[Buildroot] [PATCH v2 3/3] system cfg: remove mkpasswd MD5 format option

[Matt Weber]

As SHA256 is now default, removing weak MD5 option.  C libraries now
all support the SHA methods.
    glibc 2.7+
    uclibc (bdd8362a88 package/uclibc: defconfig: enable sha-256...)
    musl 1.1.14+

One issue this would prevent, is a host tool issue with a FIPS enabled
system where weak ciphers/methods are disabled. It seems the crypt(3)
call is impacted by /proc/sys/crypto/fips_enabled (per crypt(3) man
page). It results in mkpasswd returning "(EPERM) crypt failed."
Rather then create a Buildroot host dependency check, this patch
removes the potential corner case from being selected.

Acked-by: "Yann E. MORIN" <yann.morin.1998 at free.fr>
Cc: "Yann E. MORIN" <yann.morin.1998 at free.fr>
Signed-off-by: Matthew Weber <matthew.weber at rockwellcollins.com>
---
Changes
v1 -> v2
 - Updated description wording
---
 Config.in.legacy |  8 ++++++++
 system/Config.in | 10 ----------
 2 files changed, 8 insertions(+), 10 deletions(-)

diff --git a/Config.in.legacy b/Config.in.legacy
index 02321c8..d70654c 100644
--- a/Config.in.legacy
+++ b/Config.in.legacy
@@ -143,6 +143,14 @@ comment "----------------------------------------------------"
 endif
 
 ###############################################################################
+
+config BR2_TARGET_GENERIC_PASSWD_MD5
+	bool "target passwd md5 format support has been removed"
+	select BR2_LEGACY
+	help
+	  The default has been moved to SHA256 and all C libraries
+	  now support that method by default
+
 comment "Legacy options removed in 2018.11"
 
 config BR2_TARGET_XLOADER
diff --git a/system/Config.in b/system/Config.in
index 65c92a8..0f77b9b 100644
--- a/system/Config.in
+++ b/system/Config.in
@@ -68,16 +68,6 @@ choice
 
 	  Note: this is used at build-time, and *not* at runtime.
 
-config BR2_TARGET_GENERIC_PASSWD_MD5
-	bool "md5"
-	help
-	  Use MD5 to encode passwords.
-
-	  The default. Wildly available, and pretty good.
-	  Although pretty strong, MD5 is now an old hash function, and
-	  suffers from some weaknesses, which makes it susceptible to
-	  brute-force attacks.
-
 config BR2_TARGET_GENERIC_PASSWD_SHA256
 	bool "sha-256"
 	help
-- 
1.9.1