+ /* ctx->num is maintained in byte-oriented modes,
+ such as CFB and OFB... */
+ if ((chunk = ctx->num)) { /* borrow chunk variable */
+ unsigned char *ivp=ctx->iv;
+
+ switch (EVP_CIPHER_CTX_mode(ctx)) {
+ case EVP_CIPH_CFB_MODE:
+ if (chunk >= AES_BLOCK_SIZE)
+ return 0; /* bogus value */
+
+ if (ctx->encrypt)
+ while (chunk<AES_BLOCK_SIZE && nbytes!=0) {
+ ivp[chunk] = *(out_arg++) = *(in_arg++) ^ ivp[chunk];
+ chunk++, nbytes--;
+ }
+ else while (chunk<AES_BLOCK_SIZE && nbytes!=0) {
+ unsigned char c = *(in_arg++);
+ *(out_arg++) = c ^ ivp[chunk];
+ ivp[chunk++] = c, nbytes--;
+ }
+
+ ctx->num = chunk%AES_BLOCK_SIZE;
+ break;
+ case EVP_CIPH_OFB_MODE:
+ if (chunk >= AES_BLOCK_SIZE)
+ return 0; /* bogus value */
+
+ while (chunk<AES_BLOCK_SIZE && nbytes!=0) {
+ *(out_arg++) = *(in_arg++) ^ ivp[chunk];
+ chunk++, nbytes--;
+ }
+
+ ctx->num = chunk%AES_BLOCK_SIZE;
+ break;
+ }
+ }
+