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Fix Unbounded sprintf with sender_name in BaseChatMesh.cpp #1975

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Fix Unbounded sprintf with sender_name in BaseChatMesh.cpp #1975

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6 changes: 4 additions & 2 deletions src/helpers/BaseChatMesh.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -438,9 +438,11 @@ bool BaseChatMesh::sendGroupMessage(uint32_t timestamp, mesh::GroupChannel& chan
memcpy(temp, &timestamp, 4); // mostly an extra blob to help make packet_hash unique
temp[4] = 0; // TXT_TYPE_PLAIN

sprintf((char *) &temp[5], "%s: ", sender_name); // <sender>: <msg>
size_t prefix_buf_sz = (size_t)(MAX_TEXT_LEN + 32);
snprintf((char *) &temp[5], prefix_buf_sz, "%s: ", sender_name ? sender_name : ""); // <sender>: <msg>, bounded
((char *)&temp[5])[prefix_buf_sz - 1] = '\0';
char *ep = strchr((char *) &temp[5], 0);
int prefix_len = ep - (char *) &temp[5];
int prefix_len = (int)(ep - (char *) &temp[5]);

if (text_len + prefix_len > MAX_TEXT_LEN) text_len = MAX_TEXT_LEN - prefix_len;
memcpy(ep, text, text_len);
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