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/* $OpenBSD: crypto.c,v 1.6 2016/09/03 14:42:08 gilles Exp $ */ |
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/* |
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* Copyright (c) 2013 Gilles Chehade <gilles@openbsd.org> |
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* |
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* Permission to use, copy, modify, and distribute this software for any |
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* purpose with or without fee is hereby granted, provided that the above |
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* copyright notice and this permission notice appear in all copies. |
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* |
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* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES |
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* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF |
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* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR |
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* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES |
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* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN |
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* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF |
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* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. |
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*/ |
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#include <sys/types.h> |
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#include <sys/stat.h> |
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#include <stdlib.h> |
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#include <string.h> |
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#include <openssl/evp.h> |
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#define CRYPTO_BUFFER_SIZE 16384 |
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#define GCM_TAG_SIZE 16 |
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#define IV_SIZE 12 |
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#define KEY_SIZE 32 |
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/* bump if we ever switch from aes-256-gcm to anything else */ |
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#define API_VERSION 1 |
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int crypto_setup(const char *, size_t); |
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int crypto_encrypt_file(FILE *, FILE *); |
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int crypto_decrypt_file(FILE *, FILE *); |
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size_t crypto_encrypt_buffer(const char *, size_t, char *, size_t); |
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size_t crypto_decrypt_buffer(const char *, size_t, char *, size_t); |
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static struct crypto_ctx { |
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unsigned char key[KEY_SIZE]; |
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} cp; |
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int |
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crypto_setup(const char *key, size_t len) |
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{ |
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if (len != KEY_SIZE) |
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return 0; |
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memset(&cp, 0, sizeof cp); |
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/* openssl rand -hex 16 */ |
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memcpy(cp.key, key, sizeof cp.key); |
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return 1; |
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} |
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int |
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crypto_encrypt_file(FILE * in, FILE * out) |
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{ |
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EVP_CIPHER_CTX ctx; |
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uint8_t ibuf[CRYPTO_BUFFER_SIZE]; |
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uint8_t obuf[CRYPTO_BUFFER_SIZE]; |
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uint8_t iv[IV_SIZE]; |
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uint8_t tag[GCM_TAG_SIZE]; |
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uint8_t version = API_VERSION; |
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size_t r, w; |
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int len; |
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int ret = 0; |
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struct stat sb; |
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/* XXX - Do NOT encrypt files bigger than 64GB */ |
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if (fstat(fileno(in), &sb) < 0) |
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return 0; |
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if (sb.st_size >= 0x1000000000LL) |
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return 0; |
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/* prepend version byte*/ |
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if ((w = fwrite(&version, 1, sizeof version, out)) != sizeof version) |
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return 0; |
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/* generate and prepend IV */ |
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memset(iv, 0, sizeof iv); |
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arc4random_buf(iv, sizeof iv); |
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if ((w = fwrite(iv, 1, sizeof iv, out)) != sizeof iv) |
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return 0; |
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EVP_CIPHER_CTX_init(&ctx); |
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EVP_EncryptInit_ex(&ctx, EVP_aes_256_gcm(), NULL, cp.key, iv); |
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/* encrypt until end of file */ |
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while ((r = fread(ibuf, 1, CRYPTO_BUFFER_SIZE, in)) != 0) { |
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if (!EVP_EncryptUpdate(&ctx, obuf, &len, ibuf, r)) |
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goto end; |
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if (len && (w = fwrite(obuf, len, 1, out)) != 1) |
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goto end; |
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} |
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if (!feof(in)) |
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goto end; |
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/* finalize and write last chunk if any */ |
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if (!EVP_EncryptFinal_ex(&ctx, obuf, &len)) |
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goto end; |
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if (len && (w = fwrite(obuf, len, 1, out)) != 1) |
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goto end; |
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/* get and append tag */ |
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EVP_CIPHER_CTX_ctrl(&ctx, EVP_CTRL_GCM_GET_TAG, sizeof tag, tag); |
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if ((w = fwrite(tag, sizeof tag, 1, out)) != 1) |
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goto end; |
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fflush(out); |
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ret = 1; |
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end: |
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EVP_CIPHER_CTX_cleanup(&ctx); |
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return ret; |
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} |
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int |
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crypto_decrypt_file(FILE * in, FILE * out) |
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{ |
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EVP_CIPHER_CTX ctx; |
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uint8_t ibuf[CRYPTO_BUFFER_SIZE]; |
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uint8_t obuf[CRYPTO_BUFFER_SIZE]; |
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uint8_t iv[IV_SIZE]; |
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uint8_t tag[GCM_TAG_SIZE]; |
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uint8_t version; |
