Use of curve25519-sha256@libssh.org SSH2 key exchange sometimes fails #556

Vincent-- · 2017-08-03T08:30:46Z

What I Did

The issue appears randomly when trying to connect for the first time to the server.
I'm using a simple command line:
sftp -vvv -o PasswordAuthentication=yes -P 22 example@xxxx

Sometimes that fails with this error message:

OpenSSH_6.6.1, OpenSSL 1.0.1f 6 Jan 2014
debug1: Reading configuration data /home/vagrant/.ssh/config
debug3: ciphers ok: [aes256-ctr]
debug3: macs ok: [hmac-sha2-512]
debug3: kex names ok: [diffie-hellman-group14-sha1]
debug1: Reading configuration data /etc/ssh/ssh_config
debug3: ciphers ok: [chacha20-poly1305@openssh.com,aes256-gcm@openssh.com,aes128-gcm@openssh.com,aes256-ctr,aes192-ctr,aes128-ctr]
debug1: /etc/ssh/ssh_config line 12: Applying options for *
debug3: kex names ok: [curve25519-sha256@libssh.org,diffie-hellman-group-exchange-sha256,diffie-hellman-group14-sha1,diffie-hellman-group-exchange-sha1,diffie-hellman-group1-sha1]
debug3: macs ok: [hmac-sha2-512-etm@openssh.com,hmac-sha2-256-etm@openssh.com,hmac-ripemd160-etm@openssh.com,umac-128-etm@openssh.com,hmac-sha2-512,hmac-sha2-256,hmac-ripemd160]
debug2: ssh_connect: needpriv 0
debug1: Connecting to xxxx [xx.xx.xx.xx] port 22.
debug1: Connection established.
debug1: identity file /home/vagrant/.ssh/id_rsa type -1
debug1: identity file /home/vagrant/.ssh/id_rsa-cert type -1
debug1: identity file /home/vagrant/.ssh/id_dsa type -1
debug1: identity file /home/vagrant/.ssh/id_dsa-cert type -1
debug1: identity file /home/vagrant/.ssh/id_ecdsa type -1
debug1: identity file /home/vagrant/.ssh/id_ecdsa-cert type -1
debug1: identity file /home/vagrant/.ssh/id_ed25519 type -1
debug1: identity file /home/vagrant/.ssh/id_ed25519-cert type -1
debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-2.0-OpenSSH_6.6.1p1 Ubuntu-2ubuntu2.8
debug1: Remote protocol version 2.0, remote software version mod_sftp
debug1: no match: mod_sftp
debug2: fd 3 setting O_NONBLOCK
debug3: load_hostkeys: loading entries for host "xxxx" from file "/home/vagrant/.ssh/known_hosts"
debug3: load_hostkeys: found key type RSA in file /home/vagrant/.ssh/known_hosts:10
debug3: load_hostkeys: loaded 1 keys
debug3: load_hostkeys: loading entries for host "xxxx" from file "/etc/ssh/ssh_known_hosts"
debug3: load_hostkeys: loaded 0 keys
debug3: order_hostkeyalgs: prefer hostkeyalgs: ssh-rsa-cert-v01@openssh.com,ssh-rsa-cert-v00@openssh.com,ssh-rsa
debug1: SSH2_MSG_KEXINIT sent
debug1: SSH2_MSG_KEXINIT received
debug2: kex_parse_kexinit: curve25519-sha256@libssh.org,diffie-hellman-group-exchange-sha256,diffie-hellman-group14-sha1,diffie-hellman-group-exchange-sha1,diffie-hellman-group1-sha1
