diff --git a/Makefile.am b/Makefile.am
index 7440d134721..1e50eb89872 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -763,6 +763,7 @@ include_HEADERS = \
     lib/bitvector.h \
     lib/bloom.h \
     lib/bsearch.h \
+    lib/buf.h \
     lib/charset.h \
     lib/command.h \
     lib/crc32.h \
@@ -780,6 +781,7 @@ include_HEADERS = \
     lib/imparse.h \
     lib/iostat.h \
     lib/iptostring.h \
+    lib/libconfig.h \
     lib/libcyr_cfg.h \
     lib/lsort.h \
     lib/map.h \
@@ -810,14 +812,16 @@ include_HEADERS = \
 nodist_include_HEADERS = \
     lib/imapopts.h
 
-nobase_include_HEADERS = sieve/sieve_interface.h
+nobase_include_HEADERS = \
+    imap/message_guid.h \
+    sieve/sieve_interface.h
+
 nobase_nodist_include_HEADERS = sieve/sieve_err.h
 
 noinst_HEADERS += \
     lib/bufarray.h \
     lib/byteorder.h \
     lib/gai.h \
-    lib/libconfig.h \
     lib/md5.h \
     lib/prot.h \
     lib/ptrarray.h \
@@ -1010,7 +1014,6 @@ imap_libcyrus_imap_la_SOURCES = \
     imap/mboxname.c \
     imap/mboxname.h \
     imap/message_guid.c \
-    imap/message_guid.h \
     imap/message.c \
     imap/message.h \
     imap/message_priv.h \
diff --git a/imap/message.h b/imap/message.h
index 3412adb5904..39c2b8abd56 100644
--- a/imap/message.h
+++ b/imap/message.h
@@ -45,10 +45,12 @@
 
 #include <stdio.h>
 
+#include "arrayu64.h"
+#include "buf.h"
 #include "prot.h"
 #include "mailbox.h"
+#include "imap/message_guid.h"
 #include "strarray.h"
-#include "util.h"
 #include "charset.h"
 
