UBUNTU: SAUCE: (noup) KEYS: Support for inserting a certificate into x86 bzImage

BugLink: http://bugs.launchpad.net/bugs/1558553
The config option SYSTEM_EXTRA_CERTIFICATE reserves space in vmlinux file,
which is compressed to create the self-extracting bzImage. This patch adds the
capability of extracting the vmlinux, inserting the certificate, and
repackaging the result into a bzImage.

It only works if the resulting compressed vmlinux is smaller than the original.
Otherwise re-linking would be required. To make the reserved space allocate
actual space in bzImage, a null key is inserted into vmlinux before creating
the bzImage:

	make vmlinux
	scripts/insert-sys-cert -b vmlinux -c /dev/null
	make bzImage

After null key insertion, the script populates the rest of the reserved space
with random bytes, which have poor compression. After receiving a bzImage that
is created this way, actual certificate can be inserted into the bzImage:

	scripts/insert-sys-cert -s <System.map> -z <bzImage> -c <certfile>

Signed-off-by: Mehmet Kayaalp <mkayaalp@linux.vnet.ibm.com>
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>

diff --git a/scripts/insert-sys-cert.c b/scripts/insert-sys-cert.c
index 8902836c2342441c58b968ff078d4c8b110e9075..6c6120dad676aa0dcd03e10d0c78aba1c871cdb6 100644 (file)
--- a/scripts/insert-sys-cert.c
+++ b/scripts/insert-sys-cert.c
@@ -7,7 +7,8 @@
  * This software may be used and distributed according to the terms
  * of the GNU General Public License, incorporated herein by reference.
  *
- * Usage: insert-sys-cert [-s <System.map> -b <vmlinux> -c <certfile>
+ * Usage: insert-sys-cert [-s <System.map>] -b <vmlinux> -c <certfile>
+ *                        [-s <System.map>] -z <bzImage> -c <certfile>
  */
 
 #define _GNU_SOURCE
@@ -257,6 +258,169 @@ static char *read_file(char *file_name, int *size)
        return buf;
 }
 
+static void get_payload_info(char *bzimage, int *offset, int *size)
+{
+       unsigned int system_offset;
+       unsigned char setup_sectors;
+
+       setup_sectors = bzimage[0x1f1] + 1;
+       system_offset = setup_sectors * 512;
+       *offset = system_offset + *((int*)&bzimage[0x248]);
+       *size = *((int*)&bzimage[0x24c]);
+}
+
+static void update_payload_info(char* bzimage, int new_size)
+{
+       int offset, size;
+       get_payload_info(bzimage, &offset, &size);
+       *((int*)&bzimage[0x24c]) = new_size;
+       if (new_size < size)
+               memset(bzimage + offset + new_size, 0, size - new_size);
+}
+
+struct zipper {
+       unsigned char pattern[10];
+       int length;
+       char *command;
+       char *compress;
+};
+
+struct zipper zippers[] = {
+       {{0x7F,'E','L','F'}, 4, "cat", "cat"},
+       {{0x1F,0x8B}, 2, "gunzip", "gzip -n -f -9"},
+       {{0xFD,'7','z','X','Z',0}, 6, "unxz", "xz"},
+       {{'B','Z','h'},3, "bunzip2", "bzip2 -9"},
+       {{0xFF,'L','Z','M','A',0}, 6, "unlzma", "lzma -9"},
+       {{0xD3,'L','Z','O',0,'\r','\n',0x20,'\n'}, 9, "lzop -d", "lzop -9"}
+};
+
+static struct zipper* get_zipper(char *p) {
+       int i;
+       for (i = 0; i < sizeof(zippers)/sizeof(struct zipper); i++) {
+               if (memcmp(p, zippers[i].pattern, zippers[i].length) == 0)
+                       return &zippers[i];
+       }
+       return NULL;
+}
+
+/*
+ * This only works for x86 bzImage
+ */
+static void extract_vmlinux(char *bzimage, int bzimage_size,
+                       char **file, struct zipper **zipper)
+{
+       int r;
+       char src[15] = "vmlinux-XXXXXX";
+       char dest[15] = "vmlinux-XXXXXX";
+       char cmd[100];
+       int src_fd, dest_fd;
+       int offset, size;
+       struct zipper *z;
+
+       /* TODO: verify that bzImage is supported */
+
+       get_payload_info(bzimage, &offset, &size);
+       z = get_zipper(bzimage + offset);
+       if (z == NULL) {
+               err("Unable to determine the compression of vmlinux\n");
+               return;
+       }
+
+       src_fd = mkstemp(src);
+       if (src_fd == -1) {
+               perror("Could not create temp file");
+               return;
+       }
+
+       r = write(src_fd, bzimage + offset, size);
+       if (r != size) {
+               perror("Could not write vmlinux");
+               return;
+       }
+       dest_fd = mkstemp(dest);
+       if (dest_fd == -1) {
+               perror("Could not create temp file");
+               return;
+       }
+
+       snprintf(cmd, sizeof(cmd), "%s <%s >%s", z->command, src, dest);
+       info("Executing: %s\n", cmd);
+       r = system(cmd);
+       if (r!=0)
+               warn("Possible errors when extracting\n");
+
+       r = remove(src);
+       if (r!=0)
+               perror(src);
+
+       *file = strdup(dest);
+       *zipper = z;
+}
+
+static void repack_image(char *bzimage, int bzimage_size,
+                       char* vmlinux_file, struct zipper *z)
+{
+       char tmp[15] = "vmlinux-XXXXXX";
+       char cmd[100];
+       int fd;
+       struct stat st;
+       int new_size;
+       int r;
+       int offset, size;
+
+       get_payload_info(bzimage, &offset, &size);
+
+       fd = mkstemp(tmp);
+       if (fd == -1) {
+               perror("Could not create temp file");
+               return;
+       }
+       snprintf(cmd, sizeof(cmd), "%s <%s >%s",
+                       z->compress, vmlinux_file, tmp);
+
+       info("Executing: %s\n", cmd);
+       r = system(cmd);
+       if (r!=0)
+               warn("Possible errors when compressing\n");
+
+       r = remove(vmlinux_file);
+       if (r!=0)
+               perror(vmlinux_file);
+
+       if (fstat(fd, &st)) {
+               perror("Could not determine file size");
+               close(fd);
+
+       }
+       new_size = st.st_size;
+       if (new_size > size) {
+               err("Increase in compressed size is not supported.\n");
+               err("Old size was %d, new size is %d\n", size, new_size);
+               exit(EXIT_FAILURE);
+       }
+
+       r = read(fd, bzimage + offset, new_size);
+       if (r != new_size)
+               perror(tmp);
+
+       r = remove(tmp);
+       if (r!=0)
+               perror(tmp);
+
+       /* x86 specific patching of bzimage */
+       update_payload_info(bzimage, new_size);
+
+       /* TODO: update CRC */
+
+}
+
+static void fill_random(unsigned char *p, int n) {
+       srand(0);
+       int i;
+       for (i = 0; i < n; i++)
+               p[i] = rand();
+}
+
 static void print_sym(Elf_Ehdr *hdr, struct sym *s)
 {
        info("sym:    %s\n", s->name);
@@ -267,18 +431,23 @@ static void print_sym(Elf_Ehdr *hdr, struct sym *s)
 