debug2: kex_parse_kexinit: ssh-rsa-cert-v01@openssh.com,ssh-rsa-cert-v00@openssh.com,ssh-rsa,ecdsa-sha2-nistp256-cert-v01@openssh.com,ecdsa-sha2-nistp384-cert-v01@openssh.com,ecdsa-sha2-nistp521-cert-v01@openssh.com,ssh-ed25519-cert-v01@openssh.com,ssh-dss-cert-v01@openssh.com,ssh-dss-cert-v00@openssh.com,ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,ssh-ed25519,ssh-dss
debug2: kex_parse_kexinit: chacha20-poly1305@openssh.com,aes256-gcm@openssh.com,aes128-gcm@openssh.com,aes256-ctr,aes192-ctr,aes128-ctr
debug2: kex_parse_kexinit: chacha20-poly1305@openssh.com,aes256-gcm@openssh.com,aes128-gcm@openssh.com,aes256-ctr,aes192-ctr,aes128-ctr
debug2: kex_parse_kexinit: hmac-sha2-512-etm@openssh.com,hmac-sha2-256-etm@openssh.com,hmac-ripemd160-etm@openssh.com,umac-128-etm@openssh.com,hmac-sha2-512,hmac-sha2-256,hmac-ripemd160
debug2: kex_parse_kexinit: hmac-sha2-512-etm@openssh.com,hmac-sha2-256-etm@openssh.com,hmac-ripemd160-etm@openssh.com,umac-128-etm@openssh.com,hmac-sha2-512,hmac-sha2-256,hmac-ripemd160
debug2: kex_parse_kexinit: zlib@openssh.com,zlib,none
debug2: kex_parse_kexinit: zlib@openssh.com,zlib,none
debug2: kex_parse_kexinit:
debug2: kex_parse_kexinit:
debug2: kex_parse_kexinit: first_kex_follows 0
debug2: kex_parse_kexinit: reserved 0
debug2: kex_parse_kexinit: curve25519-sha256@libssh.org,ecdh-sha2-nistp521,ecdh-sha2-nistp384,ecdh-sha2-nistp256,diffie-hellman-group18-sha512,diffie-hellman-group16-sha512,diffie-hellman-group14-sha256,diffie-hellman-group-exchange-sha256,diffie-hellman-group-exchange-sha1,diffie-hellman-group14-sha1,rsa1024-sha1
debug2: kex_parse_kexinit: ssh-rsa,ssh-dss
debug2: kex_parse_kexinit: aes256-ctr,aes192-ctr,aes128-ctr,aes256-cbc,aes192-cbc,aes128-cbc,blowfish-ctr,blowfish-cbc,cast128-cbc,arcfour256,arcfour128,3des-ctr,3des-cbc
debug2: kex_parse_kexinit: aes256-ctr,aes192-ctr,aes128-ctr,aes256-cbc,aes192-cbc,aes128-cbc,blowfish-ctr,blowfish-cbc,cast128-cbc,arcfour256,arcfour128,3des-ctr,3des-cbc
debug2: kex_parse_kexinit: hmac-sha2-256,hmac-sha2-512,hmac-sha1,hmac-sha1-96,hmac-md5,hmac-md5-96,hmac-ripemd160,umac-64@openssh.com,umac-128@openssh.com
debug2: kex_parse_kexinit: hmac-sha2-256,hmac-sha2-512,hmac-sha1,hmac-sha1-96,hmac-md5,hmac-md5-96,hmac-ripemd160,umac-64@openssh.com,umac-128@openssh.com
debug2: kex_parse_kexinit: zlib@openssh.com,zlib,none
debug2: kex_parse_kexinit: zlib@openssh.com,zlib,none
debug2: kex_parse_kexinit:
debug2: kex_parse_kexinit:
debug2: kex_parse_kexinit: first_kex_follows 0
debug2: kex_parse_kexinit: reserved 0
debug2: mac_setup: setup hmac-sha2-512
debug1: kex: server->client aes256-ctr hmac-sha2-512 zlib@openssh.com
debug2: mac_setup: setup hmac-sha2-512
debug1: kex: client->server aes256-ctr hmac-sha2-512 zlib@openssh.com
debug1: sending SSH2_MSG_KEX_ECDH_INIT
debug1: expecting SSH2_MSG_KEX_ECDH_REPLY
Received disconnect from xx.xx.xx.xx: 3: Key exchange failed
Couldn't read packet: Connection reset by peer

On the server side:

