Use compile time detection of what features are available

Previously features were gated on the botan3 feature (which is removed here).
This didn't work well in practice as it made it difficult to add support for
features added in Botan3 after the 3.0 release.

Add declarations in botan-sys for functions added to ffi.h since 3.0.0, gated on
the detected library version. Also add interfaces for some of the new
functionality to the high level Rust crate.

.ci/build.py

@@ -23,9 +23,6 @@ def compute_features(features, for_who):
     if 'vendored' in features:
         feat.append('vendored')
 
-    if 'git' in features or 'botan3' in features:
-        feat.append('botan3')
-
     if for_who == 'lib' and 'no-std' not in features:
         feat.append('std')
 
@@ -64,7 +61,7 @@ def main(args = None):
         if "SCCACHE_MAXSIZE" not in os.environ:
             os.environ["SCCACHE_MAXSIZE"] = "2G"
 
-    KNOWN_FEATURES = ['vendored', 'git', 'no-std', 'botan3']
+    KNOWN_FEATURES = ['vendored', 'git', 'no-std']
 
     features = [] if len(args) == 1 else args[1].split(',')
 
@@ -89,7 +86,7 @@ def main(args = None):
         os.environ["DYLD_LIBRARY_PATH"] = "/usr/local/lib"
 
     homebrew_dir = "/opt/homebrew/lib"
-    if 'botan3' in features and os.access(homebrew_dir, os.R_OK):
+    if os.access(homebrew_dir, os.R_OK):
         os.environ["RUSTFLAGS"] = "-D warnings -L/opt/homebrew/lib"
         os.environ["RUSTDOCFLAGS"] = "-D warnings -L/opt/homebrew/lib"
         os.environ["DYLD_LIBRARY_PATH"] = homebrew_dir

.github/workflows/ci.yml

@@ -23,6 +23,7 @@ jobs:
     runs-on: ubuntu-24.04
 
     steps:
+      - run: sudo apt-get -qq install libbotan-2-dev
       - uses: dtolnay/rust-toolchain@master
         with:
           toolchain: nightly
@@ -84,11 +85,9 @@ jobs:
       matrix:
         include:
           - toolchain: stable
-            features: botan3
           - toolchain: stable
             features: vendored
           - toolchain: nightly
-            features: botan3
 
     steps:
       - run: brew install ccache botan

README.md

@@ -39,10 +39,15 @@ The following features are supported:
   is still required.
 * `vendored`: Build a copy of the C++ library directly, without
   relying on a system installed version.
-* `botan3`: Enable support for using APIs added in Botan 3.
-  This enables several new features, and more efficient operation.
-  This feature is implicitly enabled if you use `vendored`.
 * `static`: Enable static linking for a non-vendored, externally
   provided Botan dependency.
 * `pkg-config`: Enable finding a non-vendored, externally provided
   Botan with pkg-config. Can be used in combination with `static`.
+
+The crate detects at build time what features are exported from the C interface,
+and adjusts itself accordingly. These feature sets can be checked using
+`#[cfg(botan_ffi_YYYYMMDD)]` where YYYYMMDD can be any of
+
+* 20230403: Botan 3.0
+* 20240408: Botan 3.4
+* 20250506: Botan 3.8

botan-src/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "botan-src"
-version = "0.30701.1"
+version = "0.30701.2"
 authors = ["Rodolphe Breard <[email protected]>", "Jack Lloyd <[email protected]>"]
 description = "Sources of Botan cryptography library"
 license = "MIT"

botan-src/examples/build.rs

@@ -1,5 +1,5 @@
 fn main() {
     let (lib_dir, include_dir) = botan_src::build();
     println!("Library directory: {lib_dir}");
-    println!("Include directory: {include_dir}");
+    println!("Include directory: {}", include_dir.display());
 }

botan-src/src/lib.rs

@@ -5,7 +5,7 @@ use std::process::Command;
 const BUILD_ERROR_MSG: &str = "Unable to build botan.";
 const SRC_DIR_ERROR_MSG: &str = "Unable to find the source directory.";
 const SRC_DIR: &str = "botan";
-const INCLUDE_DIR: &str = "build/include/botan";
+const INCLUDE_DIR: &str = "build/include/public";
 
 macro_rules! pathbuf_to_string {
     ($s: ident) => {
@@ -115,14 +115,16 @@ fn make(build_dir: &str) {
     }
 }
 
-pub fn build() -> (String, String) {
+pub fn build() -> (String, std::path::PathBuf) {
     let src_dir = PathBuf::from(env!("CARGO_MANIFEST_DIR")).join(SRC_DIR);
     let build_dir = env::var_os("OUT_DIR").map_or(src_dir.to_owned(), PathBuf::from);
     let build_dir = build_dir.join("botan");
     let include_dir = build_dir.join(INCLUDE_DIR);
     let build_dir = pathbuf_to_string!(build_dir);
+    let orig_dir = env::current_dir().expect(SRC_DIR_ERROR_MSG);
     env::set_current_dir(&src_dir).expect(SRC_DIR_ERROR_MSG);
     configure(&build_dir);
     make(&build_dir);
-    (build_dir, pathbuf_to_string!(include_dir))
+    env::set_current_dir(&orig_dir).expect("Unable to restore cwd");
+    (build_dir, include_dir)
 }

botan-sys/Cargo.toml

@@ -1,9 +1,9 @@
 [package]
 name = "botan-sys"
-version = "0.11.1"
+version = "0.12.0"
 authors = ["Jack Lloyd <[email protected]>"]
-links = "botan-3"
-build = "build.rs"
+links = "botan"
+build = "build/main.rs"
 description = "FFI wrapper for Botan cryptography library"
 license = "MIT"
 homepage = "https://botan.randombit.net/"
@@ -16,11 +16,11 @@ rust-version = "1.64"
 
 [features]
 default = []
-vendored = ["botan-src", "botan3"]
-botan3 = []
+vendored = ["botan-src"]
 static = []
 pkg-config = ["dep:pkg-config"]
 
 [build-dependencies]
-botan-src = { version = "0.30701.1", optional = true, path = "../botan-src" }
+botan-src = { version = "0.30701.2", optional = true, path = "../botan-src" }
 pkg-config = { version = "0.3.30", optional = true }
+cc = "1"

botan-sys/README.md

@@ -1,7 +1,24 @@
 # botan-sys
 
 This crate contains the FFI declarations for calling the C API included in the
-[Botan](https://botan.randombit.net/) cryptography library.
+[Botan](https://botan.randombit.net/) cryptography library as well as the rules
+for linking to it.
 
 A high level Rust interface built on these declarations is included in the
 [botan](https://crates.io/crates/botan) crate.
+
+## Features
+
+* `vendored`: Build against the `botan-src` crate
+* `static`: Statically link the library. This is always used if `vendored` is set
+* `pkg-config`: Use `pkg-config` instead of probing to find the library
+
+## Environment Variables
+
+The following environment variables are used to guide features
+
+* `BOTAN_INCLUDE_DIR` the base path to where the relevant library includes are
+  found. For example if the headers are in `/opt/foo/botan-3/botan`, this
+  variable should be set to `/opt/foo`. If not set, tries a few common
+  locations. This variable is ignored if the `pkg-config` or `vendored`
+  features are used.