Add libsha2_hmac_[un]marshal

Signed-off-by: Mattias Andrée <maandree@kth.se>

1 files changed, 54 insertions, 0 deletions

diff --git a/hmac_unmarshal.c b/hmac_unmarshal.c
new file mode 100644
index 0000000..cc62d5c
--- /dev/null
+++ b/hmac_unmarshal.c
@@ -0,0 +1,54 @@
+/* See LICENSE file for copyright and license details. */
+#include "common.h"
+
+
+/**
+ * Unmarshal an HMAC state from a buffer
+ * 
+ * @param   state    Output parameter for the unmarshalled state
+ * @param   buf      The buffer from which the state shall be unmarshalled
+ * @param   bufsize  The maximum number of bytes that can be unmarshalled
+ * @return           The number of read bytes, 0 on failure
+ */
+size_t
+libsha2_hmac_unmarshal(struct libsha2_hmac_state *restrict state, const void *restrict buf_, size_t bufsize)
+{
+	const char *restrict buf = buf_;
+	size_t off = 0;
+	size_t r;
+
+	if (bufsize < sizeof(int)) {
+		errno = EINVAL;
+		return 0;
+	}
+
+	if (*(const int *)buf) { /* version */
+		errno = EINVAL;
+		return 0;
+	}
+	off += sizeof(int);
+
+	r = libsha2_unmarshal(&state->sha2_state, &buf[off], bufsize - off);
+	if (!r)
+		return 0;
+	off += r;
+
+	if (bufsize - off < sizeof(size_t) + sizeof(unsigned char) + 2 * state->sha2_state.chunk_size) {
+		errno = EINVAL;
+		return 0;
+	}
+
+	state->outsize = *(size_t *)&buf[off];
+	off += sizeof(size_t);
+
+	state->inited = *(unsigned char *)&buf[off];
+	off += sizeof(unsigned char);
+
+	memcpy(state->ipad, &buf[off], state->sha2_state.chunk_size);
+	off += state->sha2_state.chunk_size;
+
+	memcpy(state->opad, &buf[off], state->sha2_state.chunk_size);
+	off += state->sha2_state.chunk_size;
+
+	return off;
+}