New answers tagged

1

Aside from SNI, there is an option to get a multi-domain certificate. Several certificate providers offer such certificates (not endorsing anyone, Google is your friend). With a multi-domain certificate, you don't need to know the domain name at the beginning of the handshake, as the certificate is effectively valid for all the domain names listed. Here's ...


0

Wether or not a given x509 certificate can be used for the client side of a Client authed SSL connection depends on the Key Usage and Extended Key Usage options placed on the certificate by the issuing CA. You can examine an x509 cert using openssl x509 -in certfile.pem -text The Key Usage options refer to various operations that the cert is allowed to be ...


7

Without SNI, the domain first appears in cleartext in the Server Hello of the TLS handshake (In the rdnSequence of the Certificate field). With SNI, the domain first appears in cleartext in the Client Hello of the TLS handshake (In the SNI field). Source: I fired up apache2 with TLS and took packet captures before and after implementing SNI (Virtual Hosts ...


12

Yes, as long as the server and the clients support the Server-Name-Indication (or SNI) extension. This extension allows for virtual hosting for HTTPS, where you have multiple independent domains and certifications bound to a single IP address. Most clients these days do support SNI. The place where you might have issues is if you have older clients ...


0

I had the same question and discovered that mxtoolbox.com (now) provides an interface to query an SMTP server and report on whether it supports TLS. That's the only evidence we seem to be able to present that TLS is in place.


1

I just wanted to sum up the current state on this issue: A F5-engineer filed a bug at Microsoft regarding this issue that can be found here. It seems MS has accepted it and is working on a solution, so it really seems to be an SCHANNEL-issue. A possible client-side workaround seems to be to reduce the expected DH-keylength by setting the registry-value ...


1

The Firefox error is likely the key to the issue. It looks like the cert you have been given is tied to the API implementation using a custom critical extension. The x509 spec requires users of a cert to fail the operation if they encounter an extension marked critical that they do not understand. More info in rfc 5280 Look at the problem cert with openssl ...


1

Checking manual page for ssh-keygen gives hints about generating and verifying the parameters (moduli file): ssh-keygen -G moduli-2048.candidates -b 2048 ssh-keygen -T moduli-2048 -f moduli-2048.candidates which sounds for me like a proven way of doing this. But I also discourage you from doing that. The examples what can go wrong are answered in related ...


1

After reading this post you provided, they only seem to be doing MITM and re-signing the certificates that Skype is using during the transmission (something really common when we use HTTP/S proxies), but in this case, for other TCP traffic that is not HTTP. TCPcatcher may help you, more specifically, this tutorial (as a guidance, but applying for Skype ...


2

protocol HTTPS protects against connecting to false server ? It depends on what you consider a false server but given this weak phrase I would suggest the answer should be NO. Lets's see what you get with https and what you get not: You get that the browser checks if the hostname of the URL matches the certificates subject and if this certificate is ...


4

[Disclaimer: I'm one of the mitmproxy authors. My opinions may be biased. :)] sslsplit sslsplit is a transparent proxy that can intercept TLS connections using a man-in-the-middle attack. sslsplit supports plain TCP, TLS and also HTTP to the extent that it removes HPKP, HSTS and Alternate Protocol response headers. Intercepted connections can be dumped ...


1

We all need a little context. There is a difference between "untrusted" and secure. And "Trusted" does not necessarily imply Secure (or Authentic) A self-signed certificate on an isolated network with only one server and one client is probably more secure than any "trusted" certificate. And "trusted" implies ONLY that a Certificate Authority Certificate ...


1

I like to rely on the auto-fill feature of my password manager for this check. The rationale is that I will not be clever enough to match the site URL in the browser to the expected one, while a password manager will. So when I see that it has filled in the entry for the site - the site is genuine, otherwise I should start to worry. The password manager ...


0

First, quit using FTP entirely. The most common choice is to use SFTP instead Disable weak cipher suites like ones using RC4. There are other hardening steps you can take as well. The next common choice is to use FTPS instead. Disable weak cipher suites like ones using RC4. There are other hardening steps you can take as well. If you would like, you ...


2

Self-signed certificates can't be trusted because anyone is able to craft one. An attacker performing a MITM attack could easily replace any certificate by a self-signed one and impersonate any website you're browsing, even if you're using HTTPS. That's why we are using trusted Certificate Authorities to ensure that certificates cannot be falsified.


1

Both will do what you need effectively. Whether you need to use one over the other depends on your use case. From what you have described, as long as there aren't other requirements, I'd go with TLS, as it requires very little additional work on most network architectures. IPSec is just a little more convoluted to set up - but it does provide additional ...


