diff options
author | Matt Caswell <matt@openssl.org> | 2019-03-05 14:39:15 +0000 |
---|---|---|
committer | Matt Caswell <matt@openssl.org> | 2019-03-06 13:25:09 +0000 |
commit | 2a3d0ee9d59156c48973592331404471aca886d6 (patch) | |
tree | 4d7f2ae15b3b47c6ec134633787721ce660d21dd /crypto/evp/e_chacha20_poly1305.c | |
parent | 18e1e302452e6dea4500b6f981cee7e151294dea (diff) |
Prevent over long nonces in ChaCha20-Poly1305
ChaCha20-Poly1305 is an AEAD cipher, and requires a unique nonce input for
every encryption operation. RFC 7539 specifies that the nonce value (IV)
should be 96 bits (12 bytes). OpenSSL allows a variable nonce length and
front pads the nonce with 0 bytes if it is less than 12 bytes. However it
also incorrectly allows a nonce to be set of up to 16 bytes. In this case
only the last 12 bytes are significant and any additional leading bytes are
ignored.
It is a requirement of using this cipher that nonce values are unique.
Messages encrypted using a reused nonce value are susceptible to serious
confidentiality and integrity attacks. If an application changes the
default nonce length to be longer than 12 bytes and then makes a change to
the leading bytes of the nonce expecting the new value to be a new unique
nonce then such an application could inadvertently encrypt messages with a
reused nonce.
Additionally the ignored bytes in a long nonce are not covered by the
integrity guarantee of this cipher. Any application that relies on the
integrity of these ignored leading bytes of a long nonce may be further
affected.
Any OpenSSL internal use of this cipher, including in SSL/TLS, is safe
because no such use sets such a long nonce value. However user
applications that use this cipher directly and set a non-default nonce
length to be longer than 12 bytes may be vulnerable.
CVE-2019-1543
Fixes #8345
Reviewed-by: Paul Dale <paul.dale@oracle.com>
Reviewed-by: Richard Levitte <levitte@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/8406)
Diffstat (limited to 'crypto/evp/e_chacha20_poly1305.c')
-rw-r--r-- | crypto/evp/e_chacha20_poly1305.c | 4 |
1 files changed, 3 insertions, 1 deletions
diff --git a/crypto/evp/e_chacha20_poly1305.c b/crypto/evp/e_chacha20_poly1305.c index e8a323f3be..37902000a0 100644 --- a/crypto/evp/e_chacha20_poly1305.c +++ b/crypto/evp/e_chacha20_poly1305.c @@ -30,6 +30,8 @@ typedef struct { #define data(ctx) ((EVP_CHACHA_KEY *)(ctx)->cipher_data) +#define CHACHA20_POLY1305_MAX_IVLEN 12 + static int chacha_init_key(EVP_CIPHER_CTX *ctx, const unsigned char user_key[CHACHA_KEY_SIZE], const unsigned char iv[CHACHA_CTR_SIZE], int enc) @@ -533,7 +535,7 @@ static int chacha20_poly1305_ctrl(EVP_CIPHER_CTX *ctx, int type, int arg, return 1; case EVP_CTRL_AEAD_SET_IVLEN: - if (arg <= 0 || arg > CHACHA_CTR_SIZE) + if (arg <= 0 || arg > CHACHA20_POLY1305_MAX_IVLEN) return 0; actx->nonce_len = arg; return 1; |