2017-08-03 07:54:06,854 mod_sftp/1.0.0[14389]: disconnecting client (received EOF)
2017-08-03 07:54:08,264 mod_sftp/1.0.0[14443]: sent server version 'SSH-2.0-mod_sftp'
2017-08-03 07:54:08,265 mod_sftp/1.0.0[14443]: received client version 'SSH-2.0-OpenSSH_6.6.1p1 Ubuntu-2ubuntu2.8'
2017-08-03 07:54:08,265 mod_sftp/1.0.0[14443]: handling connection from SSH2 client 'OpenSSH_6.6.1p1'
2017-08-03 07:54:08,314 mod_sftp/1.0.0[14443]:  + Session key exchange: curve25519-sha256@libssh.org
2017-08-03 07:54:08,314 mod_sftp/1.0.0[14443]:  + Session server hostkey: ssh-rsa
2017-08-03 07:54:08,314 mod_sftp/1.0.0[14443]:  + Session client-to-server encryption: aes256-ctr
2017-08-03 07:54:08,314 mod_sftp/1.0.0[14443]:  + Session server-to-client encryption: aes256-ctr
2017-08-03 07:54:08,315 mod_sftp/1.0.0[14443]:  + Session client-to-server MAC: hmac-sha2-512
2017-08-03 07:54:08,315 mod_sftp/1.0.0[14443]:  + Session server-to-client MAC: hmac-sha2-512
2017-08-03 07:54:08,315 mod_sftp/1.0.0[14443]:  + Session client-to-server compression: zlib@openssh.com
2017-08-03 07:54:08,315 mod_sftp/1.0.0[14443]:  + Session server-to-client compression: zlib@openssh.com
2017-08-03 07:54:08,389 mod_sftp/1.0.0[14443]: rejecting invalid length (1 bytes) client Curve25519 key
2017-08-03 07:54:08,389 mod_sftp/1.0.0[14443]: disconnecting 88.174.204.18 (Key exchange failed)

If I try again with the exact same command line again, that works perferctly:

