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Diffstat (limited to 'src/secp256k1/contrib/lax_der_parsing.c')
-rw-r--r--src/secp256k1/contrib/lax_der_parsing.c150
1 files changed, 150 insertions, 0 deletions
diff --git a/src/secp256k1/contrib/lax_der_parsing.c b/src/secp256k1/contrib/lax_der_parsing.c
new file mode 100644
index 0000000000..5b141a9948
--- /dev/null
+++ b/src/secp256k1/contrib/lax_der_parsing.c
@@ -0,0 +1,150 @@
+/**********************************************************************
+ * Copyright (c) 2015 Pieter Wuille *
+ * Distributed under the MIT software license, see the accompanying *
+ * file COPYING or http://www.opensource.org/licenses/mit-license.php.*
+ **********************************************************************/
+
+#include <string.h>
+#include <secp256k1.h>
+
+#include "lax_der_parsing.h"
+
+int ecdsa_signature_parse_der_lax(const secp256k1_context* ctx, secp256k1_ecdsa_signature* sig, const unsigned char *input, size_t inputlen) {
+ size_t rpos, rlen, spos, slen;
+ size_t pos = 0;
+ size_t lenbyte;
+ unsigned char tmpsig[64] = {0};
+ int overflow = 0;
+
+ /* Hack to initialize sig with a correctly-parsed but invalid signature. */
+ secp256k1_ecdsa_signature_parse_compact(ctx, sig, tmpsig);
+
+ /* Sequence tag byte */
+ if (pos == inputlen || input[pos] != 0x30) {
+ return 0;
+ }
+ pos++;
+
+ /* Sequence length bytes */
+ if (pos == inputlen) {
+ return 0;
+ }
+ lenbyte = input[pos++];
+ if (lenbyte & 0x80) {
+ lenbyte -= 0x80;
+ if (pos + lenbyte > inputlen) {
+ return 0;
+ }
+ pos += lenbyte;
+ }
+
+ /* Integer tag byte for R */
+ if (pos == inputlen || input[pos] != 0x02) {
+ return 0;
+ }
+ pos++;
+
+ /* Integer length for R */
+ if (pos == inputlen) {
+ return 0;
+ }
+ lenbyte = input[pos++];
+ if (lenbyte & 0x80) {
+ lenbyte -= 0x80;
+ if (pos + lenbyte > inputlen) {
+ return 0;
+ }
+ while (lenbyte > 0 && input[pos] == 0) {
+ pos++;
+ lenbyte--;
+ }
+ if (lenbyte >= sizeof(size_t)) {
+ return 0;
+ }
+ rlen = 0;
+ while (lenbyte > 0) {
+ rlen = (rlen << 8) + input[pos];
+ pos++;
+ lenbyte--;
+ }
+ } else {
+ rlen = lenbyte;
+ }
+ if (rlen > inputlen - pos) {
+ return 0;
+ }
+ rpos = pos;
+ pos += rlen;
+
+ /* Integer tag byte for S */
+ if (pos == inputlen || input[pos] != 0x02) {
+ return 0;
+ }
+ pos++;
+
+ /* Integer length for S */
+ if (pos == inputlen) {
+ return 0;
+ }
+ lenbyte = input[pos++];
+ if (lenbyte & 0x80) {
+ lenbyte -= 0x80;
+ if (pos + lenbyte > inputlen) {
+ return 0;
+ }
+ while (lenbyte > 0 && input[pos] == 0) {
+ pos++;
+ lenbyte--;
+ }
+ if (lenbyte >= sizeof(size_t)) {
+ return 0;
+ }
+ slen = 0;
+ while (lenbyte > 0) {
+ slen = (slen << 8) + input[pos];
+ pos++;
+ lenbyte--;
+ }
+ } else {
+ slen = lenbyte;
+ }
+ if (slen > inputlen - pos) {
+ return 0;
+ }
+ spos = pos;
+ pos += slen;
+
+ /* Ignore leading zeroes in R */
+ while (rlen > 0 && input[rpos] == 0) {
+ rlen--;
+ rpos++;
+ }
+ /* Copy R value */
+ if (rlen > 32) {
+ overflow = 1;
+ } else {
+ memcpy(tmpsig + 32 - rlen, input + rpos, rlen);
+ }
+
+ /* Ignore leading zeroes in S */
+ while (slen > 0 && input[spos] == 0) {
+ slen--;
+ spos++;
+ }
+ /* Copy S value */
+ if (slen > 32) {
+ overflow = 1;
+ } else {
+ memcpy(tmpsig + 64 - slen, input + spos, slen);
+ }
+
+ if (!overflow) {
+ overflow = !secp256k1_ecdsa_signature_parse_compact(ctx, sig, tmpsig);
+ }
+ if (overflow) {
+ memset(tmpsig, 0, 64);
+ secp256k1_ecdsa_signature_parse_compact(ctx, sig, tmpsig);
+ }
+ return 1;
+}
+