Problem - Kevin Tafuro

while the two implementations share much of the same API, there are differences. In
particular, the API for encryption services that we will be using in this recipe differs
between the two. To determine which implementation is being used, we test for the
existence of the KRB5_GENERAL__ preprocessor macro, which will be defined by the
MIT implementation but not the Heimdal implementation.
Given a krb5_keyblock object, you can determine whether DES was negotiated using
the following function:
#include
int spc_krb5_isdes(krb5_keyblock *key) {
#ifdef KRB5_GENERAL__
if (key->enctype = = ENCTYPE_DES_CBC_CRC || key->enctype = = ENCTYPE_DES_CBC_MD4 ||
key->enctype = = ENCTYPE_DES_CBC_MD5 || key->enctype = = ENCTYPE_DES_CBC_RAW)
return 1;
#else
if (key->keytype = = ETYPE_DES_CBC_CRC || key->keytype = = ETYPE_DES_CBC_MD4 ||
key->keytype = = ETYPE_DES_CBC_MD5 || key->keytype = = ETYPE_DES_CBC_NONE ||
key->keytype = = ETYPE_DES_CFB64_NONE || key->keytype = = ETYPE_DES_PCBC_NONE)
return 1;
#endif
return 0;
}
The krb5_context object and the krb5_keyblock object can then be used together as
arguments to spc_krb5_encrypt( ), which we implement below. The function also
requires a buffer that holds the data to be encrypted along with the size of the buffer,
as well as a pointer to receive a dynamically allocated buffer that will hold the
encrypted data on return, and a pointer to receive the size of the encrypted data
buffer.
#include
#include
#include
#include
int spc_krb5_encrypt(krb5_context ctx, krb5_keyblock *key, void *inbuf,
size_t inlen, void **outbuf, size_t *outlen) {
#ifdef KRB5_GENERAL__
size_t blksz, newlen;
krb5_data in_data;
krb5_enc_data out_data;
if (krb5_c_block_size(ctx, key->enctype, &blksz)) return 0;
if (!(inlen % blksz)) newlen = inlen + blksz;
else newlen = ((inlen + blksz - 1) / blksz) * blksz;
in_data.magic = KV5M_DATA;
in_data.length = newlen;
in_data.data = malloc(newlen);
if (!in_data.data) return 0;
472 | Chapter 9: Networking
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