OpenSSH_6.6.1, OpenSSL 1.0.1f 6 Jan 2014
debug1: Reading configuration data /home/vagrant/.ssh/config
debug3: ciphers ok: [aes256-ctr]
debug3: macs ok: [hmac-sha2-512]
debug3: kex names ok: [diffie-hellman-group14-sha1]
debug1: Reading configuration data /etc/ssh/ssh_config
debug3: ciphers ok: [chacha20-poly1305@openssh.com,aes256-gcm@openssh.com,aes128-gcm@openssh.com,aes256-ctr,aes192-ctr,aes128-ctr]
debug1: /etc/ssh/ssh_config line 12: Applying options for *
debug3: kex names ok: [curve25519-sha256@libssh.org,diffie-hellman-group-exchange-sha256,diffie-hellman-group14-sha1,diffie-hellman-group-exchange-sha1,diffie-hellman-group1-sha1]
debug3: macs ok: [hmac-sha2-512-etm@openssh.com,hmac-sha2-256-etm@openssh.com,hmac-ripemd160-etm@openssh.com,umac-128-etm@openssh.com,hmac-sha2-512,hmac-sha2-256,hmac-ripemd160]
debug2: ssh_connect: needpriv 0
debug1: Connecting to xxxx [xx.xx.xx.xx] port 22.
debug1: Connection established.
debug1: identity file /home/vagrant/.ssh/id_rsa type -1
debug1: identity file /home/vagrant/.ssh/id_rsa-cert type -1
debug1: identity file /home/vagrant/.ssh/id_dsa type -1
debug1: identity file /home/vagrant/.ssh/id_dsa-cert type -1
debug1: identity file /home/vagrant/.ssh/id_ecdsa type -1
debug1: identity file /home/vagrant/.ssh/id_ecdsa-cert type -1
debug1: identity file /home/vagrant/.ssh/id_ed25519 type -1
debug1: identity file /home/vagrant/.ssh/id_ed25519-cert type -1
debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-2.0-OpenSSH_6.6.1p1 Ubuntu-2ubuntu2.8
debug1: Remote protocol version 2.0, remote software version mod_sftp
debug1: no match: mod_sftp
debug2: fd 3 setting O_NONBLOCK
debug3: load_hostkeys: loading entries for host "xxxx" from file "/home/vagrant/.ssh/known_hosts"
debug3: load_hostkeys: found key type RSA in file /home/vagrant/.ssh/known_hosts:10
debug3: load_hostkeys: loaded 1 keys
debug3: load_hostkeys: loading entries for host "xxxx" from file "/etc/ssh/ssh_known_hosts"
debug3: load_hostkeys: loaded 0 keys
debug3: order_hostkeyalgs: prefer hostkeyalgs: ssh-rsa-cert-v01@openssh.com,ssh-rsa-cert-v00@openssh.com,ssh-rsa
debug1: SSH2_MSG_KEXINIT sent
debug1: SSH2_MSG_KEXINIT received
debug2: kex_parse_kexinit: curve25519-sha256@libssh.org,diffie-hellman-group-exchange-sha256,diffie-hellman-group14-sha1,diffie-hellman-group-exchange-sha1,diffie-hellman-group1-sha1
debug2: kex_parse_kexinit: ssh-rsa-cert-v01@openssh.com,ssh-rsa-cert-v00@openssh.com,ssh-rsa,ecdsa-sha2-nistp256-cert-v01@openssh.com,ecdsa-sha2-nistp384-cert-v01@openssh.com,ecdsa-sha2-nistp521-cert-v01@openssh.com,ssh-ed25519-cert-v01@openssh.com,ssh-dss-cert-v01@openssh.com,ssh-dss-cert-v00@openssh.com,ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,ssh-ed25519,ssh-dss
debug2: kex_parse_kexinit: chacha20-poly1305@openssh.com,aes256-gcm@openssh.com,aes128-gcm@openssh.com,aes256-ctr,aes192-ctr,aes128-ctr
debug2: kex_parse_kexinit: chacha20-poly1305@openssh.com,aes256-gcm@openssh.com,aes128-gcm@openssh.com,aes256-ctr,aes192-ctr,aes128-ctr
debug2: kex_parse_kexinit: hmac-sha2-512-etm@openssh.com,hmac-sha2-256-etm@openssh.com,hmac-ripemd160-etm@openssh.com,umac-128-etm@openssh.com,hmac-sha2-512,hmac-sha2-256,hmac-ripemd160
debug2: kex_parse_kexinit: hmac-sha2-512-etm@openssh.com,hmac-sha2-256-etm@openssh.com,hmac-ripemd160-etm@openssh.com,umac-128-etm@openssh.com,hmac-sha2-512,hmac-sha2-256,hmac-ripemd160
debug2: kex_parse_kexinit: zlib@openssh.com,zlib,none
debug2: kex_parse_kexinit: zlib@openssh.com,zlib,none
debug2: kex_parse_kexinit:
debug2: kex_parse_kexinit:
debug2: kex_parse_kexinit: first_kex_follows 0
debug2: kex_parse_kexinit: reserved 0
debug2: kex_parse_kexinit: curve25519-sha256@libssh.org,ecdh-sha2-nistp521,ecdh-sha2-nistp384,ecdh-sha2-nistp256,diffie-hellman-group18-sha512,diffie-hellman-group16-sha512,diffie-hellman-group14-sha256,diffie-hellman-group-exchange-sha256,diffie-hellman-group-exchange-sha1,diffie-hellman-group14-sha1,diffie-hellman-group1-sha1,rsa1024-sha1
