summaryrefslogtreecommitdiff
path: root/include/crypto
diff options
context:
space:
mode:
authorArd Biesheuvel <ardb@kernel.org>2022-11-03 20:22:59 +0100
committerHerbert Xu <herbert@gondor.apana.org.au>2022-11-11 18:14:59 +0800
commit520af5da664a8edc4f4c1cd8e6e8488ecccdb7e5 (patch)
treeea52545c8ef2669dae4a5630c832f44d43ae217c /include/crypto
parentb67ce439fef69a1a339cf2743c8198e8d90e6821 (diff)
crypto: lib/aesgcm - Provide minimal library implementation
Implement a minimal library version of AES-GCM based on the existing library implementations of AES and multiplication in GF(2^128). Using these primitives, GCM can be implemented in a straight-forward manner. GCM has a couple of sharp edges, i.e., the amount of input data processed with the same initialization vector (IV) should be capped to protect the counter from 32-bit rollover (or carry), and the size of the authentication tag should be fixed for a given key. [0] The former concern is addressed trivially, given that the function call API uses 32-bit signed types for the input lengths. It is still up to the caller to avoid IV reuse in general, but this is not something we can police at the implementation level. As for the latter concern, let's make the authentication tag size part of the key schedule, and only permit it to be configured as part of the key expansion routine. Note that table based AES implementations are susceptible to known plaintext timing attacks on the encryption key. The AES library already attempts to mitigate this to some extent, but given that the counter mode encryption used by GCM operates exclusively on known plaintext by construction (the IV and therefore the initial counter value are known to an attacker), let's take some extra care to mitigate this, by calling the AES library with interrupts disabled. [0] https://nvlpubs.nist.gov/nistpubs/legacy/sp/nistspecialpublication800-38d.pdf Link: https://lore.kernel.org/all/c6fb9b25-a4b6-2e4a-2dd1-63adda055a49@amd.com/ Signed-off-by: Ard Biesheuvel <ardb@kernel.org> Tested-by: Nikunj A Dadhania <nikunj@amd.com> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Diffstat (limited to 'include/crypto')
-rw-r--r--include/crypto/gcm.h22
1 files changed, 22 insertions, 0 deletions
diff --git a/include/crypto/gcm.h b/include/crypto/gcm.h
index 9d7eff04f224..fd9df607a836 100644
--- a/include/crypto/gcm.h
+++ b/include/crypto/gcm.h
@@ -3,6 +3,9 @@
#include <linux/errno.h>
+#include <crypto/aes.h>
+#include <crypto/gf128mul.h>
+
#define GCM_AES_IV_SIZE 12
#define GCM_RFC4106_IV_SIZE 8
#define GCM_RFC4543_IV_SIZE 8
@@ -60,4 +63,23 @@ static inline int crypto_ipsec_check_assoclen(unsigned int assoclen)
return 0;
}
+
+struct aesgcm_ctx {
+ be128 ghash_key;
+ struct crypto_aes_ctx aes_ctx;
+ unsigned int authsize;
+};
+
+int aesgcm_expandkey(struct aesgcm_ctx *ctx, const u8 *key,
+ unsigned int keysize, unsigned int authsize);
+
+void aesgcm_encrypt(const struct aesgcm_ctx *ctx, u8 *dst, const u8 *src,
+ int crypt_len, const u8 *assoc, int assoc_len,
+ const u8 iv[GCM_AES_IV_SIZE], u8 *authtag);
+
+bool __must_check aesgcm_decrypt(const struct aesgcm_ctx *ctx, u8 *dst,
+ const u8 *src, int crypt_len, const u8 *assoc,
+ int assoc_len, const u8 iv[GCM_AES_IV_SIZE],
+ const u8 *authtag);
+
#endif