DH users are supposed to set a struct dh instance's ->p and ->g domain parameters (as well as the secret ->key), serialize the whole struct dh instance via the crypto_dh_encode_key() helper and pass the encoded blob on to the DH's ->set_secret(). All three currently available DH implementations (generic, drivers/crypto/hisilicon/hpre/ and drivers/crypto/qat/) would then proceed to call the crypto_dh_decode_key() helper for unwrapping the encoded struct dh instance again. Up to now, the only DH user has been the keyctl(KEYCTL_DH_COMPUTE) syscall and thus, all domain parameters have been coming from userspace. The domain parameter encoding scheme for DH's ->set_secret() has been a perfectly reasonable approach in this setting and the potential extra copy of ->p and ->g during the encoding phase didn't harm much. However, recently, the need for working with the well-known safe-prime groups' domain parameters from RFC 3526 and RFC 7919 resp. arose from two independent developments: - The NVME in-band authentication support currently being worked on ([1]) needs to install the RFC 7919 ffdhe groups' domain parameters for DH tfms. - In FIPS mode, there's effectively no sensible way for the DH implementation to conform to SP800-56Arev3 other than rejecting any parameter set not corresponding to some approved safe-prime group specified in either of these two RFCs. As the ->p arrays' lengths are in the range from 256 to 1024 bytes, it would be nice if that extra copy during the crypto_dh_encode_key() step from the NVME in-band authentication code could be avoided. Likewise, it would be great if the DH implementation's FIPS handling code could avoid attempting to match the input ->p and ->g against the individual approved groups' parameters via memcmp() if it's known in advance that the input corresponds to such one, as is the case for NVME. Introduce a enum dh_group_id for referring to any of the safe-prime groups known to the kernel. The introduction of actual such safe-prime groups alongside with their resp. P and G parameters will be deferred to later patches. As of now, the new enum contains only a single member, dh_group_id_unknown, which is meant to be associated with parameter sets not corresponding to any of the groups known to the kernel, as is needed to continue to support the current keyctl(KEYCTL_DH_COMPUTE) syscall semantics. Add a new 'group_id' member of type enum group_id to struct dh. Make crypto_dh_encode_key() include it in the serialization and to encode ->p and ->g only if it equals dh_group_id_unknown. For all other possible values of the encoded ->group_id, the receiving decoding primitive, crypto_dh_decode_key(), is made to not decode ->p and ->g from the encoded data, but to look them up in a central registry instead. The intended usage pattern is that users like NVME wouldn't set any of the struct dh's ->p or ->g directly, but only the ->group_id for the group they're interested in. They'd then proceed as usual and call crypto_dh_encode_key() on the struct dh instance, pass the encoded result on to DH's ->set_secret() and the latter would then invoke crypto_dh_decode_key(), which would then in turn lookup the parameters associated with the passed ->group_id. Note that this will avoid the extra copy of the ->p and ->g for the groups (to be made) known to the kernel and also, that a future patch can easily introduce a validation of ->group_id if in FIPS mode. As mentioned above, the introduction of actual safe-prime groups will be deferred to later patches, so for now, only introduce an empty placeholder array safe_prime_groups[] to be queried by crypto_dh_decode_key() for domain parameters associated with a given ->group_id as outlined above. Make its elements to be of the new internal struct safe_prime_group type. Among the members ->group_id, ->p and ->p_size with obvious meaning, there will also be a ->max_strength member for storing the maximum security strength supported by the associated group -- its value will be needed for the upcoming private key generation support. Finally, update the encoded secrets provided by the testmgr's DH test vectors in order to account for the additional ->group_id field expected by crypto_dh_decode_key() now. [1] https://lkml.kernel.org/r/20211122074727.25988-4-hare@xxxxxxx Signed-off-by: Nicolai Stange <nstange@xxxxxxx> --- crypto/dh_helper.c | 88 +++++++++++++++++++++++++++++++++++---------- crypto/testmgr.h | 16 +++++---- include/crypto/dh.h | 6 ++++ 3 files changed, 86 insertions(+), 24 deletions(-) diff --git a/crypto/dh_helper.c b/crypto/dh_helper.c index aabc91e4f63f..a6c9389d8219 100644 --- a/crypto/dh_helper.c +++ b/crypto/dh_helper.c @@ -10,7 +10,32 @@ #include <crypto/dh.h> #include <crypto/kpp.h> -#define DH_KPP_SECRET_MIN_SIZE (sizeof(struct kpp_secret) + 3 * sizeof(int)) +#define DH_KPP_SECRET_MIN_SIZE (sizeof(struct kpp_secret) + \ + sizeof(enum dh_group_id) + 3 * sizeof(int)) + +static const struct safe_prime_group +{ + enum dh_group_id group_id; + unsigned int max_strength; + unsigned int p_size; + const char *p; +} safe_prime_groups[] = {}; + +/* 2 is used as a generator for all safe-prime groups. */ +static const char safe_prime_group_g[] = { 2 }; + +static inline const struct safe_prime_group * +get_safe_prime_group(enum dh_group_id group_id) +{ + int i; + + for (i = 0; i < ARRAY_SIZE(safe_prime_groups); ++i) { + if (safe_prime_groups[i].group_id == group_id) + return &safe_prime_groups[i]; + } + + return NULL; +} static inline u8 *dh_pack_data(u8 *dst, u8 *end, const void *src, size_t size) { @@ -28,7 +53,10 @@ static inline const u8 *dh_unpack_data(void *dst, const void *src, size_t size) static inline unsigned int dh_data_size(const struct dh *p) { - return p->key_size + p->p_size + p->g_size; + if (p->group_id == dh_group_id_unknown) + return p->key_size + p->p_size + p->g_size; + else + return p->key_size; } unsigned int crypto_dh_key_len(const struct dh *p) @@ -50,13 +78,18 @@ int crypto_dh_encode_key(char *buf, unsigned int len, const struct dh *params) return -EINVAL; ptr = dh_pack_data(ptr, end, &secret, sizeof(secret)); + ptr = dh_pack_data(ptr, end, ¶ms->group_id, + sizeof(params->group_id)); ptr = dh_pack_data(ptr, end, ¶ms->key_size, sizeof(params->key_size)); ptr = dh_pack_data(ptr, end, ¶ms->p_size, sizeof(params->p_size)); ptr = dh_pack_data(ptr, end, ¶ms->g_size, sizeof(params->g_size)); ptr = dh_pack_data(ptr, end, params->key, params->key_size); - ptr = dh_pack_data(ptr, end, params->p, params->p_size); - ptr = dh_pack_data(ptr, end, params->g, params->g_size); + if (params->group_id == dh_group_id_unknown) { + ptr = dh_pack_data(ptr, end, params->p, params->p_size); + ptr = dh_pack_data(ptr, end, params->g, params->g_size); + } + if (ptr != end) return -EINVAL; return 0; @@ -75,12 +108,45 @@ int crypto_dh_decode_key(const char *buf, unsigned int len, struct dh *params) if (secret.type != CRYPTO_KPP_SECRET_TYPE_DH) return -EINVAL; + ptr = dh_unpack_data(¶ms->group_id, ptr, sizeof(params->group_id)); ptr = dh_unpack_data(¶ms->key_size, ptr, sizeof(params->key_size)); ptr = dh_unpack_data(¶ms->p_size, ptr, sizeof(params->p_size)); ptr = dh_unpack_data(¶ms->g_size, ptr, sizeof(params->g_size)); if (secret.len != crypto_dh_key_len(params)) return -EINVAL; + if (params->group_id == dh_group_id_unknown) { + /* Don't allocate memory. Set pointers to data within + * the given buffer + */ + params->key = (void *)ptr; + params->p = (void *)(ptr + params->key_size); + params->g = (void *)(ptr + params->key_size + params->p_size); + + /* + * Don't permit 'p' to be 0. It's not a prime number, + * and it's subject