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Correct placement of EVP_CIPHER_CTX_set_padding *after* EVP_EncryptInit

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This commit is contained in:
dmiller 2026-04-14 21:08:03 +00:00
parent b45f865fb9
commit 63c4bb589f
1 changed files with 4 additions and 31 deletions
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35
nping/Crypto.cc
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@ -133,12 +133,11 @@ int Crypto::aes128_cbc_encrypt(u8 *inbuff, size_t inlen, u8 *dst_buff, u8 *key,
EVP_CIPHER_CTX *ctx = &stack_ctx;
EVP_CIPHER_CTX_init(ctx);
#endif
EVP_CIPHER_CTX_set_padding(ctx, 0);
int result=OP_SUCCESS;
if( EVP_EncryptInit(ctx, EVP_aes_128_cbc(), key, iv)==0 ){
nping_print(DBG_4, "EVP_EncryptInit() failed");
result=OP_FAILURE;
}else if( EVP_EncryptUpdate(ctx, dst_buff, &flen, inbuff, (int)inlen)==0 ){
}else if( EVP_CIPHER_CTX_set_padding(ctx, 0) && EVP_EncryptUpdate(ctx, dst_buff, &flen, inbuff, (int)inlen)==0 ){
nping_print(DBG_4, "EVP_EncryptUpdate() failed");
result=OP_FAILURE;
}else if( EVP_EncryptFinal(ctx, dst_buff+flen, &flen2)==0 ){
@ -173,7 +172,6 @@ int Crypto::aes128_cbc_decrypt(u8 *inbuff, size_t inlen, u8 *dst_buff, u8 *key,
EVP_CIPHER_CTX *ctx = &stack_ctx;
EVP_CIPHER_CTX_init(ctx);
#endif
EVP_CIPHER_CTX_set_padding(ctx, 0);
int result=OP_SUCCESS;
if( EVP_DecryptInit(ctx, EVP_aes_128_cbc(), key, iv)==0 ){
nping_print(DBG_4, "EVP_DecryptInit() failed");
@ -181,34 +179,9 @@ int Crypto::aes128_cbc_decrypt(u8 *inbuff, size_t inlen, u8 *dst_buff, u8 *key,
}else if( EVP_DecryptUpdate(ctx, dst_buff, &flen1, inbuff, (int)inlen)==0 ){
nping_print(DBG_4, "EVP_DecryptUpdate() failed");
result=OP_FAILURE;
}else if( EVP_DecryptFinal(ctx, dst_buff+flen1, &flen2)==0 ){
nping_print(DBG_4, "OpenSSL bug: it says EVP_DecryptFinal() failed when it didn't (%s).",
ERR_error_string(ERR_peek_last_error(), NULL));
/* We do not return OP_FAILURE in this case because the
* EVP_DecryptFinal() function seems to be buggy and fails when it shouldn't.
* We are passing a buffer whose length is multiple of the AES block
* size, we've disable padding, and still, the call fails.
* The call to EVP_DecryptUpdate() says we've decrypted all blocks but
* the last one and then EVP_DecryptFinal says we have decrypted nothing.
* However I've tested this for hours and everything works fine. The
* full buffer is decrypted correctly, from the first to the last byte,
* so we return OP_SUCCESS even if OpenSSL says the opposite. */
/* NOTE for developers debugging memory issues with Valgrind:
* None of these seems to free OpenSSL's internal error structures.
* Valgrind currently reports things like:
==12849== 592 bytes in 1 blocks are still reachable in loss record 7 of 9
==12849== at 0x4C284A8: malloc (vg_replace_malloc.c:236)
==12849== by 0x531BF21: CRYPTO_malloc (in /lib/libcrypto.so.0.9.8)
==12849== by 0x537F25D: ERR_get_state (in /lib/libcrypto.so.0.9.8)
==12849== by 0x537E7BE: ERR_put_error (in /lib/libcrypto.so.0.9.8)
==12849== by 0x5381EB0: EVP_DecryptFinal_ex (in /lib/libcrypto.so.0.9.8)
==12849== by 0x429A49: Crypto::aes128_cbc_decrypt(unsigned char*...
==12849== by 0x41ABBA: EchoHeader::decrypt(unsigned char*, unsign...
*/
//ERR_clear_error();
//ERR_free_strings();
//ERR_pop_to_mark();
}else if( EVP_CIPHER_CTX_set_padding(ctx, 0) && EVP_DecryptFinal(ctx, dst_buff+flen1, &flen2)==0 ){
nping_print(DBG_4, "EVP_DecryptFinal() failed");
result=OP_FAILURE;
}
EVP_CIPHER_CTX_free(ctx);
return result;