Jun 25, 2014 a security scan turned up two ssh vulnerabilities. This is thrown because nxos maintains old hashing algorithms like hmac md5 and hmacsha196 for backwards compatibility with older ssh clients. The remote ssh server is configured to allow md5 and 96bit mac algorithms. How to check ssh weak mac algorithms enabled redhat 7. What does aes256ctshmacsha196 mean in relation to kerberos.
Can someone please tell me how to disable this in aix 5. Secure configuration of ciphersmacskex available in servu disable any 96bit hmac algorithms. The ssh server is configured to allow either md5 or 96bit mac algorithms, how to verify. Backdoors with the ms office file encryption master key and a. Using usm for authentication and message privacy oracle. Note that this plugin only checks for the options of the ssh server, and it does not check for vulnerable software versions. Check supported algorithms in openssh tanvinh nguyen. The system will attempt to use the different hmac algorithms in the sequence they are specified on the line. In the system management agent, the message digest implementation is hmac md5 96.
How do i disable md5 andor 96bit mac algorithms on a centos 6. Therefore, the authors recommend disabling dh group 1. Managing ssh security configurations involves managing the ssh key exchange algorithms and data encryption algorithms also known as ciphers. This is part two of securing ssh in the server hardening series. How to disable ssh cipher mac algorithms airheads community. Ssh weak mac algorithms enabled contact the vendor or consult product documentation to disable md5 and 96bit mac algorithms. To this end, the following is the default list for supported ciphers. I have a security requirement to disable all 96 bit and md5 hash algorithms in ssh.
The internal audit department has scanned the switches for security assessment and found the vulnerability the remote ssh server is configured to allow md5 and 96bit mac algorithms. In doing so it will detect the cryptographic properties that the server would like to use, in your typical out of the box setup cbc cipher block chaining encryption mode and md5 or 96bit mac message authentication code algorithms will be configured, both of which are considered weak. How to disable 96bit hmac algorithms and md5 based hmac algorithms on solaris sshd doc id 1682164. If option 4 is selected then delete the lines from the 5thcolumn from the file etcsshmoduli where bit size is. Our internal network security team has idntified vulnerability regarding the ssh server within the catalyst switches. Hello, i have a security requirement to disable all 96 bit and md5 hash algorithms in ssh.
The ssh server code is not based on openssh but is instead based on the ssh secure shell toolkit version 4. I have to prepare some file transfers within the company. Solution contact the vendor or consult product documentation to disable md5 and 96bit mac algorithms. Contact the vendor or consult product documentation to disable md5 and 96bit mac algorithms. Contact the vendor or consult product documentation to disable cbc mode cipher encryption, and enable ctr or gcm cipher mode encryption. How to disable 96bit hmac algorithms and md5based hmac. The administrator was talking about mandatory cipher suites aes128cbc and aes256cbc. Need to disable cbc mode cipher encryption along with md5.
Join more than 150,000 members who help it professionals do their jobs better. The highest encryption type used by active directory domain controllers for kerberos authentication traffic is aes256cts hmac sha1 96. How to check mac algorithm is enabled in ssh or not. We have installed cisco 2960x stack able switches in our organization. Based on the ssh scan result you may want to disable these encryption algorithms or ciphers. In the first section of this answer ill assume that through better hardware or and algorithmic improvements, it has become routinely feasible to exhibit a collision for sha1 by a method similar to that of xiaoyun wang, yiqun lisa yin, and hongbo yus attack, or marc stevenss attack. Cscvc79012 disable md5 and 96bit mac algorithms on fmc and ftd. How to disable md5based hmac algorithms for ssh the geek.
Based on md5, this oneway encryption uses a 96bit hash a 16 octet key length. How to disable md5based hmac algorithms for ssh the. Configuring the cisco asa ssh server to accept only version 2 is best practice. Data ontap enables you to enable or disable individual ssh key exchange algorithms and ciphers for the storage virtual machine svm according to their ssh security requirements. This is a short post on how to disable md5based hmac algorithms for ssh on linux. Ssh weak mac algorithms enabled, the ssh server is configured to allow either md5 or 96bit mac algorithms, both of which are considered weak. How to disable ssh weak mac algorithms hewlett packard. Ssh insecure hmac algorithms enabled ssh cbc mode ciphers enabled below is the update from a security scanner regarding the vulnerabilities vulnerability name. Secure configuration of ciphersmacskex available in ssh. Hardening ssh mac algorithms red hat customer portal. Ssh is configured to allow md5 and 96bit mac algorithms. Disable root login and unsing only a standard user account. Gtacknowledge is there any way to configure the mac. Allowagentforwarding specifies whether sshagent1 forwarding is permitted.
Using openssl to generate hmac using a binary key if you want to do a quick commandline generation of a hmac, then the openssl command is useful. The remote ssh server is configured to allow either md5 or 96bit mac algorithms, both of which are considered weak. Thats aes with a 256 bit symmetric key operating in cipher text stealing mode. Computationally, no two messages can have the same message digest. The solution was to disable any 96bit hmac algorithms. Addressing false positives from cbc and mac vulnerability scans. This is a short post on how to disable md5based hmac algorithm s for ssh on linux.
Plugin output the following clienttoserver method authentication code mac algorithms are supported. This version of ssh is implemented based on draftietfsecshtransport14. As per the vulnerability team ssh is configured to allow md5 and 96bit mac algorithms for client to server communication. Current nist recommendation is to use 2048bit or above. Customer detects vulnerable algorithms in his vulnerability scan. I am looking for a configuration that will satisfy their scans. Can someone please tell me how to disabl the unix and linux forums. Hostkeyalgorithms specifies the host key algorithms that the server offers. Make sure you have updated openssh package to latest available version. By joining our community you will have the ability to post topics, receive our newsletter, use the advanced search, subscribe to threads and access many other special features. Note that disabling agent forwarding does not im prove security unless users. Received a vulnerability ssh insecure hmac algorithms enabled.