[PATCH v6 2/4] KEYS: Add ELF class-independent certificate insertion support
Mehmet Kayaalp
mkayaalp at linux.vnet.ibm.com
Wed May 2 23:08:09 UTC 2018
This patch adds support for handling either 32-bit or 64-bit ELF files
by moving ELF class checks to runtime. This makes it possible to compile
the script for 64-bit, and the kernel for 32-bit (e.g. make ARCH=i386 on
x86-64). Gelf/libelf is purposely not used to avoid the build dependency.
Signed-off-by: Mehmet Kayaalp <mkayaalp at linux.vnet.ibm.com>
---
scripts/insert-sys-cert.c | 331 +++++++++++++++++++++++++-------------
1 file changed, 218 insertions(+), 113 deletions(-)
diff --git a/scripts/insert-sys-cert.c b/scripts/insert-sys-cert.c
index 8902836c2342..10a17504dc87 100644
--- a/scripts/insert-sys-cert.c
+++ b/scripts/insert-sys-cert.c
@@ -25,6 +25,7 @@
#include <fcntl.h>
#include <unistd.h>
#include <elf.h>
+#include <linux/types.h>
#define CERT_SYM "system_extra_cert"
#define USED_SYM "system_extra_cert_used"
@@ -57,6 +58,18 @@ static unsigned char endianness(void)
return ELFDATA2LSB;
}
+struct elf {
+ unsigned char *base;
+ int size;
+ unsigned char eclass;
+ unsigned char data;
+ unsigned long shoff;
+ unsigned long shnum;
+ unsigned long shentsize;
+ unsigned char *shstart;
+ unsigned long shsize;
+};
+
struct sym {
char *name;
unsigned long address;
@@ -65,24 +78,92 @@ struct sym {
int size;
};
-static unsigned long get_offset_from_address(Elf_Ehdr *hdr, unsigned long addr)
+static int read_elf_data(struct elf *elf, char *base, int size)
{
- Elf_Shdr *x;
- unsigned int i, num_sections;
+ unsigned char *e_ident;
+ Elf32_Ehdr *e32 = (Elf32_Ehdr *)base;
+ Elf64_Ehdr *e64 = (Elf64_Ehdr *)base;
- x = (void *)hdr + hdr->e_shoff;
- if (hdr->e_shnum == SHN_UNDEF)
- num_sections = x[0].sh_size;
- else
- num_sections = hdr->e_shnum;
+ elf->base = (unsigned char *)base;
+ elf->size = size;
+
+ if (size < EI_NIDENT) {
+ err("Invalid file size for ELF format.\n");
+ return -1;
+ }
+ e_ident = (unsigned char *)base;
+ if (e_ident[EI_MAG0] != ELFMAG0 || e_ident[EI_MAG1] != ELFMAG1 ||
+ e_ident[EI_MAG2] != ELFMAG2 || e_ident[EI_MAG3] != ELFMAG3) {
+ err("Invalid ELF magic.\n");
+ return -1;
+ }
+ elf->eclass = e_ident[EI_CLASS];
+ if (elf->eclass != ELFCLASS32 && elf->eclass != ELFCLASS64) {
+ err("Invalid ELF class.\n");
+ return -1;
+ }
+ elf->data = e_ident[EI_DATA];
+ if (elf->data != endianness()) {
+ err("ELF endian mismatch.\n");
+ return -1;
+ }
+ if (e_ident[EI_VERSION] != EV_CURRENT) {
+ err("Invalid ELF file version.\n");
+ return -1;
+ }
+ if (elf->eclass == ELFCLASS32) {
+ elf->shoff = e32->e_shoff;
+ elf->shnum = e32->e_shnum;
+ elf->shentsize = e32->e_shentsize;
+ } else {
+ elf->shoff = e64->e_shoff;
+ elf->shnum = e64->e_shnum;
+ elf->shentsize = e64->e_shentsize;
+ }
+ if (elf->shoff == 0 || elf->shoff > size) {
+ err("Could not find section header.\n");
+ exit(EXIT_FAILURE);
+ }
+ elf->shstart = elf->base + elf->shoff;
+ elf->shsize = elf->shnum * elf->shentsize;
+ return 0;
+}
- for (i = 1; i < num_sections; i++) {
- unsigned long start = x[i].sh_addr;
