Hi,
I was testing aes ccm encryption when I stumbled over a segmentation fault.
I was able to reproduce this error using code from the openssl demos.
I started with demos/evp/aesccm.c and added rsa key generation as used
in 'demos/tunala/cb.c' and convert this rsa key into an EVP_PKEY key as
done in 'demos/selfsign.c'.
Then I added this rsa key generation function in front of the aes ccm
encryption and decryption.
Finally, a for loop repeatedly performs the keygeneration, aes
encryption and aes decryption.
This eventually results in a segmentation fault during aes ccm
encryption (see gdb output below) on a x64 Ubuntu 12.04 with latest
openssl version as provided by ubuntu package system (1.0.1-4ubuntu5.13).
Note that the segfault only occurs if the rsa key is assigned to an
EVP_PKEY. Otherwise, if only the RSA key is generated, the segfault does
not occur.
When encountering this error in my own code I could observe that the
error occurred more often on a machine that only runs the standard
processes and is accessed remotely by ssh, compared to a local
workstation with running webbrowser, development IDE, etc., where the
error occurred rather seldom.
Hence, I have the feeling that this could be related to too little
randomness for the RNG, but I do not have any idea how to debug this.
[Note that there is another segmentation fault that occurs if I call
EVP_PKEY_free() on the generated key (see code), which I do not
understand. However, my main problem is the first segmentation fault.]
=== gdb backtrace ===
(gdb) run
Starting program: /home/hiller/openssl_bug/aesccm
AES CCM Encrypt:
Plaintext:
0000 - c8 d2 75 f9 19 e1 7d 7f-e6 9c 2a 1f 58 93 9d fe ..u...}...*.X...
0010 - 4d 40 37 91 b5 df 13 10- M@7.....
Ciphertext:
0000 - 8a 0f 3d 82 29 e4 8e 74-87 fd 95 a2 8a d3 92 c8 ..=.)..t........
0010 - 0b 36 81 d4 fb c7 bb fd- .6......
Tag:
0000 - 2d d6 ef 1c 45 d4 cc b7-23 dc 07 44 14 db 50 6d -...E...#..D..Pm
AES CCM Derypt:
Ciphertext:
0000 - 8a 0f 3d 82 29 e4 8e 74-87 fd 95 a2 8a d3 92 c8 ..=.)..t........
0010 - 0b 36 81 d4 fb c7 bb fd- .6......
Plaintext:
0000 - c8 d2 75 f9 19 e1 7d 7f-e6 9c 2a 1f 58 93 9d fe ..u...}...*.X...
0010 - 4d 40 37 91 b5 df 13 10- M@7.....
AES CCM Encrypt:
[ the output above is repeated several times ]
Program received signal SIGSEGV, Segmentation fault.
0x0000000000000090 in ?? ()
(gdb) backtrace
#0 0x0000000000000090 in ?? ()
#1 0x00007ffff7a948d4 in CRYPTO_ccm128_encrypt_ccm64 (ctx=0x604fd0,
inp=0x401240
"\310\322u\371\031\341}\177\346\234*\037X\223\235\376M@7\221\265\337\023\020",
out=0x7fffffffe0c0
"\310\322u\371\031\341}\177\346\234*\037X\223\235\376M@7\221\265\337\023\020",
len=24, stream=<optimized out>) at ccm128.c:354
#2 0x00007ffff7af1688 in aes_ccm_cipher (ctx=0x604e10,
out=0x7fffffffe0c0
"\310\322u\371\031\341}\177\346\234*\037X\223\235\376M@7\221\265\337\023\020",
in=0x401240
"\310\322u\371\031\341}\177\346\234*\037X\223\235\376M@7\221\265\337\023\020",
len=24) at e_aes.c:1275
#3 0x00007ffff7aedaa2 in EVP_EncryptUpdate (ctx=0x604e10,
out=0x7fffffffe0c0
"\310\322u\371\031\341}\177\346\234*\037X\223\235\376M@7\221\265\337\023\020",
outl=0x7fffffffe0bc,
in=0x401240
"\310\322u\371\031\341}\177\346\234*\037X\223\235\376M@7\221\265\337\023\020",
inl=<optimized out>) at evp_enc.c:314
#4 0x0000000000400e37 in aes_ccm_encrypt () at aesccm.c:106
#5 0x00000000004010ce in main (argc=1, argv=0x7fffffffe5e8) at aesccm.c:161
/* Simple AES CCM test program, uses the same NIST data used for the FIPS
* self test but uses the application level EVP APIs.
