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https://github.com/michaelrsweet/pdfio.git
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Implement pdfioFileSetPermissions.
This commit is contained in:
Michael R Sweet
parent
37e80d67b1
commit
61a7964d90
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@ -13,8 +13,7 @@ goals of PDFio are:
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- Read and write any version of PDF file
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- Provide access to pages, objects, and streams within a PDF file
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- Support reading encrypted PDF files
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- Support writing PDF files with digital signatures
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- Support reading of encrypted PDF files
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- Extract or embed useful metadata (author, creator, page information, etc.)
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- "Filter" PDF files, for example to extract a range of pages or to embed fonts
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that are missing from a PDF
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@ -389,7 +389,7 @@ pdfioArrayGetBinary(
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size_t n, // I - Index
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size_t *length) // O - Length of string
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{
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if (!a || n >= a->num_values || a->values[n].type != PDFIO_VALTYPE_BINARY || !length)
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if (!a || n >= a->num_values || a->values[n].type != PDFIO_VALTYPE_BINARY)
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{
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if (length)
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*length = 0;
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@ -398,7 +398,9 @@ pdfioArrayGetBinary(
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}
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else
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{
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*length = a->values[n].value.binary.datalen;
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if (length)
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*length = a->values[n].value.binary.datalen;
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return (a->values[n].value.binary.data);
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}
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}
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220
pdfio-file.c
220
pdfio-file.c
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@ -1034,13 +1034,219 @@ pdfioFileSetKeywords(
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}
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//
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// 'pdfioFileSetPermissions()' - Set the PDF permissions, encryption mode, and passwords.
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//
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// This function sets the PDF usage permissions, encryption mode, and
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// passwords.
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//
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// > *Note*: This function must be called before creating or copying any
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// > objects. Due to fundamental limitations in the PDF format, PDF encryption
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// > offers little protection from disclosure. Permissions are not enforced in
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// > any meaningful way.
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//
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bool // O - `true` on success, `false` otherwise
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pdfioFileSetPermissions(
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pdfio_file_t *pdf, // I - PDF file
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pdfio_permission_t permissions, // I - Use permissions
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pdfio_encryption_t encryption, // I - Type of encryption to use
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const char *owner_password, // I - Owner password, if any
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const char *user_password) // I - User password, if any
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{
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pdfio_dict_t *dict; // Encryption dictionary
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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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size_t len; // Length of password
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uint8_t owner_pad[32], // Padded owner password
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user_pad[32], // Padded user password
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perm_bytes[4], // Permissions bytes
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*file_id; // File ID bytes
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size_t file_id_len; // Length of file ID
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static uint8_t pad[32] = // Padding for passwords
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{
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0x28, 0xbf, 0x4e, 0x5e, 0x4e, 0x75, 0x8a, 0x41,
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0x64, 0x00, 0x4e, 0x56, 0xff, 0xfa, 0x01, 0x08,
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0x2e, 0x2e, 0x00, 0xb6, 0xd0, 0x68, 0x3e, 0x80,
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0x2f, 0x0c, 0xa9, 0xfe, 0x64, 0x53, 0x69, 0x7a
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};
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if (!pdf)
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return (false);
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if (pdf->num_objs > 0)
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{
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_pdfioFileError(pdf, "You must call pdfioFileSetPermissions before adding any objects.");
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return (false);
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}
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if (encryption == PDFIO_ENCRYPTION_NONE)
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return (true);
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if ((dict = pdfioDictCreate(pdf)) == NULL)
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{
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_pdfioFileError(pdf, "Unable to create encryption dictionary.");
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return (false);
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}
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pdfioDictSetName(dict, "Filter", "Standard");
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switch (encryption)
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{
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case PDFIO_ENCRYPTION_RC4_128 :
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case PDFIO_ENCRYPTION_AES_128 :
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// Create the 128-bit encryption keys...
