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crypto: make ssh2_bn_from_bin() init the bignum, drop ssh2_bn_init_from_bin()

Browse Source 
To better hide backend-specific differences and t bring the init
sub-steps (1. allocation, 2. conversion) close to each other.

Also:
- HACKING_CRYPTO.md: fix docs for `ssh2_bn_from_bin()` and
  `ssh2_bn_set_word()`.

Ref: https://github.com/libssh2/libssh2/pull/2583#discussion_r3948922721

Closes #2594
This commit is contained in:
Viktor Szakats
2026-09-07 13:42:21 +02:00
parent c3c1743a1f
commit 13e1042b99
10 changed files with 97 additions and 78 deletions
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17
src/HACKING-CRYPTO.md
View File

@@ -329,15 +329,6 @@ ssh2_bn *ssh2_bn_init(void);
```
Creates a multiple precision number (preset to zero).
```c
ssh2_bn *ssh2_bn_init_from_bin(void);
```
Create a multiple precision number intended to be set by the
`ssh2_bn_from_bin()` function (see below). Unlike `ssh2_bn_init()`, this code
may be a dummy initializer if the `ssh2_bn_from_bin()` actually allocates the
number. Returns a value of type `ssh2_bn *`.
```c
void ssh2_bn_free(ssh2_bn *bn);
```
@@ -358,17 +349,17 @@ Returns the number of bits of multiple precision number at `bn`.
int ssh2_bn_set_word(ssh2_bn *bn, uint32_t word);
```
Sets the value of `bn` to `word`.
Returns 1 on success, 0 otherwise.
Returns 0 on success, non-zero on failure.
```c
ssh2_bn *ssh2_bn_from_bin(ssh2_bn *bn, const unsigned char *bin, size_t len);
int ssh2_bn_from_bin(ssh2_bn **bn, const unsigned char *bin, size_t len);
```
Converts the positive integer in big-endian form of length `len` at `bin` into
an `ssh2_bn` and place it in `bn`. If `bn` is NULL, a new `ssh2_bn` is
an `ssh2_bn` and place it in `*bn`. If `*bn` is NULL, a new `ssh2_bn` is
created.
Returns a pointer to target `ssh2_bn` or NULL if error.
Returns 0 on success, non-zero on failure.
```c
int ssh2_bn_to_bin(ssh2_bn *bn, unsigned char *bin);

5
src/crypto.h
View File

@@ -305,11 +305,10 @@ void ssh2_bn_free(ssh2_bn *bn);
#ifndef ssh2_bn_set_word
int ssh2_bn_set_word(ssh2_bn *bn, uint32_t word);
size_t ssh2_bn_bits(const ssh2_bn *bn);
int ssh2_bn_from_bin(ssh2_bn *bn, const unsigned char *bin, size_t len);
int ssh2_bn_to_bin(const ssh2_bn *bn, unsigned char *bin);
#endif
#ifndef ssh2_bn_init_from_bin
#define ssh2_bn_init_from_bin() ssh2_bn_init()
#ifndef ssh2_bn_from_bin
int ssh2_bn_from_bin(ssh2_bn **bn, const unsigned char *bin, size_t len);
#endif
void ssh2_dh_init(ssh2_dh_ctx *dhctx);

43
src/kex.c
View File

@@ -427,8 +427,7 @@ static int kex_diffie_hellman_sha(LIBSSH2_SESSION *session,
exchange_state->ctx = ssh2_bn_ctx_new();
ssh2_dh_init(&exchange_state->x);
exchange_state->e = ssh2_bn_init(); /* g^x mod p */
exchange_state->f = ssh2_bn_init_from_bin(); /* g^(Random from
server) mod p */
exchange_state->f = NULL; /* g^(Random from server) mod p */
