391e3fbeec
Joshua Rogers
2025-10-09
Subject
libssh/sftp: fix resume corruption by avoiding O_APPEND with rresume
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lib/vssh/libssh.c+14 -8
| @@ -1154,12 +1154,18 @@ static int myssh_in_UPLOAD_INIT(struct Curl_easy *data, | |
| } | |
| } | |
| - | if(data->set.remote_append) |
| - | /* Try to open for append, but create if nonexisting */ |
| - | flags = O_WRONLY|O_CREAT|O_APPEND; |
| - | else if(data->state.resume_from > 0) |
| - | /* If we have restart position then open for append */ |
| - | flags = O_WRONLY|O_APPEND; |
| + | if(data->set.remote_append) { |
| + | /* True append mode: create if nonexisting */ |
| + | flags = O_WRONLY | O_CREAT | O_APPEND; |
| + | } |
| + | else if(data->state.resume_from > 0) { |
| + | /* |
| + | * Resume MUST NOT use O_APPEND. Many SFTP servers/impls force all |
| + | * writes to EOF when O_APPEND is set, ignoring a prior seek(). |
| + | * Open write-only and seek to the resume offset instead. |
| + | */ |
| + | flags = O_WRONLY; |
| + | } |
| else | |
| /* Clear file before writing (normal behavior) */ | |
| flags = O_WRONLY|O_CREAT|O_TRUNC; | |
| @@ -1189,8 +1195,8 @@ static int myssh_in_UPLOAD_INIT(struct Curl_easy *data, | |
| } | |
| /* If we have a restart point then we need to seek to the correct | |
| - | position. */ |
| - | if(data->state.resume_from > 0) { |
| + | position. Skip if in explicit remote append mode. */ |
| + | if(data->state.resume_from > 0 && !data->set.remote_append) { |
| int seekerr = CURL_SEEKFUNC_OK; | |
| /* Let's read off the proper amount of bytes from the input. */ | |
| if(data->set.seek_func) { | |