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Check SRP parameters early.

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Check SRP parameters when they are received so we can send back an
appropriate alert.
Reviewed-by: Kurt Roeckx <kurt@openssl.org>
This commit is contained in:
Dr. Stephen Henson
2014-08-03 21:25:22 +01:00
committed by Matt Caswell
parent 4a23b12a03
commit 0989790b87
6 changed files with 54 additions and 13 deletions
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47
ssl/tls_srp.c
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@@ -410,17 +410,46 @@ err:
return ret;
}
int srp_verify_server_param(SSL *s, int *al)
{
SRP_CTX *srp = &s->srp_ctx;
/* Sanity check parameters: we can quickly check B % N == 0
* by checking B != 0 since B < N
*/
if (BN_ucmp(srp->g, srp->N) >=0 || BN_ucmp(srp->B, srp->N) >= 0
|| BN_is_zero(srp->B))
{
*al = SSL3_AD_ILLEGAL_PARAMETER;
return 0;
}
if (BN_num_bits(srp->N) < srp->strength)
{
*al = TLS1_AD_INSUFFICIENT_SECURITY;
return 0;
}
if (srp->SRP_verify_param_callback)
{
if (srp->SRP_verify_param_callback(s, srp->SRP_cb_arg) <= 0)
{
*al = TLS1_AD_INSUFFICIENT_SECURITY;
return 0;
}
}
else if(!SRP_check_known_gN_param(srp->g, srp->N))
{
*al = TLS1_AD_INSUFFICIENT_SECURITY;
return 0;
}
return 1;
}
int SRP_Calc_A_param(SSL *s)
{
unsigned char rnd[SSL_MAX_MASTER_KEY_LENGTH];
if (BN_num_bits(s->srp_ctx.N) < s->srp_ctx.strength)
return 0;
if (s->srp_ctx.SRP_verify_param_callback ==NULL &&
!SRP_check_known_gN_param(s->srp_ctx.g,s->srp_ctx.N))
return 0;
if (RAND_bytes(rnd, sizeof(rnd)) <= 0)
return 0;
s->srp_ctx.a = BN_bin2bn(rnd,sizeof(rnd), s->srp_ctx.a);
@@ -429,10 +458,6 @@ int SRP_Calc_A_param(SSL *s)
if (!(s->srp_ctx.A = SRP_Calc_A(s->srp_ctx.a,s->srp_ctx.N,s->srp_ctx.g)))
return 0;
/* We can have a callback to verify SRP param!! */
if (s->srp_ctx.SRP_verify_param_callback !=NULL)
return s->srp_ctx.SRP_verify_param_callback(s,s->srp_ctx.SRP_cb_arg);
return 1;
}