Hello *,
thanks for the comments.
To avoid some misunderstandings here: The patch changes the content of the DEFAULT cipher list of OpenSSL. This list is used by programs such as curl and wget for establishing TLS sessions. As far as I know, it does not have effect on VPN components such as IPsec.
Further, insecure algorithm (3DES, RC4, MD5, ...) are still supported by OpenSSL, since we have not disabled them during the compilation support, which I aim to do in another patch.
In case a program uses one of those algorithm, it still works. This is because the DEFAULT cipher list does not contain all ciphers supported by OpenSSL, but those which are chosen if no specific algorithm keywords (HIGH, !aNULL, ...) are used.
The negative impacts of this patch are: (a) It might break TLS connections to _very_ outdated server which still require weak and/or broken ciphers. But, as it was in similar situations, that is the problem of those who operate the servers.
At the moment, I am not aware of such servers IPFire connects to by default. Please drop me a line if I missed one.
(b) Looking at the cipher list attached to the patch, you probably notice that TLS 1.2 ciphers without PFS (AES256-GCM and similar) are listed after TLS 1.0 ciphers with PFS.
While this does not necessarily have performance impacts, it is - with regard to security - a matter of discussion. In my point of view, it is better to use a cipher provides PFS (the transmitted contents cannot be decrypted afterwards) but uses a weak message digest algorithm (SHA1) than using a TLS 1.2 cipher with secure algos, but an attacker "just" need to steal the private key and is able to decrypt the contents.
Unfortunately, and this is basically why patches like this are necessary, OpenSSL has a very bad concept of sorting cipher suites: It just looks at the encryption algorithm (AES, CAMELLIA, ...) and its strength. For example, if you look at a snippet of the output of "openssl ciphers -v 'HIGH:!aNULL:!eNULL:!EXP:!PSK:!SRP:!DSS'":
[...] ECDH-RSA-AES256-SHA384 TLSv1.2 Kx=ECDH/RSA Au=ECDH Enc=AES(256) Mac=SHA384 ECDH-ECDSA-AES256-SHA384 TLSv1.2 Kx=ECDH/ECDSA Au=ECDH Enc=AES(256) Mac=SHA384 ECDH-RSA-AES256-SHA SSLv3 Kx=ECDH/RSA Au=ECDH Enc=AES(256) Mac=SHA1 ECDH-ECDSA-AES256-SHA SSLv3 Kx=ECDH/ECDSA Au=ECDH Enc=AES(256) Mac=SHA1 AES256-GCM-SHA384 TLSv1.2 Kx=RSA Au=RSA Enc=AESGCM(256) Mac=AEAD AES256-SHA256 TLSv1.2 Kx=RSA Au=RSA Enc=AES(256) Mac=SHA256 AES256-SHA SSLv3 Kx=RSA Au=RSA Enc=AES(256) Mac=SHA1 CAMELLIA256-SHA SSLv3 Kx=RSA Au=RSA Enc=Camellia(256) Mac=SHA1 ECDHE-RSA-AES128-GCM-SHA256 TLSv1.2 Kx=ECDH Au=RSA Enc=AESGCM(128) Mac=AEAD ECDHE-ECDSA-AES128-GCM-SHA256 TLSv1.2 Kx=ECDH Au=ECDSA Enc=AESGCM(128) Mac=AEAD ECDHE-RSA-AES128-SHA256 TLSv1.2 Kx=ECDH Au=RSA Enc=AES(128) Mac=SHA256 ECDHE-ECDSA-AES128-SHA256 TLSv1.2 Kx=ECDH Au=ECDSA Enc=AES(128) Mac=SHA256 ECDHE-RSA-AES128-SHA SSLv3 Kx=ECDH Au=RSA Enc=AES(128) Mac=SHA1 ECDHE-ECDSA-AES128-SHA SSLv3 Kx=ECDH Au=ECDSA Enc=AES(128) Mac=SHA1 [...]
Do you see it? AES256-* is preferred over the PFS-providing cipher ECDHE-RSA-AES128-... because the encryption algorithm is somewhat weaker that that one above. OpenSSL does not care weather SHA1 is used, no PFS is present, or anything else.
