Repository: incubator-mynewt-core Updated Branches: refs/heads/develop f4a9711f5 -> 94497bf2a
bootutil: ecdsa P-256: Fix handling of sizes >From David Brown: The ECDSA signature is written as two DER-encoded INTEGERS. Although the values are always 256 bits, the encoding ends up being variable length, because the encoding is signed, and therefore needs an extra zero byte to keep the number positive. This means that the length can vary by up to two bytes. The 'newt' tool handles this for signature by allowing space for the largest encoding, and padding with one or two zeros. However, the bootutil image check code insists that the length is exact, resulting in a decoding error on about 3/4 signatures. Fix this by only verifying that we have at least enough payload to hold the signature. There are later checks that will fail if the integers themselves are too large. Project: http://git-wip-us.apache.org/repos/asf/incubator-mynewt-core/repo Commit: http://git-wip-us.apache.org/repos/asf/incubator-mynewt-core/commit/94497bf2 Tree: http://git-wip-us.apache.org/repos/asf/incubator-mynewt-core/tree/94497bf2 Diff: http://git-wip-us.apache.org/repos/asf/incubator-mynewt-core/diff/94497bf2 Branch: refs/heads/develop Commit: 94497bf2af4d51046b211ffb4e676f0a7718e22c Parents: f4a9711 Author: Marko Kiiskila <ma...@runtime.io> Authored: Mon Feb 6 09:47:14 2017 -0800 Committer: Marko Kiiskila <ma...@runtime.io> Committed: Mon Feb 6 09:47:14 2017 -0800 ---------------------------------------------------------------------- boot/bootutil/src/image_ec256.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) ---------------------------------------------------------------------- http://git-wip-us.apache.org/repos/asf/incubator-mynewt-core/blob/94497bf2/boot/bootutil/src/image_ec256.c ---------------------------------------------------------------------- diff --git a/boot/bootutil/src/image_ec256.c b/boot/bootutil/src/image_ec256.c index f59a8f0..1e7354e 100644 --- a/boot/bootutil/src/image_ec256.c +++ b/boot/bootutil/src/image_ec256.c @@ -122,7 +122,7 @@ tinycrypt_decode_sig(uint32_t r[NUM_ECC_DIGITS], uint32_t s[NUM_ECC_DIGITS], if (rc) { return -1; } - if (cp + len != end) { + if (cp + len > end) { return -2; } rc = tinycrypt_read_bigint(r, &cp, end);
