transparency.rs 5.3%

9 of 169 lines run, 2 of 26 functions · run #321 on main · run missed

//! Checking a host's transparency log on fetch (spec §14.8, oxygenhub#238).
//!
//! A host that keeps a log sends its latest checkpoint with the refs, and
//! for each bookmark's attestation its entry and an inclusion proof. This
//! user remembers, per hub, the log's key and the last checkpoint seen
//! (`<oxy home>/tlog/<hub>`): the key on first sight, then never another.
//! Each new checkpoint must extend the last one, which oxy proves from the
//! hub's public tiles (C2SP tlog-tiles); one that does not means the hub
//! showed two histories, and the fetch fails. An attestation that is not
//! in the log yet, or whose proof does not verify, is only reported while
//! the log is new (oxygenhub docs/transparency.md, decision 3).

use super::*;
use crate::credentials::hub_of;
use crate::protocol::http_get;
use crate::tlog::{self, Checkpoint, Entry, Hash, HashReader, Note, Tile, TlogError};
use std::cell::RefCell;

/// Tiles fetched, by level and number, with the width fetched.
type TileCache = RefCell<HashMap<(u32, u64), (Tile, Vec<u8>)>>;

/// A hub's log as its tiles serve it, for a tree of `size` entries.
struct Tiles<'a> {
    hub: &'a str,
    size: u64,
    options: &'a RemoteOptions,
    cache: TileCache,
}

impl HashReader for Tiles<'_> {
    fn read_hashes(&self, indexes: &[u64]) -> std::result::Result<Vec<Hash>, TlogError> {
        let mut out = Vec::with_capacity(indexes.len());
        for &i in indexes {
            let (t, ..) = Tile::for_index(i);
            let key = (t.level, t.n);
            if !self.cache.borrow().contains_key(&key) {
                let held =
                    (self.size >> (tlog::TILE_HEIGHT * t.level)) - (t.n << tlog::TILE_HEIGHT);
                let tile = Tile {
                    width: held.min(tlog::TILE_WIDTH) as u32,
                    ..t
                };
                let data = http_get(&format!("{}/log/{}", self.hub, tile.path()), self.options)
                    .map_err(|e| TlogError::Read(e.to_string()))?;
                self.cache.borrow_mut().insert(key, (tile, data));
            }
            let cache = self.cache.borrow();
            let (tile, data) = &cache[&key];
            out.push(tile.hash_at(data, i)?);
        }
        Ok(out)
    }
}

/// What this user last saw of a hub's log.
struct Seen {
    identity: Identity,
    checkpoint: Checkpoint,
}

fn file_name(hub: &str) -> String {
    hub.chars()
        .map(|c| {
            if c.is_ascii_alphanumeric() || c == '.' || c == '-' {
                c
            } else {
                '_'
            }
        })
        .collect()
}

impl Repo {
    fn tlog_file(&self, hub: &str) -> PathBuf {
        self.user_config
            .parent()
            .map(Path::to_path_buf)
            .unwrap_or_else(default_home)
            .join("tlog")
            .join(file_name(hub))
    }

    fn seen_log(&self, hub: &str) -> Option<Seen> {
        let text = fs::read_to_string(self.tlog_file(hub)).ok()?;
        let (key, note) = text.split_once('\n')?;
        let identity = Identity::decode(&crate::dsse::base64_decode(key)?).ok()?;
        let note = Note::parse(note).ok()?;
        Some(Seen {
            checkpoint: Checkpoint::parse(&note.text).ok()?,
            identity,
        })
    }

    fn remember_log(&self, hub: &str, identity: &Identity, note: &Note) -> Result<()> {
        let path = self.tlog_file(hub);
        if let Some(dir) = path.parent() {
            fs::create_dir_all(dir)?;
        }
        let text = format!(
            "{}\n{}",
            crate::dsse::base64(&identity.encode()),
            note.encode()
        );
        crate::durable::write_atomic(&path, text.as_bytes())?;
        Ok(())
    }

