Skip to content
Projects
Groups
Snippets
Help
Loading...
Help
Contribute to GitLab
Sign in / Register
Toggle navigation
M
Magisk
Project
Project
Details
Activity
Cycle Analytics
Repository
Repository
Files
Commits
Branches
Tags
Contributors
Graph
Compare
Charts
Issues
0
Issues
0
List
Board
Labels
Milestones
Merge Requests
0
Merge Requests
0
CI / CD
CI / CD
Pipelines
Jobs
Schedules
Charts
Wiki
Wiki
Snippets
Snippets
Members
Members
Collapse sidebar
Close sidebar
Activity
Graph
Charts
Create a new issue
Jobs
Commits
Issue Boards
Open sidebar
Administrator
Magisk
Commits
575c4174
Commit
575c4174
authored
May 12, 2022
by
topjohnwu
Committed by
John Wu
May 12, 2022
Browse files
Options
Browse Files
Download
Email Patches
Plain Diff
More detailed comments and documentation
parent
9f7a3db8
Hide whitespace changes
Inline
Side-by-side
Showing
1 changed file
with
100 additions
and
50 deletions
+100
-50
cert.cpp
native/jni/su/cert.cpp
+100
-50
No files found.
native/jni/su/cert.cpp
View file @
575c4174
...
...
@@ -2,9 +2,13 @@
using
namespace
std
;
#define APK_SIGNING_BLOCK_MAGIC "APK Sig Block 42"
#define SIGNATURE_SCHEME_V2_MAGIC 0x7109871a
#define EOCD_MAGIC 0x6054b50
// Top-level block container
struct
signing_block
{
uint64_t
len
;
uint64_t
block_sz
;
struct
id_value_pair
{
uint64_t
len
;
...
...
@@ -14,7 +18,7 @@ struct signing_block {
};
}
id_value_pair_sequence
[
0
];
uint64_t
block_
len
;
// *MUST* be same as len
uint64_t
block_
sz_
;
// *MUST* be same as block_sz
char
magic
[
16
];
// "APK Sig Block 42"
};
...
...
@@ -59,78 +63,124 @@ struct v2_signature {
}
signer_sequence
[
0
];
};
// The structures above are just for documentation purpose
// The real parsing logic is the following
// End of central directory record
struct
EOCD
{
uint32_t
magic
;
// 0x6054b50
uint8_t
pad
[
8
];
// 8 bytes of irrelevant data
uint32_t
central_dir_sz
;
// size of central directory
uint32_t
central_dir_off
;
// offset of central directory
uint16_t
comment_sz
;
// size of comment
char
comment
[
0
];
}
__attribute__
((
packed
));
/*
* A v2/v3 signed APK has the format as following
*
* +---------------+
* | zip content |
* +---------------+
* | signing block |
* +---------------+
* | central dir |
* +---------------+
* | EOCD |
* +---------------+
*
* Scan from end of file to find EOCD, and figure our way back to the
* offset of the signing block. Next, directly extract the certificate
* from the v2 signature block.
*
* All structures above are mostly just for documentation purpose.
*
* This method extracts the first certificate of the first signer
* within the APK v2 signature block.
*/
string
read_certificate
(
int
fd
)
{
string
certificate
;
uint32_t
size4
;
uint64_t
size8
,
size_of_block
;
uint64_t
size8
;
// Find EOCD
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
// i is the absolute offset to end of file
uint16_t
comment_sz
=
0
;
lseek
(
fd
,
-
((
off_t
)
sizeof
(
comment_sz
))
-
i
,
SEEK_END
);
read
(
fd
,
&
comment_sz
,
sizeof
(
comment_sz
));
if
(
comment_sz
==
i
)
{
// Double check if we actually found the structure
lseek
(
fd
,
-
((
off_t
)
sizeof
(
EOCD
)),
SEEK_CUR
);
uint32_t
magic
=
0
;
read
(
fd
,
&
magic
,
sizeof
(
magic
));
if
(
magic
==
EOCD_MAGIC
)
{
break
;
}
}
if
(
i
==
0xffff
)
{
return
certificate
;
// Comments cannot be longer than 0xffff (overflow), abort
return
{};
}
}
