71 lines
2.4 KiB
Go
71 lines
2.4 KiB
Go
package connect
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import (
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"crypto/rand"
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"encoding/binary"
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"fmt"
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"regexp"
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"strconv"
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"strings"
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)
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var invalidDNSNameChars = regexp.MustCompile(`[^a-z0-9]`)
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// CompactUID returns a crypto random Unique Identifier string consiting of 8
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// characters of base36 encoded random value. This has roughly 41 bits of
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// entropy so is suitable for infrequently occuring events with low probability
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// of collision. It is not suitable for UUIDs for very frequent events. It's
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// main purpose is to assign unique values to CA certificate Common Names which
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// need to be unique in some providers - see CACN - but without using up large
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// amounts of the limited 64 character Common Name. It also makes the values
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// more easily digestable by humans considering there are likely to be few of
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// them ever in use.
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func CompactUID() (string, error) {
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// 48 bits (6 bytes) is enough to fill 8 bytes in base36 but it's simpler to
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// have a whole uint8 to convert from.
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var raw [8]byte
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_, err := rand.Read(raw[:])
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if err != nil {
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return "", err
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}
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i := binary.LittleEndian.Uint64(raw[:])
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return truncateTo(strconv.FormatInt(int64(i), 36), 8), nil
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}
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// CACN returns the common name for a CA certificate.
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// A uniqueID is requires because some providers (e.g.
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// Vault) cache by subject and so produce incorrect results - for example they
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// won't cross-sign an older CA certificate with the same common name since they
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// think they already have a valid cert for that CN and just return the current
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// root.
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//
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// This can be generated by any means but will be truncated to 8 chars and
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// sanitised to DNS-safe chars. CompactUID generates suitable UIDs for this
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// specific purpose.
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//
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// Format is:
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//
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// {provider}-{uniqueID_first8}.{pri|sec}.ca.<trust_domain_first_8>.consul
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//
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// trust domain is truncated to keep the whole name short
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func CACN(provider, uniqueID, trustDomain string, primaryDC bool) string {
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providerSan := invalidDNSNameChars.ReplaceAllString(strings.ToLower(provider), "")
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typ := "pri"
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if !primaryDC {
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typ = "sec"
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}
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// 32 = 7 bytes for ".consul", 8 bytes for trust domain, 8 bytes for
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// ".pri.ca.", 9 bytes for "-{uniqueID-8-b36}"
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uidSAN := invalidDNSNameChars.ReplaceAllString(strings.ToLower(uniqueID), "")
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return fmt.Sprintf("%s-%s.%s.ca.%s.consul", typ, truncateTo(uidSAN, 8),
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truncateTo(providerSan, 64-32), truncateTo(trustDomain, 8))
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}
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func truncateTo(s string, n int) string {
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if len(s) > n {
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return s[:n]
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}
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return s
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}
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