Hi all
since OpenSSL allows to do the encryption using the BIO API and since I
need the BIO API anyways for the sockets I thought I rewrite my code to
use the BIOs instead of EVPs. However I see some strange behavior. I
create a cipher BIO on the server as follows:
encbio = BIO_new(BIO_f_cipher());
BIO_set_cipher(encbio,EVP_bf_cbc(),key,NULL,1); /* 1 = encryption */
Then I set it on top of the socket bio:
BIO_push(encbio,cbio);
Now I send some data:
data_len = strlen(testmessage);
printf("---> %d\n",data_len);
while (written <= 0)
{
written = BIO_write(encbio,&data_len,sizeof(int));
if (written <= 0)
if (BIO_should_retry(encbio))
BIO_write(encbio,&data_len,sizeof(int));
}
written=0;
while (written <= 0)
{
printf("---> %s\n",testmessage);
written = BIO_write(encbio,testmessage,data_len);
if (written <= 0)
if (BIO_should_retry(encbio))
BIO_write(encbio,testmessage,data_len);
}
BIO_flush(encbio);
I create a decryption cipher bio in the same way on the client and as long
as I leave it as it is, it just works fine. The server sends data_len and
testmessage and the client receives it (and is able to decrypt it). Now I
want the client to send something back. So I set up an encryption cipher
bio on the client (like shown above) and a decryption cipher bio on the
server. So my source code looks like this:
server.c:
<encryption bio code> -> send 2 messages like above
<decryption bio code> -> receive 2 messages like above
client.c
<decryption bio code> -> receive 2 messages like above
<encryption bio code> -> send 2 messages like above
Now if I execute client and server, the client does only receive the first
message (the int data_len). It will not even receive testmessage from the
server as long as the server runs. However when I kill the server
(ctrl+c), the message arrives. That is weird since not even BIO_flush
helps. Whats going wrong here?
best regards
Carolin
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