/**
\ingroup Core_Create
\brief implementation of EME-PKCS1-v1_5-ENCODE, as defined in OpenPGP RFC
\param M
\param mLen
\param pubkey
\param EM
\return 1 if OK; else 0
*/
unsigned
encode_m_buf(const uint8_t *M, size_t mLen, const pgp_pubkey_t * pubkey,
uint8_t *EM)
{
unsigned k;
unsigned i;
/* implementation of EME-PKCS1-v1_5-ENCODE, as defined in OpenPGP RFC */
switch (pubkey->alg) {
case PGP_PKA_RSA:
k = (unsigned)BN_num_bytes(pubkey->key.rsa.n);
if (mLen > k - 11) {
(void) fprintf(stderr, "encode_m_buf: message too long\n");
return 0;
}
break;
case PGP_PKA_DSA:
case PGP_PKA_ELGAMAL:
k = (unsigned)BN_num_bytes(pubkey->key.elgamal.p);
if (mLen > k - 11) {
(void) fprintf(stderr, "encode_m_buf: message too long\n");
return 0;
}
break;
default:
(void) fprintf(stderr, "encode_m_buf: pubkey algorithm\n");
return 0;
}
/* these two bytes defined by RFC */
EM[0] = 0x00;
EM[1] = 0x02;
/* add non-zero random bytes of length k - mLen -3 */
for (i = 2; i < (k - mLen) - 1; ++i) {
do {
pgp_random(EM + i, 1);
} while (EM[i] == 0);
}
if (i < 8 + 2) {
(void) fprintf(stderr, "encode_m_buf: bad i len\n");
return 0;
}
EM[i++] = 0;
(void) memcpy(EM + i, M, mLen);
if (pgp_get_debug_level(__FILE__)) {
hexdump(stderr, "Encoded Message:", EM, mLen);
}
return 1;
}
/**
\ingroup Core_Create
\brief Creates an pgp_pk_sesskey_t struct from keydata
\param key Keydata to use
\return pgp_pk_sesskey_t struct
\note It is the caller's responsiblity to free the returned pointer
\note Currently hard-coded to use CAST5
\note Currently hard-coded to use RSA
*/
pgp_pk_sesskey_t *
pgp_create_pk_sesskey(const pgp_key_t *key, const char *ciphername)
{
/*
* Creates a random session key and encrypts it for the given key
*
* Encryption used is PK,
* can be any, we're hardcoding RSA for now
*/
const pgp_pubkey_t *pubkey;
pgp_pk_sesskey_t *sesskey;
pgp_symm_alg_t cipher;
const uint8_t *id;
pgp_crypt_t cipherinfo;
uint8_t *unencoded_m_buf;
uint8_t *encoded_m_buf;
size_t sz_encoded_m_buf;
if (memcmp(key->encid, "\0\0\0\0\0\0\0\0", 8) == 0) {
pubkey = pgp_get_pubkey(key);
id = key->sigid;
} else {
pubkey = &key->enckey;
id = key->encid;
}
/* allocate unencoded_m_buf here */
(void) memset(&cipherinfo, 0x0, sizeof(cipherinfo));
pgp_crypt_any(&cipherinfo,
cipher = pgp_str_to_cipher((ciphername) ? ciphername : "cast5"));
unencoded_m_buf = calloc(1, cipherinfo.keysize + 1 + 2);
if (unencoded_m_buf == NULL) {
(void) fprintf(stderr,
"pgp_create_pk_sesskey: can't allocate\n");
return NULL;
}
switch(pubkey->alg) {
case PGP_PKA_RSA:
sz_encoded_m_buf = BN_num_bytes(pubkey->key.rsa.n);
break;
case PGP_PKA_DSA:
case PGP_PKA_ELGAMAL:
sz_encoded_m_buf = BN_num_bytes(pubkey->key.elgamal.p);
break;
default:
sz_encoded_m_buf = 0;
break;
}
if ((encoded_m_buf = calloc(1, sz_encoded_m_buf)) == NULL) {
(void) fprintf(stderr,
"pgp_create_pk_sesskey: can't allocate\n");
free(unencoded_m_buf);
return NULL;
}
if ((sesskey = calloc(1, sizeof(*sesskey))) == NULL) {
(void) fprintf(stderr,
"pgp_create_pk_sesskey: can't allocate\n");
free(unencoded_m_buf);
free(encoded_m_buf);
return NULL;
}
if (key->type != PGP_PTAG_CT_PUBLIC_KEY) {
(void) fprintf(stderr,
"pgp_create_pk_sesskey: bad type\n");
free(unencoded_m_buf);
free(encoded_m_buf);
free(sesskey);
return NULL;
}
sesskey->version = PGP_PKSK_V3;
(void) memcpy(sesskey->key_id, id, sizeof(sesskey->key_id));
if (pgp_get_debug_level(__FILE__)) {
hexdump(stderr, "Encrypting for keyid", id, sizeof(sesskey->key_id));
}
switch (pubkey->alg) {
case PGP_PKA_RSA:
case PGP_PKA_DSA:
case PGP_PKA_ELGAMAL:
break;
default:
(void) fprintf(stderr,
"pgp_create_pk_sesskey: bad pubkey algorithm\n");
free(unencoded_m_buf);
free(encoded_m_buf);
free(sesskey);
return NULL;
}
sesskey->alg = pubkey->alg;
sesskey->symm_alg = cipher;
