[PATCH v2 2/6] s390/uv: Retrieve UV secrets support

Steffen Eiden
2024-10-02T16:05:39Z

Provide a kernel API to retrieve secrets from the UV secret store.
Add two new functions:
* `uv_get_secret_metadata` - get metadata for a given secret identifier
* `uv_retrieve_secret` - get the secret value for the secret index

With those two functions one can extract the secret for a given secret
id, if the secret is retrievable.

Signed-off-by: Steffen Eiden <seiden@linux.ibm.com>
---
arch/s390/include/asm/uv.h | 131 ++++++++++++++++++++++++++++++++++++-
arch/s390/kernel/uv.c | 127 ++++++++++++++++++++++++++++++++++-
2 files changed, 256 insertions(+), 2 deletions(-)

diff --git a/arch/s390/include/asm/uv.h b/arch/s390/include/asm/uv.h
index 94ff58336e8e..aef333aaaef4 100644
--- a/arch/s390/include/asm/uv.h
+++ b/arch/s390/include/asm/uv.h
@@ -62,6 +62,7 @@
#define UVC_CMD_ADD_SECRET 0x1031
#define UVC_CMD_LIST_SECRETS 0x1033
#define UVC_CMD_LOCK_SECRETS 0x1034
+#define UVC_CMD_RETR_SECRET 0x1035

/* Bits in installed uv calls */
enum uv_cmds_inst {
@@ -95,6 +96,7 @@ enum uv_cmds_inst {
BIT_UVC_CMD_ADD_SECRET = 29,
BIT_UVC_CMD_LIST_SECRETS = 30,
BIT_UVC_CMD_LOCK_SECRETS = 31,
+ BIT_UVC_CMD_RETR_SECRETS = 33,
};

enum uv_feat_ind {
@@ -318,7 +320,6 @@ struct uv_cb_dump_complete {
* A common UV call struct for pv guests that contains a single address
* Examples:
* Add Secret
- * List Secrets
*/
struct uv_cb_guest_addr {
struct uv_cb_header header;
@@ -327,6 +328,91 @@ struct uv_cb_guest_addr {
u64 reserved28[4];
} __packed __aligned(8);

+#define UVC_RC_RETR_SECR_BUF_SMALL 0x0109
+#define UVC_RC_RETR_SECR_STORE_EMPTY 0x010f
+#define UVC_RC_RETR_SECR_INV_IDX 0x0110
+#define UVC_RC_RETR_SECR_INV_SECRET 0x0111
+
+struct uv_cb_retr_secr {
+ struct uv_cb_header header;
+ u64 reserved08[2];
+ u16 secret_idx;
+ u16 reserved1a;
+ u32 buf_size;
+ u64 buf_addr;
+ u64 reserved28[4];
+} __packed __aligned(8);
+
+struct uv_cb_list_secrets {
+ struct uv_cb_header header;
+ u64 reserved08[2];
+ u8 reserved18[6];
+ u16 start_idx;
+ u64 list_addr;
+ u64 reserved28[4];
+} __packed __aligned(8);
+
+enum uv_secret_types {
+ UV_SECRET_INVAL = 0x0,
+ UV_SECRET_NULL = 0x1,
+ UV_SECRET_ASSOCIATION = 0x2,
+ UV_SECRET_PLAIN = 0x3,
+ UV_SECRET_AES_128 = 0x4,
+ UV_SECRET_AES_192 = 0x5,
+ UV_SECRET_AES_256 = 0x6,
+ UV_SECRET_AES_XTS_128 = 0x7,
+ UV_SECRET_AES_XTS_256 = 0x8,
+ UV_SECRET_HMAC_SHA_256 = 0x9,
+ UV_SECRET_HMAC_SHA_512 = 0xa,
+ /* 0x0b - 0x10 reserved */
+ UV_SECRET_ECDSA_P256 = 0x11,
+ UV_SECRET_ECDSA_P384 = 0x12,
+ UV_SECRET_ECDSA_P521 = 0x13,
+ UV_SECRET_ECDSA_ED25519 = 0x14,
+ UV_SECRET_ECDSA_ED448 = 0x15,
+};
+
+/**
+ * uv_secret_list_item_hdr - UV secret metadata
+ * @index: Index of the secret in the secret list
+ * @type: Type of the secret. See `enum uv_secret_types`
+ * @length: Length of the stored secret.
+ */
+struct uv_secret_list_item_hdr {
+ u16 index;
+ u16 type;
+ u32 length;
+};
+
+#define UV_SECRET_ID_LEN 32
+/**
+ * uv_secret_list_item - UV secret entry
+ * @hdr: The metadata of this secret.
+ * @id: The ID of this secret, not the secret itself.
+ */
+struct uv_secret_list_item {
+ struct uv_secret_list_item_hdr hdr;
+ u64 reserverd08;
+ u8 id[UV_SECRET_ID_LEN];
+};
+
+/**
+ * uv_secret_list - UV secret-metadata list
+ * @num_secr_stored: Number of secrets stored in this list
+ * @total_num_secrets: Number of secrets stored in the UV for this guest
+ * @next_secret_idx: positive number if there are more secrets available or zero
+ * @secrets: Up to 85 UV-secret metadata entries.
+ */
+struct uv_secret_list {
+ u16 num_secr_stored;
+ u16 total_num_secrets;
+ u16 next_secret_idx;
+ u16 reserved_06;
+ u64 reserved_08;
+ struct uv_secret_list_item secrets[85];
+} __packed __aligned(8);
+static_assert(sizeof(struct uv_secret_list) == PAGE_SIZE);
+
static inline int __uv_call(unsigned long r1, unsigned long r2)
{
int cc;
@@ -383,6 +469,45 @@ static inline int uv_cmd_nodata(u64 handle, u16 cmd, u16 *rc, u16 *rrc)
return cc ? -EINVAL : 0;
}

