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Crypto-Example/crypto_file_example.cpp at master · shanet/Crypto-Example · GitHub
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#
include
"
crypto_file_example.h
"
//
Note: This isn't a good way to encrypt large file (anything that can't be read into
//
memory in a single buffer). A better approach for this is to read in one block at a type,
//
encrypt it, write it to a file, and so on.
int
main
(
int
argc,
char
**argv) {
if
(argc !=
2
) {
fprintf
(stderr,
"
Invalid number of arguments given.
\n
Usage: %s [input file]
\n
"
, argv[
0
]);
return
1
;
}
Crypto crypto;
char
*encryptedOutput =
appendToString
(argv[
1
], (
char
*)
"
.enc
"
);
char
*decryptedOutput =
appendToString
(argv[
1
], (
char
*)
"
.dec
"
);
encryptFile
(&crypto, argv[
1
], encryptedOutput);
decryptFile
(&crypto, encryptedOutput, decryptedOutput);
free
(encryptedOutput);
free
(decryptedOutput);
return
0
;
}
void
encryptFile
(Crypto *crypto,
char
*input,
char
*output) {
//
Read the file to encrypt
unsigned
char
*plaintext;
size_t
plainTextLength =
readFile
(input, &plaintext);
printf
(
"
%d bytes to be encrypted
\n
"
, (
int
)plainTextLength);
//
Encrypt the file
unsigned
char
*ciphertext;
int
ciphertextLength = crypto->
aesEncrypt
((
const
unsigned
char
*)plaintext, plainTextLength, &ciphertext);
if
(ciphertextLength == -
1
) {
fprintf
(stderr,
"
Encryption failed
\n
"
);
exit
(
1
);
}
printf
(
"
%d bytes encrypted
\n
"
, ciphertextLength);
//
Encode the encrypted file to base64
char
*base64Ciphertext =
base64Encode
(ciphertext, ciphertextLength);
//
Write the encrypted file to its own file
writeFile
(output, (
unsigned
char
*)base64Ciphertext,
strlen
((
char
*)base64Ciphertext));
printf
(
"
Encrypted file written to
\"
%s
\"\n
"
, output);
free
(plaintext);
free
(ciphertext);
free
(base64Ciphertext);
}
void
decryptFile
(Crypto *crypto,
char
*input,
char
*output) {
//
Read the encrypted file back
unsigned
char
*base64Ciphertext;
size_t
base64CiphertextLength =
readFile
(input, &base64Ciphertext);
//
Decode the encrypted file from base64
unsigned
char
*ciphertext;
size_t
ciphertextLength =
base64Decode
((
char
*)base64Ciphertext, base64CiphertextLength, &ciphertext);
//
Decrypt the encrypted file
unsigned
char
*plaintext;
int
plaintextLength = crypto->
aesDecrypt
(ciphertext, ciphertextLength, &plaintext);
if
(plaintextLength == -
1
) {
fprintf
(stderr,
"
Decryption failed
\n
"
);
exit
(
1
);
}
printf
(
"
%d bytes decrypted
\n
"
, (
int
)plaintextLength);
//
Write the decrypted file to its own file
writeFile
(output, plaintext, plaintextLength);
printf
(
"
Decrypted file written to
\"
%s
\"\n
"
, output);
free
(base64Ciphertext);
free
(ciphertext);
free
(plaintext);
}
void
writeFile
(
char
*filename,
unsigned
char
*file,
size_t
fileLength) {
FILE
*fd =
fopen
(filename,
"
w
"
);
if
(fd ==
NULL
) {
fprintf
(stderr,
"
Failed to open file: %s
\n
"
,
strerror
(errno));
exit
(
1
);
}
size_t
bytesWritten =
fwrite
(file,
1
, fileLength, fd);
if
(bytesWritten != fileLength) {
fprintf
(stderr,
"
Failed to write file
\n
"
);
exit
(
1
);
}
fclose
(fd);
}
int
readFile
(
char
*filename,
unsigned
char
**file) {
FILE
*fd =
fopen
(filename,
"
r
"
);
if
(fd ==
NULL
) {
fprintf
(stderr,
"
Failed to open file: %s
\n
"
,
strerror
(errno));
exit
(
1
);
}
//
Determine size of the file
fseek
(fd,
0
,
SEEK_END
);
size_t
fileLength =
ftell
(fd);
fseek
(fd,
0
,
SEEK_SET
);
//
Allocate space for the file
*file = (
unsigned
char
*)
malloc
(fileLength);
if
(*file ==
NULL
) {
fprintf
(stderr,
"
Failed to allocate memory
\n
"
);
exit
(
1
);
}
//
Read the file into the buffer
size_t
bytesRead =
fread
(*file,
1
, fileLength, fd);
if
(bytesRead != fileLength) {
fprintf
(stderr,
"
Error reading file
\n
"
);
exit
(
1
);
}
fclose
(fd);
return
fileLength;
}
char
*
appendToString
(
char
*string,
char
*suffix) {
char
*appenedString = (
char
*)
malloc
(
strlen
(string) +
strlen
(suffix) +
1
);
if
(appenedString ==
NULL
) {
fprintf
(stderr,
"
Failed to allocate memory
\n
"
);
exit
(
1
);
}
sprintf
(appenedString,
"
%s%s
"
, string, suffix);
return
appenedString;
}
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