1 files changed, 99 insertions, 0 deletions
diff --git a/third_party/bearssl/src/rsa_i31_modulus.c b/third_party/bearssl/src/rsa_i31_modulus.c
new file mode 100644
index 0000000..f5f997f
--- /dev/null
+++ b/third_party/bearssl/src/rsa_i31_modulus.c
@@ -0,0 +1,99 @@
+/*
+ * Copyright (c) 2018 Thomas Pornin <[email protected]>
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining 
+ * a copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be 
+ * included in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, 
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND 
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+#include "inner.h"
+
+/* see bearssl_rsa.h */
+size_t
+br_rsa_i31_compute_modulus(void *n, const br_rsa_private_key *sk)
+{
+	uint32_t tmp[4 * (((BR_MAX_RSA_SIZE / 2) + 30) / 31) + 5];
+	uint32_t *t, *p, *q;
+	const unsigned char *pbuf, *qbuf;
+	size_t nlen, plen, qlen, tlen;
+
+	/*
+	 * Compute actual byte and lengths for p and q.
+	 */
+	pbuf = sk->p;
+	plen = sk->plen;
+	while (plen > 0 && *pbuf == 0) {
+		pbuf ++;
+		plen --;
+	}
+	qbuf = sk->q;
+	qlen = sk->qlen;
+	while (qlen > 0 && *qbuf == 0) {
+		qbuf ++;
+		qlen --;
+	}
+
+	t = tmp;
+	tlen = (sizeof tmp) / (sizeof tmp[0]);
+
+	/*
+	 * Decode p.
+	 */
+	if ((31 * tlen) < (plen << 3) + 31) {
+		return 0;
+	}
+	br_i31_decode(t, pbuf, plen);
+	p = t;
+	plen = (p[0] + 63) >> 5;
+	t += plen;
+	tlen -= plen;
+
+	/*
+	 * Decode q.
+	 */
+	if ((31 * tlen) < (qlen << 3) + 31) {
+		return 0;
+	}
+	br_i31_decode(t, qbuf, qlen);
+	q = t;
+	qlen = (q[0] + 63) >> 5;
+	t += qlen;
+	tlen -= qlen;
+
+	/*
+	 * Computation can proceed only if we have enough room for the
+	 * modulus.
+	 */
+	if (tlen < (plen + qlen + 1)) {
+		return 0;
+	}
+
+	/*
+	 * Private key already contains the modulus bit length, from which
+	 * we can infer the output length. Even if n is NULL, we still had
+	 * to decode p and q to make sure that the product can be computed.
+	 */
+	nlen = (sk->n_bitlen + 7) >> 3;
+	if (n != NULL) {
+		br_i31_zero(t, p[0]);
+		br_i31_mulacc(t, p, q);
+		br_i31_encode(n, nlen, t);
+	}
+	return nlen;
+}