[PATCH 7/8] DRBG: remove configuration of fixed values

[Stephan Mueller <smueller@chronox.de>]

SP800-90A mandates several hard-coded values. The old drbg_cores allows
the setting of these values per DRBG implementation. However, due to the
hard requirement of SP800-90A, these values are now returned globally
for each DRBG.

The ability to set such values per DRBG is therefore removed.

Signed-off-by: Stephan Mueller <smueller@chronox.de>
---
 crypto/drbg.c         | 33 ---------------------------------
 include/crypto/drbg.h | 19 ++++++-------------
 2 files changed, 6 insertions(+), 46 deletions(-)

diff --git a/crypto/drbg.c b/crypto/drbg.c
index f74859d..a556180 100644
--- a/crypto/drbg.c
+++ b/crypto/drbg.c
@@ -117,27 +117,18 @@ static const struct drbg_core drbg_cores[] = {
 	{
 		.flags = DRBG_CTR | DRBG_STRENGTH128,
 		.statelen = 32, /* 256 bits as defined in 10.2.1 */
-		.max_addtllen = 35,
-		.max_bits = 19,
-		.max_req = 48,
 		.blocklen_bytes = 16,
 		.cra_name = "ctr_aes128",
 		.backend_cra_name = "ecb(aes)",
 	}, {
 		.flags = DRBG_CTR | DRBG_STRENGTH192,
 		.statelen = 40, /* 320 bits as defined in 10.2.1 */
-		.max_addtllen = 35,
-		.max_bits = 19,
-		.max_req = 48,
 		.blocklen_bytes = 16,
 		.cra_name = "ctr_aes192",
 		.backend_cra_name = "ecb(aes)",
 	}, {
 		.flags = DRBG_CTR | DRBG_STRENGTH256,
 		.statelen = 48, /* 384 bits as defined in 10.2.1 */
-		.max_addtllen = 35,
-		.max_bits = 19,
-		.max_req = 48,
 		.blocklen_bytes = 16,
 		.cra_name = "ctr_aes256",
 		.backend_cra_name = "ecb(aes)",
@@ -147,36 +138,24 @@ static const struct drbg_core drbg_cores[] = {
 	{
 		.flags = DRBG_HASH | DRBG_STRENGTH128,
 		.statelen = 55, /* 440 bits */
-		.max_addtllen = 35,
-		.max_bits = 19,
-		.max_req = 48,
 		.blocklen_bytes = 20,
 		.cra_name = "sha1",
 		.backend_cra_name = "sha1",
 	}, {
 		.flags = DRBG_HASH | DRBG_STRENGTH256,
 		.statelen = 111, /* 888 bits */
-		.max_addtllen = 35,
-		.max_bits = 19,
-		.max_req = 48,
 		.blocklen_bytes = 48,
 		.cra_name = "sha384",
 		.backend_cra_name = "sha384",
 	}, {
 		.flags = DRBG_HASH | DRBG_STRENGTH256,
 		.statelen = 111, /* 888 bits */
-		.max_addtllen = 35,
-		.max_bits = 19,
-		.max_req = 48,
 		.blocklen_bytes = 64,
 		.cra_name = "sha512",
 		.backend_cra_name = "sha512",
 	}, {
 		.flags = DRBG_HASH | DRBG_STRENGTH256,
 		.statelen = 55, /* 440 bits */
-		.max_addtllen = 35,
-		.max_bits = 19,
-		.max_req = 48,
 		.blocklen_bytes = 32,
 		.cra_name = "sha256",
 		.backend_cra_name = "sha256",
@@ -186,36 +165,24 @@ static const struct drbg_core drbg_cores[] = {
 	{
 		.flags = DRBG_HMAC | DRBG_STRENGTH128,
 		.statelen = 20, /* block length of cipher */
-		.max_addtllen = 35,
-		.max_bits = 19,
-		.max_req = 48,
 		.blocklen_bytes = 20,
 		.cra_name = "hmac_sha1",
 		.backend_cra_name = "hmac(sha1)",
 	}, {
 		.flags = DRBG_HMAC | DRBG_STRENGTH256,
 		.statelen = 48, /* block length of cipher */
-		.max_addtllen = 35,
-		.max_bits = 19,
-		.max_req = 48,
 		.blocklen_bytes = 48,
 		.cra_name = "hmac_sha384",
 		.backend_cra_name = "hmac(sha384)",
 	}, {
 		.flags = DRBG_HMAC | DRBG_STRENGTH256,
 		.statelen = 64, /* block length of cipher */
-		.max_addtllen = 35,
-		.max_bits = 19,
-		.max_req = 48,
 		.blocklen_bytes = 64,
 		.cra_name = "hmac_sha512",
 		.backend_cra_name = "hmac(sha512)",
 	}, {
 		.flags = DRBG_HMAC | DRBG_STRENGTH256,
 		.statelen = 32, /* block length of cipher */
-		.max_addtllen = 35,
-		.max_bits = 19,
-		.max_req = 48,
 		.blocklen_bytes = 32,
 		.cra_name = "hmac_sha256",
 		.backend_cra_name = "hmac(sha256)",
diff --git a/include/crypto/drbg.h b/include/crypto/drbg.h
index 831d786..3d8e73a 100644
--- a/include/crypto/drbg.h
+++ b/include/crypto/drbg.h
@@ -82,15 +82,6 @@ typedef uint32_t drbg_flag_t;
 struct drbg_core {
 	drbg_flag_t flags;	/* flags for the cipher */
 	__u8 statelen;		/* maximum state length */
-	/*
-	 * maximum length of personalization string or additional input
-	 * string -- exponent for base 2
-	 */
-	__u8 max_addtllen;
-	/* maximum bits per RNG request -- exponent for base 2*/
-	__u8 max_bits;
-	/* maximum number of requests -- exponent for base 2 */
-	__u8 max_req;
 	__u8 blocklen_bytes;	/* block size of output in bytes */
 	char cra_name[CRYPTO_MAX_ALG_NAME]; /* mapping to kernel crypto API */
 	 /* kernel crypto API backend cipher name */
@@ -156,18 +147,20 @@ static inline __u8 drbg_keylen(struct drbg_state *drbg)
 
 static inline size_t drbg_max_request_bytes(struct drbg_state *drbg)
 {
-	/* max_bits is in bits, but buflen is in bytes */
-	return (1 << (drbg->core->max_bits - 3));
+	/* SP800-90A requires the limit 2**19 bits, but we return bytes */
+	return (1 << 16);
 }
 
 static inline size_t drbg_max_addtl(struct drbg_state *drbg)
 {
-	return (1UL<<(drbg->core->max_addtllen));
+	/* SP800-90A requires 2**35 bytes additional info str / pers str */
+	return (1UL<<35);
 }
 
 static inline size_t drbg_max_requests(struct drbg_state *drbg)
 {
-	return (1UL<<(drbg->core->max_req));
+	/* SP800-90A requires 2**48 maximum requests before reseeding */
+	return (1UL<<48);
 }
 
 /*
-- 
1.9.3