pgp_random(sesskey->key, cipherinfo.keysize);
if (pgp_get_debug_level(__FILE__)) {
hexdump(stderr, "sesskey created", sesskey->key,
cipherinfo.keysize + 1 + 2);
}
if (create_unencoded_m_buf(sesskey, &cipherinfo, &unencoded_m_buf[0]) == 0) {
free(unencoded_m_buf);
free(encoded_m_buf);
free(sesskey);
return NULL;
}
if (pgp_get_debug_level(__FILE__)) {
hexdump(stderr, "uuencoded m buf", unencoded_m_buf, cipherinfo.keysize + 1 + 2);
}
encode_m_buf(unencoded_m_buf, cipherinfo.keysize + 1 + 2, pubkey, encoded_m_buf);
/* and encrypt it */
switch (key->key.pubkey.alg) {
case PGP_PKA_RSA:
if (!pgp_rsa_encrypt_mpi(encoded_m_buf, sz_encoded_m_buf, pubkey,
&sesskey->params)) {
free(unencoded_m_buf);
free(encoded_m_buf);
free(sesskey);
return NULL;
}
break;
case PGP_PKA_DSA:
case PGP_PKA_ELGAMAL:
if (!pgp_elgamal_encrypt_mpi(encoded_m_buf, sz_encoded_m_buf, pubkey,
&sesskey->params)) {
free(unencoded_m_buf);
free(encoded_m_buf);
free(sesskey);
return NULL;
}
break;
default:
/* will not get here - for lint only */
break;
}
free(unencoded_m_buf);
free(encoded_m_buf);
return sesskey;
}
/*
* Note that we support v3 keys here because they're needed for
* verification.
*/
static unsigned
write_seckey_body(const pgp_seckey_t *key,
const uint8_t *passphrase,
const size_t pplen,
pgp_output_t *output)
{
/* RFC4880 Section 5.5.3 Secret-Key Packet Formats */
pgp_crypt_t crypted;
pgp_hash_t hash;
unsigned done = 0;
unsigned i = 0;
uint8_t *hashed;
uint8_t sesskey[CAST_KEY_LENGTH];
if (!write_pubkey_body(&key->pubkey, output)) {
return 0;
}
if (key->s2k_usage != PGP_S2KU_ENCRYPTED_AND_HASHED) {
(void) fprintf(stderr, "write_seckey_body: s2k usage\n");
return 0;
}
if (!pgp_write_scalar(output, (unsigned)key->s2k_usage, 1)) {
return 0;
}
if (key->alg != PGP_SA_CAST5) {
(void) fprintf(stderr, "write_seckey_body: algorithm\n");
return 0;
}
if (!pgp_write_scalar(output, (unsigned)key->alg, 1)) {
return 0;
}
if (key->s2k_specifier != PGP_S2KS_SIMPLE &&
key->s2k_specifier != PGP_S2KS_SALTED) {
/* = 1 \todo could also be iterated-and-salted */
(void) fprintf(stderr, "write_seckey_body: s2k spec\n");
return 0;
}
if (!pgp_write_scalar(output, (unsigned)key->s2k_specifier, 1)) {
return 0;
}
if (!pgp_write_scalar(output, (unsigned)key->hash_alg, 1)) {
return 0;
}
switch (key->s2k_specifier) {
case PGP_S2KS_SIMPLE:
/* nothing more to do */
break;
case PGP_S2KS_SALTED:
/* 8-octet salt value */
pgp_random(__UNCONST(&key->salt[0]), PGP_SALT_SIZE);
if (!pgp_write(output, key->salt, PGP_SALT_SIZE)) {
return 0;
}
break;
/*
* \todo case PGP_S2KS_ITERATED_AND_SALTED: // 8-octet salt
* value // 1-octet count break;
*/
default:
(void) fprintf(stderr,
"invalid/unsupported s2k specifier %d\n",
key->s2k_specifier);
return 0;
}
if (!pgp_write(output, &key->iv[0], pgp_block_size(key->alg))) {
return 0;
}
/*
* create the session key for encrypting the algorithm-specific
* fields
*/
switch (key->s2k_specifier) {
case PGP_S2KS_SIMPLE:
case PGP_S2KS_SALTED:
/* RFC4880: section 3.7.1.1 and 3.7.1.2 */
for (done = 0, i = 0; done < CAST_KEY_LENGTH; i++) {
unsigned hashsize;
unsigned j;
unsigned needed;
unsigned size;
uint8_t zero = 0;
/* Hard-coded SHA1 for session key */
pgp_hash_any(&hash, PGP_HASH_SHA1);
hashsize = pgp_hash_size(key->hash_alg);
needed = CAST_KEY_LENGTH - done;
size = MIN(needed, hashsize);
if ((hashed = calloc(1, hashsize)) == NULL) {
(void) fprintf(stderr, "write_seckey_body: bad alloc\n");
return 0;
}
if (!hash.init(&hash)) {
(void) fprintf(stderr, "write_seckey_body: bad alloc\n");
return 0;
}
/* preload if iterating */
for (j = 0; j < i; j++) {
/*
* Coverity shows a DEADCODE error on this
* line. This is expected since the hardcoded
* use of SHA1 and CAST5 means that it will
* not used. This will change however when
* other algorithms are supported.
