Backdoors with the ms office file encryption master key and a. Our internal network security team has idntified vulnerability regarding the ssh server within the catalyst switches. Customer detects vulnerable algorithms in his vulnerability scan. To resolve this issue, a couple of configuration changes are needed. To this end, the following is the default list for supported ciphers. Disable cbc mode cipher encryption, md5 and 96bit mac. I have to prepare some file transfers within the company. Can someone please tell me how to disable this in aix 5.
I have a security requirement to disable all 96 bit and md5 hash algorithms in ssh. Contact the vendor or consult product documentation to disable cbc mode cipher encryption, and enable ctr or gcm cipher mode encryption. Based on md5, this oneway encryption uses a 96bit hash a 16 octet key length. Solution contact the vendor or consult product documentation to disable md5 and 96bit mac algorithms. What does aes256ctshmacsha196 mean in relation to kerberos. The remote ssh server is configured to allow md5 and 96bit mac algorithms. Plugin output the following clienttoserver method authentication code mac algorithms are supported. How do i disable md5 andor 96bit mac algorithms on a centos 6. The remote ssh server is configured to allow either md5 or 96bit mac algorithms, both of which are considered weak. Ssh insecure hmac algorithms enabled ssh cbc mode ciphers enabled below is the update from a security scanner regarding the vulnerabilities vulnerability name. This is a short post on how to disable md5based hmac algorithm s for ssh on linux.
If option 4 is selected then delete the lines from the 5thcolumn from the file etcsshmoduli where bit size is. Cscvc79012 disable md5 and 96bit mac algorithms on fmc and ftd. Allowagentforwarding specifies whether sshagent1 forwarding is permitted. Managing ssh security configurations involves managing the ssh key exchange algorithms and data encryption algorithms also known as ciphers.
Contact the vendor or consult product documentation to disable md5 and 96bit mac algorithms. Based on the ssh scan result you may want to disable these encryption algorithms or ciphers. 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. Check supported algorithms in openssh tanvinh nguyen. In the system management agent, the message digest implementation is hmac md5 96. Hardening ssh mac algorithms red hat customer portal. The ssh server code is not based on openssh but is instead based on the ssh secure shell toolkit version 4. This version of ssh is implemented based on draftietfsecshtransport14.
How to disable md5based hmac algorithms for ssh the geek. Jun 25, 2014 a security scan turned up two ssh vulnerabilities. Can someone please tell me how to disabl the unix and linux forums. Configuring the cisco asa ssh server to accept only version 2 is best practice. Using usm for authentication and message privacy oracle. How to check mac algorithm is enabled in ssh or not.
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. The highest encryption type used by active directory domain controllers for kerberos authentication traffic is aes256cts hmac sha1 96. Make sure you have updated openssh package to latest available version. The administrator was talking about mandatory cipher suites aes128cbc and aes256cbc. Secure configuration of ciphersmacskex available in ssh. How to check ssh weak mac algorithms enabled redhat 7. This is thrown because nxos maintains old hashing algorithms like hmac md5 and hmacsha196 for backwards compatibility with older ssh clients. This is part two of securing ssh in the server hardening series. Hostkeyalgorithms specifies the host key algorithms that the server offers. Secure configuration of ciphersmacskex available in servu disable any 96bit hmac algorithms. Thats aes with a 256 bit symmetric key operating in cipher text stealing mode. We have installed cisco 2960x stack able switches in our organization. Ssh is configured to allow md5 and 96bit mac algorithms.
Note that disabling agent forwarding does not im prove security unless users. 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. For hmac md5 the rfc summarizes that although the security of the md5 hash function itself is severely compromised the currently known attacks on hmac md5 do not seem to indicate a practical vulnerability when used as a message authentication code, but it also adds that for a new protocol design, a ciphersuite with hmac md5 should. Ssh weak ciphers and mac algorithms uits linux team. How to disable ssh weak mac algorithms hewlett packard. How to disable 96bit hmac algorithms and md5based hmac. The ssh server is configured to allow either md5 or 96bit mac algorithms, both of which are considered weak. Therefore, the authors recommend disabling dh group 1. 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. Disable root login and unsing only a standard user account. 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 ssh server is configured to allow either md5 or 96bit mac algorithms, how to verify. The solution was to disable any 96bit hmac algorithms. The system will attempt to use the different hmac algorithms in the sequence they are specified on the line. Hello, i have a security requirement to disable all 96 bit and md5 hash algorithms in ssh. 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. Computationally, no two messages can have the same message digest. How to disable md5based hmac algorithms for ssh the. Gtacknowledge is there any way to configure the mac.
Received a vulnerability ssh insecure hmac algorithms enabled. Join more than 150,000 members who help it professionals do their jobs better. Current nist recommendation is to use 2048bit or above. Addressing false positives from cbc and mac vulnerability scans. Hello, our client ordered pentest, and as a feedback they got recommendation to disable ssh cbc mode ciphers, and allow only ctr ciphers and disable weak ssh md5 and 96bit mac algorithms on their cisco 4506e switches with cisco ios 15. Ssh weak mac algorithms enabled, the ssh server is configured to allow either md5 or 96bit mac algorithms, both of which are considered weak. As per the vulnerability team ssh is configured to allow md5 and 96bit mac algorithms for client to server communication.