T_PRF

[freeradius.git] / src / modules / rlm_eap / libeap / mppe_keys.c

diff --git a/src/modules/rlm_eap/libeap/mppe_keys.c b/src/modules/rlm_eap/libeap/mppe_keys.c
index b016c2b..16be5d1 100644 (file)
--- a/src/modules/rlm_eap/libeap/mppe_keys.c
+++ b/src/modules/rlm_eap/libeap/mppe_keys.c
@@ -86,6 +86,49 @@ static void P_hash(EVP_MD const *evp_md,
        memset(a, 0, sizeof(a));
 }
 
+/*  EAP-FAST Pseudo-Random Function (T-PRF): RFC 4851, Section 5.5 */
+void T_PRF(unsigned char const *secret, unsigned int secret_len,
+          char const *prf_label,
+          unsigned char const *seed,  unsigned int seed_len,
+          unsigned char *out, unsigned int out_len)
+{
+       size_t prf_size = strlen(prf_label);
+       size_t pos;
+       uint8_t *buf;
+
+       if (prf_size > 128) prf_size = 128;
+       prf_size++;     /* include trailing zero */
+
+       buf = talloc_size(NULL, SHA1_DIGEST_LENGTH + prf_size + seed_len + 2 + 1);
+
+       memcpy(buf + SHA1_DIGEST_LENGTH, prf_label, prf_size);
+       if (seed) memcpy(buf + SHA1_DIGEST_LENGTH + prf_size, seed, seed_len);
+       *(uint16_t *)&buf[SHA1_DIGEST_LENGTH + prf_size + seed_len] = htons(out_len);
+       buf[SHA1_DIGEST_LENGTH + prf_size + seed_len + 2] = 1;
+
+       // T1 is just the seed
+       fr_hmac_sha1(buf, buf + SHA1_DIGEST_LENGTH, prf_size + seed_len + 2 + 1, secret, secret_len);
+
+#define MIN(a,b) (((a)>(b)) ? (b) : (a))
+       memcpy(out, buf, MIN(out_len, SHA1_DIGEST_LENGTH));
+
+       pos = SHA1_DIGEST_LENGTH;
+       while (pos < out_len) {
+               buf[SHA1_DIGEST_LENGTH + prf_size + seed_len + 2]++;
+
+               fr_hmac_sha1(buf, buf, SHA1_DIGEST_LENGTH + prf_size + seed_len + 2 + 1, secret, secret_len);
+               memcpy(&out[pos], buf, MIN(out_len - pos, SHA1_DIGEST_LENGTH));
+
+               if (out_len - pos <= SHA1_DIGEST_LENGTH)
+                       break;
+
+               pos += SHA1_DIGEST_LENGTH;
+       }
+
+       memset(buf, 0, SHA1_DIGEST_LENGTH + prf_size + seed_len + 2 + 1);
+       talloc_free(buf);
+}
+
 static void PRF(unsigned char const *secret, unsigned int secret_len,
                unsigned char const *seed,   unsigned int seed_len,
                unsigned char *out, unsigned char *buf, unsigned int out_len)