[RFC 4/8] checksum: add l_checksum_new_hmac_from_key_id

Same as l_checksum_new_hmac but uses a key ID rather than a
key directly.
---
 ell/checksum.c | 17 +++++++++++++++++
 ell/checksum.h |  2 ++
 ell/ell.sym    |  1 +
 3 files changed, 20 insertions(+)

diff --git a/ell/checksum.c b/ell/checksum.c
index e17f070..dc5e61a 100644
--- a/ell/checksum.c
+++ b/ell/checksum.c
@@ -68,6 +68,10 @@ struct sockaddr_alg {
 #define SOL_ALG 279
 #endif
 
+#ifndef ALG_SET_KEY_BY_KEY_SERIAL
+#define ALG_SET_KEY_BY_KEY_SERIAL 7
+#endif
+
 struct checksum_info {
 	const char *name;
 	uint8_t digest_len;
@@ -213,6 +217,19 @@ LIB_EXPORT struct l_checksum *l_checksum_new_hmac(enum l_checksum_type type,
 					&checksum_hmac_algs[type]);
 }
 
+struct l_checksum *l_checksum_new_hmac_from_key_id(enum l_checksum_type type,
+							int32_t key_id)
+{
+	if (!is_valid_index(checksum_hmac_algs, type) ||
+			!checksum_hmac_algs[type].name)
+		return NULL;
+
+	return checksum_new_common(checksum_hmac_algs[type].name,
+					ALG_SET_KEY_BY_KEY_SERIAL,
+					&key_id, sizeof(key_id),
+					&checksum_hmac_algs[type]);
+}
+
 /**
  * l_checksum_clone:
  * @checksum: parent checksum object
diff --git a/ell/checksum.h b/ell/checksum.h
index 531fcb0..3dab13f 100644
--- a/ell/checksum.h
+++ b/ell/checksum.h
@@ -48,6 +48,8 @@ struct l_checksum *l_checksum_new(enum l_checksum_type type);
 struct l_checksum *l_checksum_new_cmac_aes(const void *key, size_t key_len);
 struct l_checksum *l_checksum_new_hmac(enum l_checksum_type type,
 					const void *key, size_t key_len);
+struct l_checksum *l_checksum_new_hmac_from_key_id(enum l_checksum_type type,
+							int32_t key_id);
 struct l_checksum *l_checksum_clone(struct l_checksum *checksum);
 
 void l_checksum_free(struct l_checksum *checksum);
diff --git a/ell/ell.sym b/ell/ell.sym
index 414b288..08252b8 100644
--- a/ell/ell.sym
+++ b/ell/ell.sym
@@ -115,6 +115,7 @@ global:
 	l_checksum_new;
 	l_checksum_new_cmac_aes;
 	l_checksum_new_hmac;
+	l_checksum_new_hmac_from_key_id;
 	l_checksum_clone;
 	l_checksum_free;
 	l_checksum_reset;
-- 
2.34.3