Month: March 2024

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SSH Error – Receive Packet Type 51 on Rocky Linux 8

If you are having SSH issues and if you turned on high verbosity and the following output is generated

# ssh -vvv XXX.XXX.XXX.XXX
.....
.....
debug1: Offering public key: debug3: send packet: type 50
debug2: we sent a publickey packet, wait for reply
debug3: receive packet: type 51
.....
.....
debug2: we did not send a packet, disable method
debug1: No more authentication methods to try.
user1@192.168.0.1: Permission denied (publickey,gssapi-with-mic,password)

According to SSH protocol (RFC 4252), these are the general authentication message codes

SSH_MSG_USERAUTH_REQUEST            50
SSH_MSG_USERAUTH_FAILURE            51
SSH_MSG_USERAUTH_SUCCESS            52
SSH_MSG_USERAUTH_BANNER             53

It means that the authentiation methods mentioned in the “Permission Denied” was not accepted. What are some of the common issues.

Type 1 (Most Common Mistake): Permission Errors on the .ssh Folder and files inside .ssh

Type 2: Incorrect Configuration Settings on the /etc/ssh/sshd_config
(Assuming you are using Password Authentication) Inside /etc/ssh/sshd_config, you should have something like

PermitRootLogin no
.....
PasswordAuthentication yes
.....
ChallengeResponseAuthentication no
.....
GSSAPIAuthentication yes
GSSAPICleanupCredentials no
.....
UsePAM yes

Type 2: Incorrect Configuration Settings on the /etc/ssh/ssh_config
In Rocky Linux 8, everything should be commented except the last line “Include /etc/ssh/ssh_config.d/*.conf”

References:

  1. How to Fix SSH Failed Permission Denied (publickey,gssapi-keyex,gssapi-with-mic)
  2. ssh receive packet: type 51
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GLIBCXX_3.4.25 and cannot support c++17.GLIBCXX Issues

If you have compiled a new appication in an updated GCC-12.3 and still wondering why the Error still surfacing like the message below when you run the binary that was compiled in the GCC-12.3 and not the system GCC: 

GLIBCXX version in Wildfly using “strings /usr/lib64/libstdc++.so.6 | grep GLIBCXX” and found the latest version in Cluster is only GLIBCXX_3.4.25 and cannot support c++17.

First step in troubleshooting is really to find out what the binary used for its Shared Object Dependencies. 

$ ldd main_fcc
./main_fcc: /lib64/libstdc++.so.6: version `GLIBCXX_3.4.29' not found (required by ./main_fcc)
./main_fcc: /lib64/libstdc++.so.6: version `GLIBCXX_3.4.26' not found (required by ./main_fcc)
	linux-vdso.so.1 (0x00007fffffbd1000)
	libstdc++.so.6 => /lib64/libstdc++.so.6 (0x00007f4827ea1000)
	libm.so.6 => /lib64/libm.so.6 (0x00007f4827b1f000)
	libgomp.so.1 => /lib64/libgomp.so.1 (0x00007f48278e7000)
	libgcc_s.so.1 => /lib64/libgcc_s.so.1 (0x00007f48276cf000)
	libpthread.so.0 => /lib64/libpthread.so.0 (0x00007f48274af000)
	libc.so.6 => /lib64/libc.so.6 (0x00007f48270ea000)
	/lib64/ld-linux-x86-64.so.2 (0x00007f4828236000)
	libdl.so.2 => /lib64/libdl.so.2 (0x00007f4826ee6000)

For the above example, “libstdc++.so.6 => /lib64/libstdc++.so.6 (0x00007f4827ea1000)”, the application seems to be pointing back to the system libraries rather than the libraries you are using. You many want to “module load …….” if you are using Module Environment or configure the PATH, LD_LIBRARY_PATH, MANPATH and CPLUS_INCLUDE_PATH of the GCC you . In the end, the Shared Object Dependencies should be pointing to 

$ ldd main_fcc
        linux-vdso.so.1 (0x00007fffffbd1000)
	libstdc++.so.6 => /usr/local/gnu/gcc-12.3/libstdc++.so.6 (0x00007f4827ea1000)
	libm.so.6 => /usr/local/gnu/gcc-12.3/libm.so.6 (0x00007f4827b1f000)
	libgomp.so.1 => /usr/local/gnu/gcc-12.3/libgomp.so.1 (0x00007f48278e7000)
	libgcc_s.so.1 => /usr/local/gnu/gcc-12.3/libgcc_s.so.1 (0x00007f48276cf000)
	libpthread.so.0 => /usr/local/gnu/gcc-12.3/libpthread.so.0 (0x00007f48274af000)
	libc.so.6 => /usr/local/gnu/gcc-12.3/libc.so.6 (0x00007f48270ea000)
	/lib64/ld-linux-x86-64.so.2 (0x00007f4828236000)
	libdl.so.2 => /usr/local/gnu/gcc-12.3/libdl.so.2 (0x00007f4826ee6000)

We have experience in VS Code Environment, where the Shared Object Dependencies was observed to be pointing back to the System Libraries even when using Environment Modules. Then it is best to put in .bashrc something the one below.

# .bashrc

# Source global definitions
if [ -f /etc/bashrc ]; then
        . /etc/bashrc
fi

# User specific aliases and functions
alias rm='rm -i'
alias cp='cp -i'
alias mv='mv -i'
alias ls='ls --color=auto'
alias egrep='egrep --color=auto'
alias fgrep='fgrep --color=auto'
alias grep='grep --color=auto'

# Uncomment the following line if you don't like systemctl's auto-paging feature:
# export SYSTEMD_PAGER=

module load gnu/gcc-12.3
module load gnu/gdb-14.2

# User specific aliases and functions