Apply state prefix to a relative "state_path".

Previously, we would prepend NGX_ACME_STATE_PREFIX to default paths and
cycle->prefix to explicitly configured paths.  This seems inconsistent
and unnecesarily confusing.

Fixes 131a681.

Author: bavshin-f5

src/conf.rs

@@ -535,10 +535,29 @@ extern "C" fn cmd_issuer_set_state_path(
 
     issuer.state_path = ptr::null_mut();
 
-    if cf.args().get(1).map(ngx_str_t::as_bytes) == Some(b"off") {
+    // NGX_CONF_TAKE1 ensures that args contains 2 elements
+    let mut path = cf.args()[1];
+
+    if path.as_bytes() == b"off" {
         return NGX_CONF_OK;
     }
 
+    // We need to add our prefix before we pass the path to ngx_conf_set_path_slot,
+    // because otherwise it will be resolved with cycle->prefix.
+    if let Some(p) = issuer::NGX_ACME_STATE_PREFIX {
+        let mut p = ngx_str_t {
+            data: p.as_ptr().cast_mut(),
+            len: p.len(),
+        };
+
+        // ngx_get_full_name does not modify input buffers.
+        if !Status(unsafe { nginx_sys::ngx_get_full_name(cf.pool, &mut p, &mut path) }).is_ok() {
+            return NGX_CONF_ERROR;
+        }
+
+        cf.args_mut()[1] = path;
+    }
+
     unsafe { nginx_sys::ngx_conf_set_path_slot(cf, cmd, ptr::from_mut(issuer).cast()) }
 }
 

src/conf/ext.rs

@@ -13,6 +13,7 @@ use ngx::ngx_conf_log_error;
 
 pub trait NgxConfExt {
     fn args(&self) -> &[ngx_str_t];
+    fn args_mut(&mut self) -> &mut [ngx_str_t];
     fn error(&self, dir: impl AsRef<[u8]>, err: &dyn StdError) -> *mut c_char;
     fn pool(&self) -> ngx::core::Pool;
 }
@@ -23,6 +24,16 @@ impl NgxConfExt for ngx_conf_t {
         unsafe { self.args.as_ref().map(|x| x.as_slice()).unwrap_or_default() }
     }
 
+    fn args_mut(&mut self) -> &mut [ngx_str_t] {
+        // SAFETY: we know that cf.args is an array of ngx_str_t
+        unsafe {
+            self.args
+                .as_mut()
+                .map(|x| x.as_slice_mut())
+                .unwrap_or_default()
+        }
+    }
+
     fn error(&self, dir: impl AsRef<[u8]>, err: &dyn StdError) -> *mut c_char {
         // ngx_conf_log_error does not modify the `cf` itself, and the log is mutable due to being a
         // pointer.

src/conf/issuer.rs

@@ -34,6 +34,7 @@ use crate::state::issuer::{IssuerContext, IssuerState};
 use crate::time::{Time, TimeRange};
 
 pub const ACCOUNT_URL_FILE: &str = "account.url";
+pub const NGX_ACME_STATE_PREFIX: Option<&str> = get_state_prefix();
 
 const ACCOUNT_KEY_FILE: &str = "account.key";
 const NGX_ACME_DEFAULT_RESOLVER_TIMEOUT: ngx_msec_t = 30000;
@@ -344,12 +345,10 @@ fn default_state_path(cf: &mut ngx_conf_t, name: &ngx_str_t) -> Result<ngx_str_t
     let mut path = Vec::new_in(cf.pool());
     let reserve = "acme_".len() + name.len + 1;
 
-    if let Some(p) = core::option_env!("NGX_ACME_STATE_PREFIX") {
-        let p = p.trim_end_matches('/');
-        path.try_reserve_exact(p.len() + reserve + 1)
+    if let Some(p) = NGX_ACME_STATE_PREFIX {
+        path.try_reserve_exact(p.len() + reserve)
             .map_err(|_| AllocError)?;
         path.extend(p.as_bytes());
-        path.push(b'/');
     }
 
     path.try_reserve_exact(reserve).map_err(|_| AllocError)?;
@@ -450,3 +449,32 @@ impl StateDir {
         Ok(cert)
     }
 }
+
+/// Returns NGX_ACME_STATE_PREFIX value with a trailing '/'.
+const fn get_state_prefix() -> Option<&'static str> {
+    const fn trim_trailing_slashes(x: &str) -> &str {
+        let mut bytes = x.as_bytes();
+        while let [rest @ .., last] = bytes {
+            if *last == b'/' {
+                bytes = rest;
+            } else {
+                break;
+            }
+        }
+        // SAFETY: the transform above cannot produce an invalid UTF-8 sequence.
+        unsafe { core::str::from_utf8_unchecked(bytes) }
+    }
+
+    const RAW_PREFIX: Option<&str> = core::option_env!("NGX_ACME_STATE_PREFIX");
+    if RAW_PREFIX.is_none() {
+        return None;
+    }
+
+    // Strip all the trailing slashes from the path.
+    const TRIMMED_PREFIX: &str = match RAW_PREFIX {
+        Some(x) => trim_trailing_slashes(x),
+        None => "", // unreachable
+    };
+
+    Some(constcat::concat!(TRIMMED_PREFIX, "/"))
+}