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From: Christian Ebner <c.ebner@proxmox.com>
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Date: Mon, 19 May 2025 13:46:10 +0200
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Subject: [pbs-devel] [RFC proxmox-backup 09/39] s3 client: add helper to
parse http date headers
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Add a helper to parse the preferred date/time format for http `Date`
headers as specified in RFC 2616 [0], which is a fixed-length subset
of the format specified in RFC 1123 [1], itself being a followup to
RFC 822 [2]. Does not implement the format as described in the
obsolete RFC 850 [3].
This allows to parse the `Date` and `Last-Modified` headers of S3 API
responses.
[0] https://datatracker.ietf.org/doc/html/rfc2616#section-3.3
[1] https://datatracker.ietf.org/doc/html/rfc1123#section-5.2.14
[2] https://datatracker.ietf.org/doc/html/rfc822#section-5
[3] https://datatracker.ietf.org/doc/html/rfc850
Signed-off-by: Christian Ebner <c.ebner@proxmox.com>
---
pbs-s3-client/src/lib.rs | 97 +++++++++++++++++++++++++++++++++++++++-
1 file changed, 96 insertions(+), 1 deletion(-)
diff --git a/pbs-s3-client/src/lib.rs b/pbs-s3-client/src/lib.rs
index 308db64d8..00fa26455 100644
--- a/pbs-s3-client/src/lib.rs
+++ b/pbs-s3-client/src/lib.rs
@@ -6,7 +6,12 @@ pub use object_key::{S3ObjectKey, S3_CONTENT_PREFIX};
use std::time::Duration;
-use anyhow::{bail, Error};
+use anyhow::{bail, Context, Error};
+
+const VALID_DAYS_OF_WEEK: [&str; 7] = ["Mon", "Tue", "Wed", "Thu", "Fri", "Sat", "Sun"];
+const VALID_MONTHS: [&str; 12] = [
+ "Jan", "Feb", "Mar", "Apr", "May", "Jun", "Jul", "Aug", "Sep", "Oct", "Nov", "Dec",
+];
#[derive(Debug)]
pub struct LastModifiedTimestamp {
@@ -121,3 +126,93 @@ impl std::str::FromStr for LastModifiedTimestamp {
}
serde_plain::derive_deserialize_from_fromstr!(LastModifiedTimestamp, "last modified timestamp");
+
+/// Preferred date format specified by RFC2616, given as fixed-length
+/// subset of RFC1123, which itself is a followup to RFC822.
+///
+/// https://datatracker.ietf.org/doc/html/rfc2616#section-3.3
+/// https://datatracker.ietf.org/doc/html/rfc1123#section-5.2.14
+/// https://datatracker.ietf.org/doc/html/rfc822#section-5
+#[derive(Debug)]
+pub struct HttpDate {
+ epoch: i64,
+}
+
+impl HttpDate {
+ pub fn to_duration(&self) -> Result<Duration, Error> {
+ let seconds = u64::try_from(self.epoch)?;
+ Ok(Duration::from_secs(seconds))
+ }
+}
+
+impl std::str::FromStr for HttpDate {
+ type Err = Error;
+
+ fn from_str(timestamp: &str) -> Result<Self, Self::Err> {
+ let input = timestamp.as_bytes();
+ if input.len() != 29 {
+ bail!("unexpected length: got {}", input.len());
+ }
+
+ let expect = |pos: usize, c: u8| {
+ if input[pos] != c {
+ bail!("unexpected char at pos {pos}");
+ }
+ Ok(())
+ };
+
+ let digit = |pos: usize| -> Result<i32, Error> {
+ let digit = input[pos] as i32;
+ if !(48..=57).contains(&digit) {
+ bail!("unexpected char at pos {pos}");
+ }
+ Ok(digit - 48)
+ };
+
+ fn check_max(i: i32, max: i32) -> Result<i32, Error> {
+ if i > max {
+ bail!("value too large ({i} > {max})");
+ }
+ Ok(i)
+ }
+
+ let mut tm = proxmox_time::TmEditor::new(true);
+
+ if !VALID_DAYS_OF_WEEK
+ .iter()
+ .any(|valid| valid.as_bytes() == &input[0..3])
+ {
+ bail!("unexpected day of week, got {:?}", &input[0..3]);
+ }
+
+ expect(3, b',').context("unexpected separator after day of week")?;
+ expect(4, b' ').context("missing space after day of week separator")?;
+ tm.set_mday(check_max(digit(5)? * 10 + digit(6)?, 31)?)?;
+ expect(7, b' ').context("unexpected separator after day")?;
+ if let Some(month) = VALID_MONTHS
+ .iter()
+ .position(|month| month.as_bytes() == &input[8..11])
+ {
+ // valid conversion to i32, position stems from fixed size array of 12 months.
+ tm.set_mon(check_max(month as i32 + 1, 12)?)?;
+ } else {
+ bail!("invalid month");
+ }
+ expect(11, b' ').context("unexpected separator after month")?;
+ tm.set_year(digit(12)? * 1000 + digit(13)? * 100 + digit(14)? * 10 + digit(15)?)?;
+ expect(16, b' ').context("unexpected separator after year")?;
+ tm.set_hour(check_max(digit(17)? * 10 + digit(18)?, 23)?)?;
+ expect(19, b':').context("unexpected separator after hour")?;
+ tm.set_min(check_max(digit(20)? * 10 + digit(21)?, 59)?)?;
+ expect(22, b':').context("unexpected separator after minute")?;
+ tm.set_sec(check_max(digit(23)? * 10 + digit(24)?, 60)?)?;
+ expect(25, b' ').context("unexpected separator after second")?;
+ if !input.ends_with(b"GMT") {
+ bail!("unexpected timezone");
+ }
+
+ let epoch = tm.into_epoch()?;
+
+ Ok(Self { epoch })
+ }
+}
--
2.39.5
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