[PATCH 2/9] nvme-keyring: add 'dhchap' key type
Hannes Reinecke
hare at suse.de
Thu Nov 27 00:06:19 PST 2025
On 11/26/25 08:46, Sagi Grimberg wrote:
>
>
> On 28/05/2025 17:05, Hannes Reinecke wrote:
>> Add a 'dhchap' keytype to store DH-HMAC-CHAP secret keys.
>> Keys are stored with a 'user-type' compatible payload, such
>> that one can use 'user_read()' to access the raw contents
>> and the 'read()' callback to get the base64-encoded key
>> data in the DH-HMAC-CHAP secret representation.
>>
>> Signed-off-by: Hannes Reinecke <hare at kernel.org>
>> ---
>> drivers/nvme/common/keyring.c | 266 ++++++++++++++++++++++++++++++++++
>> include/linux/nvme-keyring.h | 22 ++-
>> 2 files changed, 287 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/nvme/common/keyring.c b/drivers/nvme/common/
>> keyring.c
>> index 32d16c53133b..a58c93c6d495 100644
>> --- a/drivers/nvme/common/keyring.c
>> +++ b/drivers/nvme/common/keyring.c
>> @@ -4,6 +4,9 @@
>> */
>> #include <linux/module.h>
>> +#include <linux/crc32.h>
>> +#include <linux/base64.h>
>> +#include <linux/unaligned.h>
>> #include <linux/seq_file.h>
>> #include <linux/key-type.h>
>> #include <keys/user-type.h>
>> @@ -252,6 +255,262 @@ key_serial_t nvme_tls_psk_default(struct key
>> *keyring,
>> }
>> EXPORT_SYMBOL_GPL(nvme_tls_psk_default);
>> +static void nvme_dhchap_psk_describe(const struct key *key, struct
>> seq_file *m)
>> +{
>> + seq_puts(m, key->description);
>> + seq_printf(m, ": %u", key->datalen);
>> +}
>> +
>> +static bool nvme_dhchap_psk_match(const struct key *key,
>> + const struct key_match_data *match_data)
>> +{
>> + const char *match_id;
>> + size_t match_len;
>> +
>> + if (!key->description) {
>> + pr_debug("%s: no key description\n", __func__);
>> + return false;
>> + }
>> + if (!match_data->raw_data) {
>> + pr_debug("%s: no match data\n", __func__);
>> + return false;
>> + }
>> + match_id = match_data->raw_data;
>> + match_len = strlen(match_id);
>> + pr_debug("%s: match '%s' '%s' len %zd\n",
>> + __func__, match_id, key->description, match_len);
>> +
>> + return !memcmp(key->description, match_id, match_len);
>> +}
>> +
>> +static int nvme_dhchap_psk_match_preparse(struct key_match_data
>> *match_data)
>> +{
>> + match_data->lookup_type = KEYRING_SEARCH_LOOKUP_ITERATE;
>> + match_data->cmp = nvme_dhchap_psk_match;
>> + return 0;
>> +}
>> +
>> +/**
>> + * nvme_dhchap_psk_preparse - prepare DH-HMAC-CHAP key data
>> + * @prep: preparsed payload of the key data
>> + *
>> + * Decode the DH-HMAC-CHAP key data passed in in @prep and
>> + * store the resulting binary data. The binary data includes
>> + * space for the CRC, the version, and the hmac identifier,
>> + * but the data length is just the key data without the CRC.
>> + * This allows the user to read the key data via the
>> + * 'user_read()' function, but also to export the full
>> + * key data including CRC via the 'read' callback from the key type.
>> + */
>> +static int nvme_dhchap_psk_preparse(struct key_preparsed_payload *prep)
>> +{
>> + struct user_key_payload *upayload;
>> + size_t datalen = prep->datalen, keylen;
>> + int ret;
>> + u32 crc;
>> + u8 version, hmac;
>> +
>> + if (!prep->data) {
>> + pr_debug("%s: Empty data", __func__);
>> + prep->payload.data[0] = NULL;
>> + prep->quotalen = 0;
>> + return -EINVAL;
>> + }
>> +
>> + if (sscanf(prep->data, "DHHC-%01hhu:%02hhu:%*s", &version,
>> &hmac) != 2) {
>> + pr_debug("%s: invalid key data '%s'\n", __func__,
>> + (char *)prep->data);
>> + prep->payload.data[0] = NULL;
>> + prep->quotalen = 0;
>> + return -EINVAL;
>> + }
>> +
>> + /* skip header and final ':' character */
>> + datalen -= 11;
>> +
>> + /* keylen is the key length, 4 bytes CRC, 1 byte version, and 1
>> byte HMAC identifier */
>> + switch (datalen) {
>> + case 48:
>> + keylen = 38;
>> + break;
>> + case 72:
>> + keylen = 54;
>> + break;
>> + case 92:
>> + keylen = 70;
>> + break;
>> + default:
>
> This feels like random arithmetic Hannes. Really really really hard to
> review this code
> and understand if it is correct without trying to decipher the bits/
> bytes of the payload.
>
> Can we introduce well documented macros/helpers to make this code more
> explainable?
>
Sure, will do.