- unsigned long end = start + x[i].sh_size;
- unsigned long offset = x[i].sh_offset;
+static char *get_elf_string(struct elf *elf, unsigned long link,
+ unsigned long namendx)
+{
+ unsigned char *p = elf->shstart + link * elf->shentsize;
+ Elf32_Shdr *s32 = (Elf32_Shdr *)p;
+ Elf64_Shdr *s64 = (Elf64_Shdr *)p;
+ if (elf->eclass == ELFCLASS32)
+ return (char *)elf->base + s32->sh_offset + namendx;
+ else
+ return (char *)elf->base + s64->sh_offset + namendx;
+}
+
+static unsigned long get_offset_from_address(struct elf *elf,
+ unsigned long addr)
+{
+ unsigned long start, end, offset;
+ unsigned char *p = elf->shstart;
+
+ while (p < elf->shstart + elf->shsize) {
+ Elf32_Shdr *s32 = (Elf32_Shdr *)p;
+ Elf64_Shdr *s64 = (Elf64_Shdr *)p;
+
+ if (elf->eclass == ELFCLASS32) {
+ start = s32->sh_addr;
+ end = start + s32->sh_size;
+ offset = s32->sh_offset;
+ } else {
+ start = s64->sh_addr;
+ end = start + s64->sh_size;
+ offset = s64->sh_offset;
+ }
if (addr >= start && addr <= end)
return addr - start + offset;
+ p += elf->shentsize;
}
return 0;
}
@@ -90,7 +171,7 @@ static unsigned long get_offset_from_address(Elf_Ehdr *hdr, unsigned long addr)
#define LINE_SIZE 100
-static void get_symbol_from_map(Elf_Ehdr *hdr, FILE *f, char *name,
+static void get_symbol_from_map(struct elf *elf, FILE *f, char *name,
struct sym *s)
{
char l[LINE_SIZE];
@@ -125,76 +206,108 @@ static void get_symbol_from_map(Elf_Ehdr *hdr, FILE *f, char *name,
s->address = strtoul(l, NULL, 16);
if (s->address == 0)
return;
- s->offset = get_offset_from_address(hdr, s->address);
+ s->offset = get_offset_from_address(elf, s->address);
s->name = name;
- s->content = (void *)hdr + s->offset;
+ s->content = elf->base + s->offset;
}
-static Elf_Sym *find_elf_symbol(Elf_Ehdr *hdr, Elf_Shdr *symtab, char *name)
-{
- Elf_Sym *sym, *symtab_start;
- char *strtab, *symname;
- unsigned int link;
- Elf_Shdr *x;
- int i, n;
-
- x = (void *)hdr + hdr->e_shoff;
- link = symtab->sh_link;
- symtab_start = (void *)hdr + symtab->sh_offset;
- n = symtab->sh_size / symtab->sh_entsize;
- strtab = (void *)hdr + x[link].sh_offset;
-
- for (i = 0; i < n; i++) {
- sym = &symtab_start[i];
- symname = strtab + sym->st_name;
- if (strcmp(symname, name) == 0)
- return sym;
- }
- err("Unable to find symbol: %s\n", name);
- return NULL;
-}
-
-static void get_symbol_from_table(Elf_Ehdr *hdr, Elf_Shdr *symtab,
+static void get_symbol_from_table(struct elf *elf, unsigned char *symtab,
char *name, struct sym *s)
{
- Elf_Shdr *sec;
- int secndx;
- Elf_Sym *elf_sym;
- Elf_Shdr *x;
+ Elf32_Shdr *s32 = (Elf32_Shdr *)symtab;
+ Elf64_Shdr *s64 = (Elf64_Shdr *)symtab;
+ unsigned char *p;
+ unsigned long address;
+ unsigned long offset;
+ unsigned long size;
+ unsigned long entsize;
+ unsigned long link;
+ unsigned long shndx;
+ char *symname;
+ int found = 0;
- x = (void *)hdr + hdr->e_shoff;
s->size = 0;
s->address = 0;
s->offset = 0;
- elf_sym = find_elf_symbol(hdr, symtab, name);
- if (!elf_sym)
- return;
- secndx = elf_sym->st_shndx;
- if (!secndx)
+