Because of that, we need to build cipher suites (for web applications, client programs, and much more) by hand. <sarcasm>Of couse, we don't do security here...</sarcasm>
In case there are any questions left, or you disagree with something, let me know.
Best regards, Peter Müller
What would be the negative implications of this patch? Would existing tunnels on production servers stop working?
On Jan 21, 2018, at 2:55 PM, Paul Simmons mbatranch@gmail.com wrote:
On Sun, 2018-01-21 at 19:08 +0000, Michael Tremer wrote: Hello,
since there usually is a few people being opinionated about this sort of changes, I will wait a little until we get the comments in. Let's say a week.
Best, -Michael
On Sat, 2018-01-20 at 15:28 +0100, Peter Müller wrote: Only use secure cipher list for the OpenSSL DEFAULT list:
- ECDSA is preferred over RSA since it is faster and more scalable
- TLS 1.2 suites are preferred over anything older
- weak ciphers such as RC4 and 3DES have been eliminated
- AES-GCM is preferred over AES-CBC (known as "mac-then-encrypt"
problem)
- ciphers without PFS are moved to the end of the cipher list
The DEFAULT cipher list is now ("openssl ciphers -v"):
ECDHE-ECDSA-AES256-GCM-SHA384 TLSv1.2 Kx=ECDH Au=ECDSA Enc=AESGCM(256) Mac=AEAD ECDHE-ECDSA-AES256-SHA384 TLSv1.2 Kx=ECDH Au=ECDSA Enc=AES(256) Mac=SHA384 ECDHE-ECDSA-AES128-GCM-SHA256 TLSv1.2 Kx=ECDH Au=ECDSA Enc=AESGCM(128) Mac=AEAD ECDHE-ECDSA-AES128-SHA256 TLSv1.2 Kx=ECDH Au=ECDSA Enc=AES(128) Mac=SHA256 ECDHE-RSA-AES256-GCM-SHA384 TLSv1.2 Kx=ECDH Au=RSA Enc=AESGCM(256) Mac=AEAD ECDHE-RSA-AES256-SHA384 TLSv1.2 Kx=ECDH Au=RSA Enc=AES(256) Mac=SHA384 ECDHE-RSA-AES128-GCM-SHA256 TLSv1.2 Kx=ECDH Au=RSA Enc=AESGCM(128) Mac=AEAD ECDHE-RSA-AES128-SHA256 TLSv1.2 Kx=ECDH Au=RSA Enc=AES(128) Mac=SHA256 DHE-RSA-AES256-GCM-SHA384 TLSv1.2 Kx=DH Au=RSA Enc=AESGCM(256) Mac=AEAD DHE-RSA-AES256-SHA256 TLSv1.2 Kx=DH Au=RSA Enc=AES(256) Mac=SHA256 DHE-RSA-AES128-GCM-SHA256 TLSv1.2 Kx=DH Au=RSA Enc=AESGCM(128) Mac=AEAD DHE-RSA-AES128-SHA256 TLSv1.2 Kx=DH Au=RSA Enc=AES(128) Mac=SHA256 ECDHE-ECDSA-AES256-SHA SSLv3 Kx=ECDH Au=ECDSA Enc=AES(256) Mac=SHA1 ECDHE-ECDSA-AES128-SHA SSLv3 Kx=ECDH Au=ECDSA Enc=AES(128) Mac=SHA1 ECDHE-RSA-AES256-SHA SSLv3 Kx=ECDH Au=RSA Enc=AES(256) Mac=SHA1 ECDHE-RSA-AES128-SHA SSLv3 Kx=ECDH Au=RSA Enc=AES(128) Mac=SHA1 DHE-RSA-AES256-SHA SSLv3 Kx=DH Au=RSA Enc=AES(256) Mac=SHA1 DHE-RSA-CAMELLIA256-SHA SSLv3 Kx=DH Au=RSA Enc=Camellia(256) Mac=SHA1 DHE-RSA-AES128-SHA SSLv3 Kx=DH Au=RSA Enc=AES(128) Mac=SHA1 DHE-RSA-CAMELLIA128-SHA SSLv3 Kx=DH Au=RSA Enc=Camellia(128) Mac=SHA1 AES256-GCM-SHA384 TLSv1.2 Kx=RSA Au=RSA Enc=AESGCM(256) Mac=AEAD AES256-SHA256 TLSv1.2 Kx=RSA Au=RSA Enc=AES(256) Mac=SHA256 AES128-GCM-SHA256 TLSv1.2 Kx=RSA Au=RSA Enc=AESGCM(128) Mac=AEAD AES128-SHA256 TLSv1.2 Kx=RSA Au=RSA Enc=AES(128) Mac=SHA256 AES256-SHA SSLv3 Kx=RSA Au=RSA Enc=AES(256) Mac=SHA1 CAMELLIA256-SHA SSLv3 Kx=RSA Au=RSA Enc=Camellia(256) Mac=SHA1 AES128-SHA SSLv3 Kx=RSA Au=RSA Enc=AES(128) Mac=SHA1 CAMELLIA128-SHA SSLv3 Kx=RSA Au=RSA Enc=Camellia(128) Mac=SHA1
This has been discussed at 2017-12-04 (https://wiki.ipfire.org/deve l/telco/2017-12-04).