    /// Check what a refs answer from `url` says about its host's log.
    /// Fails only when the host showed two histories (or a log key other
    /// than the one it showed before); everything else is a note.
    pub(crate) fn check_log(
        &self,
        url: &str,
        ca: Option<&Path>,
        resp: &RefsResponse,
    ) -> Result<Vec<String>> {
        let (Some(text), Some(hub)) = (&resp.log, hub_of(url)) else {
            return Ok(vec![]);
        };
        let mut notes = Vec::new();
        let unchecked = |why: String| {
            Ok(vec![format!(
                "{hub}'s transparency log was not checked: {why}"
            )])
        };
        let note = match Note::parse(text) {
            Ok(n) => n,
            Err(e) => return unchecked(e.to_string()),
        };
        let cp = match Checkpoint::parse(&note.text) {
            Ok(c) => c,
            Err(e) => return unchecked(e.to_string()),
        };
        let options = RemoteOptions {
            ca: ca.map(Path::to_path_buf),
            ..RemoteOptions::default()
        };
        let seen = self.seen_log(&hub);
        let identity = match &seen {
            Some(s) => s.identity.clone(),
            None => match http_get(&format!("{hub}/.well-known/oxyhub-key"), &options)
                .and_then(|b| Ok(Identity::decode(&b)?))
            {
                Ok(i) => i,
                Err(e) => return unchecked(format!("its key could not be fetched ({e})")),
            },
        };
        let two = |why: String| {
            fail(format!(
                "{hub} showed two histories: {why}. Do not trust what it serves; tell its operator. \
                 (What this user saw of its log is in {}.)",
                self.tlog_file(&hub).display()
            ))
        };
        if let Err(e) = note.verify(&cp.origin, &identity) {
            return match &seen {
                Some(_) => two(format!(
                    "its checkpoint is not signed by the log key it showed before ({e})"
                )),
                None => unchecked(e.to_string()),
            };
        }
        if let Some(s) = &seen {
            let old = &s.checkpoint;
            if old.origin != cp.origin {
                return two(format!("its log is now {}, not {}", cp.origin, old.origin));
            }
            if cp.size < old.size {
                return two(format!(
                    "its log has {} entries, fewer than the {} it showed before",
                    cp.size, old.size
                ));
            }
            if cp.size == old.size && cp.root != old.root {
                return two(format!("two different logs of {} entries", cp.size));
            }
            if cp.size > old.size && old.size > 0 {
                let tiles = Tiles {
                    hub: &hub,
                    size: cp.size,
                    options: &options,
                    cache: RefCell::new(HashMap::new()),
                };
                match tlog::prove_consistency(cp.size, old.size, &tiles).and_then(|p| {
                    tlog::check_consistency(&p, cp.size, &cp.root, old.size, &old.root)
                }) {
                    Ok(()) => {}
                    Err(TlogError::ProofFailed) | Err(TlogError::BadIndex(_)) => {
                        return two(format!(
                            "its log of {} entries does not extend the one of {} it showed before",
                            cp.size, old.size
                        ))
                    }
                    // Keep the older checkpoint: the next fetch tries again.
                    Err(e) => return unchecked(format!("its tiles could not be read ({e})")),
                }
            }
        }
        self.remember_log(&hub, &identity, &note)?;
        let mut missing = 0;
        for r in &resp.refs {
            let Some(a) = &r.attestation else { continue };
            let Some(l) = &r.logged else {
                missing += 1;
                continue;
            };
            let fits = Entry::decode(&l.entry).is_ok_and(|e| {
                e.kind == "ref" && e.object == a.attest.hash() && e.repo == a.attest.repo
            });
            let included = fits
                && tlog::check_inclusion(
                    &l.proof,
                    cp.size,
                    &cp.root,
                    l.index,
                    &tlog::leaf_hash(&l.entry),
                )
                .is_ok();
            if !included {
                notes.push(format!(
                    "{hub}'s log entry {} for {} does not prove its attestation is in the log",
                    l.index, r.name
                ));
            }
        }
        if missing > 0 {
            notes.push(format!(
                "{} of {hub}'s attestations {} not in its transparency log yet (logged within seconds of a push; checked on a later fetch)",
                missing,
                if missing == 1 { "is" } else { "are" }
            ));
        }
        Ok(notes)
    }
}

