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author | Sebastian Rasmussen <sebras@gmail.com> | 2018-03-01 17:36:54 +0800 |
---|---|---|
committer | Sebastian Rasmussen <sebras@gmail.com> | 2018-03-22 12:33:34 +0800 |
commit | f3b0e4373af7500155e470931e5a50060f5b4612 (patch) | |
tree | aeb05f63684cc1bd5481eb1ad821038b5fed156f /source/pdf | |
parent | 188d61ef347d644b3e122754af73decdfb8d8ab1 (diff) | |
download | mupdf-f3b0e4373af7500155e470931e5a50060f5b4612.tar.xz |
Fix 699085: Use at most 16 bytes from MD5 digests.
Previously crypt->len / 8 could be 0..32. In the case
of crypt->len == 256 this meant that when an 16 byte
MD5 was computed, uninitalized key data would be
accessed because 32 bytes of key data was accessed.
Now crypt->len / 8 is limited to 0..16. So when the
16 byte MD5 is computed and later accessed only the
initialized part of the key data is accessed.
Because crypt->len / 8 is now limited to 0..16 the key
data buffer can also be shrunk to 16 bytes without
risking the code stepping over its boundaries.
Diffstat (limited to 'source/pdf')
-rw-r--r-- | source/pdf/pdf-crypt.c | 25 |
1 files changed, 11 insertions, 14 deletions
diff --git a/source/pdf/pdf-crypt.c b/source/pdf/pdf-crypt.c index 7150f66e..2e31f356 100644 --- a/source/pdf/pdf-crypt.c +++ b/source/pdf/pdf-crypt.c @@ -353,7 +353,7 @@ pdf_compute_encryption_key(fz_context *ctx, pdf_crypt *crypt, unsigned char *pas int i, n; fz_md5 md5; - n = crypt->length / 8; + n = fz_clampi(crypt->length / 8, 0, 16); /* Step 1 - copy and pad password string */ if (pwlen > 32) @@ -569,12 +569,14 @@ pdf_compute_encryption_key_r6(fz_context *ctx, pdf_crypt *crypt, unsigned char * static void pdf_compute_user_password(fz_context *ctx, pdf_crypt *crypt, unsigned char *password, size_t pwlen, unsigned char *output) { + int n = fz_clampi(crypt->length / 8, 0, 16); + if (crypt->r == 2) { fz_arc4 arc4; pdf_compute_encryption_key(ctx, crypt, password, pwlen, crypt->key); - fz_arc4_init(&arc4, crypt->key, crypt->length / 8); + fz_arc4_init(&arc4, crypt->key, n); fz_arc4_encrypt(&arc4, output, padding, 32); } @@ -584,9 +586,7 @@ pdf_compute_user_password(fz_context *ctx, pdf_crypt *crypt, unsigned char *pass unsigned char digest[16]; fz_md5 md5; fz_arc4 arc4; - int i, x, n; - - n = crypt->length / 8; + int i, x; pdf_compute_encryption_key(ctx, crypt, password, pwlen, crypt->key); @@ -649,17 +649,16 @@ pdf_authenticate_user_password(fz_context *ctx, pdf_crypt *crypt, unsigned char static int pdf_authenticate_owner_password(fz_context *ctx, pdf_crypt *crypt, unsigned char *ownerpass, size_t pwlen) { + int n = fz_clampi(crypt->length / 8, 0, 16); + if (crypt->r == 2) { unsigned char pwbuf[32]; - unsigned char key[32]; + unsigned char key[16]; unsigned char userpass[32]; - int n; fz_md5 md5; fz_arc4 arc4; - n = crypt->length / 8; - if (pwlen > 32) pwlen = 32; memcpy(pwbuf, ownerpass, pwlen); @@ -678,15 +677,13 @@ pdf_authenticate_owner_password(fz_context *ctx, pdf_crypt *crypt, unsigned char if (crypt->r == 3 || crypt->r == 4) { unsigned char pwbuf[32]; - unsigned char key[32]; + unsigned char key[16]; unsigned char xor[32]; unsigned char userpass[32]; - int i, n, x; + int i, x; fz_md5 md5; fz_arc4 arc4; - n = crypt->length / 8; - if (pwlen > 32) pwlen = 32; memcpy(pwbuf, ownerpass, pwlen); @@ -699,7 +696,7 @@ pdf_authenticate_owner_password(fz_context *ctx, pdf_crypt *crypt, unsigned char for (i = 0; i < 50; i++) { fz_md5_init(&md5); - fz_md5_update(&md5, key, 16); + fz_md5_update(&md5, key, n); fz_md5_final(&md5, key); } |