mirror of
https://github.com/michaelrsweet/pdfio.git
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Refactor PDF encryption handler to work with more files.
This commit is contained in:
Michael R Sweet
@@ -14,6 +14,7 @@ v1.6.2 - YYYY-MM-DD
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- Increased the maximum length of a single string to 128k (Issue #146)
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- Added missing range checks to `pdfioArrayCopy` and `pdfioDictCopy`.
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- Refactored PDF encryption code to fix unlocking with certain files.
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- Fixed an error propagation bug when reading too-long values (Issue #146)
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- Fixed a Clang warning.
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228
pdfio-crypto.c
228
pdfio-crypto.c
@@ -1,7 +1,7 @@
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//
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// Cryptographic support functions for PDFio.
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//
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// Copyright © 2021-2025 by Michael R Sweet.
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// Copyright © 2021-2026 by Michael R Sweet.
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//
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// Licensed under Apache License v2.0. See the file "LICENSE" for more
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// information.
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@@ -96,12 +96,14 @@ static uint8_t pdf_passpad[32] = // Padding for passwords
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// Local functions...
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//
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static void decrypt_user_key(pdfio_encryption_t encryption, const uint8_t *file_key, uint8_t user_key[32]);
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static void encrypt_user_key(pdfio_encryption_t encryption, const uint8_t *file_key, uint8_t user_key[32]);
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static void make_file_key(pdfio_encryption_t encryption, pdfio_permission_t permissions, const unsigned char *file_id, size_t file_idlen, const uint8_t *user_pad, const uint8_t *owner_key, bool encrypt_metadata, uint8_t file_key[16]);
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static void make_owner_key(pdfio_encryption_t encryption, const uint8_t *owner_pad, const uint8_t *user_pad, uint8_t owner_key[32]);
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static void decrypt_ou_key(pdfio_encryption_t encryption, const uint8_t *file_key, size_t file_keylen, uint8_t ou_key[32]);
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static void encrypt_ou_key(pdfio_encryption_t encryption, const uint8_t *file_key, size_t file_keylen, uint8_t ou_key[32]);
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static void make_file_key(pdfio_encryption_t encryption, size_t file_keylen, pdfio_permission_t permissions, const unsigned char *file_id, size_t file_idlen, const uint8_t *user_pad, const uint8_t *owner_key, bool encrypt_metadata, uint8_t file_key[16]);
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static void make_owner_key(pdfio_encryption_t encryption, size_t file_keylen, const uint8_t *owner_pad, const uint8_t *user_pad, uint8_t owner_key[32]);
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static void make_password_key(pdfio_encryption_t encryption, size_t file_keylen, const uint8_t *pad, uint8_t *key);
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static void make_user_key(const unsigned char *file_id, size_t file_idlen, uint8_t user_key[32]);
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static void pad_password(const char *password, uint8_t pad[32]);
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static bool test_password(pdfio_encryption_t encryption, size_t file_keylen, pdfio_permission_t permisions,const unsigned char *file_id, size_t file_idlen, const uint8_t *user_pad, const uint8_t *user_key, const uint8_t *owner_key, bool encrypt_metadata, uint8_t file_key[16]);
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//
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@@ -139,6 +141,7 @@ _pdfioCryptoLock(
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case PDFIO_ENCRYPTION_AES_128 :
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// Create the 128-bit encryption keys...
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pad_password(user_password, user_pad);
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pdf->file_keylen = 16;
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if (!owner_password && user_password && *user_password)
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{
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@@ -152,18 +155,17 @@ _pdfioCryptoLock(
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}
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// Compute the owner key...
