Move cert extraction to its own file

native/jni/Android.mk

@@ -33,6 +33,7 @@ LOCAL_SRC_FILES := \
     su/su.cpp \
     su/connect.cpp \
     su/pts.cpp \
+    su/cert.cpp \
     su/su_daemon.cpp \
     zygisk/entry.cpp \
     zygisk/main.cpp \

native/jni/su/cert.cpp

@@ -0,0 +1,136 @@
+#include <utils.hpp>
+
+using namespace std;
+
+// Top-level block container
+struct signing_block {
+    uint64_t len;
+
+    struct id_value_pair {
+        uint64_t len;
+        struct /* v2_signature */ {
+            uint32_t id;
+            uint8_t value[0];  // size = (len - 4)
+        };
+    } id_value_pair_sequence[0];
+
+    uint64_t block_len;   // *MUST* be same as len
+    char magic[16];       // "APK Sig Block 42"
+};
+
+struct len_prefixed {
+    uint32_t len;
+};
+
+// Generic length prefixed raw data
+struct len_prefixed_value : public len_prefixed {
+    uint8_t value[0];
+};
+
+// V2 Signature Block
+struct v2_signature {
+    uint32_t id;  // 0x7109871a
+    uint32_t signer_sequence_len;
+    struct signer : public len_prefixed {
+        struct signed_data : public len_prefixed {
+            uint32_t digest_sequence_len;
+            struct : public len_prefixed {
+                uint32_t algorithm;
+                len_prefixed_value digest;
+            } digest_sequence[0];
+
+            uint32_t certificate_sequence_len;
+            len_prefixed_value certificate_sequence[0];
+
+            uint32_t attribute_sequence_len;
+            struct attribute : public len_prefixed {
+                uint32_t id;
+                uint8_t value[0];  // size = (len - 4)
+            } attribute_sequence[0];
+        } signed_data;
+
+        uint32_t signature_sequence_len;
+        struct : public len_prefixed {
+            uint32_t id;
+            len_prefixed_value signature;
+        } signature_sequence[0];
+
+        len_prefixed_value public_key;
+    } signer_sequence[0];
+};
+
+// The structures above are just for documentation purpose
+// The real parsing logic is the following
+
+string read_certificate(int fd) {
+    string certificate;
+    uint32_t size4;
+    uint64_t size8, size_of_block;
+
+    for (int i = 0;; i++) {
+        unsigned short n;
+        lseek(fd, -i - 2, SEEK_END);
+        read(fd, &n, 2);
+        if (n == i) {
+            lseek(fd, -22, SEEK_CUR);
+            read(fd, &size4, 4);
+            if (size4 == 0x6054b50u) { // central directory end magic
+                break;
+            }
+        }
+        if (i == 0xffff) {
+            return certificate;
+        }
+    }
+
+    lseek(fd, 12, SEEK_CUR);
+
+    read(fd, &size4, 0x4);
+    lseek(fd, (off_t) (size4 - 0x18), SEEK_SET);
+
+    read(fd, &size8, 0x8);
+    char magic[0x10] = {0};
+    read(fd, magic, sizeof(magic));
+    if (memcmp(magic, "APK Sig Block 42", sizeof(magic)) != 0) {
+        return certificate;
+    }
+
+    lseek(fd, (off_t) (size4 - (size8 + 0x8)), SEEK_SET);
+    read(fd, &size_of_block, 0x8);
+    if (size_of_block != size8) {
+        return certificate;
+    }
+
+    for (;;) {
+        uint32_t id;
+        uint32_t offset;
+        read(fd, &size8, 0x8); // sequence length
+        if (size8 == size_of_block) {
+            break;
+        }
+        read(fd, &id, 0x4); // id
+        offset = 4;
+
+        if (id == 0x7109871au) {
+            read(fd, &size4, 0x4); // signer-sequence length
+            read(fd, &size4, 0x4); // signer length
+            read(fd, &size4, 0x4); // signed data length
+            offset += 0x4 * 3;
+
+            read(fd, &size4, 0x4); // digests-sequence length
+            lseek(fd, (off_t) (size4), SEEK_CUR);// skip digests
+            offset += 0x4 + size4;
+
+            read(fd, &size4, 0x4); // certificates length
+            read(fd, &size4, 0x4); // certificate length
+            offset += 0x4 * 2;
+
+            certificate.resize(size4);
+            read(fd, certificate.data(), size4);
+
+            offset += size4;
+        }
+        lseek(fd, (off_t) (size8 - offset), SEEK_CUR);
+    }
+    return certificate;
+}

native/jni/utils/files.cpp

@@ -1,10 +1,7 @@
 #include <sys/sendfile.h>
 #include <linux/fs.h>
-#include <stdlib.h>
 #include <fcntl.h>
 #include <unistd.h>
-#include <errno.h>
-#include <string.h>
 #include <libgen.h>
 
 #include <utils.hpp>
@@ -57,12 +54,12 @@ static void post_order_walk(int dirfd, const Func &fn) {
     }
 }
 