*/
hash.add(&hash, &zero, 1);
}
if (key->s2k_specifier == PGP_S2KS_SALTED) {
hash.add(&hash, key->salt, PGP_SALT_SIZE);
}
hash.add(&hash, passphrase, (unsigned)pplen);
hash.finish(&hash, hashed);
/*
* if more in hash than is needed by session key, use
* the leftmost octets
*/
(void) memcpy(&sesskey[i * hashsize],
hashed, (unsigned)size);
done += (unsigned)size;
if (done > CAST_KEY_LENGTH) {
(void) fprintf(stderr,
"write_seckey_body: short add\n");
return 0;
}
}
break;
/*
* \todo case PGP_S2KS_ITERATED_AND_SALTED: * 8-octet salt
* value * 1-octet count break;
*/
default:
(void) fprintf(stderr,
"invalid/unsupported s2k specifier %d\n",
key->s2k_specifier);
return 0;
}
/* use this session key to encrypt */
pgp_crypt_any(&crypted, key->alg);
crypted.set_iv(&crypted, key->iv);
crypted.set_crypt_key(&crypted, sesskey);
pgp_encrypt_init(&crypted);
if (pgp_get_debug_level(__FILE__)) {
hexdump(stderr, "writing: iv=", key->iv, pgp_block_size(key->alg));
hexdump(stderr, "key= ", sesskey, CAST_KEY_LENGTH);
(void) fprintf(stderr, "\nturning encryption on...\n");
}
pgp_push_enc_crypt(output, &crypted);
switch (key->pubkey.alg) {
case PGP_PKA_RSA:
case PGP_PKA_RSA_ENCRYPT_ONLY:
case PGP_PKA_RSA_SIGN_ONLY:
if (!pgp_write_mpi(output, key->key.rsa.d) ||
!pgp_write_mpi(output, key->key.rsa.p) ||
!pgp_write_mpi(output, key->key.rsa.q) ||
!pgp_write_mpi(output, key->key.rsa.u)) {
if (pgp_get_debug_level(__FILE__)) {
(void) fprintf(stderr,
"4 x mpi not written - problem\n");
}
return 0;
}
break;
case PGP_PKA_DSA:
return pgp_write_mpi(output, key->key.dsa.x);
case PGP_PKA_ELGAMAL:
return pgp_write_mpi(output, key->key.elgamal.x);
default:
return 0;
}
if (!pgp_write(output, key->checkhash, PGP_CHECKHASH_SIZE)) {
return 0;
}
pgp_writer_pop(output);
return 1;
}
int dc_pgp_symm_encrypt(dc_context_t* context,
const char* passphrase,
const void* plain, size_t plain_bytes,
char** ret_ctext_armored)
{
int success = 0;
uint8_t salt[PGP_SALT_SIZE];
pgp_crypt_t crypt_info;
uint8_t* key = NULL;
pgp_output_t* payload_output = NULL;
pgp_memory_t* payload_mem = NULL;
pgp_output_t* encr_output = NULL;
pgp_memory_t* encr_mem = NULL;
if (context==NULL || passphrase==NULL || plain==NULL || plain_bytes==0
|| ret_ctext_armored==NULL ) {
goto cleanup;
}
//printf("\n~~~~~~~~~~~~~~~~~~~~SETUP-PAYLOAD~~~~~~~~~~~~~~~~~~~~\n%s~~~~~~~~~~~~~~~~~~~~/SETUP-PAYLOAD~~~~~~~~~~~~~~~~~~~~\n",key_asc); // DEBUG OUTPUT
/* put the payload into a literal data packet which will be encrypted then, see RFC 4880, 5.7 :
"When it has been decrypted, it contains other packets (usually a literal data packet or compressed data
packet, but in theory other Symmetrically Encrypted Data packets or sequences of packets that form whole OpenPGP messages)" */
pgp_setup_memory_write(&payload_output, &payload_mem, 128);
pgp_write_litdata(payload_output, (const uint8_t*)plain, plain_bytes, PGP_LDT_BINARY);
/* create salt for the key */
pgp_random(salt, PGP_SALT_SIZE);