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make_owner_key(encryption, owner_pad, user_pad, pdf->owner_key);
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make_owner_key(encryption, pdf->file_keylen, owner_pad, user_pad, pdf->owner_key);
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pdf->owner_keylen = 32;
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// Generate the encryption key
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file_id = pdfioArrayGetBinary(pdf->id_array, 0, &file_idlen);
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make_file_key(encryption, permissions, file_id, file_idlen, user_pad, pdf->owner_key, pdf->encrypt_metadata, pdf->file_key);
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pdf->file_keylen = 16;
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make_file_key(encryption, pdf->file_keylen, permissions, file_id, file_idlen, user_pad, pdf->owner_key, pdf->encrypt_metadata, pdf->file_key);
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// Generate the user key...
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make_user_key(file_id, file_idlen, pdf->user_key);
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encrypt_user_key(encryption, pdf->file_key, pdf->user_key);
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encrypt_ou_key(encryption, pdf->file_key, pdf->file_keylen, pdf->user_key);
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pdf->user_keylen = 32;
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// Save everything in the dictionary...
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@@ -733,7 +735,7 @@ _pdfioCryptoUnlock(
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return (false);
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}
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PDFIO_DEBUG("_pdfioCryptoUnlock: user_key[%d]=%02X%02X%02X%02X...%02X%02X%02X%02X\n", (int)user_keylen, user_key[0], user_key[1], user_key[2], user_key[3], user_key[28], user_key[29], user_key[30], user_key[31]);
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PDFIO_DEBUG("_pdfioCryptoUnlock: user_key[%d]=<%02X%02X%02X%02X...%02X%02X%02X%02X>\n", (int)user_keylen, user_key[0], user_key[1], user_key[2], user_key[3], user_key[28], user_key[29], user_key[30], user_key[31]);
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memcpy(pdf->user_key, user_key, user_keylen);
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pdf->user_keylen = user_keylen;
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@@ -744,6 +746,9 @@ _pdfioCryptoUnlock(
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return (false);
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}
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PDFIO_DEBUG("_pdfioCryptoUnlock: P=%d\n", pdf->permissions);
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PDFIO_DEBUG("_pdfioCryptoUnlock: file_id(%d)=<%02X%02X%02X%02X...%02X%02X%02X%02X>\n", (int)file_idlen, file_id[0], file_id[1], file_id[2], file_id[3], file_id[12], file_id[13], file_id[14], file_id[15]);
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// Generate a base hash from known values...
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_pdfioCryptoMD5Init(&md5);
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_pdfioCryptoMD5Append(&md5, pdf_passpad, 32);
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@@ -755,56 +760,34 @@ _pdfioCryptoUnlock(
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{
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if (pdf->encryption <= PDFIO_ENCRYPTION_AES_128)
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{
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// RC4 and AES-128 encryption...
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uint8_t pad[32], // Padded password
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file_key[16], // File key
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user_pad[32], // Padded user password
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own_user_key[32], // Calculated user key
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pdf_user_key[32]; // Decrypted user key
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padkey[16], // Password key
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file_key[16]; // File key
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// Pad the supplied password, if any...
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pad_password(password, pad);
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// Generate keys to see if things match...
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PDFIO_DEBUG("_pdfioCryptoUnlock: Trying %02X%02X%02X%02X...%02X%02X%02X%02X\n", pad[0], pad[1], pad[2], pad[3], pad[28], pad[29], pad[30], pad[31]);
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PDFIO_DEBUG("_pdfioCryptoUnlock: P=%d\n", pdf->permissions);
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PDFIO_DEBUG("_pdfioCryptoUnlock: Fid(%d)=%02X%02X%02X%02X...%02X%02X%02X%02X\n", (int)file_idlen, file_id[0], file_id[1], file_id[2], file_id[3], file_id[12], file_id[13], file_id[14], file_id[15]);
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// Test the user password...