*/
#include <stdio.h>
#include <openssl/bio.h>
#include <openssl/evp.h>
#include <openssl/rsa.h>
/* AES-CCM test data from NIST public test vectors */
static const unsigned char ccm_key[] = {
0xce,0xb0,0x09,0xae,0xa4,0x45,0x44,0x51,0xfe,0xad,0xf0,0xe6,
0xb3,0x6f,0x45,0x55,0x5d,0xd0,0x47,0x23,0xba,0xa4,0x48,0xe8
};
static const unsigned char ccm_nonce[] = {
0x76,0x40,0x43,0xc4,0x94,0x60,0xb7
};
static const unsigned char ccm_adata[] = {
0x6e,0x80,0xdd,0x7f,0x1b,0xad,0xf3,0xa1,0xc9,0xab,0x25,0xc7,
0x5f,0x10,0xbd,0xe7,0x8c,0x23,0xfa,0x0e,0xb8,0xf9,0xaa,0xa5,
0x3a,0xde,0xfb,0xf4,0xcb,0xf7,0x8f,0xe4
};
static const unsigned char ccm_pt[] = {
0xc8,0xd2,0x75,0xf9,0x19,0xe1,0x7d,0x7f,0xe6,0x9c,0x2a,0x1f,
0x58,0x93,0x9d,0xfe,0x4d,0x40,0x37,0x91,0xb5,0xdf,0x13,0x10
};
static const unsigned char ccm_ct[] = {
0x8a,0x0f,0x3d,0x82,0x29,0xe4,0x8e,0x74,0x87,0xfd,0x95,0xa2,
0x8a,0xd3,0x92,0xc8,0x0b,0x36,0x81,0xd4,0xfb,0xc7,0xbb,0xfd
};
static const unsigned char ccm_tag[] = {
0x2d,0xd6,0xef,0x1c,0x45,0xd4,0xcc,0xb7,0x23,0xdc,0x07,0x44,
0x14,0xdb,0x50,0x6d
};
/** function from /openssl/demos/tunala/cb.c */
RSA *cb_generate_tmp_rsa(int keylength)
{
/* TODO: Perhaps make it so our global key can be generated on-the-fly
* after certain intervals? */
static RSA *rsa_tmp = NULL;
BIGNUM *bn = NULL;
int ok = 1;
if(!rsa_tmp) {
ok = 0;
if(!(bn = BN_new()))
goto end;
if(!BN_set_word(bn, RSA_F4))
goto end;
if(!(rsa_tmp = RSA_new()))
goto end;
if(!RSA_generate_key_ex(rsa_tmp, keylength, bn, NULL))
goto end;
ok = 1;
}
/* EVP_PKEY as used by /openssl/demos/selfsign.c */
EVP_PKEY *key;
key = EVP_PKEY_new();
if (!key) {
goto end;
}
if (!EVP_PKEY_assign_RSA(key, rsa_tmp)) {
goto end;
}
//EVP_PKEY_free(key); // uncommenting this leads to another segmentation fault
/* end of EVP_PKEY as used by /openssl/demos/selfsign.c */
end:
if(bn)
BN_free(bn);
if(!ok) {
RSA_free(rsa_tmp);
rsa_tmp = NULL;
}
return rsa_tmp;
}
void aes_ccm_encrypt(void)
{
EVP_CIPHER_CTX *ctx;
int outlen, tmplen;
unsigned char outbuf[1024];
printf("AES CCM Encrypt:\n");
printf("Plaintext:\n");
BIO_dump_fp(stdout, ccm_pt, sizeof(ccm_pt));
ctx = EVP_CIPHER_CTX_new();
/* Set cipher type and mode */
EVP_EncryptInit_ex(ctx, EVP_aes_192_ccm(), NULL, NULL, NULL);
/* Set nonce length if default 96 bits is not appropriate */
EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_CCM_SET_IVLEN, sizeof(ccm_nonce), NULL);
/* Set tag length */
EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_CCM_SET_TAG, sizeof(ccm_tag), NULL);
/* Initialise key and IV */
EVP_EncryptInit_ex(ctx, NULL, NULL, ccm_key, ccm_nonce);
/* Set plaintext length: only needed if AAD is used */
EVP_EncryptUpdate(ctx, NULL, &outlen, NULL, sizeof(ccm_pt));
/* Zero or one call to specify any AAD */
EVP_EncryptUpdate(ctx, NULL, &outlen, ccm_adata, sizeof(ccm_adata));
/* Encrypt plaintext: can only be called once */
EVP_EncryptUpdate(ctx, outbuf, &outlen, ccm_pt, sizeof(ccm_pt));
/* Output encrypted block */
printf("Ciphertext:\n");
BIO_dump_fp(stdout, outbuf, outlen);
/* Finalise: note get no output for CCM */
EVP_EncryptFinal_ex(ctx, outbuf, &outlen);
/* Get tag */
EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_CCM_GET_TAG, 16, outbuf);
/* Output tag */
printf("Tag:\n");
BIO_dump_fp(stdout, outbuf, 16);
EVP_CIPHER_CTX_free(ctx);
}
void aes_ccm_decrypt(void)
{
EVP_CIPHER_CTX *ctx;
int outlen, tmplen, rv;
unsigned char outbuf[1024];
printf("AES CCM Derypt:\n");
printf("Ciphertext:\n");
BIO_dump_fp(stdout, ccm_ct, sizeof(ccm_ct));
ctx = EVP_CIPHER_CTX_new();
/* Select cipher */
EVP_DecryptInit_ex(ctx, EVP_aes_192_ccm(), NULL, NULL, NULL);
/* Set nonce length, omit for 96 bits */
EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_CCM_SET_IVLEN, sizeof(ccm_nonce), NULL);
/* Set expected tag value */
EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_CCM_SET_TAG,
sizeof(ccm_tag), (void *)ccm_tag);
/* Specify key and IV */
EVP_DecryptInit_ex(ctx, NULL, NULL, ccm_key, ccm_nonce);
/* Set ciphertext length: only needed if we have AAD */
EVP_DecryptUpdate(ctx, NULL, &outlen, NULL, sizeof(ccm_ct));
/* Zero or one call to specify any AAD */
EVP_DecryptUpdate(ctx, NULL, &outlen, ccm_adata, sizeof(ccm_adata));
/* Decrypt plaintext, verify tag: can only be called once */
rv = EVP_DecryptUpdate(ctx, outbuf, &outlen, ccm_ct, sizeof(ccm_ct));
/* Output decrypted block: if tag verify failed we get nothing */
if (rv > 0)
{
printf("Plaintext:\n");
BIO_dump_fp(stdout, outbuf, outlen);
}
else
printf("Plaintext not available: tag verify failed.\n");
EVP_CIPHER_CTX_free(ctx);
}
int main(int argc, char **argv)
{
int i;
for( i=0; i<1000; i++)
{
cb_generate_tmp_rsa(2048);
aes_ccm_encrypt();
aes_ccm_decrypt();
}
}