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if (user_password)
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{
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// Copy the user password and pad it with the special PDF pad bytes
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if ((len = strlen(user_password)) > sizeof(user_pad))
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len = sizeof(user_pad);
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if (len > 0)
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memcpy(user_pad, user_password, len);
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if (len < sizeof(user_pad))
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memcpy(user_pad + len, pad, sizeof(user_pad) - len);
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}
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else
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{
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// Use default (pad) password
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memcpy(user_pad, pad, sizeof(user_pad));
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}
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if (owner_password && *owner_password)
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{
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// Copy the owner password and pad it with the special PDF pad bytes
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if ((len = strlen(owner_password)) > sizeof(owner_pad))
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len = sizeof(owner_pad);
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if (len > 0)
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memcpy(owner_pad, owner_password, len);
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if (len < sizeof(owner_pad))
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memcpy(owner_pad + len, pad, sizeof(owner_pad) - len);
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}
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else
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{
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// Generate a random owner password...
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_pdfioCryptoMakeRandom(owner_pad, sizeof(owner_pad));
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}
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// Compute the owner key...
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_pdfioCryptoMD5Init(&md5);
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_pdfioCryptoMD5Append(&md5, owner_pad, 32);
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_pdfioCryptoMD5Finish(&md5, digest);
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// MD5 the result 50 more 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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_pdfioCryptoMD5Finish(&md5, digest);
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}
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// Copy the padded user password...
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memcpy(pdf->owner_key, user_pad, sizeof(pdf->owner_key));
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// Encrypt the result 20 times...
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for (i = 0; i < 20; i ++)
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{
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uint8_t encrypt_key[16];// RC4 encryption key
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// XOR each byte in the digest with the loop counter to make a key...
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for (j = 0; j < sizeof(encrypt_key); j ++)
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encrypt_key[j] = (uint8_t)(digest[j] ^ i);
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_pdfioCryptoRC4Init(&rc4, encrypt_key, sizeof(encrypt_key));
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_pdfioCryptoRC4Crypt(&rc4, pdf->owner_key, sizeof(pdf->owner_key));
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}
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// Generate the encryption key
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perm_bytes[0] = (uint8_t)permissions;
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perm_bytes[1] = (uint8_t)(permissions >> 8);
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perm_bytes[2] = (uint8_t)(permissions >> 16);
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perm_bytes[3] = (uint8_t)(permissions >> 24);
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file_id = pdfioArrayGetBinary(pdf->id_array, 0, &file_id_len);
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_pdfioCryptoMD5Init(&md5);
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_pdfioCryptoMD5Append(&md5, user_pad, 32);
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_pdfioCryptoMD5Append(&md5, pdf->owner_key, 32);
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_pdfioCryptoMD5Append(&md5, perm_bytes, 4);
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_pdfioCryptoMD5Append(&md5, file_id, file_id_len);
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_pdfioCryptoMD5Finish(&md5, digest);
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// MD5 the result 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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_pdfioCryptoMD5Finish(&md5, digest);
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}
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memcpy(pdf->encryption_key, digest, 16);
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// Generate the user key...
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_pdfioCryptoMD5Init(&md5);
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_pdfioCryptoMD5Append(&md5, pad, 32);
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_pdfioCryptoMD5Append(&md5, file_id, file_id_len);
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_pdfioCryptoMD5Finish(&md5, pdf->user_key);
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memset(pdf->user_key + 16, 0, 16);
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// Encrypt the result 20 times...
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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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digest[j] = (uint8_t)(pdf->encryption_key[j] ^ i);
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_pdfioCryptoRC4Init(&rc4, digest, 16);
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_pdfioCryptoRC4Crypt(&rc4, pdf->user_key, sizeof(pdf->user_key));
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}
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// Save everything in the dictionary...
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pdfioDictSetNumber(dict, "Length", 128);
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pdfioDictSetBinary(dict, "O", pdf->owner_key, sizeof(pdf->owner_key));
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pdfioDictSetNumber(dict, "P", (int)permissions);
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pdfioDictSetNumber(dict, "R", encryption == PDFIO_ENCRYPTION_RC4_128 ? 3 : 4);
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pdfioDictSetNumber(dict, "V", encryption == PDFIO_ENCRYPTION_RC4_128 ? 3 : 4);
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pdfioDictSetBinary(dict, "U", pdf->user_key, sizeof(pdf->user_key));
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break;
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case PDFIO_ENCRYPTION_AES_256 :
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// TODO: Implement AES-256 (/V 6 /R 6)
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default :
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_pdfioFileError(pdf, "Encryption mode %d not supported for writing.", (int)encryption);
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return (false);
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}
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if ((pdf->encrypt_obj = pdfioFileCreateObj(pdf, dict)) == NULL)
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{
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_pdfioFileError(pdf, "Unable to create encryption object.");
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return (false);
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}
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pdfioObjClose(pdf->encrypt_obj);
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pdf->encryption = encryption;
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pdf->permissions = permissions;
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return (true);
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}
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//
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// 'pdfioFileSetSubject()' - Set the subject for a PDF file.