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PDFIO_DEBUG("_pdfioCryptoUnlock: Trying <%02X%02X%02X%02X...%02X%02X%02X%02X>\n", pad[0], pad[1], pad[2], pad[3], pad[28], pad[29], pad[30], pad[31]);
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make_owner_key(pdf->encryption, pad, pdf->owner_key, user_pad);
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PDFIO_DEBUG("_pdfioCryptoUnlock: Upad=%02X%02X%02X%02X...%02X%02X%02X%02X\n", user_pad[0], user_pad[1], user_pad[2], user_pad[3], user_pad[28], user_pad[29], user_pad[30], user_pad[31]);
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make_file_key(pdf->encryption, pdf->permissions, file_id, file_idlen, user_pad, pdf->owner_key, pdf->encrypt_metadata, file_key);
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PDFIO_DEBUG("_pdfioCryptoUnlock: Fown=%02X%02X%02X%02X...%02X%02X%02X%02X\n", file_key[0], file_key[1], file_key[2], file_key[3], file_key[12], file_key[13], file_key[14], file_key[15]);
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make_user_key(file_id, file_idlen, own_user_key);
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PDFIO_DEBUG("_pdfioCryptoUnlock: U=%02X%02X%02X%02X...%02X%02X%02X%02X\n", pdf->user_key[0], pdf->user_key[1], pdf->user_key[2], pdf->user_key[3], pdf->user_key[28], pdf->user_key[29], pdf->user_key[30], pdf->user_key[31]);
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PDFIO_DEBUG("_pdfioCryptoUnlock: Uown=%02X%02X%02X%02X...%02X%02X%02X%02X\n", own_user_key[0], own_user_key[1], own_user_key[2], own_user_key[3], own_user_key[28], own_user_key[29], own_user_key[30], own_user_key[31]);
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if (!memcmp(own_user_key, pdf->user_key, sizeof(own_user_key)))
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if (test_password(pdf->encryption, pdf->file_keylen, pdf->permissions, file_id, file_idlen, pad, pdf->user_key, pdf->owner_key, pdf->encrypt_metadata, file_key))
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{
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// Matches!
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memcpy(pdf->file_key, file_key, sizeof(pdf->file_key));
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memcpy(pdf->file_key, file_key, pdf->file_keylen);
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memcpy(pdf->password, pad, sizeof(pdf->password));
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return (true);
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}
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// Not the owner password, try the user password...
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make_file_key(pdf->encryption, pdf->permissions, file_id, file_idlen, pad, pdf->owner_key, pdf->encrypt_metadata, file_key);
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PDFIO_DEBUG("_pdfioCryptoUnlock: Fuse=%02X%02X%02X%02X...%02X%02X%02X%02X\n", file_key[0], file_key[1], file_key[2], file_key[3], file_key[12], file_key[13], file_key[14], file_key[15]);
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// Test the owner password...
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make_password_key(pdf->encryption, pdf->file_keylen, pad, padkey);
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make_user_key(file_id, file_idlen, own_user_key);
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memcpy(pad, pdf->owner_key, sizeof(pad));
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decrypt_ou_key(pdf->encryption, padkey, pdf->file_keylen, pad);
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memcpy(pdf_user_key, pdf->user_key, sizeof(pdf_user_key));
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decrypt_user_key(pdf->encryption, file_key, pdf_user_key);
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PDFIO_DEBUG("_pdfioCryptoUnlock: Uuse=%02X%02X%02X%02X...%02X%02X%02X%02X\n", user_key[0], user_key[1], user_key[2], user_key[3], user_key[28], user_key[29], user_key[30], user_key[31]);
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PDFIO_DEBUG("_pdfioCryptoUnlock: Updf=%02X%02X%02X%02X...%02X%02X%02X%02X\n", pdf_user_key[0], pdf_user_key[1], pdf_user_key[2], pdf_user_key[3], pdf_user_key[28], pdf_user_key[29], pdf_user_key[30], pdf_user_key[31]);
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if (!memcmp(pad, pdf_user_key, 32) || !memcmp(own_user_key, pdf_user_key, 16))
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if (test_password(pdf->encryption, pdf->file_keylen, pdf->permissions, file_id, file_idlen, pad, pdf->user_key, pdf->owner_key, pdf->encrypt_metadata, file_key))
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{
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// Matches!
