1 files changed, 90 insertions, 0 deletions
diff --git a/fticks_hashmac.c b/fticks_hashmac.c
new file mode 100644
index 0000000..eb0d29b
--- /dev/null
+++ b/fticks_hashmac.c
@@ -0,0 +1,90 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <errno.h>
+#include <ctype.h>
+#include <nettle/sha.h>
+#include <nettle/hmac.h>
+#include "fticks_hashmac.h"
+
+static void
+_format_hash(const uint8_t *hash, size_t out_len, uint8_t *out)
+{
+    int ir, iw;
+
+    for (ir = 0, iw = 0; iw <= out_len - 3; ir++, iw += 2)
+	sprintf((char *) out + iw, "%02x", hash[ir % SHA256_DIGEST_SIZE]);
+}
+
+static void
+_hash(const uint8_t *in,
+      const uint8_t *key,
+      size_t out_len,
+      uint8_t *out)
+{
+    if (key == NULL) {
+	struct sha256_ctx ctx;
+	uint8_t hash[SHA256_DIGEST_SIZE];
+
+	sha256_init(&ctx);
+	sha256_update(&ctx, strlen((char *) in), in);
+	sha256_digest(&ctx, sizeof(hash), hash);
+	_format_hash(hash, out_len, out);
+    }
+    else {
+	struct hmac_sha256_ctx ctx;
+	uint8_t hash[SHA256_DIGEST_SIZE];
+
+	hmac_sha256_set_key(&ctx, strlen((char *) key), key);
+	hmac_sha256_update(&ctx, strlen((char *) in), in);
+	hmac_sha256_digest(&ctx, sizeof(hash), hash);
+	_format_hash(hash, out_len, out);
+    }
+}
+
+/** Hash the Ethernet MAC address in \a IN, keying a HMAC with \a KEY
+    unless \a KEY is NULL.  If \a KEY is null \a IN is hashed with an
+    ordinary cryptographic hash function such as SHA-2.
+
+    \a IN and \a KEY are NULL terminated strings.
+
+    \a IN is supposed to be an Ethernet MAC address and is sanitised
+    by lowercasing it, removing all but [0-9a-f] and truncating it at
+    the first ';' found.  The truncation is done because RADIUS
+    supposedly has a praxis of tacking on SSID to the MAC address in
+    Calling-Station-Id.
+
+    \return 0 on success, -ENOMEM on out of memory.
+*/
+int
+fticks_hashmac(const uint8_t *in,
+	       const uint8_t *key,
+	       size_t out_len,
+	       uint8_t *out)
+{
+    uint8_t *in_copy = NULL;
+    uint8_t *p = NULL;
+    int i;
+
+    in_copy = calloc(1, strlen((const char *) in) + 1);
+    if (in_copy == NULL)
+	return -ENOMEM;
+
+    /* Sanitise and lowercase 'in' into 'in_copy'.  */
+    for (i = 0, p = in_copy; in[i] != '\0'; i++) {
+	if (in[i] == ';') {
+	    *p++ = '\0';
+	    break;
+	}
+	if (in[i] >= '0' && in[i] <= '9') {
+	    *p++ = in[i];
+	}
+	else if (tolower(in[i]) >= 'a' && tolower(in[i]) <= 'f') {
+	    *p++ = tolower(in[i]);
+	}
+    }
+
+    _hash(in_copy, key, out_len, out);
+    free(in_copy);
+    return 0;
+}