1 files changed, 322 insertions, 0 deletions
diff --git a/src/basic/khash.c b/src/basic/khash.c
new file mode 100644
index 0000000..847f257
--- /dev/null
+++ b/src/basic/khash.c
@@ -0,0 +1,322 @@
+/* SPDX-License-Identifier: LGPL-2.1+ */
+
+#include <linux/if_alg.h>
+#include <stdbool.h>
+#include <sys/socket.h>
+
+#include "alloc-util.h"
+#include "fd-util.h"
+#include "hexdecoct.h"
+#include "khash.h"
+#include "macro.h"
+#include "missing.h"
+#include "string-util.h"
+#include "util.h"
+
+/* On current kernels the maximum digest (according to "grep digestsize /proc/crypto | sort -u") is actually 32, but
+ * let's add some extra room, the few wasted bytes don't really matter... */
+#define LONGEST_DIGEST 128
+
+struct khash {
+        int fd;
+        char *algorithm;
+        uint8_t digest[LONGEST_DIGEST+1];
+        size_t digest_size;
+        bool digest_valid;
+};
+
+int khash_supported(void) {
+        static const union {
+                struct sockaddr sa;
+                struct sockaddr_alg alg;
+        } sa = {
+                .alg.salg_family = AF_ALG,
+                .alg.salg_type = "hash",
+                .alg.salg_name = "sha256", /* a very common algorithm */
+        };
+
+        static int cached = -1;
+
+        if (cached < 0) {
+                _cleanup_close_ int fd1 = -1, fd2 = -1;
+                uint8_t buf[LONGEST_DIGEST+1];
+
+                fd1 = socket(AF_ALG, SOCK_SEQPACKET|SOCK_CLOEXEC, 0);
+                if (fd1 < 0) {
+                        /* The kernel returns EAFNOSUPPORT if AF_ALG is not supported at all */
+                        if (IN_SET(errno, EAFNOSUPPORT, EOPNOTSUPP))
+                                return (cached = false);
+
+                        return -errno;
+                }
+
+                if (bind(fd1, &sa.sa, sizeof(sa)) < 0) {
+                        /* The kernel returns ENOENT if the selected algorithm is not supported at all. We use a check
+                         * for SHA256 as a proxy for whether the whole API is supported at all. After all it's one of
+                         * the most common hash functions, and if it isn't supported, that's ample indication that
+                         * something is really off. */
+
+                        if (IN_SET(errno, ENOENT, EOPNOTSUPP))
+                                return (cached = false);
+
+                        return -errno;
+                }
+
+                fd2 = accept4(fd1, NULL, 0, SOCK_CLOEXEC);
+                if (fd2 < 0) {
+                        if (errno == EOPNOTSUPP)
+                                return (cached = false);
+
+                        return -errno;
+                }
+
+                if (recv(fd2, buf, sizeof(buf), 0) < 0) {
+                        /* On some kernels we get ENOKEY for non-keyed hash functions (such as sha256), let's refuse
+                         * using the API in those cases, since the kernel is
+                         * broken. https://github.com/systemd/systemd/issues/8278 */
+
+                        if (IN_SET(errno, ENOKEY, EOPNOTSUPP))
+                                return (cached = false);
+                }
+
+                cached = true;
+        }
+
+        return cached;
+}
+
+int khash_new_with_key(khash **ret, const char *algorithm, const void *key, size_t key_size) {
+        union {
+                struct sockaddr sa;
+                struct sockaddr_alg alg;
+        } sa = {
+                .alg.salg_family = AF_ALG,
+                .alg.salg_type = "hash",
+        };
+
+        _cleanup_(khash_unrefp) khash *h = NULL;
+        _cleanup_close_ int fd = -1;
+        int supported;
+        ssize_t n;
+
+        assert(ret);
+        assert(key || key_size == 0);
+
+        /* Filter out an empty algorithm early, as we do not support an algorithm by that name. */
+        if (isempty(algorithm))
+                return -EINVAL;
+
+        /* Overly long hash algorithm names we definitely do not support */
+        if (strlen(algorithm) >= sizeof(sa.alg.salg_name))
+                return -EOPNOTSUPP;
+
+        supported = khash_supported();
+        if (supported < 0)
+                return supported;
+        if (supported == 0)
+                return -EOPNOTSUPP;
+
+        fd = socket(AF_ALG, SOCK_SEQPACKET|SOCK_CLOEXEC, 0);
+        if (fd < 0)
+                return -errno;
+
+        strcpy((char*) sa.alg.salg_name, algorithm);
