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A Tale of a Trailing Dot (2022)
Trailing dots on host names in URLs is the gift that keeps on giving. Let me take you through a dwindling story of how the dot is handled differently in different places through the stack of an Internet client. The evil trailing dot. DNS When a given host name is to be resolved to an … Continue reading A tale of a trailing dot →
In 2022, someone found a web site that actually requires a trailing dot in the Host: header to respond correctly and reported it to the curl project. Axel Chong figured out that for a curl build without PSL knowledge, the server could set a cookie for a TLD if you just made sure to end the name with a dot. Since curl now keeps the trailing dot in the name and did not do it before, there was a second important string comparison that broke in unexpected ways that Axel figured out and reported.
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