ssh: send ext-info-c only once

In accordance to RFC8308, send ext-info-c only during the first key
exchange. Some server implementations such as OpenSSH 7 will send an
extInfoMsg message each time when ext-info-c is received. This results
in a closed connection, as our client does not expect this message while
handling the mux.

See regarding the
behaviour of OpenSSH if it sees ext-info-c in later key exchanges.

Fixes golang/go#51808

Change-Id: Id94f1ef73cec6147136246b0b6048b57db92660d
GitHub-Last-Rev: fcfe5ed37306136219854031abc809e0dc9b3124
GitHub-Pull-Request: golang/crypto#208
Reviewed-by: Filippo Valsorda <>
Run-TryBot: Filippo Valsorda <>
TryBot-Result: Gopher Robot <>
Trust: Roland Shoemaker <>
1 file changed
tree: e42e2e09a4fc622fa6ea023613eaf6329721486e
  1. acme/
  2. argon2/
  3. bcrypt/
  4. blake2b/
  5. blake2s/
  6. blowfish/
  7. bn256/
  8. cast5/
  9. chacha20/
  10. chacha20poly1305/
  11. cryptobyte/
  12. curve25519/
  13. ed25519/
  14. hkdf/
  15. internal/
  16. md4/
  17. nacl/
  18. ocsp/
  19. openpgp/
  20. otr/
  21. pbkdf2/
  22. pkcs12/
  23. poly1305/
  24. ripemd160/
  25. salsa20/
  26. scrypt/
  27. sha3/
  28. ssh/
  29. tea/
  30. twofish/
  31. xtea/
  32. xts/
  33. .gitattributes
  34. .gitignore
  36. codereview.cfg
  39. go.mod
  40. go.sum

Go Cryptography

Go Reference

This repository holds supplementary Go cryptography libraries.


The easiest way to install is to run go get -u You can also manually git clone the repository to $GOPATH/src/

Report Issues / Send Patches

This repository uses Gerrit for code changes. To learn how to submit changes to this repository, see

The main issue tracker for the crypto repository is located at Prefix your issue with “x/crypto:” in the subject line, so it is easy to find.

Note that contributions to the cryptography package receive additional scrutiny due to their sensitive nature. Patches may take longer than normal to receive feedback.