openssl_decrypt.c File Reference

#include "crypto/openssl_decrypt.h"
#include <assert.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#include <openssl/aes.h>
#include <openssl/err.h>
#include <openssl/evp.h>
#include "crypto/crc.h"
#include "crypto/md5.h"
#include "crypto/openssl_encrypt.h"
#include "debug.h"
#include "lib_common.h"
#include "utils/macros.h"

Include dependency graph for openssl_decrypt.c:

Go to the source code of this file.

Classes
struct	openssl_decrypt

Macros
#define	CHECK(action, errmsg)
#define	GCM_TAG_LEN   16
#define	MOD_NAME   "[decrypt] "

Functions
static int	openssl_decrypt (struct openssl_decrypt *decrypt, const char *ciphertext, int ciphertext_len, const char *aad, int aad_len, char *plaintext, enum openssl_mode mode)
static void	openssl_decrypt_destroy (struct openssl_decrypt *s)
static int	openssl_decrypt_init (struct openssl_decrypt **state, const char *passphrase)
	REGISTER_MODULE (openssl_decrypt, &functions, LIBRARY_CLASS_UNDEFINED, OPENSSL_DECRYPT_ABI_VERSION)

Variables
static const struct openssl_decrypt_info	functions

Macro Definition Documentation

CHECK

#define CHECK	(		action,
			errmsg )

Value:

do { int rc = action; if (rc != 1) { log_msg(LOG_LEVEL_ERROR, MOD_NAME errmsg ": %s\n", ERR_error_string(ERR_get_error(), NULL)); return 0; } } while(0)

Definition at line 117 of file openssl_decrypt.c.

Referenced by openssl_decrypt().

GCM_TAG_LEN

#define GCM_TAG_LEN   16

Definition at line 69 of file openssl_decrypt.c.

Referenced by openssl_decrypt().

MOD_NAME

#define MOD_NAME   "[decrypt] "

Definition at line 70 of file openssl_decrypt.c.

Referenced by openssl_decrypt(), and openssl_decrypt_init().

Function Documentation

openssl_decrypt()

static int openssl_decrypt ( struct openssl_decrypt * decrypt, const char * ciphertext, int ciphertext_len, const char * aad, int aad_len, char * plaintext, enum openssl_mode mode )

static

Definition at line 119 of file openssl_decrypt.c.

{
        const EVP_CIPHER *cipher = get_cipher(mode);
        if (cipher == NULL) {
                log_msg(LOG_LEVEL_ERROR, MOD_NAME "Cipher %d not available!\n", (int) mode);
                return 0;
        }
        uint32_t data_len;
        memcpy(&data_len, ciphertext, sizeof(uint32_t));
        assert ((size_t) ciphertext_len >= data_len + sizeof(uint32_t) + 16 + sizeof(uint32_t));
        ciphertext += sizeof(uint32_t);
        const unsigned char *iv = (const unsigned char *) ciphertext;
        ciphertext += 16;
        ciphertext_len -= 20;
 
        CHECK(EVP_CipherInit(decrypt->ctx, cipher, decrypt->key_hash, iv, 0), "Unable to initialize cipher");
        CHECK(EVP_CIPHER_CTX_ctrl(decrypt->ctx, EVP_CTRL_GCM_SET_IVLEN, 16, NULL), "set IV len"); // default IV len is presumably 12 bytes
 
        int out_len = 0;
        if (mode == MODE_AES128_GCM) {
                ciphertext_len -= GCM_TAG_LEN;
                if (aad && aad_len > 0) {
                        if (!EVP_DecryptUpdate(decrypt->ctx, NULL, &out_len, (void *) aad, aad_len)) {
                                log_msg(LOG_LEVEL_ERROR, MOD_NAME "AAD processing: %s\n", ERR_error_string(ERR_get_error(), NULL));
                        }
                }
        }
        CHECK(EVP_CipherUpdate(decrypt->ctx, (unsigned char *) plaintext, &out_len, (const unsigned char *) ciphertext, ciphertext_len), "EVP_CipherUpdate");
        int total_len = out_len;
        if (mode == MODE_AES128_GCM) {
                CHECK(EVP_CIPHER_CTX_ctrl(decrypt->ctx, EVP_CTRL_GCM_SET_TAG, GCM_TAG_LEN, (void *) (ciphertext + ciphertext_len)), "GCM set tag");
        }
        CHECK(EVP_CipherFinal(decrypt->ctx, (unsigned char *) plaintext + out_len, &out_len), "EVP_CipherFinal");
        total_len += out_len;
 
        if (mode != MODE_AES128_GCM) {
                uint32_t expected_crc = 0;
                assert((size_t) total_len >= data_len + sizeof expected_crc);
                memcpy(&expected_crc, plaintext + data_len, sizeof expected_crc);
                uint32_t crc = crc32buf(aad, aad_len);
                crc = crc32buf_with_oldcrc(plaintext, data_len, crc);
                if (crc != expected_crc) {
                        log_msg(LOG_LEVEL_WARNING, MOD_NAME "Warning: Packet dropped AES - wrong CRC!\n");
                        return 0;
                }
        }
 
        return data_len;
}

References CHECK, crc32buf(), crc32buf_with_oldcrc(), openssl_decrypt::ctx, GCM_TAG_LEN, get_cipher, openssl_decrypt::key_hash, LOG_LEVEL_ERROR, LOG_LEVEL_WARNING, log_msg(), MOD_NAME, mode, and MODE_AES128_GCM.

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openssl_decrypt_destroy()

static void openssl_decrypt_destroy ( struct openssl_decrypt * s )

static

Definition at line 108 of file openssl_decrypt.c.

{
        if(!s) {
                return;
        }
        EVP_CIPHER_CTX_free(s->ctx);
        free(s);
}

References openssl_decrypt::ctx.

openssl_decrypt_init()

static int openssl_decrypt_init ( struct openssl_decrypt ** state, const char * passphrase )

static

Definition at line 81 of file openssl_decrypt.c.

{
        struct openssl_decrypt *s =
                calloc(1, sizeof(struct openssl_decrypt));
 
        char pass[STR_LEN];
        snprintf_ch(pass, "%s", passphrase);
        // used only by encrypt, drop option
        if (strstr(pass, ":cipher=")) {
                 *strstr(pass, ":cipher=") = '\0';
        }
 
        MD5CTX context;
 
        MD5Init(&context);
        MD5Update(&context, (const unsigned char *) pass,
                        strlen(pass));
        MD5Final(s->key_hash, &context);
 
        s->ctx = EVP_CIPHER_CTX_new();
        log_msg(LOG_LEVEL_INFO, MOD_NAME "Enabled stream decryption.\n");
 
        *state = s;
        return 0;
}

References openssl_decrypt::ctx, openssl_decrypt::key_hash, LOG_LEVEL_INFO, log_msg(), MD5Final(), MD5Init(), MD5Update(), MOD_NAME, snprintf_ch, state, and STR_LEN.

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REGISTER_MODULE()

REGISTER_MODULE	(	openssl_decrypt	,
		&	functions,
		LIBRARY_CLASS_UNDEFINED	,
		OPENSSL_DECRYPT_ABI_VERSION	)

Variable Documentation

functions

const struct openssl_decrypt_info functions

static

Initial value:

= {
        openssl_decrypt_init,
        openssl_decrypt_destroy,
        openssl_decrypt,
}

Definition at line 172 of file openssl_decrypt.c.

                                                     {
        openssl_decrypt_init,
        openssl_decrypt_destroy,
        openssl_decrypt,
};