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Move null pointer checks to before FROMFIELD.

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This fixes an oversight in commit 0fc2d3b45: if a key creation
function returns a null 'ssh_key *', then adjusting the pointer's
address using FROMFIELD is a mistake, both in technical C terms
(undefined behaviour) and practically speaking because it will foil
the subsequent check against NULL. Instead, if we're going to check a
pointer against NULL, we must do it _before_ applying this kind of
address-adjusting type conversion.
This commit is contained in:
Simon Tatham
2018-05-31 18:32:09 +01:00
parent 2cf07bb8fe
commit 619f6722d8
3 changed files with 40 additions and 23 deletions
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23
sshecc.c
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@ -1734,8 +1734,10 @@ struct ecsign_extra {
static void ecdsa_freekey(ssh_key *key)
{
struct ec_key *ec = FROMFIELD(key, struct ec_key, sshk);
if (!ec) return;
struct ec_key *ec;
if (!key) return;
ec = FROMFIELD(key, struct ec_key, sshk);
if (ec->publicKey.x)
freebn(ec->publicKey.x);
@ -1909,15 +1911,16 @@ static ssh_key *ecdsa_createkey(const ssh_keyalg *self,
const void *pub_blob, int pub_len,
const void *priv_blob, int priv_len)
{
ssh_key *sshk;
struct ec_key *ec;
struct ec_point *publicKey;
const char *pb = (const char *) priv_blob;
ec = FROMFIELD(ecdsa_newkey(self, pub_blob, pub_len),
struct ec_key, sshk);
if (!ec) {
sshk = ecdsa_newkey(self, pub_blob, pub_len);
if (!sshk)
return NULL;
}
ec = FROMFIELD(sshk, struct ec_key, sshk);
if (ec->publicKey.curve->type != EC_WEIERSTRASS
&& ec->publicKey.curve->type != EC_EDWARDS) {
@ -2147,13 +2150,15 @@ static void ecdsa_openssh_fmtkey(ssh_key *key, BinarySink *bs)
static int ecdsa_pubkey_bits(const ssh_keyalg *self,
const void *blob, int len)
{
ssh_key *sshk;
struct ec_key *ec;
int ret;
ec = FROMFIELD(ecdsa_newkey(self, blob, len),
struct ec_key, sshk);
if (!ec)
sshk = ecdsa_newkey(self, blob, len);
if (!sshk)
return -1;
ec = FROMFIELD(sshk, struct ec_key, sshk);
ret = ec->publicKey.curve->fieldBits;
ecdsa_freekey(&ec->sshk);