>> + pr_debug("%s: Invalid data length %lu\n", __func__, datalen);
>> + prep->payload.data[0] = NULL;
>> + prep->quotalen = 0;
>> + return -EINVAL;
>> + }
>> +
>> + upayload = kzalloc(sizeof(*upayload) + keylen, GFP_KERNEL);
>> + if (!upayload) {
>> + prep->payload.data[0] = NULL;
>> + prep->quotalen = 0;
>> + return -ENOMEM;
>> + }
>> +
>> + /* decode the data */
>> + prep->quotalen = keylen;
>> + prep->payload.data[0] = upayload;
>> + ret = base64_decode(prep->data + 10, datalen, upayload->data);
>> + if (ret < 0) {
>> + pr_debug("%s: Failed to decode key %s\n",
>> + __func__, (char *)prep->data + 10);
>> + return ret;
>> + }
>> + ret -= 4;
>> + crc = ~crc32(~0, upayload->data, ret);
>> + if (get_unaligned_le32(upayload->data + ret) != crc) {
>> + pr_debug("%s: CRC mismatch for key\n", __func__);
>> + /* CRC mismatch */
>> + return -EKEYREJECTED;
>> + }
>> + upayload->data[ret + 4] = version;
>> + upayload->data[ret + 5] = hmac;
>
> Again some more inline random arithmetic.
>
I described it briefly in the function description, but will
be updating it to give a detailed layout of the keys.
>> + upayload->datalen = ret;
>> + return 0;
>> +}
>> +
>> +static long nvme_dhchap_psk_read(const struct key *key, char *buffer,
>> size_t buflen)
>> +{
>> + const struct user_key_payload *upayload;
>> + size_t datalen, keylen;
>> + u8 version, hmac;
>> + long ret;
>> +
>> + upayload = user_key_payload_locked(key);
>> + switch (upayload->datalen) {
>> + case 32:
>> + keylen = 59;
>
> Some more random arithmetic...
>
See above, will be moved into a helper function.
>> + break;
>> + case 48:
>> + keylen = 83;
>> + break;
>> + case 64:
>> + keylen = 103;
>> + break;
>> + default:
>> + return -EINVAL;
>> + }
>> +
>> + if (!buffer || buflen == 0)
>> + return keylen;
>> +
>> + if (buflen < keylen)
>> + return -EINVAL;
>> +
>> + memset(buffer, 0, buflen);
>> + version = upayload->data[upayload->datalen + 4];
>> + hmac = upayload->data[upayload->datalen + 5];
>> + ret = sprintf(buffer, "DHHC-%01hhu:%02hhu:", version, hmac);
>> + if (ret < 0)
>> + return -ENOKEY;
>> + /* Include the trailing CRC */
>> + datalen = upayload->datalen + 4;
>> + ret += base64_encode(upayload->data, datalen, buffer + ret);
>> + buffer[ret] = ':';
>> + ret++;
>> + return ret;
>> +}
>> +
>> +static struct key_type nvme_dhchap_psk_key_type = {
>> + .name = "dhchap",
>> + .flags = KEY_TYPE_NET_DOMAIN,
>> + .preparse = nvme_dhchap_psk_preparse,
>> + .free_preparse = user_free_preparse,
>> + .match_preparse = nvme_dhchap_psk_match_preparse,
>> + .instantiate = generic_key_instantiate,
>> + .revoke = user_revoke,
>> + .destroy = user_destroy,
>> + .describe = nvme_dhchap_psk_describe,
>> + .read = nvme_dhchap_psk_read,
>> +};
>> +
>> +struct key *nvme_dhchap_psk_refresh(struct key *keyring,
>> + const u8 *data, size_t data_len)
>
> Is there a call-site to this? I don't see one...
>
Hmm. I thought there was, but I'll check.
Will be moving it into the patch requiring it.
>> +{
>> + key_perm_t keyperm =
>> + KEY_POS_SEARCH | KEY_POS_VIEW | KEY_POS_READ |
>> + KEY_POS_WRITE | KEY_POS_LINK | KEY_POS_SETATTR |
>> + KEY_USR_SEARCH | KEY_USR_VIEW | KEY_USR_READ;
>> + char *identity;
>> + key_ref_t keyref;
>> + key_serial_t keyring_id;
>> + struct key *key;
>> + uuid_t key_uuid;
>> +
>> + if (data == NULL || !data_len)
>> + return ERR_PTR(-EINVAL);
>> +
>> + generate_random_uuid(key_uuid.b);
>> + identity = kasprintf(GFP_KERNEL, "%pU", &key_uuid);
>> + if (!identity)
>> + return ERR_PTR(-ENOMEM);
>> + if (!keyring)
>> + keyring = nvme_keyring;
>> + keyring_id = key_serial(keyring);
>> +
>> + pr_debug("keyring %x generate dhchap psk '%s'\n",
>> + keyring_id, identity);
>> + keyref = key_create(make_key_ref(keyring, true),
>> + "dhchap", identity, data, data_len,
>> + keyperm, KEY_ALLOC_NOT_IN_QUOTA |
>> + KEY_ALLOC_BUILT_IN |
>> + KEY_ALLOC_BYPASS_RESTRICTION);
>> + if (IS_ERR(keyref)) {
>> + pr_warn("refresh dhchap psk '%s' failed, error %ld\n",
>> + identity, PTR_ERR(keyref));
>> + kfree(identity);
>> + return ERR_PTR(-ENOKEY);
>> + }
>> + key = key_ref_to_ptr(keyref);
>> + pr_debug("generated dhchap psk %08x\n", key_serial(key));
>> + kfree(identity);
>> + return key;
>> +}
>> +EXPORT_SYMBOL_GPL(nvme_dhchap_psk_refresh);
>> +
>> +struct key *nvme_dhchap_psk_lookup(struct key *keyring, const char
>> *identity)
>
> Same...
>
See above. Will be moving it into the patch requiring it.
Cheers,
Hannes
--
Dr. Hannes Reinecke Kernel Storage Architect
hare at suse.de +49 911 74053 688
SUSE Software Solutions GmbH, Frankenstr. 146, 90461 Nürnberg
HRB 36809 (AG Nürnberg), GF: I. Totev, A. McDonald, W. Knoblich
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