+/** uv_list_secrets() - Do a List Secrets UVC
+ * @buf: Buffer to write list into; size of one page
+ * @start_idx: The smallest index that should be included in the list.
+ * For the fist invocation use 0.
+ * @rc: Pointer to store the return code or NULL.
+ * @rrc: Pointer to store the return reason code or NULL.
+ *
+ * This function calls the List Secrets UVC. The result is written into `buf`,
+ * that needs to be at least one page of writable memory.
+ * `buf` consists of:
+ * * %struct uv_secret_list_hdr
+ * * %struct uv_secret_list_item (multiple)
+ *
+ * For `start_idx` use _0_ for the first call. If there are more secrets available
+ * but could not fit into the page then `rc` is `UVC_RC_MORE_DATA`.
+ * In this case use `uv_secret_list_hdr.next_secret_idx` for `start_idx`.
+ *
+ * Context: might sleep
+ *
+ * Return: The UVC condition code
+ */
+static inline int uv_list_secrets(u8 *buf, u16 start_idx, u16 *rc, u16 *rrc)
+{
+ struct uv_cb_list_secrets uvcb = {
+ .header.len = sizeof(uvcb),
+ .header.cmd = UVC_CMD_LIST_SECRETS,
+ .start_idx = start_idx,
+ .list_addr = (u64)buf,
+ };
+ int cc = uv_call_sched(0, (u64)&uvcb);
+
+ if (rc)
+ *rc = uvcb.header.rc;
+ if (rrc)
+ *rrc = uvcb.header.rrc;
+
+ return cc;
+}
+
struct uv_info {
unsigned long inst_calls_list[4];
unsigned long uv_base_stor_len;
@@ -469,6 +594,10 @@ static inline int uv_remove_shared(unsigned long addr)
return share(addr, UVC_CMD_REMOVE_SHARED_ACCESS);
}

+int uv_get_secret_metadata(const u8 secret_id[UV_SECRET_ID_LEN],
+ struct uv_secret_list_item_hdr *secret);
+int uv_retrieve_secret(u16 secret_idx, u8 *buf, size_t buf_size);
+
extern int prot_virt_host;

