linux-kernel - [PATCH 2/2] crypto: make the sha1 library optional

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Date:   Sat,  9 Jul 2022 14:18:49 -0700
From:   Eric Biggers <ebiggers@...nel.org>
To:     linux-crypto@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
        "Jason A . Donenfeld " <Jason@...c4.com>
Subject: [PATCH 2/2] crypto: make the sha1 library optional

From: Eric Biggers <ebiggers@...gle.com>

Since the Linux RNG no longer uses sha1_transform(), the SHA-1 library
is no longer needed unconditionally.  Make it possible to build the
Linux kernel without the SHA-1 library by putting it behind a kconfig
option, and selecting this new option from the kconfig options that gate
the remaining users: CRYPTO_SHA1 for crypto/sha1_generic.c, BPF for
kernel/bpf/core.c, and IPV6 for net/ipv6/addrconf.c.

Unfortunately, since BPF is selected by NET, for now this can only make
a difference for kernels built without networking support.

Signed-off-by: Eric Biggers <ebiggers@...gle.com>
---
 crypto/Kconfig      | 1 +
 init/Kconfig        | 1 +
 lib/crypto/Kconfig  | 3 +++
 lib/crypto/Makefile | 3 ++-
 net/ipv6/Kconfig    | 1 +
 5 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/crypto/Kconfig b/crypto/Kconfig
index 59489a300cd100..bf15ca5eb9d367 100644
--- a/crypto/Kconfig
+++ b/crypto/Kconfig
@@ -880,6 +880,7 @@ config CRYPTO_RMD160
 config CRYPTO_SHA1
 	tristate "SHA1 digest algorithm"
 	select CRYPTO_HASH
+	select CRYPTO_LIB_SHA1
 	help
 	  SHA-1 secure hash standard (FIPS 180-1/DFIPS 180-2).
 
diff --git a/init/Kconfig b/init/Kconfig
index c984afc489dead..d8d0b4bdfe4195 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1472,6 +1472,7 @@ config HAVE_PCSPKR_PLATFORM
 # interpreter that classic socket filters depend on
 config BPF
 	bool
+	select CRYPTO_LIB_SHA1
 
 menuconfig EXPERT
 	bool "Configure standard kernel features (expert users)"
diff --git a/lib/crypto/Kconfig b/lib/crypto/Kconfig
index 2082af43d51fbe..9ff549f63540fa 100644
--- a/lib/crypto/Kconfig
+++ b/lib/crypto/Kconfig
@@ -121,6 +121,9 @@ config CRYPTO_LIB_CHACHA20POLY1305
 	select CRYPTO_LIB_POLY1305
 	select CRYPTO_ALGAPI
 
+config CRYPTO_LIB_SHA1
+	tristate
+
 config CRYPTO_LIB_SHA256
 	tristate
 
diff --git a/lib/crypto/Makefile b/lib/crypto/Makefile
index d28111ba54fcb2..919cbb2c220d61 100644
--- a/lib/crypto/Makefile
+++ b/lib/crypto/Makefile
@@ -34,7 +34,8 @@ libpoly1305-y					:= poly1305-donna32.o
 libpoly1305-$(CONFIG_ARCH_SUPPORTS_INT128)	:= poly1305-donna64.o
 libpoly1305-y					+= poly1305.o
 
-obj-y						+= sha1.o
+obj-$(CONFIG_CRYPTO_LIB_SHA1)			+= libsha1.o
+libsha1-y					:= sha1.o
 
 obj-$(CONFIG_CRYPTO_LIB_SHA256)			+= libsha256.o
 libsha256-y					:= sha256.o
diff --git a/net/ipv6/Kconfig b/net/ipv6/Kconfig
index bf2e5e5fe14273..658bfed1df8b17 100644
--- a/net/ipv6/Kconfig
+++ b/net/ipv6/Kconfig
@@ -7,6 +7,7 @@
 menuconfig IPV6
 	tristate "The IPv6 protocol"
 	default y
+	select CRYPTO_LIB_SHA1
 	help
 	  Support for IP version 6 (IPv6).
 
-- 
2.37.0