4

Shorter answer. A lot of answers here, but none seems to get straight to the point: Without a neutral and recognized third party—such as a certificate authority—verifying certificate ownership, a certificate is meaningless. Longer answer. To better understand, when doing something like creating an HTTPS connection you have the following chain: A client ...


0

It seems they are different tools which achieve the same result. They don't really break TLS though. Both tools just perform a MITM, initiate the TLS handshake to the server and then send the victim a HTTP page. So if the victim is aware he will notice a missing green key in his browser. To avoid these types of attacks, HSTS was invented which forces the ...


8

Actually, self-signed certificates can be secure, just not under the model we're using now. Under the wide-spread CA (certificate authority) model that everyone uses currently, the purpose of the certificate being signed by a trusted CA is to provide authentication. When we get a certificate, all we really see is 1's and 0's coming in from the jack in ...


2

Any application must be given the list of "root certificates" to be trusted. In case of a browser, there is a defined list that comes by default with any browser, but this list does not contain your certificate. Imagine you don't need to actually give the list of certificates that you trust, then anyone would be able to setup a https website that an ...


30

Self-signed certificates are inherently not trusted by your browser because a certificate itself doesn't form any trust, the trust comes from being signed by a certificate that EVERYONE trusts. Your browser simply doesn't trust your self-signed certificate as if it were a root certificate. To make your browser accept your certificate, go into your browsers ...


38

You need to import the root certificate into the trust store for the browser. Once the browser knows you trust this root certificate, all certificates signed by this will show up as trusted. Note that this will only make the connection trusted for you, any others who don't have the root certificate installed will still receive an error.


0

Check out Let's Encrypt https://letsencrypt.org (currently in beta). Let's Encrypt is a non-profit that gives out SSL certs for free, and whose goal is widespread adoption of TLS security and to ease the pain of certificate configuration by allowing automatic config and renewal. I have not used this service yet, but it sounds promising, and is sponsored by ...


3

Making a new protocol to replace SSL/TLS would make sense only if the new protocol was "better" in some substantial way. Though SSL/TLS has a few known shortcomings, making anything better is harder (much harder) than it may seem. And people who are working on that have decided that it should still be called TLS. TLS-1.3, to be precise.


2

The best practice is to trust the root CA, for very practical reasons. Root CAs are a special beast and are expected to have very long lifetimes (20 years or more) because they require replacement in the client software, which is usually a manual process. Intermediate and server certificates are expected to change frequently - in some cases (load ...


1

If you want to trust any certificate issued by A or B you put these into the trust store. If you want to accept only this specific certificate as trusted than you should only add this certificate. But you are right that you get problems when the certificates gets renewed. If you just want to trust this specific certificate only but want to accept it also if ...


2

As far as I understand the aim of LoadRunner (i.e. the software which VuGen is part of) is to simulate a real client like a browser. If a browser connects first to a web site which requires a client certificate then the browser has to interact with the user to find out which certificate should be used and to get the password for the private key. In this case ...


6

There is a very extensive article at Wikipedia and it does not make sense to reiterate everything here. But to give you some highlights: It replaces OpenSSL on OpenBSD, OS X since 10.11 and on some other systems. It started with throwing away lots of stuff which was considered useless for the target platforms or insecure by design and it also added some ...


3

The whole grading mechanism is more propaganda and public relations than actual security. If you want good security, then you must mind the details and understand how things work internally. If you want a good grade then you should do whatever it takes to have a good grade. An "A+" from SSL Labs is a very nifty thing to add at the end of a report, but it ...


2

Flexible SSL does not provide end-to-end encryption. From here: you can see that the CloudFlare link to the server is unencrypted. However, as the user link to CloudFlare is, this mitigates most typical Man-In-The-Middle scenarios. For example, ranging from Mallory on the coffee shop wifi connection, to rogue employees at an ISP, all the way up to ...


0

Steve DM's answer (checking and bookmarking the page) is better from an absolute security standpoint, but another viable (and possibly more user friendly) option is to tell them to Google the bank every time instead of clicking on a link. This way, you rely on Google taking you to the right place rather than some shady link and your observational skills. ...


2

Essentially your question is one of authentication. In this case, it's users authenticating the bank website is actually the bank. I think you're right, and the user is going to have difficulty in authenticating the bank through the URL (many banks have multiple URLs for instance). You're also correct that users aren't terribly sophisticated about URLs, ...


4

How can I identify the cipher mode which is used by TLS? There are many ways to enumerate your cipher suites and protocols enabled on your sever. Here are solutions that are assessment or script based that have little overhead and are light on the technical requirements. If it is externally available: Try out SSL Labs' test here: ...


