IMA: remove the dependency on CRYPTO_MD5

MD5 is a weak digest algorithm that shouldn't be used for cryptographic
operation. It hinders the efficiency of a patch set that aims to limit
the digests allowed for the extended file attribute namely security.ima.
MD5 is no longer a requirement for IMA, nor should it be used there.

The sole place where we still use the MD5 algorithm inside IMA is setting
the ima_hash algorithm to MD5, if the user supplies 'ima_hash=md5'
parameter on the command line.  With commit ab60368 ("ima: Fallback
to the builtin hash algorithm"), setting "ima_hash=md5" fails gracefully
when CRYPTO_MD5 is not set:
	ima: Can not allocate md5 (reason: -2)
	ima: Allocating md5 failed, going to use default hash algorithm sha256

Remove the CRYPTO_MD5 dependency for IMA.

Signed-off-by: THOBY Simon <[email protected]>
Reviewed-by: Lakshmi Ramasubramanian <[email protected]>
[[email protected]: include commit number in patch description for
stable.]
Cc: [email protected] # 4.17
Signed-off-by: Mimi Zohar <[email protected]>

security/integrity/ima/Kconfig

@@ -6,7 +6,6 @@ config IMA
 	select SECURITYFS
 	select CRYPTO
 	select CRYPTO_HMAC
-	select CRYPTO_MD5
 	select CRYPTO_SHA1
 	select CRYPTO_HASH_INFO
 	select TCG_TPM if HAS_IOMEM && !UML