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key: properly parse short DER private keys #2519

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Merged
jamescowens merged 1 commit into from
May 29, 2022
Merged

key: properly parse short DER private keys #2519

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36 changes: 22 additions & 14 deletions src/key.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -38,21 +38,29 @@ int ec_seckey_import_der(const secp256k1_context* ctx, unsigned char *out32, con
}
seckey++;
/* sequence length constructor */
if (end - seckey < 1 || !(*seckey & 0x80u)) {
if (end - seckey < 1) {
return 0;
}
ptrdiff_t lenb = *seckey & ~0x80u; seckey++;
if (lenb < 1 || lenb > 2) {
return 0;
}
if (end - seckey < lenb) {
return 0;
}
/* sequence length */
ptrdiff_t len = seckey[lenb-1] | (lenb > 1 ? seckey[lenb-2] << 8 : 0u);
seckey += lenb;
if (end - seckey < len) {
return 0;
if (!(*seckey & 0x80u)) {
/* sequence lengths are stored in a single byte if < 128 */
size_t len = *seckey; seckey++;
if (len + 2 != seckeylen) {
return 0;
}
} else {
ptrdiff_t lenb = *seckey & ~0x80u; seckey++;
if (lenb < 1 || lenb > 2) {
return 0;
}
if (end - seckey < lenb) {
return 0;
}
/* sequence length */
ptrdiff_t len = seckey[lenb-1] | (lenb > 1 ? seckey[lenb-2] << 8 : 0u);
seckey += lenb;
if (end - seckey < len) {
return 0;
}
}
/* sequence element 0: version number (=1) */
if (end - seckey < 3 || seckey[0] != 0x02u || seckey[1] != 0x01u || seckey[2] != 0x01u) {
Expand Down Expand Up @@ -313,4 +321,4 @@ void ECC_Stop() {
if (ctx) {
secp256k1_context_destroy(ctx);
}
}
}