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size_t r, w; |
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off_t sz; |
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int len; |
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int ret = 0; |
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struct stat sb; |
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/* input file too small to be an encrypted file */ |
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if (fstat(fileno(in), &sb) < 0) |
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return 0; |
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if (sb.st_size <= (off_t) (sizeof version + sizeof tag + sizeof iv)) |
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return 0; |
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sz = sb.st_size; |
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/* extract tag */ |
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if (fseek(in, -sizeof(tag), SEEK_END) == -1) |
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return 0; |
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if ((r = fread(tag, 1, sizeof tag, in)) != sizeof tag) |
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return 0; |
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if (fseek(in, 0, SEEK_SET) == -1) |
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return 0; |
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/* extract version */ |
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if ((r = fread(&version, 1, sizeof version, in)) != sizeof version) |
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return 0; |
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if (version != API_VERSION) |
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return 0; |
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/* extract IV */ |
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memset(iv, 0, sizeof iv); |
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if ((r = fread(iv, 1, sizeof iv, in)) != sizeof iv) |
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return 0; |
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/* real ciphertext length */ |
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sz -= sizeof version; |
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sz -= sizeof iv; |
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sz -= sizeof tag; |
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EVP_CIPHER_CTX_init(&ctx); |
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EVP_DecryptInit_ex(&ctx, EVP_aes_256_gcm(), NULL, cp.key, iv); |
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/* set expected tag */ |
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EVP_CIPHER_CTX_ctrl(&ctx, EVP_CTRL_GCM_SET_TAG, sizeof tag, tag); |
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/* decrypt until end of ciphertext */ |
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while (sz) { |
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if (sz > CRYPTO_BUFFER_SIZE) |
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r = fread(ibuf, 1, CRYPTO_BUFFER_SIZE, in); |
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else |
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r = fread(ibuf, 1, sz, in); |
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if (!r) |
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break; |
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if (!EVP_DecryptUpdate(&ctx, obuf, &len, ibuf, r)) |
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goto end; |
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if (len && (w = fwrite(obuf, len, 1, out)) != 1) |
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goto end; |
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sz -= r; |
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} |
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if (ferror(in)) |
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goto end; |
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/* finalize, write last chunk if any and perform authentication check */ |
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if (!EVP_DecryptFinal_ex(&ctx, obuf, &len)) |
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goto end; |
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if (len && (w = fwrite(obuf, len, 1, out)) != 1) |
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goto end; |
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fflush(out); |
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ret = 1; |
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end: |
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EVP_CIPHER_CTX_cleanup(&ctx); |
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return ret; |
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} |
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size_t |
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crypto_encrypt_buffer(const char *in, size_t inlen, char *out, size_t outlen) |
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{ |
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EVP_CIPHER_CTX ctx; |
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uint8_t iv[IV_SIZE]; |
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uint8_t tag[GCM_TAG_SIZE]; |
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uint8_t version = API_VERSION; |
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off_t sz; |
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int olen; |
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int len = 0; |
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int ret = 0; |
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/* output buffer does not have enough room */ |
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if (outlen < inlen + sizeof version + sizeof tag + sizeof iv) |
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return 0; |
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/* input should not exceed 64GB */ |
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sz = inlen; |
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if (sz >= 0x1000000000LL) |
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return 0; |
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/* prepend version */ |
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*out = version; |
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len++; |
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/* generate IV */ |
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memset(iv, 0, sizeof iv); |
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arc4random_buf(iv, sizeof iv); |
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memcpy(out + len, iv, sizeof iv); |
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len += sizeof iv; |
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EVP_CIPHER_CTX_init(&ctx); |
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EVP_EncryptInit_ex(&ctx, EVP_aes_256_gcm(), NULL, cp.key, iv); |
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/* encrypt buffer */ |
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if (!EVP_EncryptUpdate(&ctx, out + len, &olen, in, inlen)) |
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goto end; |
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len += olen; |
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/* finalize and write last chunk if any */ |
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if (!EVP_EncryptFinal_ex(&ctx, out + len, &olen)) |
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goto end; |
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len += olen; |
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/* get and append tag */ |
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EVP_CIPHER_CTX_ctrl(&ctx, EVP_CTRL_GCM_GET_TAG, sizeof tag, tag); |
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memcpy(out + len, tag, sizeof tag); |
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ret = len + sizeof tag; |
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end: |
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EVP_CIPHER_CTX_cleanup(&ctx); |
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return ret; |
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} |
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size_t |
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crypto_decrypt_buffer(const char *in, size_t inlen, char *out, size_t outlen) |
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{ |
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EVP_CIPHER_CTX ctx; |
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uint8_t iv[IV_SIZE]; |
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uint8_t tag[GCM_TAG_SIZE]; |