-enum visit_result {
-    CONTINUE, SKIP, TERMINATE
+enum walk_result {
+    CONTINUE, SKIP, ABORT
 };
 
 template <typename Func>
-static visit_result pre_order_walk(int dirfd, const Func &fn) {
+static walk_result pre_order_walk(int dirfd, const Func &fn) {
     auto dir = xopen_dir(dirfd);
     if (!dir) {
         close(dirfd);
@@ -75,12 +72,13 @@ static visit_result pre_order_walk(int dirfd, const Func &fn) {
             break;
         case SKIP:
             continue;
-            case TERMINATE:
-                return TERMINATE;
+        case ABORT:
+            return ABORT;
         }
         if (entry->d_type == DT_DIR) {
             int fd = xopenat(dirfd, entry->d_name, O_RDONLY | O_CLOEXEC);
-            if (pre_order_walk(fd, fn) == TERMINATE) return TERMINATE;
+            if (pre_order_walk(fd, fn) == ABORT)
+                return ABORT;
         }
     }
     return CONTINUE;
@@ -419,7 +417,7 @@ void backup_folder(const char *dir, vector<raw_file> &files) {
     char path[PATH_MAX];
     xrealpath(dir, path);
     int len = strlen(path);
-    pre_order_walk(xopen(dir, O_RDONLY), [&](int dfd, dirent *entry) -> visit_result {
+    pre_order_walk(xopen(dir, O_RDONLY), [&](int dfd, dirent *entry) -> walk_result {
         int fd = xopenat(dfd, entry->d_name, O_RDONLY);
         if (fd < 0)
             return SKIP;
@@ -526,13 +524,13 @@ mmap_data::mmap_data(const char *name, bool rw) {
 
 string find_apk_path(const char *pkg) {
     char buf[PATH_MAX];
-    pre_order_walk(xopen("/data/app", O_RDONLY), [&](int dfd, dirent *entry) -> visit_result {
+    pre_order_walk(xopen("/data/app", O_RDONLY), [&](int dfd, dirent *entry) -> walk_result {
         if (entry->d_type != DT_DIR)
             return SKIP;
         size_t len = strlen(pkg);
         if (strncmp(entry->d_name, pkg, len) == 0 && entry->d_name[len] == '-') {
             fd_pathat(dfd, entry->d_name, buf, sizeof(buf));
-            return TERMINATE;
+            return ABORT;
         } else if (strncmp(entry->d_name, "~~", 2) == 0) {
             return CONTINUE;
         } else return SKIP;
@@ -540,82 +538,3 @@ string find_apk_path(const char *pkg) {
     string path(buf);
     return path.append("/base.apk");
 }
-
-string read_certificate(string app_path) {
-    string certificate;
-    uint32_t size4;
-    uint64_t size8, size_of_block;
-
-    int fd = xopen(app_path.data(), O_RDONLY);
-    if (fd < 0) {
-        return certificate;
-    }
-    run_finally f([&] { close(fd); });
-
-    for (int i = 0;; i++) {
-        unsigned short n;
-        lseek(fd, -i - 2, SEEK_END);
-        read(fd, &n, 2);
-        if (n == i) {
-            lseek(fd, -22, SEEK_CUR);
-            read(fd, &size4, 4);
-            if (size4 == 0x6054b50u) { // central directory end magic
-                break;
-            }
-        }
-        if (i == 0xffff) {
-            return certificate;
-        }
-    }
-
-    lseek(fd, 12, SEEK_CUR);
-
-    read(fd, &size4, 0x4);
-    lseek(fd, (off_t) (size4 - 0x18), SEEK_SET);
-
-    read(fd, &size8, 0x8);
-    unsigned char buffer[0x10] = {0};
-    read(fd, buffer, 0x10);
-    if (memcmp(buffer, "APK Sig Block 42", 0x10) != 0) {
-        return certificate;
-    }
-
-    lseek(fd, (off_t) (size4 - (size8 + 0x8)), SEEK_SET);
-    read(fd, &size_of_block, 0x8);
-    if (size_of_block != size8) {
-        return certificate;
-    }
-
-    for (;;) {
-        uint32_t id;
-        uint32_t offset;
-        read(fd, &size8, 0x8); // sequence length
-        if (size8 == size_of_block) {
-            break;
-        }
-        read(fd, &id, 0x4); // id
-        offset = 4;
-
-        if (id == 0x7109871au) {
-            read(fd, &size4, 0x4); // signer-sequence length
-            read(fd, &size4, 0x4); // signer length
-            read(fd, &size4, 0x4); // signed data length
-            offset += 0x4 * 3;
-
-            read(fd, &size4, 0x4); // digests-sequence length
-            lseek(fd, (off_t) (size4), SEEK_CUR);// skip digests
-            offset += 0x4 + size4;
-
-            read(fd, &size4, 0x4); // certificates length
-            read(fd, &size4, 0x4); // certificate length
-            offset += 0x4 * 2;
-
-            certificate.resize(size4);
-            read(fd, certificate.data(), size4);
-
-            offset += size4;
-        }
-        lseek(fd, (off_t) (size8 - offset), SEEK_CUR);
-    }
-    return certificate;
-}

native/jni/utils/files.hpp

@@ -101,9 +101,7 @@ void clone_dir(int src, int dest);
 void parse_mnt(const char *file, const std::function<bool(mntent*)> &fn);
 void backup_folder(const char *dir, std::vector<raw_file> &files);
 void restore_folder(const char *dir, std::vector<raw_file> &files);
-
 std::string find_apk_path(const char *pkg);
-std::string read_certificate(std::string app_path);
 
 template <typename T>
 void full_read(const char *filename, T &buf, size_t &size) {