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Additional file handling for randomly generated machine-ids #11185

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e81c47f
added an machine-id file handling for randomly generated uuids in a f…
dietWall Nov 19, 2025
53141bf
code formatting according contribution guidelines
dietWall Nov 19, 2025
8eae3c0
Merge branch 'fluent:master' into dietWall/fix_machine_id_in_docker
dietWall Nov 19, 2025
3ef7444
more code formatting guidelines
dietWall Nov 19, 2025
aed26a3
more suggested changes, code formatting and fixed some compiler warnigs
dietWall Nov 19, 2025
b08cc3b
Merge branch 'dietWall/fix_machine_id_in_docker' of github.com:dietWa…
dietWall Nov 19, 2025
7164855
hardened file permissions
dietWall Nov 19, 2025
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56 changes: 54 additions & 2 deletions src/flb_utils.c
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Original file line number Diff line number Diff line change
Expand Up @@ -2043,13 +2043,40 @@ static int machine_id_read_and_sanitize(char *path,
return 0;
}

static int write_uuid_to_file(const char* filename, char* uuid)
{
int fd;
size_t uuid_len;

if (filename == NULL || uuid == NULL) {
return FLB_FALSE;
}

/* write uuid to file */
fd = open(filename, O_CREAT | O_WRONLY | O_TRUNC, 0600);
if (fd == -1) {
return FLB_FALSE;
}

uuid_len = strlen(uuid);

if (write(fd, uuid, uuid_len) != uuid_len) {
close(fd);
return FLB_FALSE;
}

close(fd);
return FLB_TRUE;
}

int flb_utils_get_machine_id(char **out_id, size_t *out_size)
{
int ret;
char *id;
size_t bytes;
char *uuid;
int fallback = FLB_FALSE;
char *fallback_id_file = "/tmp/flb-machine-id"; /*should reside in current working directory*/

#ifdef __linux__
char *dbus_var = "/var/lib/dbus/machine-id";
Expand Down Expand Up @@ -2084,6 +2111,22 @@ int flb_utils_get_machine_id(char **out_id, size_t *out_size)
return 0;
}
}

if (access(fallback_id_file, F_OK) == 0){
ret = machine_id_read_and_sanitize(fallback_id_file, &id, &bytes);
if (ret == 0){
if (bytes == 0) {
/* guid is somewhat corrupted */
fallback = FLB_TRUE;
goto fallback;
}
}

*out_id = id;
*out_size = bytes;
return 0;
Comment on lines +2123 to +2127
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@chatgpt-codex-connector chatgpt-codex-connector bot Nov 19, 2025

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P1 Badge Return uninitialized fallback ID on read failure

If a fallback machine-id file exists but machine_id_read_and_sanitize fails (e.g., unreadable or malformed), ret remains non‑zero yet the code still assigns id/bytes to the outputs and returns success because the return block sits outside the ret == 0 guard. In that scenario id and bytes are uninitialized, so callers can receive a garbage pointer/size or crash instead of regenerating an ID. The return should stay within the successful read path or jump to the fallback path when the read fails.

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}

#elif defined(__FreeBSD__) || defined(__NetBSD__) || \
defined(__OpenBSD__) || defined(__DragonFly__)

Expand Down Expand Up @@ -2175,7 +2218,7 @@ int flb_utils_get_machine_id(char **out_id, size_t *out_size)
#endif

fallback:

flb_warn("falling back on random machine UUID");

/* generate a random uuid */
Expand All @@ -2185,15 +2228,24 @@ int flb_utils_get_machine_id(char **out_id, size_t *out_size)
return -1;
}
ret = flb_utils_uuid_v4_gen(uuid);

if (ret == 0) {

ret = write_uuid_to_file(fallback_id_file, uuid);
if (ret == FLB_FALSE){
/*
* writing failed, next uuid generation will be random again
* log a warning message and return
*/
flb_warn("failed to write machine-id to file %s", fallback_id_file);
}
*out_id = uuid;
*out_size = strlen(uuid);
if (fallback == FLB_TRUE) {
return 2;
}
return 0;
}

return -1;
}

Expand Down