79 lines
2.0 KiB
Go
79 lines
2.0 KiB
Go
package dns
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import (
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"net"
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"strings"
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"time"
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lru "github.com/hashicorp/golang-lru/v2"
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)
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type lookupCacheEntry struct {
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cachedName string
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timestamp time.Time
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}
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var lookupCacheValidity = 30 * time.Second
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var lookupCache *lru.Cache[string, lookupCacheEntry]
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var defaultPagesRepo = "pages"
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// GetTargetFromDNS searches for CNAME or TXT entries on the request domain ending with MainDomainSuffix.
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// If everything is fine, it returns the target data.
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func GetTargetFromDNS(domain, mainDomainSuffix, firstDefaultBranch string) (targetOwner, targetRepo, targetBranch string) {
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// Get CNAME or TXT
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var cname string
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var err error
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if lookupCache == nil {
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lookupCache, err = lru.New[string, lookupCacheEntry](4096)
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if err != nil {
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panic(err) // This should only happen if 4096 < 0 at the time of writing, which should be reason enough to panic.
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}
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}
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if entry, ok := lookupCache.Get(domain); ok && time.Now().Before(entry.timestamp.Add(lookupCacheValidity)) {
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cname = entry.cachedName
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} else {
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cname, err = net.LookupCNAME(domain)
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cname = strings.TrimSuffix(cname, ".")
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if err != nil || !strings.HasSuffix(cname, mainDomainSuffix) {
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cname = ""
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// TODO: check if the A record matches!
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names, err := net.LookupTXT(domain)
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if err == nil {
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for _, name := range names {
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name = strings.TrimSuffix(strings.TrimSpace(name), ".")
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if strings.HasSuffix(name, mainDomainSuffix) {
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cname = name
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break
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}
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}
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}
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}
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_ = lookupCache.Add(domain, lookupCacheEntry{
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cname,
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time.Now(),
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})
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}
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if cname == "" {
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return
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}
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cnameParts := strings.Split(strings.TrimSuffix(cname, mainDomainSuffix), ".")
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targetOwner = cnameParts[len(cnameParts)-1]
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if len(cnameParts) > 1 {
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targetRepo = cnameParts[len(cnameParts)-2]
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}
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if len(cnameParts) > 2 {
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targetBranch = cnameParts[len(cnameParts)-3]
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}
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if targetRepo == "" {
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targetRepo = defaultPagesRepo
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}
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if targetBranch == "" && targetRepo != defaultPagesRepo {
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targetBranch = firstDefaultBranch
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}
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// if targetBranch is still empty, the caller must find the default branch
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return
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}
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