git: ba839bc9d3ee - stable/13 - rtld: extract header validation into new helper check_elf_headers()

[Konstantin Belousov]

The branch stable/13 has been updated by kib:

URL: 
https://cgit.FreeBSD.org/src/commit/?id=ba839bc9d3eef8d2f68f298c76842fb215cd8ed4

commit ba839bc9d3eef8d2f68f298c76842fb215cd8ed4
Author:     Konstantin Belousov <k...@freebsd.org>
AuthorDate: 2021-11-11 17:51:26 +0000
Commit:     Konstantin Belousov <k...@freebsd.org>
CommitDate: 2021-12-13 00:58:22 +0000

    rtld: extract header validation into new helper check_elf_headers()
    
    (cherry picked from commit 63fc4e820c86f5dedb80cc31b7918deb284b455e)
---
 libexec/rtld-elf/map_object.c | 60 ++++++++++++++++++++++++-------------------
 libexec/rtld-elf/rtld.h       |  1 +
 2 files changed, 35 insertions(+), 26 deletions(-)

diff --git a/libexec/rtld-elf/map_object.c b/libexec/rtld-elf/map_object.c
index b725fe93b8f6..2da323c115cc 100644
--- a/libexec/rtld-elf/map_object.c
+++ b/libexec/rtld-elf/map_object.c
@@ -345,6 +345,39 @@ error:
     return (NULL);
 }
 
+bool
+check_elf_headers(const Elf_Ehdr *hdr, const char *path)
+{
+       if (!IS_ELF(*hdr)) {
+               _rtld_error("%s: invalid file format", path);
+               return (false);
+       }
+       if (hdr->e_ident[EI_CLASS] != ELF_TARG_CLASS ||
+           hdr->e_ident[EI_DATA] != ELF_TARG_DATA) {
+               _rtld_error("%s: unsupported file layout", path);
+               return (false);
+       }
+       if (hdr->e_ident[EI_VERSION] != EV_CURRENT ||
+           hdr->e_version != EV_CURRENT) {
+               _rtld_error("%s: unsupported file version", path);
+               return (false);
+       }
+       if (hdr->e_type != ET_EXEC && hdr->e_type != ET_DYN) {
+               _rtld_error("%s: unsupported file type", path);
+               return (false);
+       }
+       if (hdr->e_machine != ELF_TARG_MACH) {
+               _rtld_error("%s: unsupported machine", path);
+               return (false);
+       }
+       if (hdr->e_phentsize != sizeof(Elf_Phdr)) {
+               _rtld_error(
+           "%s: invalid shared object: e_phentsize != sizeof(Elf_Phdr)", path);
+               return (false);
+       }
+       return (true);
+}
+
 static Elf_Ehdr *
 get_elf_header(int fd, const char *path, const struct stat *sbp,
     Elf_Phdr **phdr_p)
@@ -366,39 +399,14 @@ get_elf_header(int fd, const char *path, const struct 
stat *sbp,
        }
 
        /* Make sure the file is valid */
-       if (!IS_ELF(*hdr)) {
-               _rtld_error("%s: invalid file format", path);
+       if (!check_elf_headers(hdr, path))
                goto error;
-       }
-       if (hdr->e_ident[EI_CLASS] != ELF_TARG_CLASS ||
-           hdr->e_ident[EI_DATA] != ELF_TARG_DATA) {
-               _rtld_error("%s: unsupported file layout", path);
-               goto error;
-       }
-       if (hdr->e_ident[EI_VERSION] != EV_CURRENT ||
-           hdr->e_version != EV_CURRENT) {
-               _rtld_error("%s: unsupported file version", path);
-               goto error;
-       }
-       if (hdr->e_type != ET_EXEC && hdr->e_type != ET_DYN) {
-               _rtld_error("%s: unsupported file type", path);
-               goto error;
-       }
-       if (hdr->e_machine != ELF_TARG_MACH) {
-               _rtld_error("%s: unsupported machine", path);
-               goto error;
-       }
 
        /*
         * We rely on the program header being in the first page.  This is
         * not strictly required by the ABI specification, but it seems to
         * always true in practice.  And, it simplifies things considerably.
         */
-       if (hdr->e_phentsize != sizeof(Elf_Phdr)) {
-               _rtld_error(
-           "%s: invalid shared object: e_phentsize != sizeof(Elf_Phdr)", path);
-               goto error;
-       }
        if (phdr_in_zero_page(hdr)) {
                phdr = (Elf_Phdr *)((char *)hdr + hdr->e_phoff);
        } else {
diff --git a/libexec/rtld-elf/rtld.h b/libexec/rtld-elf/rtld.h
index b216e80115bc..48b3ad526828 100644
--- a/libexec/rtld-elf/rtld.h
+++ b/libexec/rtld-elf/rtld.h
@@ -405,6 +405,7 @@ void free_tls_offset(Obj_Entry *obj);
 const Ver_Entry *fetch_ventry(const Obj_Entry *obj, unsigned long);
 int convert_prot(int elfflags);
 void *_get_tp(void);   /* libc implementation */
+bool check_elf_headers(const Elf_Ehdr *hdr, const char *path);
 
 /*
  * MD function declarations.