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memcpy(pdf->file_key, file_key, sizeof(pdf->file_key));
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memcpy(pdf->file_key, file_key, pdf->file_keylen);
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memcpy(pdf->password, pad, sizeof(pdf->password));
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return (true);
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@@ -832,14 +815,15 @@ _pdfioCryptoUnlock(
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//
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// 'decrypt_user_key()' - Decrypt the user key.
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// 'decrypt_ou_key()' - Decrypt the user key.
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//
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static void
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decrypt_user_key(
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decrypt_ou_key(
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pdfio_encryption_t encryption, // I - Type of encryption
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const uint8_t *file_key, // I - File encryption key
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uint8_t user_key[32]) // IO - User key
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size_t file_keylen, // I - Length of file encryption key
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uint8_t ou_key[32]) // IO - Owner/User key
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{
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size_t i, j; // Looping vars
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_pdfio_rc4_t rc4; // RC4 encryption context
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@@ -849,38 +833,38 @@ decrypt_user_key(
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{
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// Encrypt the result once...
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_pdfioCryptoRC4Init(&rc4, file_key, 5);
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_pdfioCryptoRC4Crypt(&rc4, user_key, user_key, 32);
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_pdfioCryptoRC4Crypt(&rc4, ou_key, ou_key, 32);
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}
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else
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{
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// Encrypt the result 20 times...
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uint8_t key[16]; // Current encryption key
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for (i = 19; i > 0; i --)
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for (i = 20; i > 0;)
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{
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// XOR each byte in the key with the loop counter...
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for (j = 0; j < 16; j ++)
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i --;
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for (j = 0; j < file_keylen; j ++)
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key[j] = (uint8_t)(file_key[j] ^ i);
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_pdfioCryptoRC4Init(&rc4, key, 16);
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_pdfioCryptoRC4Crypt(&rc4, user_key, user_key, 32);
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_pdfioCryptoRC4Init(&rc4, key, file_keylen);
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_pdfioCryptoRC4Crypt(&rc4, ou_key, ou_key, 32);
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}
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_pdfioCryptoRC4Init(&rc4, file_key, 16);
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_pdfioCryptoRC4Crypt(&rc4, user_key, user_key, 32);
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}
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}
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//
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// 'encrypt_user_key()' - Encrypt the user key.
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// 'encrypt_ou_key()' - Encrypt the owner/user key.
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//
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static void
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encrypt_user_key(
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encrypt_ou_key(
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pdfio_encryption_t encryption, // I - Type of encryption
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const uint8_t *file_key, // I - File encryption key
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uint8_t user_key[32]) // IO - User key
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size_t file_keylen, // I - Length of file encryption key
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uint8_t ou_key[32]) // IO - Owner/User key
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{
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size_t i, j; // Looping vars
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_pdfio_rc4_t rc4; // RC4 encryption context
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@@ -890,7 +874,7 @@ encrypt_user_key(
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{
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// Encrypt the result once...
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_pdfioCryptoRC4Init(&rc4, file_key, 5);
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_pdfioCryptoRC4Crypt(&rc4, user_key, user_key, 32);
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_pdfioCryptoRC4Crypt(&rc4, ou_key, ou_key, 32);
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}
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else
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{
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@@ -900,11 +884,11 @@ encrypt_user_key(
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for (i = 0; i < 20; i ++)
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{
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// XOR each byte in the key with the loop counter...