debug2: kex_parse_kexinit: ssh-rsa,ssh-dss
debug2: kex_parse_kexinit: aes128-ctr,aes192-ctr,aes256-ctr,arcfour256,arcfour128,aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,aes192-cbc,aes256-cbc
debug2: kex_parse_kexinit: aes128-ctr,aes192-ctr,aes256-ctr,arcfour256,arcfour128,aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,aes192-cbc,aes256-cbc
debug2: kex_parse_kexinit: hmac-md5,hmac-sha1,umac-64@openssh.com,umac-128@openssh.com,hmac-sha2-256,hmac-sha2-512,hmac-ripemd160,hmac-sha1-96,hmac-md5-96
debug2: kex_parse_kexinit: hmac-md5,hmac-sha1,umac-64@openssh.com,umac-128@openssh.com,hmac-sha2-256,hmac-sha2-512,hmac-ripemd160,hmac-sha1-96,hmac-md5-96
debug2: kex_parse_kexinit: zlib@openssh.com,zlib,none
debug2: kex_parse_kexinit: zlib@openssh.com,zlib,none
debug2: kex_parse_kexinit:
debug2: kex_parse_kexinit:
debug2: kex_parse_kexinit: first_kex_follows 0
debug2: kex_parse_kexinit: reserved 0
debug2: mac_setup: setup hmac-sha2-512
debug1: kex: server->client aes256-ctr hmac-sha2-512 zlib@openssh.com
debug2: mac_setup: setup hmac-sha2-512
debug1: kex: client->server aes256-ctr hmac-sha2-512 zlib@openssh.com
debug1: sending SSH2_MSG_KEX_ECDH_INIT
debug1: expecting SSH2_MSG_KEX_ECDH_REPLY
debug1: Server host key: RSA 61:5f:20:c7:d0:59:ad:d6:bd:8f:a4:84:20:7c:24:3d
debug3: load_hostkeys: loading entries for host "xxxx" from file "/home/vagrant/.ssh/known_hosts"
debug3: load_hostkeys: found key type RSA in file /home/vagrant/.ssh/known_hosts:10
debug3: load_hostkeys: loaded 1 keys
debug3: load_hostkeys: loading entries for host "xxxx" from file "/etc/ssh/ssh_known_hosts"
debug3: load_hostkeys: loaded 0 keys
debug3: load_hostkeys: loading entries for host "xx.xx.xx.xx" from file "/home/vagrant/.ssh/known_hosts"
debug3: load_hostkeys: found key type RSA in file /home/vagrant/.ssh/known_hosts:11
debug3: load_hostkeys: loaded 1 keys
debug3: load_hostkeys: loading entries for host "xx.xx.xx.xx" from file "/etc/ssh/ssh_known_hosts"
debug3: load_hostkeys: loaded 0 keys
debug1: Host 'xxxx' is known and matches the RSA host key.
debug1: Found key in /home/vagrant/.ssh/known_hosts:10
debug1: ssh_rsa_verify: signature correct
debug2: kex_derive_keys
debug2: set_newkeys: mode 1
debug1: SSH2_MSG_NEWKEYS sent
debug1: expecting SSH2_MSG_NEWKEYS
debug2: set_newkeys: mode 0
debug1: SSH2_MSG_NEWKEYS received
debug1: SSH2_MSG_SERVICE_REQUEST sent
debug2: service_accept: ssh-userauth
debug1: SSH2_MSG_SERVICE_ACCEPT received
debug2: key: /home/vagrant/.ssh/id_rsa ((nil)),
debug2: key: /home/vagrant/.ssh/id_dsa ((nil)),
debug2: key: /home/vagrant/.ssh/id_ecdsa ((nil)),
debug2: key: /home/vagrant/.ssh/id_ed25519 ((nil)),
debug1: Authentications that can continue: publickey,password
debug3: start over, passed a different list publickey,password
debug3: preferred publickey,keyboard-interactive,password
debug3: authmethod_lookup publickey
debug3: remaining preferred: keyboard-interactive,password
debug3: authmethod_is_enabled publickey
debug1: Next authentication method: publickey
debug1: Trying private key: /home/vagrant/.ssh/id_rsa
debug3: no such identity: /home/vagrant/.ssh/id_rsa: No such file or directory
debug1: Trying private key: /home/vagrant/.ssh/id_dsa
debug3: no such identity: /home/vagrant/.ssh/id_dsa: No such file or directory
debug1: Trying private key: /home/vagrant/.ssh/id_ecdsa
debug3: no such identity: /home/vagrant/.ssh/id_ecdsa: No such file or directory
debug1: Trying private key: /home/vagrant/.ssh/id_ed25519
debug3: no such identity: /home/vagrant/.ssh/id_ed25519: No such file or directory
debug2: we did not send a packet, disable method
debug3: authmethod_lookup password
debug3: remaining preferred: ,password
debug3: authmethod_is_enabled password
debug1: Next authentication method: password
example@xxxxxxx's password:

On the server side:

2017-08-03 07:54:41,490 mod_sftp/1.0.0[14446]: sent server version 'SSH-2.0-mod_sftp'
2017-08-03 07:54:41,491 mod_sftp/1.0.0[14446]: received client version 'SSH-2.0-OpenSSH_6.6.1p1 Ubuntu-2ubuntu2.8'
2017-08-03 07:54:41,491 mod_sftp/1.0.0[14446]: handling connection from SSH2 client 'OpenSSH_6.6.1p1'
2017-08-03 07:54:41,539 mod_sftp/1.0.0[14446]:  + Session key exchange: curve25519-sha256@libssh.org
2017-08-03 07:54:41,539 mod_sftp/1.0.0[14446]:  + Session server hostkey: ssh-rsa
2017-08-03 07:54:41,539 mod_sftp/1.0.0[14446]:  + Session client-to-server encryption: aes256-ctr
2017-08-03 07:54:41,540 mod_sftp/1.0.0[14446]:  + Session server-to-client encryption: aes256-ctr
2017-08-03 07:54:41,540 mod_sftp/1.0.0[14446]:  + Session client-to-server MAC: hmac-sha2-512
2017-08-03 07:54:41,540 mod_sftp/1.0.0[14446]:  + Session server-to-client MAC: hmac-sha2-512
2017-08-03 07:54:41,541 mod_sftp/1.0.0[14446]:  + Session client-to-server compression: zlib@openssh.com
2017-08-03 07:54:41,541 mod_sftp/1.0.0[14446]:  + Session server-to-client compression: zlib@openssh.com
2017-08-03 07:54:41,775 mod_sftp/1.0.0[14446]: sending acceptable userauth methods: publickey,password

What I Expected/Wanted

Be able to connect every times :-)

ProFTPD Version and Configuration

$ proftpd -V
Compile-time Settings:
  Version: 1.3.6 (stable)
  Platform: LINUX [Linux 3.13.0-32-generic x86_64]
  Built: Mon Jul 31 2017 20:16:33 UTC
  Built With:
    configure  '--prefix=/usr' '--mandir=/usr/share/man' '--sysconfdir=/etc/proftpd' '--localstatedir=/var/run' '--libexecdir=/usr/lib/proftpd' '--enable-sendfile' '--enable-facl' '--enable-dso' '--enable-autoshadow' '--enable-ctrls' '--enable-openssl' '--with-modules=mod_rename:mod_sql:mod_sql_passwd:mod_sql_mysql:mod_sftp:mod_sftp_sql' '--with-includes=/usr/local/include' '--with-libraries=/usr/local/lib' '--enable-nls' '--build' 'x86_64-linux-gnu' 'build_alias=x86_64-linux-gnu' 'CFLAGS=-O2'

  CFLAGS: -g2 -O2 -Wall -fno-omit-frame-pointer
  LDFLAGS: -L$(top_srcdir)/lib  -rdynamic -L/usr/local/lib -L/usr/lib/x86_64-linux-gnu
  LIBS: -lacl  -lssl -lcrypto -lsodium -lcap  -lm -lmysqlclient -lz  -lpam  -lcrypto -lsupp -lattr -lcrypt -ldl

  Files:
    Configuration File:
      /etc/proftpd/proftpd.conf
    Pid File:
      /var/run/proftpd.pid
    Scoreboard File:
      /var/run/proftpd.scoreboard
    Header Directory:
      /usr/include/proftpd
    Shared Module Directory:
      /usr/lib/proftpd

  Info:
    + Max supported UID: 4294967295
    + Max supported GID: 4294967295

  Features:
    + Autoshadow support
    + Controls support
    + curses support
    - Developer support
    + DSO support
    + IPv6 support
    + Largefile support
    - Lastlog support
    - Memcache support
    + ncurses support
    + NLS support
    - Redis support
    + Sodium support
    + OpenSSL support
    - PCRE support
    + POSIX ACL support
    + Shadow file support
    + Sendfile support
    + Trace support
    + xattr support