exchange_state->k = ssh2_bn_init(); /* The shared secret: f^x mod p */
/* Zero the whole thing out */
@@ -557,7 +556,7 @@ static int kex_diffie_hellman_sha(LIBSSH2_SESSION *session,
goto clean_exit;
}
if(ssh2_bn_from_bin(exchange_state->f,
if(ssh2_bn_from_bin(&exchange_state->f,
exchange_state->f_value,
exchange_state->f_value_len)) {
ret = ssh2_err(session, LIBSSH2_ERROR_HOSTKEY_INIT,
@@ -761,8 +760,7 @@ static int kex_method_diffie_hellman_group1_sha1_key_exchange(
if(key_state->state == ssh2_NB_state_idle) {
/* g == 2 */
key_state->p = ssh2_bn_init_from_bin(); /* SSH2 defined value
(p_value) */
key_state->p = NULL; /* SSH2 defined value (p_value) */
key_state->g = ssh2_bn_init(); /* SSH2 defined value (2) */
/* Initialize P and G */
@@ -771,7 +769,7 @@ static int kex_method_diffie_hellman_group1_sha1_key_exchange(
"Failed to allocate key state g.");
goto clean_exit;
}
if(!key_state->p || ssh2_bn_from_bin(key_state->p, p_value, 128)) {
if(ssh2_bn_from_bin(&key_state->p, p_value, 128)) {
ret = ssh2_err(session, LIBSSH2_ERROR_ALLOC,
"Failed to allocate key state p.");
goto clean_exit;
@@ -856,8 +854,7 @@ static int kex_method_diffie_hellman_group14_key_exchange(
int ret;
if(key_state->state == ssh2_NB_state_idle) {
key_state->p = ssh2_bn_init_from_bin(); /* SSH2 defined value
(p_value) */
key_state->p = NULL; /* SSH2 defined value (p_value) */
key_state->g = ssh2_bn_init(); /* SSH2 defined value (2) */
/* g == 2 */
@@ -867,8 +864,7 @@ static int kex_method_diffie_hellman_group14_key_exchange(
"Failed to allocate key state g.");
goto clean_exit;
}
else if(!key_state->p ||
ssh2_bn_from_bin(key_state->p, p_value, 256)) {
else if(ssh2_bn_from_bin(&key_state->p, p_value, 256)) {
ret = ssh2_err(session, LIBSSH2_ERROR_ALLOC,
"Failed to allocate key state p.");
goto clean_exit;
@@ -968,8 +964,7 @@ static int kex_method_diffie_hellman_group16_sha512_key_exchange(
int ret;
if(key_state->state == ssh2_NB_state_idle) {
key_state->p = ssh2_bn_init_from_bin(); /* SSH2 defined value
(p_value) */
key_state->p = NULL; /* SSH2 defined value (p_value) */
key_state->g = ssh2_bn_init(); /* SSH2 defined value (2) */
/* g == 2 */
@@ -979,7 +974,7 @@ static int kex_method_diffie_hellman_group16_sha512_key_exchange(
"Failed to allocate key state g.");
goto clean_exit;
}
if(!key_state->p || ssh2_bn_from_bin(key_state->p, p_value, 512)) {
if(ssh2_bn_from_bin(&key_state->p, p_value, 512)) {
ret = ssh2_err(session, LIBSSH2_ERROR_ALLOC,
"Failed to allocate key state p.");
goto clean_exit;
@@ -1101,8 +1096,7 @@ static int kex_method_diffie_hellman_group18_sha512_key_exchange(
int ret;
if(key_state->state == ssh2_NB_state_idle) {
key_state->p = ssh2_bn_init_from_bin(); /* SSH2 defined value
(p_value) */
key_state->p = NULL; /* SSH2 defined value (p_value) */
key_state->g = ssh2_bn_init(); /* SSH2 defined value (2) */
/* g == 2 */
@@ -1112,8 +1106,7 @@ static int kex_method_diffie_hellman_group18_sha512_key_exchange(
