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Fix: [Network] Determining GetNetworkRevisionString could overflow and underflow its buffer

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Tagged releases are not affected
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rubidium42 2021-06-13 23:06:15 +02:00 committed by rubidium42
parent 7b135a8269
commit 9e32c618f9
1 changed files with 20 additions and 29 deletions
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49
src/network/core/game_info.cpp
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@ -36,45 +36,36 @@ NetworkServerGameInfo _network_game_info; ///< Information about our game.
/**
* Get the network version string used by this build.
* The returned string is guaranteed to be at most NETWORK_REVISON_LENGTH bytes.
* The returned string is guaranteed to be at most NETWORK_REVISON_LENGTH bytes including '\0' terminator.
*/
const char *GetNetworkRevisionString()
{
/* This will be allocated on heap and never free'd, but only once so not a "real" leak. */
static char *network_revision = nullptr;
static std::string network_revision;
if (!network_revision) {
/* Start by taking a chance on the full revision string. */
network_revision = stredup(_openttd_revision);
/* Ensure it's not longer than the packet buffer length. */
if (strlen(network_revision) >= NETWORK_REVISION_LENGTH) network_revision[NETWORK_REVISION_LENGTH - 1] = '\0';
/* Tag names are not mangled further. */
if (network_revision.empty()) {
std::string network_revision = _openttd_revision;
if (_openttd_revision_tagged) {
Debug(net, 3, "Network revision name: {}", network_revision);
return network_revision;
}
/* Tagged; do not mangle further, though ensure it's not too long. */
if (network_revision.size() >= NETWORK_REVISION_LENGTH) network_revision.resize(NETWORK_REVISION_LENGTH - 1);
} else {
/* Not tagged; add the githash suffix while ensuring the string does not become too long. */
assert(_openttd_revision_modified < 3);
std::string githash_suffix = fmt::format("-{}{}", "gum"[_openttd_revision_modified], _openttd_revision_hash);
if (githash_suffix.size() > GITHASH_SUFFIX_LEN) githash_suffix.resize(GITHASH_SUFFIX_LEN);
/* Prepare a prefix of the git hash.
* Size is length + 1 for terminator, +2 for -g prefix. */
assert(_openttd_revision_modified < 3);
char githash_suffix[GITHASH_SUFFIX_LEN + 1] = "-";
githash_suffix[1] = "gum"[_openttd_revision_modified];
for (uint i = 2; i < GITHASH_SUFFIX_LEN; i++) {
githash_suffix[i] = _openttd_revision_hash[i-2];
}
/* Where did the hash start in the original string? Overwrite from that position, unless that would create a too long string. */
size_t hash_end = network_revision.find_last_of('-');
if (hash_end == std::string::npos) hash_end = network_revision.size();
if (hash_end + githash_suffix.size() >= NETWORK_REVISION_LENGTH) hash_end = NETWORK_REVISION_LENGTH - githash_suffix.size() - 1;
/* Where did the hash start in the original string?
* Overwrite from that position, unless that would go past end of packet buffer length. */
ptrdiff_t hashofs = strrchr(_openttd_revision, '-') - _openttd_revision;
if (hashofs + strlen(githash_suffix) + 1 > NETWORK_REVISION_LENGTH) hashofs = strlen(network_revision) - strlen(githash_suffix);
/* Replace the git hash in revision string. */
strecpy(network_revision + hashofs, githash_suffix, network_revision + NETWORK_REVISION_LENGTH);
assert(strlen(network_revision) < NETWORK_REVISION_LENGTH); // strlen does not include terminator, constant does, hence strictly less than
/* Replace the git hash in revision string. */
network_revision.replace(hash_end, std::string::npos, githash_suffix);
}
assert(network_revision.size() < NETWORK_REVISION_LENGTH); // size does not include terminator, constant does, hence strictly less than
Debug(net, 3, "Network revision name: {}", network_revision);
}
return network_revision;
return network_revision.c_str();
}
/**