/* S2K */
#define SYMM_ALGO PGP_SA_AES_128
if (!pgp_crypt_any(&crypt_info, SYMM_ALGO)) {
goto cleanup;
}
int s2k_spec = PGP_S2KS_ITERATED_AND_SALTED; // 0=simple, 1=salted, 3=salted+iterated
int s2k_iter_id = 96; // 0=1024 iterations, 96=65536 iterations
#define HASH_ALG PGP_HASH_SHA256
if ((key = pgp_s2k_do(passphrase, crypt_info.keysize, s2k_spec, HASH_ALG, salt, s2k_iter_id))==NULL) {
goto cleanup;
}
/* encrypt the payload using the key using AES-128 and put it into
OpenPGP's "Symmetric-Key Encrypted Session Key" (Tag 3, https://tools.ietf.org/html/rfc4880#section-5.3) followed by
OpenPGP's "Symmetrically Encrypted Data Packet" (Tag 18, https://tools.ietf.org/html/rfc4880#section-5.13 , better than Tag 9) */
pgp_setup_memory_write(&encr_output, &encr_mem, 128);
pgp_writer_push_armor_msg(encr_output);
/* Tag 3 - PGP_PTAG_CT_SK_SESSION_KEY */
pgp_write_ptag (encr_output, PGP_PTAG_CT_SK_SESSION_KEY);
pgp_write_length (encr_output, 1/*version*/
+ 1/*symm. algo*/
+ 1/*s2k_spec*/
+ 1/*S2 hash algo*/
+ ((s2k_spec==PGP_S2KS_SALTED || s2k_spec==PGP_S2KS_ITERATED_AND_SALTED)? PGP_SALT_SIZE : 0)/*the salt*/
+ ((s2k_spec==PGP_S2KS_ITERATED_AND_SALTED)? 1 : 0)/*number of iterations*/);
pgp_write_scalar (encr_output, 4, 1); // 1 octet: version
pgp_write_scalar (encr_output, SYMM_ALGO, 1); // 1 octet: symm. algo
pgp_write_scalar (encr_output, s2k_spec, 1); // 1 octet: s2k_spec
pgp_write_scalar (encr_output, HASH_ALG, 1); // 1 octet: S2 hash algo
if (s2k_spec==PGP_S2KS_SALTED || s2k_spec==PGP_S2KS_ITERATED_AND_SALTED) {
pgp_write (encr_output, salt, PGP_SALT_SIZE); // 8 octets: the salt
}
if (s2k_spec==PGP_S2KS_ITERATED_AND_SALTED) {
pgp_write_scalar (encr_output, s2k_iter_id, 1); // 1 octet: number of iterations
}
// for(int j=0; j<AES_KEY_LENGTH; j++) { printf("%02x", key[j]); } printf("\n----------------\n");
/* Tag 18 - PGP_PTAG_CT_SE_IP_DATA */
//pgp_write_symm_enc_data((const uint8_t*)payload_mem->buf, payload_mem->length, PGP_SA_AES_128, key, encr_output); //-- would generate Tag 9
{
uint8_t* iv = calloc(1, crypt_info.blocksize); if (iv==NULL) { goto cleanup; }
crypt_info.set_iv(&crypt_info, iv);
free(iv);
crypt_info.set_crypt_key(&crypt_info, &key[0]);
pgp_encrypt_init(&crypt_info);
pgp_write_se_ip_pktset(encr_output, payload_mem->buf, payload_mem->length, &crypt_info);
crypt_info.decrypt_finish(&crypt_info);
}
/* done with symmetric key block */
pgp_writer_close(encr_output);
*ret_ctext_armored = dc_null_terminate((const char*)encr_mem->buf, encr_mem->length);
//printf("\n~~~~~~~~~~~~~~~~~~~~SYMMETRICALLY ENCRYPTED~~~~~~~~~~~~~~~~~~~~\n%s~~~~~~~~~~~~~~~~~~~~/SYMMETRICALLY ENCRYPTED~~~~~~~~~~~~~~~~~~~~\n",encr_string); // DEBUG OUTPUT
success = 1;
cleanup:
if (payload_output) { pgp_output_delete(payload_output); }
if (payload_mem) { pgp_memory_free(payload_mem); }
if (encr_output) { pgp_output_delete(encr_output); }
if (encr_mem) { pgp_memory_free(encr_mem); }
free(key);
return success;
}