  Tunable Options:
    PR_TUNABLE_BUFFER_SIZE = 1024
    PR_TUNABLE_DEFAULT_RCVBUFSZ = 8192
    PR_TUNABLE_DEFAULT_SNDBUFSZ = 8192
    PR_TUNABLE_ENV_MAX = 2048
    PR_TUNABLE_GLOBBING_MAX_MATCHES = 100000
    PR_TUNABLE_GLOBBING_MAX_RECURSION = 8
    PR_TUNABLE_HASH_TABLE_SIZE = 40
    PR_TUNABLE_LOGIN_MAX = 256
    PR_TUNABLE_NEW_POOL_SIZE = 512
    PR_TUNABLE_PATH_MAX = 4096
    PR_TUNABLE_SCOREBOARD_BUFFER_SIZE = 80
    PR_TUNABLE_SCOREBOARD_SCRUB_TIMER = 30
    PR_TUNABLE_SELECT_TIMEOUT = 30
    PR_TUNABLE_TIMEOUTIDENT = 10
    PR_TUNABLE_TIMEOUTIDLE = 600
    PR_TUNABLE_TIMEOUTLINGER = 10
    PR_TUNABLE_TIMEOUTLOGIN = 300
    PR_TUNABLE_TIMEOUTNOXFER = 300
    PR_TUNABLE_TIMEOUTSTALLED = 3600
    PR_TUNABLE_XFER_SCOREBOARD_UPDATES = 10

Configuration are available in my previous bug reports, see #547

The text was updated successfully, but these errors were encountered:

algorithm, the KEXINIT routine would sometimes incorrectly determine the payload length. This would lead to unexpected log messages like: rejecting invalid length (...) client Curve25519 key

Issue #556: When using the "curve25519-sha256@libssh.org" key exchange

Castaglia · 2017-08-04T03:54:57Z

Thanks for the report! This should now be fixed in master (and backported to the 1.3.6 branch).

Vincent-- · 2017-08-04T05:42:49Z

Wow! That was quick 👍 Thank you for that.
Any new release planned for 1.3.6 soon? Or should I update my build code to download directly from 1.3.6 branch?

Castaglia · 2017-08-04T14:41:16Z

I'm still receiving issues and bug reports that lead to fixes for the 1.3.6 branch, and I'd like get as many of this in as I can. So no maintenance release planned as yet. For now, then, probably better to download and use the 1.3.6 branch from GitHub.

Vincent-- · 2017-08-04T14:53:34Z

Thanks for the update. I've disabled curve25519 in the conf as a workaround and I'll stick to v1.3.6 until v1.3.6a is available.

Castaglia self-assigned this Aug 4, 2017

Castaglia added bug backport labels Aug 4, 2017

Castaglia added this to the 1.3.7 milestone Aug 4, 2017

Castaglia changed the title ~~Rejecting invalid length (1 bytes) client Curve25519 key~~ Use of curve25519-sha256@libssh.org" SSH2 key exchange sometimes fails Aug 4, 2017

Castaglia changed the title ~~Use of curve25519-sha256@libssh.org" SSH2 key exchange sometimes fails~~ Use of curve25519-sha256@libssh.org SSH2 key exchange sometimes fails Aug 4, 2017

Castaglia added a commit that referenced this issue Aug 4, 2017

Updated NEWS for backport of fix for Issue #556.

6ccfc06

Castaglia added a commit that referenced this issue Aug 4, 2017

Merge pull request #557 from proftpd/sftp-curve25519

58f459e

Issue #556: When using the "curve25519-sha256@libssh.org" key exchange

Castaglia added a commit that referenced this issue Aug 4, 2017

Updated NEWS for Issue #556.

80e0750

Castaglia closed this as completed Aug 4, 2017

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Use of curve25519-sha256@libssh.org SSH2 key exchange sometimes fails #556

Use of curve25519-sha256@libssh.org SSH2 key exchange sometimes fails #556

Vincent-- commented Aug 3, 2017

Castaglia commented Aug 4, 2017

Vincent-- commented Aug 4, 2017

Castaglia commented Aug 4, 2017

Vincent-- commented Aug 4, 2017

Use of curve25519-sha256@libssh.org SSH2 key exchange sometimes fails #556

Use of curve25519-sha256@libssh.org SSH2 key exchange sometimes fails #556

Comments

Vincent-- commented Aug 3, 2017

What I Did

What I Expected/Wanted

ProFTPD Version and Configuration

Castaglia commented Aug 4, 2017

Vincent-- commented Aug 4, 2017

Castaglia commented Aug 4, 2017

Vincent-- commented Aug 4, 2017