c23bc84be4
Daniel Stenberg
2026-09-01
Subject
CURLOPT_USERNAME.md: ambient username caveats
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docs/libcurl/opts/CURLOPT_USERNAME.md+14 -6
| @@ -32,17 +32,17 @@ CURLcode curl_easy_setopt(CURL *handle, CURLOPT_USERNAME, | |
| Pass a char pointer as parameter, which should be pointing to the | |
| null-terminated username to use for the transfer. | |
| - | CURLOPT_USERNAME(3) sets the username to be used in protocol |
| - | authentication. You should not use this option together with the (older) |
| - | CURLOPT_USERPWD(3) option. |
| + | CURLOPT_USERNAME(3) sets the username to be used in protocol authentication. |
| + | You should not use this option together with the (older) CURLOPT_USERPWD(3) |
| + | option. |
| When using Kerberos V5 authentication with a Windows based server, you should | |
| include the domain name in order for the server to successfully obtain a | |
| Kerberos Ticket. If you do not then the initial part of the authentication | |
| handshake may fail. | |
| - | When using NTLM, the username can be specified without the domain name |
| - | should the server be part of a single domain and forest. |
| + | When using NTLM, the username can be specified without the domain name should |
| + | the server be part of a single domain and forest. |
| To include the domain name use either Down-Level Logon Name or UPN (User | |
| Principal Name) formats. For example, **EXAMPLE\user** and | |
| @@ -57,9 +57,17 @@ CURLOPT_PASSWORD(3) and CURLOPT_LOGIN_OPTIONS(3) options. | |
| The application does not have to keep the string around after setting this | |
| option. | |
| + | For some authentication methods (`Negotiate`, or `NTLM` when built to use |
| + | SSPI), setting it to a zero-length string (`""`) makes libcurl use an implied |
| + | *ambient* user decided by the environment. libcurl cannot identify this user |
| + | and may reuse an authenticated connection for a later transfer on the same |
| + | easy handle. If the ambient user changes while that connection remains |
| + | reusable, the later transfer can be authenticated as the previous user. |
| + | Applications must prevent such reuse when changing ambient users. |
| + | |
| # DEFAULT | |
| - | blank |
| + | NULL |
| # %PROTOCOLS% | |