lseek
(
fd
,
12
,
SEEK_CUR
);
read
(
fd
,
&
size4
,
0x4
);
lseek
(
fd
,
(
off_t
)
(
size4
-
0x18
),
SEEK_SET
);
// We are now at EOCD + sizeof(magic)
// Seek and read central_dir_off to find start of central directory
uint32_t
central_dir_off
=
0
;
{
constexpr
off_t
off
=
offsetof
(
EOCD
,
central_dir_off
)
-
sizeof
(
EOCD
::
magic
);
lseek
(
fd
,
off
,
SEEK_CUR
);
}
read
(
fd
,
&
central_dir_off
,
sizeof
(
central_dir_off
));
read
(
fd
,
&
size8
,
0x8
);
char
magic
[
0x10
]
=
{
0
};
// Next, find the start of the APK signing block
{
constexpr
int
off
=
sizeof
(
signing_block
::
block_sz_
)
+
sizeof
(
signing_block
::
magic
);
lseek
(
fd
,
(
off_t
)
(
central_dir_off
-
off
),
SEEK_SET
);
}
read
(
fd
,
&
size8
,
sizeof
(
size8
));
// size8 = block_sz_
char
magic
[
sizeof
(
signing_block
::
magic
)]
=
{
0
};
read
(
fd
,
magic
,
sizeof
(
magic
));
if
(
memcmp
(
magic
,
"APK Sig Block 42"
,
sizeof
(
magic
))
!=
0
)
{
return
certificate
;
if
(
memcmp
(
magic
,
APK_SIGNING_BLOCK_MAGIC
,
sizeof
(
magic
))
!=
0
)
{
// Invalid signing block magic, abort
return
{};
}
lseek
(
fd
,
(
off_t
)
(
size4
-
(
size8
+
0x8
)),
SEEK_SET
);
read
(
fd
,
&
size_of_block
,
0x8
);
if
(
size_of_block
!=
size8
)
{
return
certificate
;
uint64_t
signing_blk_sz
=
0
;
lseek
(
fd
,
(
off_t
)
(
central_dir_off
-
size8
-
sizeof
(
signing_blk_sz
)),
SEEK_SET
);
read
(
fd
,
&
signing_blk_sz
,
sizeof
(
signing_blk_sz
));
if
(
signing_blk_sz
!=
size8
)
{
// block_sz != block_sz_, invalid signing block format, abort
return
{};
}
// Finally, we are now at the beginning of the id-value pair sequence
for
(;;)
{
uint32_t
id
;
uint32_t
offset
;
read
(
fd
,
&
size8
,
0x8
);
// sequence length
if
(
size8
==
size_of_block
)
{
read
(
fd
,
&
size8
,
sizeof
(
size8
));
// id-value pair length
if
(
size8
==
signing_blk_sz
)
{
// Outside of the id-value pair sequence; actually reading block_sz_
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
;
uint32_t
id
;
read
(
fd
,
&
id
,
sizeof
(
id
));
if
(
id
==
SIGNATURE_SCHEME_V2_MAGIC
)
{
read
(
fd
,
&
size4
,
sizeof
(
size4
));
// signer sequence length
read
(
fd
,
&
size4
,
sizeof
(
size4
));
// signer length
read
(
fd
,
&
size4
,
sizeof
(
size4
));
// signed data length
read
(
fd
,
&
size4
,
0x4
);
// digests-sequence length
lseek
(
fd
,
(
off_t
)
(
size4
),
SEEK_CUR
);
// skip digests
offset
+=
0x4
+
size4
;
read
(
fd
,
&
size4
,
sizeof
(
size4
));
// digest sequence length
lseek
(
fd
,
(
off_t
)
(
size4
),
SEEK_CUR
);
// skip all digests
read
(
fd
,
&
size4
,
0x4
);
// certificates length
read
(
fd
,
&
size4
,
0x4
);
// certificate length
offset
+=
0x4
*
2
;
read
(
fd
,
&
size4
,
sizeof
(
size4
));
// cert sequence length
read
(
fd
,
&
size4
,
sizeof
(
size4
));
// cert length
certificate
.
resize
(
size4
);
read
(
fd
,
certificate
.
data
(),
size4
);
string
cert
;
cert
.
resize
(
size4
);
read
(
fd
,
cert
.
data
(),
size4
);
offset
+=
size4
;
return
cert
;
}
else
{
// Skip this id-value pair
lseek
(
fd
,
(
off_t
)
(
size8
-
sizeof
(
id
)),
SEEK_CUR
);
}
lseek
(
fd
,
(
off_t
)
(
size8
-
offset
),
SEEK_CUR
);
}
return
certificate
;
return
{}
;
}
Write
Preview
Markdown
is supported
0%
Try again
or
attach a new file
Attach a file
Cancel
You are about to add
0
people
to the discussion. Proceed with caution.
Finish editing this message first!
Cancel
Please
register
or
sign in
to comment