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authorJason A. Donenfeld <Jason@zx2c4.com>2019-11-08 15:22:32 +0300
committerHerbert Xu <herbert@gondor.apana.org.au>2019-11-17 04:02:43 +0300
commit0ed42a6f431e930b2e8fae21955406e09fe75d70 (patch)
treeeff8cd4d432e1ba4788bf968b94a32f223b7f4dc /include/crypto
parented0356eda153f6a95649e11feb7b07083caf9e20 (diff)
downloadlinux-0ed42a6f431e930b2e8fae21955406e09fe75d70.tar.xz
crypto: curve25519 - generic C library implementations
This contains two formally verified C implementations of the Curve25519 scalar multiplication function, one for 32-bit systems, and one for 64-bit systems whose compiler supports efficient 128-bit integer types. Not only are these implementations formally verified, but they are also the fastest available C implementations. They have been modified to be friendly to kernel space and to be generally less horrendous looking, but still an effort has been made to retain their formally verified characteristic, and so the C might look slightly unidiomatic. The 64-bit version comes from HACL*: https://github.com/project-everest/hacl-star The 32-bit version comes from Fiat: https://github.com/mit-plv/fiat-crypto Information: https://cr.yp.to/ecdh.html Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com> [ardb: - move from lib/zinc to lib/crypto - replace .c #includes with Kconfig based object selection - drop simd handling and simplify support for per-arch versions ] Signed-off-by: Ard Biesheuvel <ardb@kernel.org> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Diffstat (limited to 'include/crypto')
-rw-r--r--include/crypto/curve25519.h71
1 files changed, 71 insertions, 0 deletions
diff --git a/include/crypto/curve25519.h b/include/crypto/curve25519.h
new file mode 100644
index 000000000000..4e6dc840b159
--- /dev/null
+++ b/include/crypto/curve25519.h
@@ -0,0 +1,71 @@
+/* SPDX-License-Identifier: GPL-2.0 OR MIT */
+/*
+ * Copyright (C) 2015-2019 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
+ */
+
+#ifndef CURVE25519_H
+#define CURVE25519_H
+
+#include <crypto/algapi.h> // For crypto_memneq.
+#include <linux/types.h>
+#include <linux/random.h>
+
+enum curve25519_lengths {
+ CURVE25519_KEY_SIZE = 32
+};
+
+extern const u8 curve25519_null_point[];
+extern const u8 curve25519_base_point[];
+
+void curve25519_generic(u8 out[CURVE25519_KEY_SIZE],
+ const u8 scalar[CURVE25519_KEY_SIZE],
+ const u8 point[CURVE25519_KEY_SIZE]);
+
+void curve25519_arch(u8 out[CURVE25519_KEY_SIZE],
+ const u8 scalar[CURVE25519_KEY_SIZE],
+ const u8 point[CURVE25519_KEY_SIZE]);
+
+void curve25519_base_arch(u8 pub[CURVE25519_KEY_SIZE],
+ const u8 secret[CURVE25519_KEY_SIZE]);
+
+static inline
+bool __must_check curve25519(u8 mypublic[CURVE25519_KEY_SIZE],
+ const u8 secret[CURVE25519_KEY_SIZE],
+ const u8 basepoint[CURVE25519_KEY_SIZE])
+{
+ if (IS_ENABLED(CONFIG_CRYPTO_ARCH_HAVE_LIB_CURVE25519))
+ curve25519_arch(mypublic, secret, basepoint);
+ else
+ curve25519_generic(mypublic, secret, basepoint);
+ return crypto_memneq(mypublic, curve25519_null_point,
+ CURVE25519_KEY_SIZE);
+}
+
+static inline bool
+__must_check curve25519_generate_public(u8 pub[CURVE25519_KEY_SIZE],
+ const u8 secret[CURVE25519_KEY_SIZE])
+{
+ if (unlikely(!crypto_memneq(secret, curve25519_null_point,
+ CURVE25519_KEY_SIZE)))
+ return false;
+
+ if (IS_ENABLED(CONFIG_CRYPTO_ARCH_HAVE_LIB_CURVE25519))
+ curve25519_base_arch(pub, secret);
+ else
+ curve25519_generic(pub, secret, curve25519_base_point);
+ return crypto_memneq(pub, curve25519_null_point, CURVE25519_KEY_SIZE);
+}
+
+static inline void curve25519_clamp_secret(u8 secret[CURVE25519_KEY_SIZE])
+{
+ secret[0] &= 248;
+ secret[31] = (secret[31] & 127) | 64;
+}
+
+static inline void curve25519_generate_secret(u8 secret[CURVE25519_KEY_SIZE])
+{
+ get_random_bytes_wait(secret, CURVE25519_KEY_SIZE);
+ curve25519_clamp_secret(secret);
+}
+
+#endif /* CURVE25519_H */