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1		//! Checking a host's transparency log on fetch (spec §14.8, oxygenhub#238).
2		//!
3		//! A host that keeps a log sends its latest checkpoint with the refs, and
4		//! for each bookmark's attestation its entry and an inclusion proof. This
5		//! user remembers, per hub, the log's key and the last checkpoint seen
6		//! (`<oxy home>/tlog/<hub>`): the key on first sight, then never another.
7		//! Each new checkpoint must extend the last one, which oxy proves from the
8		//! hub's public tiles (C2SP tlog-tiles); one that does not means the hub
9		//! showed two histories, and the fetch fails. An attestation that is not
10		//! in the log yet, or whose proof does not verify, is only reported while
11		//! the log is new (oxygenhub docs/transparency.md, decision 3).
12
13		use super::*;
14		use crate::credentials::hub_of;
15		use crate::protocol::http_get;
16		use crate::tlog::{self, Checkpoint, Entry, Hash, HashReader, Note, Tile, TlogError};
17		use std::cell::RefCell;
18
19		/// Tiles fetched, by level and number, with the width fetched.
20		type TileCache = RefCell<HashMap<(u32, u64), (Tile, Vec<u8>)>>;
21
22		/// A hub's log as its tiles serve it, for a tree of `size` entries.
23		struct Tiles<'a> {
24		hub: &'a str,
25		size: u64,
26		options: &'a RemoteOptions,
27		cache: TileCache,
28		}
29
30		impl HashReader for Tiles<'_> {
31	0×	fn read_hashes(&self, indexes: &[u64]) -> std::result::Result<Vec<Hash>, TlogError> {
32	0×	let mut out = Vec::with_capacity(indexes.len());
33	0×	for &i in indexes {
34	0×	let (t, ..) = Tile::for_index(i);
35	0×	let key = (t.level, t.n);
36	0×	if !self.cache.borrow().contains_key(&key) {
37	0×	let held =
38	0×	(self.size >> (tlog::TILE_HEIGHT * t.level)) - (t.n << tlog::TILE_HEIGHT);
39	0×	let tile = Tile {
40	0×	width: held.min(tlog::TILE_WIDTH) as u32,
41	0×	..t
42	0×	};
43	0×	let data = http_get(&format!("{}/log/{}", self.hub, tile.path()), self.options)
44	0×	.map_err(\|e\| TlogError::Read(e.to_string()))?;
45	0×	self.cache.borrow_mut().insert(key, (tile, data));
46	0×	}
47	0×	let cache = self.cache.borrow();
48	0×	let (tile, data) = &cache[&key];
49	0×	out.push(tile.hash_at(data, i)?);
50		}
51	0×	Ok(out)
52	0×	}
53		}
54
55		/// What this user last saw of a hub's log.
56		struct Seen {
57		identity: Identity,
58		checkpoint: Checkpoint,
59		}
60
61	0×	fn file_name(hub: &str) -> String {
62	0×	hub.chars()
63	0×	.map(\|c\| {
64	0×	if c.is_ascii_alphanumeric() \|\| c == '.' \|\| c == '-' {
65	0×	c
66		} else {
67	0×	'_'
68		}
69	0×	})
70	0×	.collect()
71	0×	}
72
73		impl Repo {
74	0×	fn tlog_file(&self, hub: &str) -> PathBuf {
75	0×	self.user_config
76	0×	.parent()
77	0×	.map(Path::to_path_buf)
78	0×	.unwrap_or_else(default_home)
79	0×	.join("tlog")
80	0×	.join(file_name(hub))
81	0×	}
82
83	0×	fn seen_log(&self, hub: &str) -> Option<Seen> {
84	0×	let text = fs::read_to_string(self.tlog_file(hub)).ok()?;
85	0×	let (key, note) = text.split_once('\n')?;
86	0×	let identity = Identity::decode(&crate::dsse::base64_decode(key)?).ok()?;
87	0×	let note = Note::parse(note).ok()?;
88		Some(Seen {
89	0×	checkpoint: Checkpoint::parse(&note.text).ok()?,
90	0×	identity,
91		})
92	0×	}
93
94	0×	fn remember_log(&self, hub: &str, identity: &Identity, note: &Note) -> Result<()> {
95	0×	let path = self.tlog_file(hub);
96	0×	if let Some(dir) = path.parent() {
97	0×	fs::create_dir_all(dir)?;
98	0×	}
99	0×	let text = format!(
100		"{}\n{}",
101	0×	crate::dsse::base64(&identity.encode()),
102	0×	note.encode()
103		);
104	0×	crate::durable::write_atomic(&path, text.as_bytes())?;
105	0×	Ok(())
106	0×	}
107
108		/// Check what a refs answer from `url` says about its host's log.
109		/// Fails only when the host showed two histories (or a log key other
110		/// than the one it showed before); everything else is a note.
111	359×	pub(crate) fn check_log(
112	359×	&self,
113	359×	url: &str,
114	359×	ca: Option<&Path>,
115	359×	resp: &RefsResponse,
