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crypto: rsa-pkcs1pad - Fix regression from leading zeros

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As the software RSA implementation now produces fixed-length
output, we need to eliminate leading zeros in the calling code
instead.

This patch does just that for pkcs1pad signature verification.

Fixes: 9b45b7bba3 ("crypto: rsa - Generate fixed-length output")
Reported-by: Stephan Mueller <smueller@chronox.de>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
This commit is contained in:
Herbert Xu 2016-07-03 10:46:11 +08:00
parent 98eca72fa0
commit 27710b8ea3
1 changed files with 22 additions and 16 deletions
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36
crypto/rsa-pkcs1pad.c
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@ -456,49 +456,55 @@ static int pkcs1pad_verify_complete(struct akcipher_request *req, int err)
struct akcipher_instance *inst = akcipher_alg_instance(tfm);
struct pkcs1pad_inst_ctx *ictx = akcipher_instance_ctx(inst);
const struct rsa_asn1_template *digest_info = ictx->digest_info;
unsigned int dst_len;
unsigned int pos;
if (err == -EOVERFLOW)
/* Decrypted value had no leading 0 byte */
err = -EINVAL;
u8 *out_buf;
if (err)
goto done;
if (req_ctx->child_req.dst_len != ctx->key_size - 1) {
err = -EINVAL;
dst_len = req_ctx->child_req.dst_len;
if (dst_len < ctx->key_size - 1)
goto done;
out_buf = req_ctx->out_buf;
if (dst_len == ctx->key_size) {
if (out_buf[0] != 0x00)
/* Decrypted value had no leading 0 byte */
goto done;
dst_len--;
out_buf++;
}
err = -EBADMSG;
if (req_ctx->out_buf[0] != 0x01)
if (out_buf[0] != 0x01)
goto done;
for (pos = 1; pos < req_ctx->child_req.dst_len; pos++)
if (req_ctx->out_buf[pos] != 0xff)
for (pos = 1; pos < dst_len; pos++)
if (out_buf[pos] != 0xff)
break;
if (pos < 9 || pos == req_ctx->child_req.dst_len ||
req_ctx->out_buf[pos] != 0x00)
if (pos < 9 || pos == dst_len || out_buf[pos] != 0x00)
goto done;
pos++;
if (memcmp(req_ctx->out_buf + pos, digest_info->data,
digest_info->size))
if (memcmp(out_buf + pos, digest_info->data, digest_info->size))
goto done;
pos += digest_info->size;
err = 0;
if (req->dst_len < req_ctx->child_req.dst_len - pos)
if (req->dst_len < dst_len - pos)
err = -EOVERFLOW;
req->dst_len = req_ctx->child_req.dst_len - pos;
req->dst_len = dst_len - pos;
if (!err)
sg_copy_from_buffer(req->dst,
sg_nents_for_len(req->dst, req->dst_len),
req_ctx->out_buf + pos, req->dst_len);
out_buf + pos, req->dst_len);
done:
kzfree(req_ctx->out_buf);