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https://github.com/clearml/dropbear
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check for zero K value from curve25519
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550b3056fd
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@ -760,6 +760,7 @@ void kexcurve25519_comb_key(struct kex_curve25519_param *param, buffer *buf_pub_
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unsigned char out[CURVE25519_LEN];
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const unsigned char* Q_C = NULL;
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const unsigned char* Q_S = NULL;
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char zeroes[CURVE25519_LEN] = {0};
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if (buf_pub_them->len != CURVE25519_LEN)
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{
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@ -767,6 +768,11 @@ void kexcurve25519_comb_key(struct kex_curve25519_param *param, buffer *buf_pub_
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}
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curve25519_donna(out, param->priv, buf_pub_them->data);
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if (constant_time_memcmp(zeroes, out, CURVE25519_LEN) == 0) {
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dropbear_exit("Bad curve25519");
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}
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m_mp_alloc_init_multi(&ses.dh_K, NULL);
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bytes_to_mp(ses.dh_K, out, CURVE25519_LEN);
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m_burn(out, sizeof(out));
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