBase := r.fallbackCh, r.fallbackBase
+	r.mu.Unlock()
+
+	payload, channel, originBase, err := r.rewrite(string(upstreamXML), kidHint, fbCh, fbBase)
+	if channel != "" || originBase != "" {
+		r.Prime(channel, originBase)
+	}
+	return payload, err
+}
+
+func (r *Rewriter) rewrite(xmlText, kidHint, fallbackChannel, fallbackBase string) (payload []byte, channel, originBase string, err error) {
+	cfg := r.cfg
+	channel, originBase = r.originFromXML(xmlText)
+	resolvedKid := mpd.ExtractDefaultKID(xmlText)
+	if resolvedKid == "" && kidHint != "" {
+		resolvedKid, _ = mpd.KIDToUUID(kidHint)
+	}
+	if (channel == "" || originBase == "") && resolvedKid != "" {
+		if mapped, base, ok := r.ResolveKID(mpd.KIDHex(resolvedKid)); ok {
+			if channel == "" {
+				channel = mapped
+			}
+			if originBase == "" {
+				originBase = base
+			}
+		}
+	}
+	if channel == "" {
+		channel = fallbackChannel
+	}
+	if originBase == "" {
+		originBase = fallbackBase
+	}
+	if channel != "" && originBase == "" {
+		originBase = cfg.Origins[channel]
+	}
+	if channel != "" && originBase != "" && r.usesEncoderTimeline(channel) {
+		if resolvedKid == "" {
+			resolvedKid = cfg.KIDs[channel]
+		}
+		if resolvedKid == "" {
+			return nil, "", "", fmt.Errorf("%s: no KID for synthetic MPD channel %s", Name, channel)
+		}
+		payload, err = mpd.BuildSynthetic(cfg.Synthetic, channel, originBase, resolvedKid)
+		return payload, channel, originBase, err
+	}
+	return nil, channel, originBase, fmt.Errorf("%s rewrite: unsupported MPD (no encoder channel); channel=%q", Name, channel)
+}
+
+func (r *Rewriter) usesEncoderTimeline(channel string) bool {
+	ok, _ := regexp.MatchString(r.cfg.EncoderChannelRE, channel)
+	return ok
+}
+
+// originFromXML finds the origin BaseURL and derives the encoder channel from it.
+func (r *Rewriter) originFromXML(xmlText string) (channel, base string) {
+	marker := r.cfg.OriginMarker
+	if marker == "" {
+		marker = ".isml"
+	}
+	for _, m := range reBaseURL.FindAllStringSubmatch(xmlText, -1) {
+		text := strings.TrimSpace(m[1])
+		idx := strings.Index(text, marker)
+		if idx < 0 {
+			continue
+		}
+		base = text[:idx] + marker + "/"
+		parts := strings.Split(strings.TrimSuffix(base, "/"), "/")
+		channel = strings.TrimSuffix(parts[len(parts)-1], marker)
+		if channel != "" {
+			return channel, base
+		}
+	}
+	return "", ""
+}