From 0cf43f509f72128196e23f5ade7e512a72152cc6 Mon Sep 17 00:00:00 2001
From: Herbert Xu <herbert@gondor.apana.org.au>
Date: Thu, 22 Sep 2016 17:04:57 +0800
Subject: [PATCH] crypto: rsa-pkcs1pad - Handle leading zero for decryption
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 decryption while signature
verification was fixed in an earlier patch.
Fixes: 9b45b7bba3d2 ("crypto: rsa - Generate fixed-length output")
Reported-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
---
crypto/rsa-pkcs1pad.c | 41 ++++++++++++++++++++++++-----------------
1 file changed, 24 insertions(+), 17 deletions(-)
diff --git a/crypto/rsa-pkcs1pad.c b/crypto/rsa-pkcs1pad.c
index 877019a6d3ea8..8baab4307f7b9 100644
--- a/crypto/rsa-pkcs1pad.c
+++ b/crypto/rsa-pkcs1pad.c
@@ -298,41 +298,48 @@ static int pkcs1pad_decrypt_complete(struct akcipher_request *req, int err)
struct crypto_akcipher *tfm = crypto_akcipher_reqtfm(req);
struct pkcs1pad_ctx *ctx = akcipher_tfm_ctx(tfm);
struct pkcs1pad_request *req_ctx = akcipher_request_ctx(req);
+ 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;
+ 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++;
}
- if (req_ctx->out_buf[0] != 0x02) {
- err = -EINVAL;
+ if (out_buf[0] != 0x02)
goto done;
- }
- for (pos = 1; pos < req_ctx->child_req.dst_len; pos++)
- if (req_ctx->out_buf[pos] == 0x00)
+
+ for (pos = 1; pos < dst_len; pos++)
+ if (out_buf[pos] == 0x00)
break;
- if (pos < 9 || pos == req_ctx->child_req.dst_len) {
- err = -EINVAL;
+ if (pos < 9 || pos == dst_len)
goto done;
- }
pos++;
- if (req->dst_len < req_ctx->child_req.dst_len - pos)
+ err = 0;
+
+ 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);
--
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