From 0cf43f509f72128196e23f5ade7e512a72152cc6 Mon Sep 17 00:00:00 2001 From: Herbert Xu 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 Signed-off-by: Herbert Xu --- 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 877019a..8baab43 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); -- 2.7.4