 /* (draft standard) MIME tspecials */
diff --git a/lib/buf.h b/lib/buf.h
new file mode 100644
index 00000000000..a25563036b7
--- /dev/null
+++ b/lib/buf.h
@@ -0,0 +1,117 @@
+/*
+ * Copyright (c) 2024 Carnegie Mellon University.  All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ *
+ * 3. The name "Carnegie Mellon University" must not be used to
+ *    endorse or promote products derived from this software without
+ *    prior written permission. For permission or any legal
+ *    details, please contact
+ *      Carnegie Mellon University
+ *      Center for Technology Transfer and Enterprise Creation
+ *      4615 Forbes Avenue
+ *      Suite 302
+ *      Pittsburgh, PA  15213
+ *      (412) 268-7393, fax: (412) 268-7395
+ *      innovation@andrew.cmu.edu
+ *
+ * 4. Redistributions of any form whatsoever must retain the following
+ *    acknowledgment:
+ *    "This product includes software developed by Computing Services
+ *     at Carnegie Mellon University (http://www.cmu.edu/computing/)."
+ *
+ * CARNEGIE MELLON UNIVERSITY DISCLAIMS ALL WARRANTIES WITH REGARD TO
+ * THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
+ * AND FITNESS, IN NO EVENT SHALL CARNEGIE MELLON UNIVERSITY BE LIABLE
+ * FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN
+ * AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING
+ * OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#ifndef INCLUDED_BUF_H
+#define INCLUDED_BUF_H
+
+/* Examine the name of a file, and return a single character
+ *  (as an int) that can be used as the name of a hash
+ *  directory.  Caller is responsible for skipping any prefix
+ *  of the name.
+ */
+int dir_hash_c(const char *name, int full);
+
+#include <stddef.h>
+#define BUF_MMAP    (1<<1)
+typedef unsigned long long int modseq_t;
+
+struct buf {
+    char *s;
+    size_t len;
+    size_t alloc;
+    unsigned flags;
+};
+#define BUF_INITIALIZER { NULL, 0, 0, 0 }
+
+#define buf_new() ((struct buf *) xzmalloc(sizeof(struct buf)))
+#define buf_destroy(b) do { buf_free((b)); free((b)); } while (0)
+#define buf_ensure(b, n) do { if ((b)->alloc < (b)->len + (n)) _buf_ensure((b), (n)); } while (0)
+#define buf_putc(b, c) do { buf_ensure((b), 1); (b)->s[(b)->len++] = (c); } while (0)
+
+void _buf_ensure(struct buf *buf, size_t len);
+const char *buf_cstring(const struct buf *buf);
+const char *buf_cstringnull(const struct buf *buf);
+const char *buf_cstringnull_ifempty(const struct buf *buf);
+const char *buf_cstring_or_empty(const struct buf *buf);
+char *buf_newcstring(struct buf *buf);
+char *buf_release(struct buf *buf);
+char *buf_releasenull(struct buf *buf);
+void buf_getmap(struct buf *buf, const char **base, size_t *len);
+size_t buf_len(const struct buf *buf);
+const char *buf_base(const struct buf *buf);
+void buf_reset(struct buf *buf);
+void buf_setcstr(struct buf *buf, const char *str);
+void buf_setmap(struct buf *buf, const char *base, size_t len);
+void buf_copy(struct buf *dst, const struct buf *src);
+void buf_append(struct buf *dst, const struct buf *src);
+void buf_appendcstr(struct buf *buf, const char *str);
+void buf_appendoverlap(struct buf *buf, const char *str);
+void buf_appendmap(struct buf *buf, const char *base, size_t len);
+void buf_cowappendmap(struct buf *buf, const char *base, unsigned int len);
+void buf_cowappendfree(struct buf *buf, char *base, unsigned int len);
+void buf_insert(struct buf *dst, unsigned int off, const struct buf *src);
+void buf_insertcstr(struct buf *buf, unsigned int off, const char *str);
+void buf_insertmap(struct buf *buf, unsigned int off, const char *base, int len);
+void buf_printf(struct buf *buf, const char *fmt, ...)
+                __attribute__((format(printf, 2, 3)));
+void buf_replace_buf(struct buf *buf, size_t offset, size_t length,
+                     const struct buf *replace);
+int buf_replace_all(struct buf *buf, const char *match,
+                    const char *replace);
+int buf_replace_char(struct buf *buf, char match, char replace);
+void buf_remove(struct buf *buf, unsigned int off, unsigned int len);
+int buf_cmp(const struct buf *, const struct buf *);
+int buf_findchar(const struct buf *, unsigned int off, int c);
+int buf_findline(const struct buf *buf, const char *line);
+void buf_init_ro(struct buf *buf, const char *base, size_t len);
+void buf_initm(struct buf *buf, char *base, int len);
+void buf_initmcstr(struct buf *buf, char *str);
+void buf_init_ro_cstr(struct buf *buf, const char *str);
+void buf_refresh_mmap(struct buf *buf, int onceonly, int fd,
+                   const char *fname, size_t size, const char *mboxname);
+void buf_free(struct buf *buf);
+void buf_move(struct buf *dst, struct buf *src);
+const char *buf_lcase(struct buf *buf);
+const char *buf_ucase(struct buf *buf);
+const char *buf_tocrlf(struct buf *buf);
+void buf_trim(struct buf *buf);
+
+#endif /* INCLUDED_BUF_H */
diff --git a/lib/charset.h b/lib/charset.h
index 5fba6fd2d38..283f0035d73 100644
--- a/lib/charset.h
+++ b/lib/charset.h
@@ -68,7 +68,7 @@
 #define MIME_MAX_HEADER_LENGTH 78
 #define MIME_MAX_LINE_LENGTH 998
 
-#include "util.h"
+#include "buf.h"
 #include "xsha1.h"
 
 #define charset_base64_len_unpadded(n) \
diff --git a/lib/util.h b/lib/util.h
index 6cdd95a2717..d081161a4bc 100644
--- a/lib/util.h
+++ b/lib/util.h
@@ -65,6 +65,7 @@
 #define	STDERR_FILENO	2	/* Standard error output.  */
 #endif
 
+#include "buf.h"
 #include "xmalloc.h"
 
 /* version string printable in gdb tracking */
@@ -106,7 +107,6 @@ typedef unsigned short bit32;
 #endif
 
 typedef unsigned long long int bit64;
-typedef unsigned long long int modseq_t;
 #define MODSEQ_FMT "%llu"
 #define atomodseq_t(s) strtoull(s, NULL, 10)
 char *modseqtoa(modseq_t modseq);
@@ -191,12 +191,6 @@ int strcmpnull(const char *a, const char *b);
 extern keyvalue *kv_bsearch (const char *key, keyvalue *kv, int nelem,
                                int (*cmpf)(const char *s1, const char *s2));
 
-/* Examine the name of a file, and return a single character
- *  (as an int) that can be used as the name of a hash
- *  directory.  Caller is responsible for skipping any prefix
- *  of the name.
- */
-extern int dir_hash_c(const char *name, int full);
 /*
  * Like dir_hash_c() but builds the result as a single-byte
  * C string in the provided buffer, and returns the buffer,
@@ -279,80 +273,18 @@ extern int64_t now_ms(void);
 
 extern clock_t sclock(void);
 