+ if (elf->eclass == ELFCLASS32) {
+ offset = s32->sh_offset;
+ size = s32->sh_size;
+ entsize = s32->sh_entsize;
+ link = s32->sh_link;
+ } else {
+ offset = s64->sh_offset;
+ size = s64->sh_size;
+ entsize = s64->sh_entsize;
+ link = s64->sh_link;
+ }
+
+ p = elf->base + offset;
+ while (p < elf->base + offset + size) {
+ Elf32_Sym *sym32 = (Elf32_Sym *)p;
+ Elf64_Sym *sym64 = (Elf64_Sym *)p;
+ unsigned long namendx;
+
+ if (elf->eclass == ELFCLASS32) {
+ namendx = sym32->st_name;
+ shndx = sym32->st_shndx;
+ } else {
+ namendx = sym64->st_name;
+ shndx = sym64->st_shndx;
+ }
+
+ symname = get_elf_string(elf, link, namendx);
+ if (strcmp(symname, name) == 0 && shndx) {
+ found = 1;
+ if (elf->eclass == ELFCLASS32) {
+ s->size = sym32->st_size;
+ s->address = sym32->st_value;
+ } else {
+ s->size = sym64->st_size;
+ s->address = sym64->st_value;
+ }
+ break;
+ }
+ p += entsize;
+ }
+
+ if (!found)
return;
- sec = &x[secndx];
- s->size = elf_sym->st_size;
- s->address = elf_sym->st_value;
- s->offset = s->address - sec->sh_addr
- + sec->sh_offset;
+
+ p = elf->shstart + shndx * elf->shentsize;
+ s32 = (Elf32_Shdr *)p;
+ s64 = (Elf64_Shdr *)p;
+
+ if (elf->eclass == ELFCLASS32) {
+ offset = s32->sh_offset;
+ address = s32->sh_addr;
+ } else {
+ offset = s64->sh_offset;
+ address = s64->sh_addr;
+ }
+
+ s->offset = s->address - address + offset;
s->name = name;
- s->content = (void *)hdr + s->offset;
+ s->content = elf->base + s->offset;
}
-static Elf_Shdr *get_symbol_table(Elf_Ehdr *hdr)
+static unsigned char *get_symbol_table(struct elf *elf)
{
- Elf_Shdr *x;
- unsigned int i, num_sections;
-
- x = (void *)hdr + hdr->e_shoff;
- if (hdr->e_shnum == SHN_UNDEF)
- num_sections = x[0].sh_size;
- else
- num_sections = hdr->e_shnum;
-
- for (i = 1; i < num_sections; i++)
- if (x[i].sh_type == SHT_SYMTAB)
- return &x[i];
+ unsigned char *p = elf->shstart;
+
+ while (p < elf->shstart + elf->shsize) {
+ Elf32_Shdr *s32 = (Elf32_Shdr *)p;
+ Elf64_Shdr *s64 = (Elf64_Shdr *)p;
+
+ if (elf->eclass == ELFCLASS32) {
+ if (s32->sh_type == SHT_SYMTAB)
+ return p;
+ } else {
+ if (s64->sh_type == SHT_SYMTAB)
+ return p;
+ }
+ p += elf->shentsize;
+ }
return NULL;
}
@@ -257,7 +370,7 @@ static char *read_file(char *file_name, int *size)
return buf;
}
-static void print_sym(Elf_Ehdr *hdr, struct sym *s)
+static void print_sym(struct sym *s)
{
info("sym: %s\n", s->name);
info("addr: 0x%lx\n", s->address);
@@ -277,14 +390,14 @@ int main(int argc, char **argv)
char *cert_file = NULL;
int vmlinux_size;
int cert_size;
- Elf_Ehdr *hdr;
+ char *vmlinux;
char *cert;
FILE *system_map;
- unsigned long *lsize;
int *used;
int opt;
- Elf_Shdr *symtab = NULL;
struct sym cert_sym, lsize_sym, used_sym;
+ struct elf elf;
+ unsigned char *symtab = NULL;
while ((opt = getopt(argc, argv, "b:c:s:")) != -1) {
switch (opt) {
@@ -311,39 +424,16 @@ int main(int argc, char **argv)
if (!cert)
exit(EXIT_FAILURE);
- hdr = map_file(vmlinux_file, &vmlinux_size);
- if (!hdr)
+ vmlinux = map_file(vmlinux_file, &vmlinux_size);
+ if (!vmlinux)
exit(EXIT_FAILURE);
