dropbear: Disable legacy/insecure options

PATCH New Stefan Sørensen 4 participants 4 messages Jul 3, 2018 – Jul 4, 2018

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Stefan Sørensen

author

2018-07-03 07:48 UTC #0 lore raw

PATCH v3 1/1 dropbear: Disable legacy/insecure options

Dropbear by default enables a number of algorithms that are now considered insecure and should only be used when legacy support is required:
3DES encryption
Blowfish encryption
SHA1-96 message integrity
CBC encryption mode
DSA public keys
Diffie-Hellman Group1 key exchange

So disable them by default, but add a config option for bringing them back. Furthermore the Blowfish legacy algorithm is unconditionally disabled

Signed-off-by Stefan S?rensen <[email protected]>

---
Changes v2->v3:
* Rebase on 037b8616257067282e375edca9af19418a0e7a4a

Changes v1->v2:
* Mention that the Blowfish algorithm has been disabled

 package/dropbear/Config.in   | 10 ++++++++++
 package/dropbear/dropbear.mk | 12 +++++++++++-
 2 files changed, 21 insertions(+), 1 deletion(-)

package/dropbear/Config.in +10 -0

index 5d6b83b6d1..62f77bad9d 100644
@@ -56,4 +56,14 @@ config BR2_PACKAGE_DROPBEAR_LASTLOG
 	  Enable logging of dropbear access to lastlog. Notice that
 	  Buildroot does not generate lastlog by default.
 
+config BR2_PACKAGE_DROPBEAR_LEGACY_CRYPTO
+	bool "enable legacy crypto"
+	help
+	  Enable legacy and possibly insecure algorithms:
+	    3DES encryption
+	    SHA1-96 message integrity
+	    CBC encryption mode
+	    DSA public keys
+	    Diffie-Hellman Group1 key exchange
+
 endif

package/dropbear/dropbear.mk +11 -1

index bb902bc7ce..7b1468cfb1 100644
@@ -56,13 +56,23 @@ endef
 DROPBEAR_POST_EXTRACT_HOOKS += DROPBEAR_SVR_PASSWORD_AUTH
 endif
 
+define DROPBEAR_DISABLE_LEGACY_CRYPTO
+	echo '#define DROPBEAR_3DES 0'                  >> $(@D)/localoptions.h
+	echo '#define DROPBEAR_ENABLE_CBC_MODE 0'       >> $(@D)/localoptions.h
+	echo '#define DROPBEAR_SHA1_96_HMAC 0'          >> $(@D)/localoptions.h
+	echo '#define DROPBEAR_DSS 0'                   >> $(@D)/localoptions.h
+	echo '#define DROPBEAR_DH_GROUP1 0'             >> $(@D)/localoptions.h
+endef
+ifneq ($(BR2_PACKAGE_DROPBEAR_LEGACY_CRYPTO),y)
+DROPBEAR_POST_EXTRACT_HOOKS += DROPBEAR_DISABLE_LEGACY_CRYPTO
+endif
+
 define DROPBEAR_ENABLE_REVERSE_DNS
 	echo '#define DO_HOST_LOOKUP 1'                 >> $(@D)/localoptions.h
 endef
 
 define DROPBEAR_BUILD_FEATURED
 	echo '#define DROPBEAR_SMALL_CODE 0'            >> $(@D)/localoptions.h
-	echo '#define DROPBEAR_BLOWFISH 1'              >> $(@D)/localoptions.h
 	echo '#define DROPBEAR_TWOFISH128 1'            >> $(@D)/localoptions.h
 	echo '#define DROPBEAR_TWOFISH256 1'            >> $(@D)/localoptions.h
 endef

Signature · 1 line

2.17.1

Baruch Siach

2018-07-03 10:38 UTC #1 lore raw

PATCH v3 1/1 dropbear: Disable legacy/insecure options

Hi Stefan,

Quoted 9 lines · Stefan S?rensen

Dropbear by default enables a number of algorithms that are now considered insecure and should only be used when legacy support is required:
3DES encryption
Blowfish encryption
SHA1-96 message integrity
CBC encryption mode
DSA public keys
Diffie-Hellman Group1 key exchange

Quoted 4 lines

So disable them by default, but add a config option for bringing them back. Furthermore the Blowfish legacy algorithm is unconditionally disabled
Signed-off-by Stefan S?rensen <[email protected]>

Reviewed-by Baruch Siach <[email protected]>

baruch

Signature · 3 lines

     http://baruch.siach.name/blog/                  ~. .~   Tk Open Systems
=}------------------------------------------------ooO--U--Ooo------------{=
   - baruch at tkos.co.il - tel: +972.52.368.4656, http://www.tkos.co.il -

Thomas De Schampheleire

2018-07-04 08:45 UTC #2 lore raw

PATCH v3 1/1 dropbear: Disable legacy/insecure options

Quoted 12 lines · Baruch Siach

Hi Stefan,
Quoted 9 lines · Stefan S?rensen
Dropbear by default enables a number of algorithms that are now considered insecure and should only be used when legacy support is required:
3DES encryption
Blowfish encryption
SHA1-96 message integrity
CBC encryption mode
DSA public keys
Diffie-Hellman Group1 key exchange

Quoted 6 lines

Quoted 4 lines
So disable them by default, but add a config option for bringing them back. Furthermore the Blowfish legacy algorithm is unconditionally disabled
Signed-off-by Stefan S?rensen <[email protected]>
Reviewed-by Baruch Siach <[email protected]>

Reviewed-by Thomas De Schampheleire <[email protected]>

Thomas Petazzoni

Applied

2018-07-04 19:44 UTC #3 lore raw

PATCH v3 1/1 dropbear: Disable legacy/insecure options

In reply to Stefan Sørensen

Hello,

Quoted 9 lines · Stefan S?rensen

Dropbear by default enables a number of algorithms that are now considered insecure and should only be used when legacy support is required:
3DES encryption
Blowfish encryption
SHA1-96 message integrity
CBC encryption mode
DSA public keys
Diffie-Hellman Group1 key exchange

Quoted 7 lines

So disable them by default, but add a config option for bringing them back. Furthermore the Blowfish legacy algorithm is unconditionally disabled
Signed-off-by Stefan S?rensen <[email protected]>
---
Changes v2->v3:
* Rebase on 037b8616257067282e375edca9af19418a0e7a4a

Applied to master, thanks.

Thomas

Signature · 3 lines

Thomas Petazzoni, CTO, Bootlin (formerly Free Electrons)
Embedded Linux and Kernel engineering
https://bootlin.com