"Failed to allocate key state g.");
goto clean_exit;
}
else if(!key_state->p ||
ssh2_bn_from_bin(key_state->p, p_value, 1024)) {
else if(ssh2_bn_from_bin(&key_state->p, p_value, 1024)) {
ret = ssh2_err(session, LIBSSH2_ERROR_ALLOC,
"Failed to allocate key state p.");
goto clean_exit;
@@ -1150,8 +1143,8 @@ static int kex_method_diffie_hellman_group_exchange_sha1_key_exchange(
int rc;
if(key_state->state == ssh2_NB_state_idle) {
key_state->p = ssh2_bn_init_from_bin();
key_state->g = ssh2_bn_init_from_bin();
key_state->p = NULL;
key_state->g = NULL;
/* Ask for a P and G pair */
key_state->request[0] = SSH_MSG_KEX_DH_GEX_REQUEST;
ssh2_htonu32(key_state->request + 1, SSH2_DH_GEX_MINGROUP);
@@ -1222,7 +1215,7 @@ static int kex_method_diffie_hellman_group_exchange_sha1_key_exchange(
goto dh_gex_clean_exit;
}
if(ssh2_bn_from_bin(key_state->p, p, p_len)) {
if(ssh2_bn_from_bin(&key_state->p, p, p_len)) {
ret = ssh2_err(session, LIBSSH2_ERROR_PROTO, "Invalid DH-SHA1 p");
goto dh_gex_clean_exit;
}
@@ -1235,7 +1228,7 @@ static int kex_method_diffie_hellman_group_exchange_sha1_key_exchange(
goto dh_gex_clean_exit;
}
if(ssh2_bn_from_bin(key_state->g, g, g_len)) {
if(ssh2_bn_from_bin(&key_state->g, g, g_len)) {
ret = ssh2_err(session, LIBSSH2_ERROR_PROTO, "Invalid DH-SHA1 g");
goto dh_gex_clean_exit;
}
@@ -1270,8 +1263,8 @@ static int kex_method_diffie_hellman_group_exchange_sha256_key_exchange(
int rc;
if(key_state->state == ssh2_NB_state_idle) {
key_state->p = ssh2_bn_init_from_bin();
key_state->g = ssh2_bn_init_from_bin();
key_state->p = NULL;
key_state->g = NULL;
/* Ask for a P and G pair */
key_state->request[0] = SSH_MSG_KEX_DH_GEX_REQUEST;
ssh2_htonu32(key_state->request + 1, SSH2_DH_GEX_MINGROUP);
@@ -1343,7 +1336,7 @@ static int kex_method_diffie_hellman_group_exchange_sha256_key_exchange(
goto dh_gex_clean_exit;
}
if(ssh2_bn_from_bin(key_state->p, p, p_len)) {
if(ssh2_bn_from_bin(&key_state->p, p, p_len)) {
ret = ssh2_err(session, LIBSSH2_ERROR_PROTO,
"Invalid DH-SHA256 p");
goto dh_gex_clean_exit;
@@ -1357,7 +1350,7 @@ static int kex_method_diffie_hellman_group_exchange_sha256_key_exchange(
goto dh_gex_clean_exit;
}
if(ssh2_bn_from_bin(key_state->g, g, g_len)) {
if(ssh2_bn_from_bin(&key_state->g, g, g_len)) {
ret = ssh2_err(session, LIBSSH2_ERROR_PROTO,
"Invalid DH-SHA256 g");
goto dh_gex_clean_exit;

4
src/libgcrypt.h
View File

@@ -116,11 +116,9 @@
#define ssh2_bn struct gcry_mpi
#define ssh2_bn_init() gcry_mpi_new(0)
#define ssh2_bn_init_from_bin() NULL /* because gcry_mpi_scan()
creates a new bignum */
#define ssh2_bn_set_word(bn, word) gcry_mpi_set_ui(bn, word)
#define ssh2_bn_from_bin(bn, bin, len) \
gcry_mpi_scan(&(bn), GCRYMPI_FMT_USG, bin, len, NULL)
gcry_mpi_scan(bn, GCRYMPI_FMT_USG, bin, len, NULL)
#define ssh2_bn_to_bin(bn, bin) \
gcry_mpi_print(GCRYMPI_FMT_USG, bin, ssh2_bn_bytes(bn), NULL, bn)
#define ssh2_bn_bytes(bn) \

14
src/mbedtls.c
View File