25

I was going to suggest that ensuring that the login screen for the online banking system showed the name of the bank in green, in the address bar might work. But then I started wondering if any of the local banks I know about did that properly. It's less encouraging than I'd hoped. For these nine fairly large banks, 6 provide the name of the bank in the ...


35

Why security indicators fail vs. phishing There is no action that can be taken that is economically viable. Put another way, it's too effortful to defend against phishing attacks. See 'So long and no thanks for the externalities' for an example on the US economy and information workers. You are correct that checking for URL correctness is error-prone, and ...


-2

Yes. Use an app that is definitely connecting to the site. Or. Check the https. Verify the url. Make sure the url is short enough to visually see tampering. Also, maybe some examples of homographic attacks.


1

NONE cipher can be available in opera 12. It is disabled by default. There seems to be TLS_RSA_NULL_SHA and SHA2, I have only tested sha. For test server, I used openssl s_server, it also requires some special configuration (NULL cipher not enabled by default). Even, when connection successfully, there were some security warning, in browser. openssl used was ...


2

First, SSL stopped at version 3.0, which is massively flawed. TLS is currently at 1.2 (plus a lot of activity in the TLS 1.3 working group). This is generally a matter of acronym - hopefully when you say SSL encrypted, you actually mean TLS, and you specifically mean TLS 1.2 with AEAD ciphers. Second, for TLS of any type, both protocol version and cipher ...


2

It's not really related to Active Directory or Group Policy. That's just one way to do it. If someone can install their own root cert in your trusted store(s) then they can issue fake certs and everything thing looks legit. See Charles Proxy. One legit use for this is to allow tools like Snort to monitor encrypted traffic on a network. Some applications ...


2

This got me thinking, if I was on a public network somewhere, could they issue their own certificate making it appear trusted, and therefore giving me a green padlock on my bank site for example? Yes. does it appear trusted because of a group policy telling the PC to trust the cert? Yes. (Or some other mechanism telling the PC to trust the cert. ...


1

This is a subset of the TLS (or SSL, for really out of date setups) cipher suite negotiation. I go into more detail in My answer to Recommended ssl_ciphers for security, compatibility - Perfect Forward secrecy, but the long and short of it is: Per the TLS 1.2 document RFC 5246 starting at section 7.4.1.2 to see, in the short short form, the cipher suite ...


4

Is it supported by any browsers for accessing any web-sites over the https:// address scheme? I think you are referring to TLS_NULL_WITH_NULL_NULL or similar ciphers were no encryption is done. None of the current browsers offers this cipher and I don't think that there will be a reason in the future to offer such more than weak ciphers because you ...


1

It highly depends on the kind of data you offer for downloading and what kind of trust relationship there is between the user and your site. Just take a closer look at what HTTPS offers and what not: It offers some kind of privacy through encryption. If the data are already encrypted by other means then you don't need another layer of encryption. If the ...


2

Mandatory encryption presents at least one thing that non-encrypted communication doesn't. Truly encrypted communication (at least http over SSL) is impossible to cache and requires more bandwidth. Requiring SSL/TLS would limit the case for non-sensitive information from being cached by some intermediate proxy server. Encryption also has a cost. It adds ...


8

There is no technical reason to limit HTTP/2 to TLS. Communication without TLS has its technical use, no matter if this is unencrypted traffic or if the traffic is encrypted by other means (VPN etc). Restricting HTTP/2 to TLS in the standard would bind the use of the HTTP/2 protocol to the use of TLS for political(*) reasons only. Such bindings for ...


0

An X.509 certificate is a format for sharing a public key along with the name of the entity that holds that public/private key pair and optional extensions such as usage. It is usually signed by a certificate authority in order that it is trusted. A X.509 certificate is used in many applications that rely on public/private keys for authentication and/or ...


0

X509 is the type for SSL certificates, these can differ in the purpose they have. When using a SSL connection with a server you use a X509 certificate with the purpose of server authentication: TLS Web Server Authentication (1.3.6.1.5.5.7.3.1) when using it for client authentication (2 way SSL) you need a certificate with TLS Web Client Authentication ...


7

My guess is that this site is using Server Name Indication (SNI). In this case the served certificates depends on the hostname specified in the SNI extension and will often differ if no SNI extension is used. I.e. it will be some completely different default certificate or it will be some old certificate because they only replaced the certificate used for ...


4

If you are using OpenVPN for your organization it is probably better not to use any public certificates for OpenVPN but create your own CA and only accept certificates issued by this CA. This is actually the way proposed in the OpenVPN Howto. This way you are in full control of the certificates and even if some of the public CA's gets compromised and issues ...



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