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#include "secret.h"
#include <limits.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <openssl/crypto.h>
#include <openssl/evp.h>
#include <openssl/rand.h>
#include "util.h"
#define SECRET_PREFIX "enc:v1:"
#define SECRET_KEY_LEN 32
#define SECRET_NONCE_LEN 12
#define SECRET_TAG_LEN 16
static int hex_val(int c)
{
if (c >= '0' && c <= '9')
return c - '0';
if (c >= 'a' && c <= 'f')
return c - 'a' + 10;
if (c >= 'A' && c <= 'F')
return c - 'A' + 10;
return -1;
}
static int secret_key(unsigned char out[SECRET_KEY_LEN])
{
const char *s = getenv("BOKFD_SECRET_KEY");
if (!s || !*s)
return -1;
size_t n = strlen(s);
if (n == 2 * SECRET_KEY_LEN) {
int hex = 1;
for (size_t i = 0; i < n && hex; i++)
if (hex_val((unsigned char)s[i]) < 0)
hex = 0;
if (hex) {
for (size_t i = 0; i < SECRET_KEY_LEN; i++)
out[i] = (unsigned char)((hex_val(s[2 * i]) << 4) |
hex_val(s[2 * i + 1]));
return 0;
}
}
if (n % 4 == 1 || n > 172)
return -1;
char padded[176];
memcpy(padded, s, n);
while (n % 4)
padded[n++] = '=';
padded[n] = '\0';
unsigned char *raw = NULL;
size_t raw_n = 0;
if (util_b64_decode(padded, n, &raw, &raw_n) != 0)
return -1;
int ok = raw_n == SECRET_KEY_LEN;
if (ok)
memcpy(out, raw, SECRET_KEY_LEN);
free(raw);
return ok ? 0 : -1;
}
int secret_available(void)
{
unsigned char key[SECRET_KEY_LEN] = { 0 };
int ok = secret_key(key) == 0;
OPENSSL_cleanse(key, sizeof key);
return ok;
}
int secret_encrypt(const char *plain, char **out)
{
if (out)
*out = NULL;
if (!plain || !out)
return -1;
size_t plen = strlen(plain);
if (plen > (size_t)INT_MAX)
return -1;
unsigned char key[SECRET_KEY_LEN], nonce[SECRET_NONCE_LEN];
if (secret_key(key) != 0)
return -1;
if (RAND_bytes(nonce, SECRET_NONCE_LEN) != 1) {
OPENSSL_cleanse(key, sizeof key);
return -1;
}
size_t clen = plen + SECRET_TAG_LEN;
unsigned char *ct = xmalloc(clen);
EVP_CIPHER_CTX *ctx = EVP_CIPHER_CTX_new();
int len = 0, total = 0, ok = 0;
if (ctx &&
EVP_EncryptInit_ex(ctx, EVP_aes_256_gcm(), NULL, NULL, NULL) == 1 &&
EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_GCM_SET_IVLEN, SECRET_NONCE_LEN,
NULL) == 1 &&
EVP_EncryptInit_ex(ctx, NULL, NULL, key, nonce) == 1 &&
EVP_EncryptUpdate(ctx, ct, &len, (const unsigned char *)plain,
(int)plen) == 1) {
total = len;
ok = EVP_EncryptFinal_ex(ctx, ct + total, &len) == 1;
total += len;
}
if (ok)
ok = EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_GCM_GET_TAG, SECRET_TAG_LEN,
ct + total) == 1;
EVP_CIPHER_CTX_free(ctx);
OPENSSL_cleanse(key, sizeof key);
if (!ok || total != (int)plen) {
free(ct);
return -1;
}
total += SECRET_TAG_LEN;
char *nonce_b64 = util_b64(nonce, sizeof nonce);
char *ct_b64 = util_b64(ct, (size_t)total);
free(ct);
size_t olen =
strlen(SECRET_PREFIX) + strlen(nonce_b64) + 1 + strlen(ct_b64) + 1;
char *s = xmalloc(olen);
snprintf(s, olen, "%s%s:%s", SECRET_PREFIX, nonce_b64, ct_b64);
free(nonce_b64);
free(ct_b64);
*out = s;
return 0;
}
int secret_decrypt(const char *stored, char **out)
{
if (out)
*out = NULL;
if (!stored || !out)
return -1;
if (strncmp(stored, SECRET_PREFIX, strlen(SECRET_PREFIX)) != 0)
return -1;
const char *p = stored + strlen(SECRET_PREFIX);
const char *sep = strchr(p, ':');
if (!sep || sep == p || !sep[1])
return -1;
unsigned char key[SECRET_KEY_LEN];
if (secret_key(key) != 0)
return -1;
unsigned char *nonce = NULL, *ct = NULL;
size_t nonce_n = 0, ct_n = 0;
if (util_b64_decode(p, (size_t)(sep - p), &nonce, &nonce_n) != 0) {
OPENSSL_cleanse(key, sizeof key);
return -1;
}
if (util_b64_decode(sep + 1, strlen(sep + 1), &ct, &ct_n) != 0) {
free(nonce);
OPENSSL_cleanse(key, sizeof key);
return -1;
}
if (nonce_n != SECRET_NONCE_LEN || ct_n < SECRET_TAG_LEN ||
ct_n - SECRET_TAG_LEN > (size_t)INT_MAX) {
free(nonce);
free(ct);
OPENSSL_cleanse(key, sizeof key);
return -1;
}
size_t plen = ct_n - SECRET_TAG_LEN;
unsigned char *pt = xmalloc(plen + 1);
EVP_CIPHER_CTX *ctx = EVP_CIPHER_CTX_new();
int len = 0, total = 0, ok = 0;
if (ctx &&
EVP_DecryptInit_ex(ctx, EVP_aes_256_gcm(), NULL, NULL, NULL) == 1 &&
EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_GCM_SET_IVLEN, SECRET_NONCE_LEN,
NULL) == 1 &&
EVP_DecryptInit_ex(ctx, NULL, NULL, key, nonce) == 1 &&
EVP_DecryptUpdate(ctx, pt, &len, ct, (int)plen) == 1) {
total = len;
if (EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_GCM_SET_TAG, SECRET_TAG_LEN,
ct + plen) == 1)
ok = EVP_DecryptFinal_ex(ctx, pt + total, &len) == 1;
total += len;
}
EVP_CIPHER_CTX_free(ctx);
OPENSSL_cleanse(key, sizeof key);
free(nonce);
free(ct);
if (!ok || total != (int)plen) {
OPENSSL_cleanse(pt, plen + 1);
free(pt);
return -1;
}
pt[total] = '\0';
*out = (char *)pt;
return 0;
}
int secret_key_is_secret(const char *key)
{
return key && strcmp(key, "smtp_password") == 0;
}
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