Ensure only strong MAC algorithms are used

MediaNivel 1Automatizadalinux

Descripción

This variable limits the types of MAC algorithms that SSH can use during communication.

Cómo se verifica

Método de auditoría: Comando de shell

shell

alt0() { command -v grep >/dev/null 2>&1 || { echo "step1: grep not installed"; return 1; }; command -v sshd >/dev/null 2>&1 || { echo "step1: sshd not installed"; return 1; }; o=$(bash -c 'sshd -T | grep -i "MACs"' 2>&1); printf '%s\n' "$o" | tr -s ' \t' '  ' | sed 's/^ //;s/ $//' | grep -Fxq -- 'Weak MAC algorithms:' || { echo step1: missing 'Weak MAC algorithms:'; return 1; }; printf '%s\n' "$o" | tr -s ' \t' '  ' | sed 's/^ //;s/ $//' | grep -Fxq -- hmac-md5 || { echo step1: missing hmac-md5; return 1; }; printf '%s\n' "$o" | tr -s ' \t' '  ' | sed 's/^ //;s/ $//' | grep -Fxq -- hmac-md5-96 || { echo step1: missing hmac-md5-96; return 1; }; printf '%s\n' "$o" | tr -s ' \t' '  ' | sed 's/^ //;s/ $//' | grep -Fxq -- hmac-ripemd160 || { echo step1: missing hmac-ripemd160; return 1; }; printf '%s\n' "$o" | tr -s ' \t' '  ' | sed 's/^ //;s/ $//' | grep -Fxq -- hmac-sha1 || { echo step1: missing hmac-sha1; return 1; }; printf '%s\n' "$o" | tr -s ' \t' '  ' | sed 's/^ //;s/ $//' | grep -Fxq -- hmac-sha1-96 || { echo step1: missing hmac-sha1-96; return 1; }; printf '%s\n' "$o" | tr -s ' \t' '  ' | sed 's/^ //;s/ $//' | grep -Fxq -- umac-64@openssh.com || { echo step1: missing umac-64@openssh.com; return 1; }; printf '%s\n' "$o" | tr -s ' \t' '  ' | sed 's/^ //;s/ $//' | grep -Fxq -- umac-128@openssh.com || { echo step1: missing umac-128@openssh.com; return 1; }; printf '%s\n' "$o" | tr -s ' \t' '  ' | sed 's/^ //;s/ $//' | grep -Fxq -- hmac-md5-etm@openssh.com || { echo step1: missing hmac-md5-etm@openssh.com; return 1; }; printf '%s\n' "$o" | tr -s ' \t' '  ' | sed 's/^ //;s/ $//' | grep -Fxq -- hmac-md5-96-etm@openssh.com || { echo step1: missing hmac-md5-96-etm@openssh.com; return 1; }; printf '%s\n' "$o" | tr -s ' \t' '  ' | sed 's/^ //;s/ $//' | grep -Fxq -- hmac-ripemd160-etm@openssh.com || { echo step1: missing hmac-ripemd160-etm@openssh.com; return 1; }; printf '%s\n' "$o" | tr -s ' \t' '  ' | sed 's/^ //;s/ $//' | grep -Fxq -- hmac-sha1-etm@openssh.com || { echo step1: missing hmac-sha1-etm@openssh.com; return 1; }; printf '%s\n' "$o" | tr -s ' \t' '  ' | sed 's/^ //;s/ $//' | grep -Fxq -- hmac-sha1-96-etm@openssh.com || { echo step1: missing hmac-sha1-96-etm@openssh.com; return 1; }; printf '%s\n' "$o" | tr -s ' \t' '  ' | sed 's/^ //;s/ $//' | grep -Fxq -- umac-64-etm@openssh.com || { echo step1: missing umac-64-etm@openssh.com; return 1; }; printf '%s\n' "$o" | tr -s ' \t' '  ' | sed 's/^ //;s/ $//' | grep -Fxq -- umac-128-etm@openssh.com || { echo step1: missing umac-128-etm@openssh.com; return 1; }; }; if alt0; then echo compliant; fi

Salida esperada: compliant

Cómo se corrige

Método de corrección: Guía o parche de infraestructura

Edit the /etc/ssh/sshd_config file and add/modify the MACs line to contain a comma separated list of the site approved MACs Example: MACs hmac-sha2-512-etm@openssh.com,hmac-sha2-256-etm@openssh.com,hmac-sha2- 512,hmac-sha2-256 Restart sshd : systemctl restart sshd

Propiedades

Sistemas operativos: alinux-2
Etiquetas: cis-convertedlinux
Referencia: CIS Aliyun Linux 2 Benchmark v1.0.0 ARCHIVE - 5.2.13

Verificar este host

Ejecute esto en un equipo que tenga permiso para auditar. El escaneo es de solo lectura.

shell

tmaegis scan --target linux