 static void print_usage(char *e)
 {
-       printf("Usage %s [-s <System.map>] -b <vmlinux> -c <certfile>\n", e);
+       printf("Usage: %s [-s <System.map>] -b <vmlinux> -c <certfile>\n", e);
+       printf("       %s [-s <System.map>] -z <bzImage> -c <certfile>\n", e);
 }
 
 int main(int argc, char **argv)
 {
        char *system_map_file = NULL;
        char *vmlinux_file = NULL;
+       char *bzimage_file = NULL;
        char *cert_file = NULL;
        int vmlinux_size;
+       int bzimage_size;
        int cert_size;
        Elf_Ehdr *hdr;
        char *cert;
+       char *bzimage = NULL;
+       struct zipper *z = NULL;
        FILE *system_map;
        unsigned long *lsize;
        int *used;
@@ -286,7 +455,7 @@ int main(int argc, char **argv)
        Elf_Shdr *symtab = NULL;
        struct sym cert_sym, lsize_sym, used_sym;
 
-       while ((opt = getopt(argc, argv, "b:c:s:")) != -1) {
+       while ((opt = getopt(argc, argv, "b:z:c:s:")) != -1) {
                switch (opt) {
                case 's':
                        system_map_file = optarg;
@@ -294,6 +463,9 @@ int main(int argc, char **argv)
                case 'b':
                        vmlinux_file = optarg;
                        break;
+               case 'z':
+                       bzimage_file = optarg;
+                       break;
                case 'c':
                        cert_file = optarg;
                        break;
@@ -302,7 +474,9 @@ int main(int argc, char **argv)
                }
        }
 
-       if (!vmlinux_file || !cert_file) {
+       if (!cert_file ||
+       (!vmlinux_file && !bzimage_file) ||
+       (vmlinux_file && bzimage_file)) {
                print_usage(argv[0]);
                exit(EXIT_FAILURE);
        }
@@ -311,6 +485,16 @@ int main(int argc, char **argv)
        if (!cert)
                exit(EXIT_FAILURE);
 
+       if (bzimage_file) {
+               bzimage = map_file(bzimage_file, &bzimage_size);
+               if (!bzimage)
+                       exit(EXIT_FAILURE);
+
+               extract_vmlinux(bzimage, bzimage_size, &vmlinux_file, &z);
+               if (!vmlinux_file)
+                       exit(EXIT_FAILURE);
+       }
+
        hdr = map_file(vmlinux_file, &vmlinux_size);
        if (!hdr)
                exit(EXIT_FAILURE);
@@ -386,7 +570,7 @@ int main(int argc, char **argv)
        }
 
        /* If the existing cert is the same, don't overwrite */
-       if (cert_size == *used &&
+       if (cert_size > 0 && cert_size == *used &&
            strncmp(cert_sym.content, cert, cert_size) == 0) {
                warn("Certificate was already inserted.\n");
                exit(EXIT_SUCCESS);
@@ -396,9 +580,11 @@ int main(int argc, char **argv)
                warn("Replacing previously inserted certificate.\n");
 
        memcpy(cert_sym.content, cert, cert_size);
+
        if (cert_size < cert_sym.size)
-               memset(cert_sym.content + cert_size,
-                       0, cert_sym.size - cert_size);
+               /* This makes the reserved space incompressable */
+               fill_random(cert_sym.content + cert_size,
+                               cert_sym.size - cert_size);
 
        *lsize = *lsize + cert_size - *used;
        *used = cert_size;
@@ -406,5 +592,15 @@ int main(int argc, char **argv)
                                                cert_sym.address);
        info("Used %d bytes out of %d bytes reserved.\n", *used,
                                                 cert_sym.size);
+
+       if (munmap(hdr, vmlinux_size) == -1) {
+               perror(vmlinux_file);
+               exit(EXIT_FAILURE);
+       }
+
+       if (bzimage) {
+               repack_image(bzimage, bzimage_size, vmlinux_file, z);
+       }
+
        exit(EXIT_SUCCESS);
 }