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for (j = 0; j < 16; j ++)
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for (j = 0; j < file_keylen; j ++)
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key[j] = (uint8_t)(file_key[j] ^ i);
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_pdfioCryptoRC4Init(&rc4, key, 16);
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_pdfioCryptoRC4Crypt(&rc4, user_key, user_key, 32);
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_pdfioCryptoRC4Init(&rc4, key, file_keylen);
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_pdfioCryptoRC4Crypt(&rc4, ou_key, ou_key, 32);
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}
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}
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}
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@@ -917,6 +901,7 @@ encrypt_user_key(
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static void
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make_file_key(
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pdfio_encryption_t encryption, // I - Type of encryption
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size_t file_keylen, // I - Encryption key length
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pdfio_permission_t permissions, // I - File permissions
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const unsigned char *file_id, // I - File ID value
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size_t file_idlen, // I - Length of file ID
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@@ -962,14 +947,14 @@ make_file_key(
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for (i = 0; i < 50; i ++)
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{
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_pdfioCryptoMD5Init(&md5);
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_pdfioCryptoMD5Append(&md5, digest, 16);
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_pdfioCryptoMD5Append(&md5, digest, file_keylen);
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_pdfioCryptoMD5Finish(&md5, digest);
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}
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}
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PDFIO_DEBUG("make_file_key: file_key[16]=<%02X%02X%02X%02X...%02X%02X%02X%02X>\n", digest[0], digest[1], digest[2], digest[3], digest[12], digest[13], digest[14], digest[15]);
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memcpy(file_key, digest, 16);
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memcpy(file_key, digest, file_keylen);
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}
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@@ -980,57 +965,57 @@ make_file_key(
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static void
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make_owner_key(
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pdfio_encryption_t encryption, // I - Type of encryption
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size_t file_keylen, // I - Length of encryption key
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const uint8_t *owner_pad, // I - Padded owner password
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const uint8_t *user_pad, // I - Padded user password
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uint8_t owner_key[32]) // O - Owner key value
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{
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size_t i, j; // Looping vars
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_pdfio_md5_t md5; // MD5 context
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uint8_t digest[16]; // 128-bit MD5 digest
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_pdfio_rc4_t rc4; // RC4 encryption context
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uint8_t key[16]; // Base encryption key
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// Hash the owner password...
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make_password_key(encryption, file_keylen, owner_pad, key);
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// Copy and encrypt the padded user password...
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memcpy(owner_key, user_pad, 32);
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decrypt_ou_key(encryption, key, file_keylen, owner_key);
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}
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//
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// 'make_password_key()' - Make a password key.
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//
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static void
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make_password_key(
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pdfio_encryption_t encryption, // I - Type of encryption
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size_t file_keylen, // I - Length of encryption key
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const uint8_t *pad, // I - Padded password
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uint8_t *key) // O - Key data
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{
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size_t i; // Looping var
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_pdfio_md5_t md5; // MD5 context
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uint8_t digest[16]; // 128-bit MD5 digest
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// Hash the padded password...
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_pdfioCryptoMD5Init(&md5);
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_pdfioCryptoMD5Append(&md5, owner_pad, 32);
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_pdfioCryptoMD5Append(&md5, pad, 32);
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_pdfioCryptoMD5Finish(&md5, digest);
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if (encryption != PDFIO_ENCRYPTION_RC4_40)
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{
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// Hash the hash another 50 times...
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for (i = 0; i < 50; i ++)
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{
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_pdfioCryptoMD5Init(&md5);
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_pdfioCryptoMD5Append(&md5, digest, 16);
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_pdfioCryptoMD5Append(&md5, digest, file_keylen);
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_pdfioCryptoMD5Finish(&md5, digest);
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}
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}
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// Copy and encrypt the padded user password...
