static VALUE
ossl_cipher_update(VALUE self, VALUE data)
{
EVP_CIPHER_CTX *ctx;
char *in;
int in_len, out_len;
VALUE str;
StringValue(data);
in = RSTRING(data)->ptr;
if ((in_len = RSTRING(data)->len) == 0)
rb_raise(rb_eArgError, "data must not be empty");
GetCipher(self, ctx);
str = rb_str_new(0, in_len+EVP_CIPHER_CTX_block_size(ctx));
if (!EVP_CipherUpdate(ctx, RSTRING(str)->ptr, &out_len, in, in_len))
ossl_raise(eCipherError, NULL);
assert(out_len < RSTRING(str)->len);
RSTRING(str)->len = out_len;
RSTRING(str)->ptr[out_len] = 0;
return str;
}
/*
* call-seq:
* cipher.auth_tag([ tag_len ] -> string
*
* Gets the authentication tag generated by Authenticated Encryption Cipher
* modes (GCM for example). This tag may be stored along with the ciphertext,
* then set on the decryption cipher to authenticate the contents of the
* ciphertext against changes. If the optional integer parameter +tag_len+ is
* given, the returned tag will be +tag_len+ bytes long. If the parameter is
* omitted, the maximum length of 16 bytes will be returned. For maximum
* security, the default of 16 bytes should be chosen.
*
* The tag may only be retrieved after calling Cipher#final.
*/
static VALUE
ossl_cipher_get_auth_tag(int argc, VALUE *argv, VALUE self)
{
VALUE vtag_len;
EVP_CIPHER_CTX *ctx;
int nid, tag_len;
if (rb_scan_args(argc, argv, "01", &vtag_len) == 0) {
tag_len = 16;
} else {
tag_len = NUM2INT(vtag_len);
}
GetCipher(self, ctx);
nid = EVP_CIPHER_CTX_nid(ctx);
if (ossl_is_gcm(nid)) {
return ossl_get_gcm_auth_tag(ctx, tag_len);
} else {
ossl_raise(eCipherError, "authentication tag not supported by this cipher");
return Qnil; /* dummy */
}
}
/*
* call-seq:
* cipher.auth_tag = string -> string
*
* Sets the authentication tag to verify the contents of the
* ciphertext. The tag must be set after calling Cipher#decrypt,
* Cipher#key= and Cipher#iv=, but before assigning the associated
* authenticated data using Cipher#auth_data= and of course, before
* decrypting any of the ciphertext. After all decryption is
* performed, the tag is verified automatically in the call to
* Cipher#final.
*/
static VALUE
ossl_cipher_set_auth_tag(VALUE self, VALUE vtag)
{
EVP_CIPHER_CTX *ctx;
int nid;
unsigned char *tag;
int tag_len;
StringValue(vtag);
tag = (unsigned char *) RSTRING_PTR(vtag);
tag_len = RSTRING_LENINT(vtag);
GetCipher(self, ctx);
nid = EVP_CIPHER_CTX_nid(ctx);
if (ossl_is_gcm(nid)) {
ossl_set_gcm_auth_tag(ctx, tag, tag_len);
} else {
ossl_raise(eCipherError, "authentication tag not supported by this cipher");
}
return vtag;
}
static VALUE
ossl_cipher_set_tag(VALUE self, VALUE data)
{
EVP_CIPHER_CTX *ctx;
char *in = NULL;
int in_len = 0;
StringValue(data);
in = (unsigned char *) RSTRING_PTR(data);
in_len = RSTRING_LEN(data);
GetCipher(self, ctx);
#ifndef EVP_CTRL_GCM_SET_TAG
ossl_raise(eCipherError, "your version of OpenSSL doesn't support GCM");
#else
if (!EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_GCM_SET_TAG, in_len, in))
ossl_raise(eCipherError, NULL);
#endif
return data;
}