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/* Copyright (C) 2014 mod_auth_gssapi authors - See COPYING for (C) terms */
#include <openssl/evp.h>
#include <openssl/hmac.h>
#include <openssl/rand.h>
#include <stdbool.h>
#include "crypto.h"
#define TAGSIZE 16
struct seal_key {
const EVP_CIPHER *cipher;
unsigned char *ekey;
};
apr_status_t SEAL_KEY_CREATE(apr_pool_t *p, struct seal_key **skey,
struct databuf *key)
{
struct seal_key *n;
int keylen;
int ret;
n = apr_pcalloc(p, sizeof(*n));
if (!n) return ENOMEM;
n->cipher = EVP_aes_256_gcm();
if (!n->cipher) {
ret = EFAULT;
goto done;
}
keylen = n->cipher->key_len;
n->ekey = apr_palloc(p, keylen);
if (!n->ekey) {
ret = ENOMEM;
goto done;
}
if (key) {
if (key->length < keylen) {
ret = EINVAL;
goto done;
}
memcpy(n->ekey, key->value, keylen);
} else {
ret = apr_generate_random_bytes(n->ekey, keylen);
if (ret != 0) {
ret = EFAULT;
goto done;
}
}
ret = 0;
done:
if (ret) {
free(n->ekey);
free(n);
} else {
*skey = n;
}
return ret;
}
apr_status_t SEAL_BUFFER(apr_pool_t *p, struct seal_key *skey,
struct databuf *plain, struct databuf *cipher)
{
apr_status_t err = EFAULT;
EVP_CIPHER_CTX ctx = {};
int minlen;
int outlen;
int ret;
EVP_CIPHER_CTX_init(&ctx);
/* Add space for padding, IV and tag. */
minlen = plain->length / skey->cipher->block_size + 1;
minlen *= skey->cipher->block_size;
minlen += skey->cipher->iv_len + TAGSIZE;
if (cipher->length < minlen) {
cipher->length = minlen;
cipher->value = apr_palloc(p, cipher->length);
if (!cipher->value) {
err = ENOMEM;
goto done;
}
}
/* Generate IV. */
ret = apr_generate_random_bytes(cipher->value, skey->cipher->iv_len);
if (ret != 0) goto done;
cipher->length = skey->cipher->iv_len;
ret = EVP_EncryptInit_ex(&ctx, skey->cipher, NULL,
skey->ekey, cipher->value);
if (ret != 1) goto done;
/* Encrypt the data. */
outlen = 0;
ret = EVP_EncryptUpdate(&ctx, &cipher->value[cipher->length],
&outlen, plain->value, plain->length);
if (ret != 1) goto done;
cipher->length += outlen;
outlen = 0;
ret = EVP_EncryptFinal_ex(&ctx, &cipher->value[cipher->length], &outlen);
if (ret != 1) goto done;
cipher->length += outlen;
/* Get the tag */
ret = EVP_CIPHER_CTX_ctrl(&ctx, EVP_CTRL_GCM_GET_TAG, TAGSIZE,
&cipher->value[cipher->length]);
if (ret != 1) goto done;
cipher->length += TAGSIZE;
err = 0;
done:
EVP_CIPHER_CTX_cleanup(&ctx);
return err;
}
apr_status_t UNSEAL_BUFFER(apr_pool_t *p, struct seal_key *skey,
struct databuf *cipher, struct databuf *plain)
{
apr_status_t err = EFAULT;
EVP_CIPHER_CTX ctx = {};
int outlen;
int ret;
EVP_CIPHER_CTX_init(&ctx);
if (plain->length < cipher->length - skey->cipher->iv_len - TAGSIZE) {
plain->length = cipher->length - skey->cipher->iv_len - TAGSIZE;
plain->value = apr_palloc(p, plain->length);
if (!plain->value) {
err = ENOMEM;
goto done;
}
}
ret = EVP_DecryptInit_ex(&ctx, skey->cipher, NULL,
skey->ekey, cipher->value);
if (ret != 1) goto done;
plain->length = 0;
outlen = 0;
ret = EVP_DecryptUpdate(&ctx, plain->value, &outlen,
&cipher->value[skey->cipher->iv_len],
cipher->length - skey->cipher->iv_len - TAGSIZE);
if (ret != 1) goto done;
plain->length += outlen;
ret = EVP_CIPHER_CTX_ctrl(&ctx, EVP_CTRL_GCM_SET_TAG, TAGSIZE,
&cipher->value[cipher->length - TAGSIZE]);
if (ret != 1) goto done;
outlen = 0;
ret = EVP_DecryptFinal_ex(&ctx, &plain->value[plain->length], &outlen);
if (ret != 1) goto done;
plain->length += outlen;
err = 0;
done:
EVP_CIPHER_CTX_cleanup(&ctx);
return err;
}
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