Commit c23ce70f authored by Hubert Chathi's avatar Hubert Chathi
Browse files

improve handling of olm_session_describe when buffer is too short

parent 2dbeea2f
......@@ -387,7 +387,10 @@ OLM_EXPORT int olm_session_has_received_message(
/**
* Write a null-terminated string describing the internal state of an olm
* session to the buffer provided for debugging and logging purposes.
* session to the buffer provided for debugging and logging purposes. If the
* buffer is not large enough to hold the entire string, it will be truncated
* and will end with "...". A buffer length of 600 will be enough to hold any
* output.
*/
OLM_EXPORT void olm_session_describe(OlmSession * session, char *buf, size_t buflen);
......
......@@ -398,39 +398,71 @@ std::size_t olm::Session::decrypt(
return result;
}
// make the description end with "..." instead of stopping abruptly with no
// warning
void elide_description(char *end) {
end[-3] = '.';
end[-2] = '.';
end[-1] = '.';
end[0] = '\0';
}
void olm::Session::describe(char *describe_buffer, size_t buflen) {
if (buflen == 0) return;
// how much of the buffer is remaining (this is an int rather than a size_t
// because it will get compared to the return value from snprintf)
int remaining = buflen;
// do nothing if we have a zero-length buffer, or if buflen > INT_MAX,
// resulting in an overflow
if (remaining <= 0) return;
describe_buffer[0] = '\0';
char *buf_pos = describe_buffer;
// we need at least 23 characters to get any sort of meaningful
// information, so bail if we don't have that. (But more importantly, we
// need it to be at least 4 so that elide_description doesn't go out of
// bounds.)
if (remaining < 23) return;
int size;
// check that snprintf didn't return an error or reach the end of the buffer
#define CHECK_SIZE_AND_ADVANCE \
if (size > remaining) { \
return elide_description(describe_buffer + remaining - 1); \
} else if (size > 0) { \
describe_buffer += size; \
remaining -= size; \
} else { \
return; \
}
size = snprintf(
buf_pos, buflen - (buf_pos - describe_buffer),
describe_buffer, remaining,
"sender chain index: %d ", ratchet.sender_chain[0].chain_key.index
);
if (size > 0) buf_pos += size;
CHECK_SIZE_AND_ADVANCE;
size = snprintf(describe_buffer, remaining, "receiver chain indices:");
CHECK_SIZE_AND_ADVANCE;
size = snprintf(buf_pos, buflen - (buf_pos - describe_buffer), "receiver chain indices:");
if (size > 0) buf_pos += size;
for (size_t i = 0; i < ratchet.receiver_chains.size(); ++i) {
size = snprintf(
buf_pos, buflen - (buf_pos - describe_buffer),
describe_buffer, remaining,
" %d", ratchet.receiver_chains[i].chain_key.index
);
if (size > 0) buf_pos += size;
CHECK_SIZE_AND_ADVANCE;
}
size = snprintf(buf_pos, buflen - (buf_pos - describe_buffer), " skipped message keys:");
if (size >= 0) buf_pos += size;
size = snprintf(describe_buffer, remaining, " skipped message keys:");
CHECK_SIZE_AND_ADVANCE;
for (size_t i = 0; i < ratchet.skipped_message_keys.size(); ++i) {
size = snprintf(
buf_pos, buflen - (buf_pos - describe_buffer),
describe_buffer, remaining,
" %d", ratchet.skipped_message_keys[i].message_key.index
);
if (size > 0) buf_pos += size;
CHECK_SIZE_AND_ADVANCE;
}
#undef CHECK_SIZE_AND_ADVANCE
}
namespace {
......
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