- if (vmlinux_size < sizeof(*hdr)) {
- err("Invalid ELF file.\n");
- exit(EXIT_FAILURE);
- }
-
- if ((hdr->e_ident[EI_MAG0] != ELFMAG0) ||
- (hdr->e_ident[EI_MAG1] != ELFMAG1) ||
- (hdr->e_ident[EI_MAG2] != ELFMAG2) ||
- (hdr->e_ident[EI_MAG3] != ELFMAG3)) {
- err("Invalid ELF magic.\n");
+ if (read_elf_data(&elf, vmlinux, vmlinux_size)) {
+ err("Unable to read ELF file.\n");
exit(EXIT_FAILURE);
}
- if (hdr->e_ident[EI_CLASS] != CURRENT_ELFCLASS) {
- err("ELF class mismatch.\n");
- exit(EXIT_FAILURE);
- }
-
- if (hdr->e_ident[EI_DATA] != endianness()) {
- err("ELF endian mismatch.\n");
- exit(EXIT_FAILURE);
- }
-
- if (hdr->e_shoff > vmlinux_size) {
- err("Could not find section header.\n");
- exit(EXIT_FAILURE);
- }
-
- symtab = get_symbol_table(hdr);
+ symtab = get_symbol_table(&elf);
if (!symtab) {
warn("Could not find the symbol table.\n");
if (!system_map_file) {
@@ -357,27 +447,28 @@ int main(int argc, char **argv)
perror(system_map_file);
exit(EXIT_FAILURE);
}
- get_symbol_from_map(hdr, system_map, CERT_SYM, &cert_sym);
- get_symbol_from_map(hdr, system_map, USED_SYM, &used_sym);
- get_symbol_from_map(hdr, system_map, LSIZE_SYM, &lsize_sym);
+ get_symbol_from_map(&elf, system_map, CERT_SYM, &cert_sym);
+ get_symbol_from_map(&elf, system_map, USED_SYM, &used_sym);
+ get_symbol_from_map(&elf, system_map, LSIZE_SYM, &lsize_sym);
cert_sym.size = used_sym.address - cert_sym.address;
} else {
info("Symbol table found.\n");
if (system_map_file)
warn("System.map is ignored.\n");
- get_symbol_from_table(hdr, symtab, CERT_SYM, &cert_sym);
- get_symbol_from_table(hdr, symtab, USED_SYM, &used_sym);
- get_symbol_from_table(hdr, symtab, LSIZE_SYM, &lsize_sym);
+ get_symbol_from_table(&elf, symtab, CERT_SYM, &cert_sym);
+ get_symbol_from_table(&elf, symtab, USED_SYM, &used_sym);
+ get_symbol_from_table(&elf, symtab, LSIZE_SYM, &lsize_sym);
}
- if (!cert_sym.offset || !lsize_sym.offset || !used_sym.offset)
+ if (!cert_sym.offset || !lsize_sym.offset || !used_sym.offset) {
+ err("Unable to find symbols.\n");
exit(EXIT_FAILURE);
+ }
- print_sym(hdr, &cert_sym);
- print_sym(hdr, &used_sym);
- print_sym(hdr, &lsize_sym);
+ print_sym(&cert_sym);
+ print_sym(&used_sym);
+ print_sym(&lsize_sym);
- lsize = (unsigned long *)lsize_sym.content;
used = (int *)used_sym.content;
if (cert_sym.size < cert_size) {
@@ -400,11 +491,25 @@ int main(int argc, char **argv)
memset(cert_sym.content + cert_size,
0, cert_sym.size - cert_size);
- *lsize = *lsize + cert_size - *used;
+ if (elf.eclass == ELFCLASS64) {
+ u64 *lsize;
+
+ lsize = (u64 *)lsize_sym.content;
+ *lsize = *lsize + cert_size - *used;
+ } else {
+ u32 *lsize;
+
+ lsize = (u32 *)lsize_sym.content;
+ *lsize = *lsize + cert_size - *used;
+ }
*used = cert_size;
info("Inserted the contents of %s into %lx.\n", cert_file,
cert_sym.address);
info("Used %d bytes out of %d bytes reserved.\n", *used,
cert_sym.size);
+ if (munmap(vmlinux, vmlinux_size) == -1) {
+ perror(vmlinux_file);
+ exit(EXIT_FAILURE);
+ }
exit(EXIT_SUCCESS);
}
--
2.17.0
--
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