lkml.org 
[lkml]   [2022]   [Apr]   [14]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Subject[PATCH 5.4 076/475] crypto: rsa-pkcs1pad - correctly get hash from source scatterlist
    Date
    From: Eric Biggers <ebiggers@google.com>

    commit e316f7179be22912281ce6331d96d7c121fb2b17 upstream.

    Commit c7381b012872 ("crypto: akcipher - new verify API for public key
    algorithms") changed akcipher_alg::verify to take in both the signature
    and the actual hash and do the signature verification, rather than just
    return the hash expected by the signature as was the case before. To do
    this, it implemented a hack where the signature and hash are
    concatenated with each other in one scatterlist.

    Obviously, for this to work correctly, akcipher_alg::verify needs to
    correctly extract the two items from the scatterlist it is given.
    Unfortunately, it doesn't correctly extract the hash in the case where
    the signature is longer than the RSA key size, as it assumes that the
    signature's length is equal to the RSA key size. This causes a prefix
    of the hash, or even the entire hash, to be taken from the *signature*.

    (Note, the case of a signature longer than the RSA key size should not
    be allowed in the first place; a separate patch will fix that.)

    It is unclear whether the resulting scheme has any useful security
    properties.

    Fix this by correctly extracting the hash from the scatterlist.

    Fixes: c7381b012872 ("crypto: akcipher - new verify API for public key algorithms")
    Cc: <stable@vger.kernel.org> # v5.2+
    Reviewed-by: Vitaly Chikunov <vt@altlinux.org>
    Signed-off-by: Eric Biggers <ebiggers@google.com>
    Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    crypto/rsa-pkcs1pad.c | 2 +-
    1 file changed, 1 insertion(+), 1 deletion(-)

    --- a/crypto/rsa-pkcs1pad.c
    +++ b/crypto/rsa-pkcs1pad.c
    @@ -494,7 +494,7 @@ static int pkcs1pad_verify_complete(stru
    sg_nents_for_len(req->src,
    req->src_len + req->dst_len),
    req_ctx->out_buf + ctx->key_size,
    - req->dst_len, ctx->key_size);
    + req->dst_len, req->src_len);
    /* Do the actual verification step. */
    if (memcmp(req_ctx->out_buf + ctx->key_size, out_buf + pos,
    req->dst_len) != 0)

    \
     
     \ /
      Last update: 2022-04-14 16:23    [W:3.783 / U:0.028 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site