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int olen; |
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int len = 0; |
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int ret = 0; |
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273 |
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/* out does not have enough room */ |
274 |
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if (outlen < inlen - sizeof tag + sizeof iv) |
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return 0; |
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/* extract tag */ |
278 |
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memcpy(tag, in + inlen - sizeof tag, sizeof tag); |
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inlen -= sizeof tag; |
280 |
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281 |
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/* check version */ |
282 |
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if (*in != API_VERSION) |
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return 0; |
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in++; |
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inlen--; |
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287 |
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/* extract IV */ |
288 |
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memset(iv, 0, sizeof iv); |
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memcpy(iv, in, sizeof iv); |
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inlen -= sizeof iv; |
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in += sizeof iv; |
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EVP_CIPHER_CTX_init(&ctx); |
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EVP_DecryptInit_ex(&ctx, EVP_aes_256_gcm(), NULL, cp.key, iv); |
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/* set expected tag */ |
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EVP_CIPHER_CTX_ctrl(&ctx, EVP_CTRL_GCM_SET_TAG, sizeof tag, tag); |
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299 |
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/* decrypt buffer */ |
300 |
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if (!EVP_DecryptUpdate(&ctx, out, &olen, in, inlen)) |
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goto end; |
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len += olen; |
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/* finalize, write last chunk if any and perform authentication check */ |
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if (!EVP_DecryptFinal_ex(&ctx, out + len, &olen)) |
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goto end; |
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ret = len + olen; |
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end: |
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EVP_CIPHER_CTX_cleanup(&ctx); |
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return ret; |
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} |
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314 |
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#if 0 |
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int |
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main(int argc, char *argv[]) |
317 |
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{ |
318 |
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if (argc != 3) { |
319 |
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printf("usage: crypto <key> <buffer>\n"); |
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return 1; |
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} |
322 |
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323 |
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if (!crypto_setup(argv[1], strlen(argv[1]))) { |
324 |
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printf("crypto_setup failed\n"); |
325 |
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return 1; |
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} |
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328 |
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{ |
329 |
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char encbuffer[4096]; |
330 |
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size_t enclen; |
331 |
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char decbuffer[4096]; |
332 |
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size_t declen; |
333 |
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334 |
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printf("encrypt/decrypt buffer: "); |
335 |
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enclen = crypto_encrypt_buffer(argv[2], strlen(argv[2]), |
336 |
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encbuffer, sizeof encbuffer); |
337 |
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338 |
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/* uncomment below to provoke integrity check failure */ |
339 |
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/* |
340 |
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* encbuffer[13] = 0x42; |
341 |
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* encbuffer[14] = 0x42; |
342 |
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* encbuffer[15] = 0x42; |
343 |
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* encbuffer[16] = 0x42; |
344 |
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*/ |
345 |
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346 |
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declen = crypto_decrypt_buffer(encbuffer, enclen, |
347 |
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decbuffer, sizeof decbuffer); |
348 |
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if (declen != 0 && !strncmp(argv[2], decbuffer, declen)) |
349 |
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printf("ok\n"); |
350 |
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else |
351 |
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printf("nope\n"); |
352 |
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} |
353 |
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354 |
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{ |
355 |
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FILE *fpin; |
356 |
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FILE *fpout; |
357 |
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printf("encrypt/decrypt file: "); |
358 |
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359 |
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fpin = fopen("/etc/passwd", "r"); |
360 |
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fpout = fopen("/tmp/passwd.enc", "w"); |
361 |
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if (!crypto_encrypt_file(fpin, fpout)) { |
362 |
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printf("encryption failed\n"); |
363 |
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return 1; |
364 |
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} |
365 |
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fclose(fpin); |
366 |
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fclose(fpout); |
367 |
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368 |
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/* uncomment below to provoke integrity check failure */ |
369 |
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/* |
370 |
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* fpin = fopen("/tmp/passwd.enc", "a"); |
371 |
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* fprintf(fpin, "borken"); |
372 |
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* fclose(fpin); |
373 |
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*/ |
374 |
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fpin = fopen("/tmp/passwd.enc", "r"); |
375 |
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fpout = fopen("/tmp/passwd.dec", "w"); |
376 |
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if (!crypto_decrypt_file(fpin, fpout)) |
377 |
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printf("nope\n"); |
378 |
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else |
379 |
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printf("ok\n"); |
380 |
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fclose(fpin); |
381 |
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fclose(fpout); |
382 |
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} |
383 |
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384 |
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385 |
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return 0; |
386 |
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} |
387 |
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#endif |