@@ -373,6 +373,20 @@ void ssh2_bn_free(ssh2_bn *bn)
}
}
int ssh2_bn_from_bin(ssh2_bn **bn, const unsigned char *bin, size_t len)
{
if(!bn || !bin || !len)
return -1;
if(!*bn) {
*bn = ssh2_bn_init();
if(!*bn)
return -1;
}
return mbedtls_mpi_read_binary(*bn, bin, len);
}
static int mbed_bn_random(ssh2_bn *bn, int bits, int top, int bottom)
{
size_t len;

1
src/mbedtls.h
View File

@@ -219,7 +219,6 @@ struct ssh2_mbed_cipher_ctx {
#define ssh2_bn mbedtls_mpi
#define ssh2_bn_set_word(bn, word) mbedtls_mpi_lset(bn, word)
#define ssh2_bn_from_bin(bn, bin, len) mbedtls_mpi_read_binary(bn, bin, len)
#define ssh2_bn_to_bin(bn, bin) \
mbedtls_mpi_write_binary(bn, bin, mbedtls_mpi_size(bn))
#define ssh2_bn_bytes(bn) mbedtls_mpi_size(bn)

14
src/openssl.c
View File

@@ -3715,4 +3715,18 @@ void ssh2_dh_dtor(ssh2_dh_ctx *dhctx)
*dhctx = NULL;
}
int ssh2_bn_from_bin(ssh2_bn **bn, const unsigned char *bin, size_t len)
{
if(!bn || !bin || !len)
return -1;
if(!*bn) {
*bn = ssh2_bn_init();
if(!*bn)
return -1;
}
return BN_bin2bn(bin, (int)len, *bn) ? 0 : -1;
}
#endif /* LIBSSH2_OPENSSL || LIBSSH2_WOLFSSL */

1
src/openssl.h
View File

@@ -344,7 +344,6 @@ typedef enum {
#define ssh2_bn BIGNUM
#define ssh2_bn_init() BN_new()
#define ssh2_bn_set_word(bn, word) !BN_set_word(bn, word)
#define ssh2_bn_from_bin(bn, bin, l) (BN_bin2bn(bin, (int)(l), bn) ? 0 : -1)
#define ssh2_bn_to_bin(bn, bin) (BN_bn2bin(bn, bin) <= 0)
#define ssh2_bn_bytes(bn) ((size_t)BN_num_bytes(bn))
#define ssh2_bn_bits(bn) ((size_t)BN_num_bits(bn))

50
src/os400qc3.c
View File

@@ -460,29 +460,37 @@ size_t ssh2_bn_bits(const ssh2_bn *bn)
return 0;
}
int ssh2_bn_from_bin(ssh2_bn *bn, const unsigned char *bin, size_t len)
int ssh2_bn_from_bin(ssh2_bn **bn, const unsigned char *bin, size_t len)
{
size_t i;
if(!bn || (len && !bin))
return -1;
if(!*bn) {
*bn = ssh2_bn_init();
if(!*bn)
return -1;
}
for(; len && !*bin; len--)
bin++;
if(bn_resize(bn, len))
if(bn_resize(*bn, len))
return -1;
for(i = len; i--;)
bn->bignum[i] = *bin++;
(*bn)->bignum[i] = *bin++;
return 0;
}
int ssh2_bn_set_word(ssh2_bn *bn, uint32_t word)
{
if(!bn)
return -1;
word = htonl(word);
return ssh2_bn_from_bin(bn, (unsigned char *)&word, sizeof(word));
return ssh2_bn_from_bin(&bn, (unsigned char *)&word, sizeof(word));
}
int ssh2_bn_to_bin(const ssh2_bn *bn, unsigned char *bin)
@@ -1173,8 +1181,8 @@ int ssh2_rsa_new(ssh2_rsa_ctx **rsa, LIBSSH2_SESSION *session,
const unsigned char *coeffdata, size_t coefflen)
{
ssh2_rsa_ctx *ctx;
ssh2_bn *e = ssh2_bn_init_from_bin();
ssh2_bn *n = ssh2_bn_init_from_bin();
ssh2_bn *e = NULL;
ssh2_bn *n = NULL;
ssh2_bn *d = NULL;
ssh2_bn *p = NULL;
ssh2_bn *q = NULL;
@@ -1193,25 +1201,19 @@ int ssh2_rsa_new(ssh2_rsa_ctx **rsa, LIBSSH2_SESSION *session,
if(!ctx)
ret = -1;
if(!ret) {
ssh2_bn_from_bin(e, edata, elen);
ssh2_bn_from_bin(n, ndata, nlen);
ssh2_bn_from_bin(&e, edata, elen);
ssh2_bn_from_bin(&n, ndata, nlen);
if(!e || !n)