116	359×	) -> Result<Vec<String>> {
117	359×	let (Some(text), Some(hub)) = (&resp.log, hub_of(url)) else {
118	359×	return Ok(vec![]);
119		};
120	0×	let mut notes = Vec::new();
121	0×	let unchecked = \|why: String\| {
122	0×	Ok(vec![format!(
123	0×	"{hub}'s transparency log was not checked: {why}"
124	0×	)])
125	0×	};
126	0×	let note = match Note::parse(text) {
127	0×	Ok(n) => n,
128	0×	Err(e) => return unchecked(e.to_string()),
129		};
130	0×	let cp = match Checkpoint::parse(&note.text) {
131	0×	Ok(c) => c,
132	0×	Err(e) => return unchecked(e.to_string()),
133		};
134	0×	let options = RemoteOptions {
135	0×	ca: ca.map(Path::to_path_buf),
136	0×	..RemoteOptions::default()
137	0×	};
138	0×	let seen = self.seen_log(&hub);
139	0×	let identity = match &seen {
140	0×	Some(s) => s.identity.clone(),
141	0×	None => match http_get(&format!("{hub}/.well-known/oxyhub-key"), &options)
142	0×	.and_then(\|b\| Ok(Identity::decode(&b)?))
143		{
144	0×	Ok(i) => i,
145	0×	Err(e) => return unchecked(format!("its key could not be fetched ({e})")),
146		},
147		};
148	0×	let two = \|why: String\| {
149	0×	fail(format!(
150		"{hub} showed two histories: {why}. Do not trust what it serves; tell its operator. \
151		(What this user saw of its log is in {}.)",
152	0×	self.tlog_file(&hub).display()
153		))
154	0×	};
155	0×	if let Err(e) = note.verify(&cp.origin, &identity) {
156	0×	return match &seen {
157	0×	Some(_) => two(format!(
158	0×	"its checkpoint is not signed by the log key it showed before ({e})"
159	0×	)),
160	0×	None => unchecked(e.to_string()),
161		};
162	0×	}
163	0×	if let Some(s) = &seen {
164	0×	let old = &s.checkpoint;
165	0×	if old.origin != cp.origin {
166	0×	return two(format!("its log is now {}, not {}", cp.origin, old.origin));
167	0×	}
168	0×	if cp.size < old.size {
169	0×	return two(format!(
170	0×	"its log has {} entries, fewer than the {} it showed before",
171	0×	cp.size, old.size
172	0×	));
173	0×	}
174	0×	if cp.size == old.size && cp.root != old.root {
175	0×	return two(format!("two different logs of {} entries", cp.size));
176	0×	}
177	0×	if cp.size > old.size && old.size > 0 {
178	0×	let tiles = Tiles {
179	0×	hub: &hub,
180	0×	size: cp.size,
181	0×	options: &options,
182	0×	cache: RefCell::new(HashMap::new()),
183	0×	};
184	0×	match tlog::prove_consistency(cp.size, old.size, &tiles).and_then(\|p\| {
185	0×	tlog::check_consistency(&p, cp.size, &cp.root, old.size, &old.root)
186	0×	}) {
187	0×	Ok(()) => {}
188		Err(TlogError::ProofFailed) \| Err(TlogError::BadIndex(_)) => {
189	0×	return two(format!(
190	0×	"its log of {} entries does not extend the one of {} it showed before",
191	0×	cp.size, old.size
192	0×	))
193		}
194		// Keep the older checkpoint: the next fetch tries again.
195	0×	Err(e) => return unchecked(format!("its tiles could not be read ({e})")),
196		}
197	0×	}
198	0×	}
199	0×	self.remember_log(&hub, &identity, &note)?;
200	0×	let mut missing = 0;
201	0×	for r in &resp.refs {
202	0×	let Some(a) = &r.attestation else { continue };
203	0×	let Some(l) = &r.logged else {
204	0×	missing += 1;
205	0×	continue;
206		};
207	0×	let fits = Entry::decode(&l.entry).is_ok_and(\|e\| {
208	0×	e.kind == "ref" && e.object == a.attest.hash() && e.repo == a.attest.repo
209	0×	});
210	0×	let included = fits
211	0×	&& tlog::check_inclusion(
212	0×	&l.proof,
213	0×	cp.size,
214	0×	&cp.root,
215	0×	l.index,
216	0×	&tlog::leaf_hash(&l.entry),
217	0×	)
218	0×	.is_ok();
219	0×	if !included {
220	0×	notes.push(format!(
221	0×	"{hub}'s log entry {} for {} does not prove its attestation is in the log",
222	0×	l.index, r.name
223	0×	));
224	0×	}
225		}
226	0×	if missing > 0 {
227	0×	notes.push(format!(
228		"{} of {hub}'s attestations {} not in its transparency log yet (logged within seconds of a push; checked on a later fetch)",
229		missing,
230	0×	if missing == 1 { "is" } else { "are" }
231		));
232	0×	}
233	0×	Ok(notes)
234	359×	}
235		}

Coverage / crates/oxy-core/src/repo/transparency.rs 5.3%

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