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fix(caps): correct capability v3 byte order and lock securebits #88

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fix(caps): correct capability v3 byte order and lock securebits #88

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31 changes: 18 additions & 13 deletions src/caps.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -337,11 +337,11 @@ fn capset(result: &CapInternalResult) -> anyhow::Result<()> {
let err = syscall(libc::SYS_capset, &result.header, &result.data);
if err < 0 {
let effective =
((result.data[0].effective as u64) << 32) | result.data[1].effective as u64;
((result.data[1].effective as u64) << 32) | result.data[0].effective as u64;
let permitted =
((result.data[0].permitted as u64) << 32) | result.data[1].permitted as u64;
((result.data[1].permitted as u64) << 32) | result.data[0].permitted as u64;
let inheritable =
((result.data[0].inheritable as u64) << 32) | result.data[1].inheritable as u64;
((result.data[1].inheritable as u64) << 32) | result.data[0].inheritable as u64;

Err(anyhow!(
"capset(2) failed: {:x} {:x} {:x} (error = {err})",
Expand All @@ -367,10 +367,11 @@ pub fn get_caps() -> anyhow::Result<CapResult> {

capget(&mut iresult)?;

let effective = ((iresult.data[0].effective as u64) << 32) | iresult.data[1].effective as u64;
let permitted = ((iresult.data[0].permitted as u64) << 32) | iresult.data[1].permitted as u64;
// Linux capability v3: data[0] = caps 0-31, data[1] = caps 32+
let effective = ((iresult.data[1].effective as u64) << 32) | iresult.data[0].effective as u64;
let permitted = ((iresult.data[1].permitted as u64) << 32) | iresult.data[0].permitted as u64;
let inheritable =
((iresult.data[0].inheritable as u64) << 32) | iresult.data[1].inheritable as u64;
((iresult.data[1].inheritable as u64) << 32) | iresult.data[0].inheritable as u64;

let finalresult = CapResult {
effective,
Expand Down Expand Up @@ -399,17 +400,18 @@ pub fn set_caps(caps: CapResult) -> anyhow::Result<()> {
version: _LINUX_CAPABILITY_VERSION_3,
pid,
},
// Linux capability v3: data[0] = caps 0-31, data[1] = caps 32+
data: [
CapInternalData {
effective: (caps.effective >> 32) as u32,
permitted: (caps.permitted >> 32) as u32,
inheritable: (caps.inheritable >> 32) as u32,
},
CapInternalData {
effective: caps.effective as u32,
permitted: caps.permitted as u32,
inheritable: caps.inheritable as u32,
},
CapInternalData {
effective: (caps.effective >> 32) as u32,
permitted: (caps.permitted >> 32) as u32,
inheritable: (caps.inheritable >> 32) as u32,
},
],
};

Expand All @@ -419,10 +421,13 @@ pub fn set_caps(caps: CapResult) -> anyhow::Result<()> {
}

pub fn set_keep_caps() -> anyhow::Result<()> {
let ret = unsafe { libc::prctl(PR_SET_SECUREBITS, SECBIT_NO_SETUID_FIXUP) };
// Lock securebits to prevent clearing before cap drop.
// SECBIT_NO_SETUID_FIXUP (4) | SECBIT_NO_SETUID_FIXUP_LOCKED (8) | SECBIT_KEEP_CAPS_LOCKED (32)
let bits = SECBIT_NO_SETUID_FIXUP | 8 | SECBIT_KEEP_CAPS_LOCKED;
let ret = unsafe { libc::prctl(PR_SET_SECUREBITS, bits) };
if ret < 0 {
Err(anyhow!(
"failed to set SECBIT_NO_SETUID_FIXUP: {}",
"failed to set securebits: {}",
io::Error::last_os_error()
))
} else {
Expand Down