+        if (bind(fd, &sa.sa, sizeof(sa)) < 0) {
+                if (errno == ENOENT)
+                        return -EOPNOTSUPP;
+                return -errno;
+        }
+
+        if (key) {
+                if (setsockopt(fd, SOL_ALG, ALG_SET_KEY, key, key_size) < 0)
+                        return -errno;
+        }
+
+        h = new0(khash, 1);
+        if (!h)
+                return -ENOMEM;
+
+        h->fd = accept4(fd, NULL, 0, SOCK_CLOEXEC);
+        if (h->fd < 0)
+                return -errno;
+
+        h->algorithm = strdup(algorithm);
+        if (!h->algorithm)
+                return -ENOMEM;
+
+        /* Temporary fix for rc kernel bug: https://bugzilla.redhat.com/show_bug.cgi?id=1395896 */
+        (void) send(h->fd, NULL, 0, 0);
+
+        /* Figure out the digest size */
+        n = recv(h->fd, h->digest, sizeof(h->digest), 0);
+        if (n < 0)
+                return -errno;
+        if (n >= LONGEST_DIGEST) /* longer than what we expected? If so, we don't support this */
+                return -EOPNOTSUPP;
+
+        h->digest_size = (size_t) n;
+        h->digest_valid = true;
+
+        /* Temporary fix for rc kernel bug: https://bugzilla.redhat.com/show_bug.cgi?id=1395896 */
+        (void) send(h->fd, NULL, 0, 0);
+
+        *ret = h;
+        h = NULL;
+
+        return 0;
+}
+
+int khash_new(khash **ret, const char *algorithm) {
+        return khash_new_with_key(ret, algorithm, NULL, 0);
+}
+
+khash* khash_unref(khash *h) {
+        if (!h)
+                return NULL;
+
+        safe_close(h->fd);
+        free(h->algorithm);
+        return mfree(h);
+}
+
+int khash_dup(khash *h, khash **ret) {
+        _cleanup_(khash_unrefp) khash *copy = NULL;
+
+        assert(h);
+        assert(ret);
+
+        copy = newdup(khash, h, 1);
+        if (!copy)
+                return -ENOMEM;
+
+        copy->fd = -1;
+        copy->algorithm = strdup(h->algorithm);
+        if (!copy->algorithm)
+                return -ENOMEM;
+
+        copy->fd = accept4(h->fd, NULL, 0, SOCK_CLOEXEC);
+        if (copy->fd < 0)
+                return -errno;
+
+        *ret = TAKE_PTR(copy);
+
+        return 0;
+}
+
+const char *khash_get_algorithm(khash *h) {
+        assert(h);
+
+        return h->algorithm;
+}
+
+size_t khash_get_size(khash *h) {
+        assert(h);
+
+        return h->digest_size;
+}
+
+int khash_reset(khash *h) {
+        ssize_t n;
+
+        assert(h);
+
+        n = send(h->fd, NULL, 0, 0);
+        if (n < 0)
+                return -errno;
+
+        h->digest_valid = false;
+
+        return 0;
+}
+
+int khash_put(khash *h, const void *buffer, size_t size) {
+        ssize_t n;
+
+        assert(h);
+        assert(buffer || size == 0);
+
+        if (size <= 0)
+                return 0;
+
+        n = send(h->fd, buffer, size, MSG_MORE);
+        if (n < 0)
+                return -errno;
+
+        h->digest_valid = false;
+
+        return 0;
+}
+
+int khash_put_iovec(khash *h, const struct iovec *iovec, size_t n) {
+        struct msghdr mh = {
+                mh.msg_iov = (struct iovec*) iovec,
+                mh.msg_iovlen = n,
+        };
+        ssize_t k;
+
+        assert(h);
+        assert(iovec || n == 0);
+
+        if (n <= 0)
+                return 0;
+
+        k = sendmsg(h->fd, &mh, MSG_MORE);
+        if (k < 0)
+                return -errno;
+
+        h->digest_valid = false;
+
+        return 0;
+}
+
+static int retrieve_digest(khash *h) {
+        ssize_t n;
+
+        assert(h);
+
+        if (h->digest_valid)
+                return 0;
+
+        n = recv(h->fd, h->digest, h->digest_size, 0);
+        if (n < 0)
+                return n;
+        if ((size_t) n != h->digest_size) /* digest size changed? */
+                return -EIO;
+
+        h->digest_valid = true;
+
+        return 0;
+}
+
+int khash_digest_data(khash *h, const void **ret) {
+        int r;
+
+        assert(h);
+        assert(ret);
+
+        r = retrieve_digest(h);
+        if (r < 0)
+                return r;
+
+        *ret = h->digest;
+        return 0;
+}
+
+int khash_digest_string(khash *h, char **ret) {
+        int r;
+        char *p;
+
+        assert(h);
+        assert(ret);
+
+        r = retrieve_digest(h);
+        if (r < 0)
+                return r;
+
+        p = hexmem(h->digest, h->digest_size);
+        if (!p)
+                return -ENOMEM;
+
+        *ret = p;
+        return 0;
+}