-#define BUF_MMAP    (1<<1)
-
-struct buf {
-    char *s;
-    size_t len;
-    size_t alloc;
-    unsigned flags;
-};
-#define BUF_INITIALIZER { NULL, 0, 0, 0 }
-
-#define buf_new() ((struct buf *) xzmalloc(sizeof(struct buf)))
-#define buf_destroy(b) do { buf_free((b)); free((b)); } while (0)
-#define buf_ensure(b, n) do { if ((b)->alloc < (b)->len + (n)) _buf_ensure((b), (n)); } while (0)
-#define buf_putc(b, c) do { buf_ensure((b), 1); (b)->s[(b)->len++] = (c); } while (0)
-
-void _buf_ensure(struct buf *buf, size_t len);
-const char *buf_cstring(const struct buf *buf);
-const char *buf_cstringnull(const struct buf *buf);
-const char *buf_cstringnull_ifempty(const struct buf *buf);
-const char *buf_cstring_or_empty(const struct buf *buf);
-char *buf_newcstring(struct buf *buf);
-char *buf_release(struct buf *buf);
-char *buf_releasenull(struct buf *buf);
-void buf_getmap(struct buf *buf, const char **base, size_t *len);
 int buf_getline(struct buf *buf, FILE *fp);
-size_t buf_len(const struct buf *buf);
-const char *buf_base(const struct buf *buf);
-void buf_reset(struct buf *buf);
 void buf_truncate(struct buf *buf, ssize_t len);
-void buf_setcstr(struct buf *buf, const char *str);
-void buf_setmap(struct buf *buf, const char *base, size_t len);
-void buf_copy(struct buf *dst, const struct buf *src);
-void buf_append(struct buf *dst, const struct buf *src);
-void buf_appendcstr(struct buf *buf, const char *str);
-void buf_appendoverlap(struct buf *buf, const char *str);
 void buf_appendbit32(struct buf *buf, bit32 num);
 void buf_appendbit64(struct buf *buf, bit64 num);
-void buf_appendmap(struct buf *buf, const char *base, size_t len);
-void buf_cowappendmap(struct buf *buf, const char *base, unsigned int len);
-void buf_cowappendfree(struct buf *buf, char *base, unsigned int len);
-void buf_insert(struct buf *dst, unsigned int off, const struct buf *src);
-void buf_insertcstr(struct buf *buf, unsigned int off, const char *str);
-void buf_insertmap(struct buf *buf, unsigned int off, const char *base, int len);
 void buf_vprintf(struct buf *buf, const char *fmt, va_list args)
                 __attribute__((format(printf, 2, 0)));
-void buf_printf(struct buf *buf, const char *fmt, ...)
-                __attribute__((format(printf, 2, 3)));
-void buf_replace_buf(struct buf *buf, size_t offset, size_t length,
-                     const struct buf *replace);
-int buf_replace_all(struct buf *buf, const char *match,
-                    const char *replace);
-int buf_replace_char(struct buf *buf, char match, char replace);
 #ifdef ENABLE_REGEX
 int buf_replace_all_re(struct buf *buf, const regex_t *,
                        const char *replace);
 int buf_replace_one_re(struct buf *buf, const regex_t *,
                        const char *replace);
 #endif
-void buf_remove(struct buf *buf, unsigned int off, unsigned int len);
-int buf_cmp(const struct buf *, const struct buf *);
-int buf_findchar(const struct buf *, unsigned int off, int c);
-int buf_findline(const struct buf *buf, const char *line);
-void buf_init_ro(struct buf *buf, const char *base, size_t len);
-void buf_initm(struct buf *buf, char *base, int len);
-void buf_initmcstr(struct buf *buf, char *str);
-void buf_init_ro_cstr(struct buf *buf, const char *str);
-void buf_refresh_mmap(struct buf *buf, int onceonly, int fd,
-                   const char *fname, size_t size, const char *mboxname);
-void buf_free(struct buf *buf);
-void buf_move(struct buf *dst, struct buf *src);
-const char *buf_lcase(struct buf *buf);
-const char *buf_ucase(struct buf *buf);
-const char *buf_tocrlf(struct buf *buf);
-void buf_trim(struct buf *buf);
 
 /*
  * Given a list of strings, terminated by (char *)NULL,
diff --git a/sieve/sieve_interface.h b/sieve/sieve_interface.h
index e2a5e31a7da..e54b3de4767 100644
--- a/sieve/sieve_interface.h
+++ b/sieve/sieve_interface.h
@@ -51,8 +51,8 @@
 #define SIEVE_OK (0)
 
 #include "arrayu64.h"
+#include "buf.h"
 #include "strarray.h"
-#include "util.h"
 #include "sieve/sieve_err.h"
 
 /* external sieve types */