new ClientHellos and Extensions (#116)

* Implement certificate compression

Certificate compression is defined in RFC 8879:
https://datatracker.ietf.org/doc/html/rfc8879

This implementation is client-side only, for server certificates.

* Fix missing LOC

* Add more fingerprints

* Implement ALPS extension

* Merge commit fcaacdbbe7

- At this commit, github.com/Noooste/utls remained at the original upstream LICENSE

* added HelloChrome102 and HelloFirefox102

* Randomly include ALPS in HelloRandomized

Co-authored-by: Harry Harpham <harry@getlantern.org>
Co-authored-by: Sleeyax <yourd3veloper@gmail.com>
Co-authored-by: Rod Hynes <rod-hynes@users.noreply.github.com>

u_prng.go

@@ -19,6 +19,7 @@ import (
 	"math/rand"
 	"sync"
 
+	"golang.org/x/crypto/hkdf"
 	"golang.org/x/crypto/sha3"
 )
 
@@ -39,6 +40,21 @@ func NewPRNGSeed() (*PRNGSeed, error) {
 	return seed, nil
 }
 
+// newSaltedPRNGSeed creates a new seed derived from an existing seed and a
+// salt. A HKDF is applied to the seed and salt.
+//
+// newSaltedPRNGSeed is intended for use cases where a single seed needs to be
+// used in distinct contexts to produce independent random streams.
+func newSaltedPRNGSeed(seed *PRNGSeed, salt string) (*PRNGSeed, error) {
+	saltedSeed := new(PRNGSeed)
+	_, err := io.ReadFull(
+		hkdf.New(sha3.New256, seed[:], []byte(salt), nil), saltedSeed[:])
+	if err != nil {
+		return nil, err
+	}
+	return saltedSeed, nil
+}
+
 // prng is a seeded, unbiased PRNG based on SHAKE256. that is suitable for use
 // cases such as obfuscation. Seeding is based on crypto/rand.Read.
 //
@@ -78,6 +94,16 @@ func newPRNGWithSeed(seed *PRNGSeed) (*prng, error) {
 	return p, nil
 }
 
+// newPRNGWithSaltedSeed initializes a new PRNG using a seed derived from an
+// existing seed and a salt with NewSaltedSeed.
+func newPRNGWithSaltedSeed(seed *PRNGSeed, salt string) (*prng, error) {
+	saltedSeed, err := newSaltedPRNGSeed(seed, salt)
+	if err != nil {
+		return nil, err
+	}
+	return newPRNGWithSeed(saltedSeed)
+}
+
 // Read reads random bytes from the PRNG stream into b. Read conforms to
 // io.Reader and always returns len(p), nil.
 func (p *prng) Read(b []byte) (int, error) {