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Merge pull request #129 from ozbenh/ossl-helpers
Create helpers for openssl AES use
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| Original file line number | Diff line number | Diff line change |
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| /* | ||
| * ossl_helpers.c -- Helper wrappers around openssl functions | ||
| * | ||
| * This program is free software; you can redistribute it and/or modify | ||
| * it under the terms of the GNU General Public License as published by | ||
| * the Free Software Foundation; either version 2 of the License, or | ||
| * (at your option) any later version. | ||
| * | ||
| * This program is distributed in the hope that it will be useful, | ||
| * but WITHOUT ANY WARRANTY; without even the implied warranty of | ||
| * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | ||
| * GNU General Public License for more details. | ||
| * | ||
| * You should have received a copy of the GNU General Public License | ||
| * along with this program; if not, write to the Free Software | ||
| * Foundation, Inc., 51 Franklin Street, Suite 500, Boston, MA 02110-1335 USA | ||
| */ | ||
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|
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| #include <unistd.h> | ||
| #include <stdlib.h> | ||
| #include <string.h> | ||
| #include <sys/types.h> | ||
| #include <sys/stat.h> | ||
| #include <fcntl.h> | ||
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| #include "ossl_helpers.h" | ||
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| #include <openssl/conf.h> | ||
| #include <openssl/evp.h> | ||
| #include <openssl/err.h> | ||
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| struct ossl_aes_ctx | ||
| { | ||
| EVP_CIPHER_CTX *c; | ||
| const unsigned char *key; | ||
| const unsigned char *iv; | ||
| }; | ||
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| void ossl_aes_random_key(unsigned char *key, const unsigned char *pepper) | ||
| { | ||
| static unsigned char default_key[AES_BLOCK] = { | ||
| 0x00,0x10,0x20,0x30,0x40,0x50,0x60,0x70, | ||
| 0x80,0x90,0xa0,0xb0,0xc0,0xd0,0xe0,0xf0 | ||
| }; /* AES data reduction key */ | ||
| unsigned char stack_junk[AES_BLOCK]; | ||
| int fd, i; | ||
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| /* Try getting some randomness from the kernel */ | ||
| fd = open("/dev/urandom", O_RDONLY); | ||
| if (fd >= 0) { | ||
| int r = read(fd, key, sizeof key); | ||
| close(fd); | ||
| } | ||
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| /* Mix in our default key */ | ||
| for (i = 0; i < AES_BLOCK && pepper; i++) | ||
| key[i] ^= default_key[i]; | ||
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| /* Mix in stack junk */ | ||
| for (i = 0; i < AES_BLOCK && pepper; i++) | ||
| key[i] ^= stack_junk[i]; | ||
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| /* Spice it up if we can */ | ||
| for (i = 0; i < AES_BLOCK && pepper; i++) | ||
| key[i] ^= pepper[i]; | ||
| } | ||
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| struct ossl_aes_ctx *ossl_aes_init(const unsigned char *key, | ||
| const unsigned char *iv) | ||
| { | ||
| struct ossl_aes_ctx *ctx; | ||
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| ctx = malloc(sizeof(*ctx)); | ||
| if (!ctx) | ||
| return NULL; | ||
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| ctx->c = EVP_CIPHER_CTX_new(); | ||
| if (!ctx->c) { | ||
| free(ctx); | ||
| return NULL; | ||
| } | ||
| ctx->key = key; | ||
| ctx->iv = iv; | ||
| return ctx; | ||
| } | ||
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| void ossl_aes_exit(struct ossl_aes_ctx *ctx) | ||
| { | ||
| EVP_CIPHER_CTX_free(ctx->c); | ||
| free(ctx); | ||
| } | ||
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| int ossl_aes_encrypt(struct ossl_aes_ctx *ctx, | ||
| unsigned char *plaintext, int plaintext_len, | ||
| unsigned char *ciphertext) | ||
| { | ||
| int len, ciphertext_len; | ||
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| if(1 != EVP_EncryptInit_ex(ctx->c, EVP_aes_128_cbc(), NULL, ctx->key, ctx->iv)) | ||
| return 0; | ||
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| /* | ||
| * Provide the message to be encrypted, and obtain the encrypted output. | ||
| * EVP_EncryptUpdate can be called multiple times if necessary | ||
| */ | ||
| if(1 != EVP_EncryptUpdate(ctx->c, ciphertext, &len, plaintext, plaintext_len)) | ||
| return 0; | ||
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| ciphertext_len = len; | ||
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| /* | ||
| * Finalise the encryption. Further ciphertext bytes may be written at | ||
| * this stage. | ||
| */ | ||
| if(1 != EVP_EncryptFinal_ex(ctx->c, ciphertext + len, &len)) | ||
| return 0; | ||
| ciphertext_len += len; | ||
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| return ciphertext_len; | ||
| } | ||
|
|
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,58 @@ | ||
| /* | ||
| * ossl_helpers.h -- Helper wrappers around openssl functions | ||
| * | ||
| * This program is free software; you can redistribute it and/or modify | ||
| * it under the terms of the GNU General Public License as published by | ||
| * the Free Software Foundation; either version 2 of the License, or | ||
| * (at your option) any later version. | ||
| * | ||
| * This program is distributed in the hope that it will be useful, | ||
| * but WITHOUT ANY WARRANTY; without even the implied warranty of | ||
| * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | ||
| * GNU General Public License for more details. | ||
| * | ||
| * You should have received a copy of the GNU General Public License | ||
| * along with this program; if not, write to the Free Software | ||
| * Foundation, Inc., 51 Franklin Street, Suite 500, Boston, MA 02110-1335 USA | ||
| */ | ||
|
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| #ifndef OSSL_HELPERS__H | ||
| #define OSSL_HELPERS__H | ||
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| #define AES_BLOCK 16 | ||
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| struct ossl_aes_ctx; | ||
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| extern int ossl_aes_encrypt(struct ossl_aes_ctx *ctx, | ||
| unsigned char *plaintext, int plaintext_len, | ||
| unsigned char *ciphertext); | ||
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| extern struct ossl_aes_ctx *ossl_aes_init(const unsigned char *key, | ||
| const unsigned char *iv); | ||
| extern void ossl_aes_exit(struct ossl_aes_ctx *ctx); | ||
| extern void ossl_aes_random_key(unsigned char *key, const unsigned char *pepper); | ||
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| static inline int ossl_aes_mangle(struct ossl_aes_ctx *ctx, unsigned char *data, | ||
| size_t size) | ||
| { | ||
| int ciphertext_len; | ||
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| /* | ||
| * Buffer for ciphertext. Ensure the buffer is long enough for the | ||
| * ciphertext which may be longer than the plaintext, depending on the | ||
| * algorithm and mode. | ||
| * | ||
| * For AES, one extra AES block should be sufficient. | ||
| */ | ||
| unsigned char ciphertext[size + AES_BLOCK]; | ||
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| /* Encrypt the plaintext */ | ||
| ciphertext_len = ossl_aes_encrypt(ctx, data, size, ciphertext); | ||
| if (!ciphertext_len) | ||
| return -1; | ||
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| memcpy(data, ciphertext, size); | ||
| return ciphertext_len; | ||
| } | ||
|
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| #endif /* OSSL_HELPERS__H */ |
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