crypto: rsa-pkcs1pad - Fix regression from leading zeros
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: 9b45b7bba3d2 ("crypto: rsa - Generate fixed-length output")
Reported-by: Stephan Mueller <smueller@chronox.de>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
diff --git a/crypto/rsa-pkcs1pad.c b/crypto/rsa-pkcs1pad.c
index 8ccfdd7..880d3db 100644
--- a/crypto/rsa-pkcs1pad.c
+++ b/crypto/rsa-pkcs1pad.c
@@ -456,49 +456,55 @@
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;
+ 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);