to corner cases such as 'mod 0' + * being undefined or crypto_kpp_maxsize() returning + * 0. + */ + if (memchr_inv(params->p, 0, params->p_size) == NULL) + return -EINVAL; + + } else { + const struct safe_prime_group *g; + + g = get_safe_prime_group(params->group_id); + if (!g) + return -EINVAL; + + params->key = (void *)ptr; + + params->p = g->p; + params->p_size = g->p_size; + params->g = safe_prime_group_g; + params->g_size = sizeof(safe_prime_group_g); + } + /* * Don't permit the buffer for 'key' or 'g' to be larger than 'p', since * some drivers assume otherwise. @@ -89,20 +155,6 @@ int crypto_dh_decode_key(const char *buf, unsigned int len, struct dh *params) params->g_size > params->p_size) return -EINVAL; - /* Don't allocate memory. Set pointers to data within - * the given buffer - */ - params->key = (void *)ptr; - params->p = (void *)(ptr + params->key_size); - params->g = (void *)(ptr + params->key_size + params->p_size); - - /* - * Don't permit 'p' to be 0. It's not a prime number, and it's subject - * to corner cases such as 'mod 0' being undefined or - * crypto_kpp_maxsize() returning 0. - */ - if (memchr_inv(params->p, 0, params->p_size) == NULL) - return -EINVAL; return 0; } diff --git a/crypto/testmgr.h b/crypto/testmgr.h index 7f7d5ae48721..a8983c8626fa 100644 --- a/crypto/testmgr.h +++ b/crypto/testmgr.h @@ -1244,13 +1244,15 @@ static const struct kpp_testvec dh_tv_template[] = { .secret = #ifdef __LITTLE_ENDIAN "\x01\x00" /* type */ - "\x11\x02" /* len */ + "\x15\x02" /* len */ + "\x00\x00\x00\x00" /* group_id == dh_group_id_unknown */ "\x00\x01\x00\x00" /* key_size */ "\x00\x01\x00\x00" /* p_size */ "\x01\x00\x00\x00" /* g_size */ #else "\x00\x01" /* type */ - "\x02\x11" /* len */ + "\x02\x15" /* len */ + "\x00\x00\x00\x00" /* group_id == dh_group_id_unknown */ "\x00\x00\x01\x00" /* key_size */ "\x00\x00\x01\x00" /* p_size */ "\x00\x00\x00\x01" /* g_size */ @@ -1342,7 +1344,7 @@ static const struct kpp_testvec dh_tv_template[] = { "\xd3\x34\x49\xad\x64\xa6\xb1\xc0\x59\x28\x75\x60\xa7\x8a\xb0\x11" "\x56\x89\x42\x74\x11\xf5\xf6\x5e\x6f\x16\x54\x6a\xb1\x76\x4d\x50" "\x8a\x68\xc1\x5b\x82\xb9\x0d\x00\x32\x50\xed\x88\x87\x48\x92\x17", - .secret_size = 529, + .secret_size = 533, .b_public_size = 256, .expected_a_public_size = 256, .expected_ss_size = 256, @@ -1351,13 +1353,15 @@ static const struct kpp_testvec dh_tv_template[] = { .secret = #ifdef __LITTLE_ENDIAN "\x01\x00" /* type */ - "\x11\x02" /* len */ + "\x15\x02" /* len */ + "\x00\x00\x00\x00" /* group_id == dh_group_id_unknown */ "\x00\x01\x00\x00" /* key_size */ "\x00\x01\x00\x00" /* p_size */ "\x01\x00\x00\x00" /* g_size */ #else "\x00\x01" /* type */ - "\x02\x11" /* len */ + "\x02\x15" /* len */ + "\x00\x00\x00\x00" /* group_id == dh_group_id_unknown */ "\x00\x00\x01\x00" /* key_size */ "\x00\x00\x01\x00" /* p_size */ "\x00\x00\x00\x01" /* g_size */ @@ -1449,7 +1453,7 @@ static const struct kpp_testvec dh_tv_template[] = { "\x5e\x5a\x64\xbd\xf6\x85\x04\xe8\x28\x6a\xac\xef\xce\x19\x8e\x9a" "\xfe\x75\xc0\x27\x69\xe3\xb3\x7b\x21\xa7\xb1\x16\xa4\x85\x23\xee" "\xb0\x1b\x04\x6e\xbd\xab\x16\xde\xfd\x86\x6b\xa9\x95\xd7\x0b\xfd", - .secret_size = 529, + .secret_size = 533, .b_public_size = 256, .expected_a_public_size = 256, .expected_ss_size = 256, diff --git a/include/crypto/dh.h b/include/crypto/dh.h index 67f3f6bca527..15d8b2dfe4a2 100644 --- a/include/crypto/dh.h +++ b/include/crypto/dh.h @@ -19,6 +19,11 @@ * the KPP API function call of crypto_kpp_set_secret. */ +/** enum dh_group_id - identify well-known domain parameter sets */ +enum dh_group_id { + dh_group_id_unknown = 0, +}; + /** * struct dh - define a DH private key * @@ -30,6 +35,7 @@ * @g_size: Size of DH generator G */ struct dh { + enum dh_group_id group_id; const void *key; const void *p; const void *g; -- 2.26.2