ret = -1;
}
if(!ret && ddata) {
/* Private key. */
d = ssh2_bn_init_from_bin();
ssh2_bn_from_bin(d, ddata, dlen);
p = ssh2_bn_init_from_bin();
ssh2_bn_from_bin(p, pdata, plen);
q = ssh2_bn_init_from_bin();
ssh2_bn_from_bin(q, qdata, qlen);
e1 = ssh2_bn_init_from_bin();
ssh2_bn_from_bin(e1, e1data, e1len);
e2 = ssh2_bn_init_from_bin();
ssh2_bn_from_bin(e2, e2data, e2len);
coeff = ssh2_bn_init_from_bin();
ssh2_bn_from_bin(coeff, coeffdata, coefflen);
ssh2_bn_from_bin(&d, ddata, dlen);
ssh2_bn_from_bin(&p, pdata, plen);
ssh2_bn_from_bin(&q, qdata, qlen);
ssh2_bn_from_bin(&e1, e1data, e1len);
ssh2_bn_from_bin(&e2, e2data, e2len);
ssh2_bn_from_bin(&coeff, coeffdata, coefflen);
if(!d || !p || !q || !e1 || !e2 || !coeff)
ret = -1;
@@ -1289,6 +1291,8 @@ int ssh2_dh_key_pair(ssh2_dh_ctx *dhctx, ssh2_bn *pub, const ssh2_bn *g,
(void)bnctx;
if(!pub)
return -1;
if(group_order <= 0)
return -1;
@@ -1319,7 +1323,7 @@ int ssh2_dh_key_pair(ssh2_dh_ctx *dhctx, ssh2_bn *pub, const ssh2_bn *g,
asn1delete(pkcs3);
if(errcode.Bytes_Available)
return -1;
return ssh2_bn_from_bin(pub, (unsigned char *)pubkey, pubkeylen);
return ssh2_bn_from_bin(&pub, (unsigned char *)pubkey, pubkeylen);
}
int ssh2_dh_validate(const ssh2_bn *f, const ssh2_bn *p)
@@ -1356,6 +1360,8 @@ int ssh2_dh_secret(ssh2_dh_ctx *dhctx, ssh2_bn *secret,
(void)bnctx;
if(!secret)
return -1;
if(ssh2_dh_validate(f, p))
return -1;
@@ -1369,7 +1375,7 @@ int ssh2_dh_secret(ssh2_dh_ctx *dhctx, ssh2_bn *secret,
&secretbufsize, &secretbuflen, &errcode);
if(errcode.Bytes_Available)
return -1;
return ssh2_bn_from_bin(secret, (unsigned char *)secretbuf, secretbuflen);
return ssh2_bn_from_bin(&secret, (unsigned char *)secretbuf, secretbuflen);
}
void ssh2_dh_dtor(ssh2_dh_ctx *dhctx)

26
src/wincng.c
View File

@@ -318,7 +318,7 @@ size_t ssh2_bn_bits(const ssh2_bn *bn)
return bits;
}
int ssh2_bn_from_bin(ssh2_bn *bn, const unsigned char *bin, size_t len)
int ssh2_bn_from_bin(ssh2_bn **bn, const unsigned char *bin, size_t len)
{
unsigned char *bignum;
size_t offset, length, bits;
@@ -326,24 +326,30 @@ int ssh2_bn_from_bin(ssh2_bn *bn, const unsigned char *bin, size_t len)
if(!bn || !bin || !len)
return -1;
if(wcng_bn_resize(bn, len))
if(!*bn) {
*bn = ssh2_bn_init();
if(!*bn)
return -1;
}
if(wcng_bn_resize(*bn, len))
return -1;
memcpy(bn->bignum, bin, len);
memcpy((*bn)->bignum, bin, len);
bits = ssh2_bn_bits(bn);
bits = ssh2_bn_bits(*bn);
length = (bits + 7) / 8;
offset = bn->length - length;
offset = (*bn)->length - length;
if(offset > 0) {
memmove(bn->bignum, bn->bignum + offset, length);
memmove((*bn)->bignum, (*bn)->bignum + offset, length);
ssh2_explicit_zero(bn->bignum + length, offset);
ssh2_explicit_zero((*bn)->bignum + length, offset);
bignum = realloc(bn->bignum, length);
bignum = realloc((*bn)->bignum, length);
if(bignum) {
bn->bignum = bignum;
bn->length = length;
(*bn)->bignum = bignum;
(*bn)->length = length;
}
else
return -1;