Adds the support of key derivation using the scheme hkdf.
This scheme is defined in rfc5869.
Signed-off-by: Philippe Reynes <philippe.rey...@softathome.com>
---
include/u-boot/sha256.h | 8 ++++++++
lib/sha256.c | 42 +++++++++++++++++++++++++++++++++++++++++
2 files changed, 50 insertions(+)
diff --git a/include/u-boot/sha256.h b/include/u-boot/sha256.h
index 7aa4c54d0d4..46d20bf9b79 100644
--- a/include/u-boot/sha256.h
+++ b/include/u-boot/sha256.h
@@ -6,6 +6,9 @@
#define SHA256_SUM_LEN 32
#define SHA256_DER_LEN 19
+#define SHA256_HKDF_MAX_INFO_LEN 256
+#define SHA256_HKDF_MAX_DATA_LEN (SHA256_HKDF_MAX_INFO_LEN + SHA256_SUM_LEN +
1)
+
extern const uint8_t sha256_der_prefix[];
/* Reset watchdog each time we process this many bytes */
@@ -28,4 +31,9 @@ void sha256_hmac(const unsigned char *key, int keylen,
const unsigned char *input, unsigned int ilen,
unsigned char *output);
+void sha256_hkdf(const unsigned char *salt, int saltlen,
+ const unsigned char *ikm, int ikmlen,
+ const unsigned char *info, int infolen,
+ unsigned char *output, int outputlen);
+
#endif /* _SHA256_H */
diff --git a/lib/sha256.c b/lib/sha256.c
index 64f6b48974b..9a4fd452cd8 100644
--- a/lib/sha256.c
+++ b/lib/sha256.c
@@ -338,3 +338,45 @@ void sha256_hmac(const unsigned char *key, int keylen,
memset(tmpbuf, 0, 32);
memset(&ctx, 0, sizeof(sha256_context));
}
+
+static void sha256_hkdf_expand(const unsigned char *prk, int prklen,
+ const unsigned char *info, int infolen,
+ unsigned char *okm, int okmlen)
+{
+ unsigned char t[SHA256_SUM_LEN];
+ unsigned char data[SHA256_HKDF_MAX_DATA_LEN];
+ int i, l = (okmlen + SHA256_SUM_LEN - 1) / SHA256_SUM_LEN;
+ int tlen, datalen, len, offset = 0;
+
+ for (i = 1; i <= l; i++) {
+ tlen = (i == 1) ? 0 : SHA256_SUM_LEN;
+ memcpy(&data[0], &t[0], tlen);
+ datalen = tlen;
+ memcpy(&data[datalen], info, infolen);
+ datalen += infolen;
+ data[datalen] = i;
+ datalen++;
+
+ sha256_hmac(prk, prklen, data, datalen, t);
+
+ len = (okmlen > SHA256_SUM_LEN) ? SHA256_SUM_LEN : okmlen;
+ memcpy(&okm[offset], t, len);
+ offset += len;
+ okmlen -= len;
+ }
+}
+
+void sha256_hkdf(const unsigned char *salt, int saltlen,
+ const unsigned char *ikm, int ikmlen,
+ const unsigned char *info, int infolen,
+ unsigned char *output, int outputlen)
+{
+ unsigned char prk[SHA256_SUM_LEN];
+
+ /* Step 1: Extract */
+ sha256_hmac(salt, saltlen, ikm, ikmlen, prk);
+
+ /* Step 2: Expand */
+ sha256_hkdf_expand(prk, SHA256_SUM_LEN, info, infolen,
+ output, outputlen);
+}
--
2.25.1