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memcpy(owner_key, user_pad, 32);
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if (encryption == PDFIO_ENCRYPTION_RC4_40)
|
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{
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// Encrypt once...
|
||||
_pdfioCryptoRC4Init(&rc4, digest, 5);
|
||||
_pdfioCryptoRC4Crypt(&rc4, owner_key, owner_key, 32);
|
||||
}
|
||||
else
|
||||
{
|
||||
// Encrypt 20 times...
|
||||
uint8_t encrypt_key[16]; // RC4 encryption key
|
||||
|
||||
for (i = 20; i > 0;)
|
||||
{
|
||||
// XOR each byte in the digest with the loop counter to make a key...
|
||||
i --;
|
||||
|
||||
for (j = 0; j < sizeof(encrypt_key); j ++)
|
||||
encrypt_key[j] = (uint8_t)(digest[j] ^ i);
|
||||
|
||||
_pdfioCryptoRC4Init(&rc4, encrypt_key, sizeof(encrypt_key));
|
||||
_pdfioCryptoRC4Crypt(&rc4, owner_key, owner_key, 32);
|
||||
}
|
||||
}
|
||||
// Copy the key portion of the hashed password to the key...
|
||||
memcpy(key, digest, file_keylen);
|
||||
}
|
||||
|
||||
|
||||
@@ -1085,3 +1070,52 @@ pad_password(const char *password, // I - Password string or `NULL`
|
||||
if (len < 32)
|
||||
memcpy(pad + len, pdf_passpad, 32 - len);
|
||||
}
|
||||
|
||||
|
||||
//
|
||||
// 'test_password()' - Test a user password...
|
||||
//
|
||||
|
||||
static bool // O - `true` if password is correct, `false` otherwise
|
||||
test_password(
|
||||
pdfio_encryption_t encryption, // I - Type of encryption
|
||||
size_t file_keylen, // I - Length of encryption key
|
||||
pdfio_permission_t permissions, // I - File permissions
|
||||
const unsigned char *file_id, // I - File ID value
|
||||
size_t file_idlen, // I - Length of file ID
|
||||
const uint8_t *user_pad, // I - Padded user password
|
||||
const uint8_t *user_key, // I - User key
|
||||
const uint8_t *owner_key, // I - Owner key
|
||||
bool encrypt_metadata,
|
||||
// I - Encrypt metadata?
|
||||
uint8_t file_key[16]) // O - Encryption key
|
||||
{
|
||||
uint8_t pdf_user_key[32]; // Decrypted user key
|
||||
|
||||
|
||||
// Make the file key...
|
||||
make_file_key(encryption, file_keylen, permissions, file_id, file_idlen, user_pad, owner_key, encrypt_metadata, file_key);
|
||||
|
||||
// Decrypt the user key using the file key...
|
||||
memcpy(pdf_user_key, user_key, sizeof(pdf_user_key));
|
||||
decrypt_ou_key(encryption, file_key, file_keylen, pdf_user_key);
|
||||
PDFIO_DEBUG("test_password: pdf_user_key[32]=<%02X%02X%02X%02X...%02X%02X%02X%02X>\n", pdf_user_key[0], pdf_user_key[1], pdf_user_key[2], pdf_user_key[3], pdf_user_key[28], pdf_user_key[29], pdf_user_key[30], pdf_user_key[31]);
|
||||
|
||||
if (encryption == PDFIO_ENCRYPTION_RC4_40 && !memcmp(pdf_user_key, pdf_passpad, 32))
|
||||
{
|
||||
// 40-bit encryption just compares the eecrypted user key matches...
|
||||
return (true);
|
||||
}
|
||||
else
|
||||
{
|
||||
// 128-bit encryption needs to match the calculated user key...
|
||||
uint8_t own_user_key[32]; // Calculated user key
|
||||
|
||||
// Calculate what the user key should be...
|
||||
make_user_key(file_id, file_idlen, own_user_key);
|
||||
PDFIO_DEBUG("test_password: own_user_key[32]=<%02X%02X%02X%02X...%02X%02X%02X%02X>\n", own_user_key[0], own_user_key[1], own_user_key[2], own_user_key[3], own_user_key[28], own_user_key[29], own_user_key[30], own_user_key[31]);
|
||||
|
||||
// Return whether they match...
|
||||
return (!memcmp(pdf_user_key, own_user_key, 16));
|
||||
}
|
||||
}
|
||||
|
||||
Reference in New Issue
Block a user