static inline int is_prot_virt_host(void)
diff --git a/arch/s390/kernel/uv.c b/arch/s390/kernel/uv.c
index 9646f773208a..410f96e06cba 100644
--- a/arch/s390/kernel/uv.c
+++ b/arch/s390/kernel/uv.c
@@ -2,7 +2,7 @@
/*
* Common Ultravisor functions and initialization
*
- * Copyright IBM Corp. 2019, 2020
+ * Copyright IBM Corp. 2019, 2024
*/
#define KMSG_COMPONENT "prot_virt"
#define pr_fmt(fmt) KMSG_COMPONENT ": " fmt
@@ -787,3 +787,128 @@ static int __init uv_info_init(void)
return rc;
}
device_initcall(uv_info_init);
+
+/*
+ * Find the secret with the secret_id in the provided list
+ *
+ * Context: might sleep
+ */
+static int find_secret_in_page(const u8 secret_id[UV_SECRET_ID_LEN],
+ const struct uv_secret_list *list,
+ struct uv_secret_list_item_hdr *secret)
+{
+ u16 i;
+
+ for (i = 0; i < list->total_num_secrets; i++) {
+ if (memcmp(secret_id, list->secrets[i].id, UV_SECRET_ID_LEN) == 0) {
+ *secret = list->secrets[i].hdr;
+ return 0;
+ }
+ }
+ return -ENOENT;
+}
+
+/*
+ * Do the actual search for `uv_get_secret_metadata`
+ *
+ * Context: might sleep
+ */
+static int find_secret(const u8 secret_id[UV_SECRET_ID_LEN],
+ struct uv_secret_list *list,
+ struct uv_secret_list_item_hdr *secret)
+{
+ u16 start_idx = 0;
+ u16 list_rc;
+ int ret;
+
+ do {
+ uv_list_secrets((u8 *)list, start_idx, &list_rc, NULL);
+ if (!(list_rc == UVC_RC_EXECUTED || list_rc == UVC_RC_MORE_DATA)) {
+ if (list_rc == UVC_RC_INV_CMD)
+ return -ENODEV;
+ else
+ return -EIO;
+ }
+ ret = find_secret_in_page(secret_id, list, secret);
+ if (ret == 0)
+ return ret;
+ start_idx = list->next_secret_idx;
+ } while (list_rc == UVC_RC_MORE_DATA && start_idx < list->next_secret_idx);
+
+ return -ENOENT;
+}
+
+/**
+ * uv_get_secret_metadata() - get secret metadata for a given secret id
+ * @secret_id: search pattern
+ * @secret: output data, containing the secret's metadata
+ *
+ * Search for a secret with the given secret_id in the Ultravisor secret store.
+ *
+ * Context: might sleep
+ *
+ * Return:
+ * * %0: - Found entry; secret->idx and secret->type are valid
+ * * %ENOENT - No entry found
+ * * %ENODEV: - Not supported: UV not available or command not available
+ * * %EIO: - Other unexpected UV error
+ */
+int uv_get_secret_metadata(const u8 secret_id[UV_SECRET_ID_LEN],
+ struct uv_secret_list_item_hdr *secret)
+{
+ struct uv_secret_list *buf;
+ int rc;
+
+ buf = kzalloc(sizeof(*buf), GFP_KERNEL);
+ rc = find_secret(secret_id, buf, secret);
+ kfree(buf);
+ return rc;
+}
+EXPORT_SYMBOL_GPL(uv_get_secret_metadata);
+
+/**
+ * uv_retrieve_secret() - get the secret value for the secret index
+ * @secret_idx: Secret index for which the secret should be retrieved
+ * @buf: Buffer to store retrieved secret
+ * @buf_size: Size of the buffer. The correct buffer size is reported as part of
+ * the result from `uv_get_secret_metadata`
+ *
+ * Calls the Retrieve Secret UVC and translates the UV return code into an errno.
+ *
+ * Context: might sleep
+ *
+ * Return:
+ * * %0 - Entry found; buffer contains a valid secret
+ * * %ENOENT: - No entry found or secret at the index is non-retrievable
+ * * %ENODEV: - Not supported: UV not available or command not available
+ * * %EINVAL: - Buffer too small for content
+ * * %EIO: - Other unexpected UV error
+ */
+int uv_retrieve_secret(u16 secret_idx, u8 *buf, size_t buf_size)
+{
+ struct uv_cb_retr_secr uvcb = {
+ .header.len = sizeof(uvcb),
+ .header.cmd = UVC_CMD_RETR_SECRET,
+ .secret_idx = secret_idx,
+ .buf_addr = (u64)buf,
+ .buf_size = buf_size,
+ };
+
+ uv_call_sched(0, (u64)&uvcb);
+
+ switch (uvcb.header.rc) {
+ case UVC_RC_EXECUTED:
+ return 0;
+ case UVC_RC_INV_CMD:
+ return -ENODEV;
+ case UVC_RC_RETR_SECR_STORE_EMPTY:
+ case UVC_RC_RETR_SECR_INV_SECRET:
+ case UVC_RC_RETR_SECR_INV_IDX:
+ return -ENOENT;
+ case UVC_RC_RETR_SECR_BUF_SMALL:
+ return -EINVAL;
+ default:
+ return -EIO;
+ }
+}
+EXPORT_SYMBOL_GPL(uv_retrieve_secret);
--
2.43.0