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--- aix:aix_ssh_howto [2024/06/04 14:45]
manu [Boost ssh connection]
+++ aix:aix_ssh_howto [2025/01/15 23:25] (current)
manu [List ciphers and Macs on client]
@@ Line 251: / Line 251: @@
 To prevent usage for specific Ciphers or KexAlgorithms, you can also exclude some:
-  kexalgorithms  -*sha1,*sha1-*
+  KexAlgorithms -*sha1,*sha1-*
-  macs -*sha1,*sha1-*
+  MACs -*sha1,*sha1-*
 Full specs (second example)
@@ Line 294: / Line 294: @@
 </cli>
+==== Add timeout ====
+If an host doesn't answer, the timeout will stop the connexion
+<cli prompt='#'>
+#  ssh -o ConnectTimeout=10 $i uname
+</cli>
 ==== Boost ssh connection ====
@@ Line 310: / Line 316: @@
 </cli>
+==== Bad cipher or MAC ====
+I can specify the cipher and the MAC:
+  ssh <user@ip> -c aes256-cbc -m hmac-sha1
+==== no matching host key type found ====
+Error with sha1 keys
+<cli prompt='>'>
+[root@aixa001]/root/scripts> ssh -oKexAlgorithms=+diffie-hellman-group1-sha1 USERID@10.0.1.11
+Unable to negotiate with 10.0.1.11 port 22: no matching host key type found. Their offer: ssh-rsa
+[root@aixa001]/root/scripts> ssh -o HostKeyAlgorithms=+ssh-rsa USERID@10.0.1.11
+The authenticity of host '10.0.1.11 (10.0.1.11)' can't be established.
+RSA key fingerprint is SHA256:fEia4p8Ylxxxxxxxxxxxxxxx23gMy3Iq0bmtmk/1Q.
+This key is not known by any other names.
+Are you sure you want to continue connecting (yes/no/[fingerprint])? yes
+Warning: Permanently added '10.0.1.11' (RSA) to the list of known hosts.
+(USERID@10.0.1.11) Enter login password:
+</cli>
+You can also add some paramters into **/etc/ssh/ssh_config**, or for a specific user **~/.ssh/config**\\
+**Ex** for the error Their offer: ssh-dss
+~/.ssh/config
+<code>
+Host my.host.com *.myinsecure.net 10.0.1.*
+    HostkeyAlgorithms +ssh-dss
+    PubkeyAcceptedKeyTypes +ssh-dss
+    KexAlgorithms diffie-hellman-group1-sha1
+</code>
+Or in command line
+  ssh -v -o HostKeyAlgorithms=ssh-dss -o KexAlgorithms=diffie-hellman-group14-sha1 my.host.com
 ==== Disable SSH prompt ====
@@ Line 325: / Line 367: @@
 LogLevel ERROR
 </code>
+==== Error: hostfile_replace_entries ====
+Error:
+<cli prompt='>'>
+[root@aix001]/root> ssh server001
+update_known_hosts: hostfile_replace_entries failed for /root/.ssh/known_hosts: Operation not permitted
+</cli>
+Resolution
+<cli prompt='>'>
+[root@aix001]/root> ssh-keyscan -H server001 >> ~/.ssh/known_hosts
+# server001 SSH-2.0-OpenSSH_8.1
+# server001 SSH-2.0-OpenSSH_8.1
+# server001 SSH-2.0-OpenSSH_8.1
+# server001 SSH-2.0-OpenSSH_8.1
+</cli>
 ==== Edit a file on a remote host ====
 Use ssh command with **-t** option
+==== SCP Connection closed ====
+Use the option **-O** tells SCP to use legacy SCP protocol for file transfers
+<cli prompt='#'>
+[root@aix001]/root/scripts# scp  count_path.sh padmin@vios01:/tmp
+scp: Connection closed
+[root@aix001]/root/scripts# scp -O  count_path.sh padmin@vios01:/tmp
+count_path.sh                                        100% 1972     1.9MB/s   00:00
+</cli>
+**Note:** Since OpenSSH 8.8 the scp utility uses the SFTP protocol by default. The -O option must be used to use the legacy SCP protocol.
+==== List ciphers and Macs on client ====
+  * Ciphers: ssh -Q cipher
+  * MACs: ssh -Q mac
+  * KexAlgorithms: ssh -Q kex
+  * PubkeyAcceptedKeyTypes: ssh -Q key
+You can also remotely probe a ssh server for its supported ciphers with recent nmap versions:
+<cli prompt='#'>
+# nmap --script ssh2-enum-algos -sV -p <port> <host>
+</cli>
+<cli prompt='#'>
+[root@vios]/etc/ssh# ssh -Q cipher
+des-cbc
+aes128-cbc
+aes192-cbc
+aes256-cbc
+aes128-ctr
+aes192-ctr
+aes256-ctr
+aes128-gcm@openssh.com
+aes256-gcm@openssh.com
+chacha20-poly1305@openssh.com
+[root@vios]/etc/ssh# ssh -Q mac
+hmac-sha1
+hmac-sha1-96
+hmac-sha2-256
+hmac-sha2-512
+hmac-md5
+hmac-md5-96
+umac-64@openssh.com
+umac-128@openssh.com
+hmac-sha1-etm@openssh.com
+hmac-sha1-96-etm@openssh.com
+hmac-sha2-256-etm@openssh.com
+hmac-sha2-512-etm@openssh.com
+hmac-md5-etm@openssh.com
+hmac-md5-96-etm@openssh.com
+umac-64-etm@openssh.com
+umac-128-etm@openssh.com
+</cli>
+==== Connection slow ====
+Check using **ssh -vvv <hostname>**, if it hangs on
+  debug1: Next authentication method: gssapi-with-mic
+Change the following parameter in the file **/etc/ssh/sshd_config**
+    GSSAPIAuthentication no
+FIXME On some new Linux versions, check also the files located in the folder **/etc/ssh/sshd_config.d/**

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