Signed-off-by: Peter Müller peter.mueller@link38.eu Cc: Michael Tremer michael.tremer@ipfire.org
lfs/openssl | 2 +- src/patches/openssl-1.0.2n-weak-ciphers.patch | 12 ++++++++++++ 2 files changed, 13 insertions(+), 1 deletion(-) create mode 100644 src/patches/openssl-1.0.2n-weak-ciphers.patch
diff --git a/lfs/openssl b/lfs/openssl index 6050768ec..65d738d0f 100644 --- a/lfs/openssl +++ b/lfs/openssl @@ -126,7 +126,7 @@ $(TARGET) : $(patsubst %,$(DIR_DL)/%,$(objects)) @rm -rf $(DIR_APP) && cd $(DIR_SRC) && tar zxf $(DIR_DL)/$(DL_FILE) cd $(DIR_APP) && patch -Np1 < $(DIR_SRC)/src/patches/openssl-1.0.0-beta5-enginesdir.patch cd $(DIR_APP) && patch -Np1 < $(DIR_SRC)/src/patches/openssl-1.0.2a-rpmbuild.patch
- cd $(DIR_APP) && patch -Np1 <
$(DIR_SRC)/src/patches/openssl-1.0.2h-weak-ciphers.patch
- cd $(DIR_APP) && patch -Np1 <
$(DIR_SRC)/src/patches/openssl-1.0.2n-weak-ciphers.patch cd $(DIR_APP) && patch -Np1 < $(DIR_SRC)/src/patches/openssl-1.0.2g-disable-sslv2v3.patch
# i586 specific patches diff --git a/src/patches/openssl-1.0.2n-weak-ciphers.patch b/src/patches/openssl-1.0.2n-weak-ciphers.patch new file mode 100644 index 000000000..9fb4051e3 --- /dev/null +++ b/src/patches/openssl-1.0.2n-weak-ciphers.patch @@ -0,0 +1,12 @@ +diff -Naur openssl-1.0.2n-orig/ssl/ssl.h openssl-1.0.2n/ssl/ssl.h +--- openssl-1.0.2n-orig/ssl/ssl.h 2017-12-07 14:16:42.000000000 +0100 ++++ openssl-1.0.2n/ssl/ssl.h 2018-01-20 11:56:02.477927590 +0100 +@@ -338,7 +338,7 @@
- The following cipher list is used by default. It also is
substituted when
- an application-defined cipher list string starts with
'DEFAULT'.
- */
+-# define SSL_DEFAULT_CIPHER_LIST "ALL:!EXPORT:!LOW:!aNULL:!eNULL:!SSLv2" ++# define SSL_DEFAULT_CIPHER_LIST "kEECDH+ECDSA:kEECDH:kEDH:HIGH:+SHA:+kRSA:!aNULL:!eNULL:!LOW:!3DES: !MD5:!EXP:!PSK:!SRP:!kECDH:!IDEA:!SEED:!RC4:!kDH:!DSS"
- /*
- As of OpenSSL 1.0.0, ssl_create_cipher_list() in
ssl/ssl_ciph.c always
- starts with a reasonable order, and all we have to do for
DEFAULT is
Since some IPFire users are ignorant of the latest and greatest security discussions, implementing this patch will help many of us to adhere to best practices. Therefore, I support this patch.
Best, Paul Simmons