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//
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void
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pdfioFileSetSubject(pdfio_file_t *pdf, // I - PDF file
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const char *value)// I - Value
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pdfioFileSetSubject(
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pdfio_file_t *pdf, // I - PDF file
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const char *value) // I - Value
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{
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if (pdf && pdf->info)
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pdfioDictSetString(pdf->info->value.value.dict, "Subject", pdfioStringCreate(pdf, value));
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@ -1702,9 +1908,9 @@ load_xref(pdfio_file_t *pdf, // I - PDF file
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PDFIO_DEBUG("load_xref: Root=%p(%lu)\n", pdf->root, (unsigned long)pdf->root->number);
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pdf->info = pdfioDictGetObj(pdf->trailer, "Info");
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pdf->encrypt = pdfioDictGetObj(pdf->trailer, "Encrypt");
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pdf->id_array = pdfioDictGetArray(pdf->trailer, "ID");
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pdf->info = pdfioDictGetObj(pdf->trailer, "Info");
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pdf->encrypt_obj = pdfioDictGetObj(pdf->trailer, "Encrypt");
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pdf->id_array = pdfioDictGetArray(pdf->trailer, "ID");
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return (load_pages(pdf, pdfioDictGetObj(pdfioObjGetDict(pdf->root), "Pages")));
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}
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@ -1819,8 +2025,8 @@ write_trailer(pdfio_file_t *pdf) // I - PDF file
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goto done;
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}
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if (pdf->encrypt)
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pdfioDictSetObj(pdf->trailer, "Encrypt", pdf->encrypt);
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if (pdf->encrypt_obj)
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pdfioDictSetObj(pdf->trailer, "Encrypt", pdf->encrypt_obj);
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if (pdf->id_array)
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pdfioDictSetArray(pdf->trailer, "ID", pdf->id_array);
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pdfioDictSetObj(pdf->trailer, "Info", pdf->info);
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@ -255,6 +255,12 @@ struct _pdfio_file_s // PDF file structure
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pdfio_error_cb_t error_cb; // Error callback
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void *error_data; // Data for error callback
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pdfio_encryption_t encryption; // Encryption mode
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pdfio_permission_t permissions; // Access permissions (encrypted PDF files)
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uint8_t encryption_key[16], // Object encryption key
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owner_key[32], // Owner encryption key
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user_key[32]; // User encryption key
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// Active file data
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int fd; // File descriptor
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char buffer[8192], // Read/write buffer
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@ -265,7 +271,7 @@ struct _pdfio_file_s // PDF file structure
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pdfio_obj_t *root; // Root object/dictionary
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pdfio_obj_t *info; // Information object
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pdfio_obj_t *pages_root; // Root pages object
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pdfio_obj_t *encrypt; // Encryption object/dictionary
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pdfio_obj_t *encrypt_obj; // De/Encryption object/dictionary
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pdfio_obj_t *cp1252_obj, // CP1252 font encoding object
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*unicode_obj; // Unicode font encoding object
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pdfio_array_t *id_array; // ID array
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24
pdfio.h
24
pdfio.h
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@ -59,6 +59,14 @@ typedef struct _pdfio_file_s pdfio_file_t;
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// PDF file
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typedef bool (*pdfio_error_cb_t)(pdfio_file_t *pdf, const char *message, void *data);
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// Error callback
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typedef enum pdfio_encryption_e // PDF encryption modes
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{
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PDFIO_ENCRYPTION_NONE = 0, // No encryption
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PDFIO_ENCRYPTION_RC4_40, // 40-bit RC4 encryption (PDF 1.3)
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PDFIO_ENCRYPTION_RC4_128, // 128-bit RC4 encryption (PDF 1.4)
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PDFIO_ENCRYPTION_AES_128, // 128-bit AES encryption (PDF 1.6)
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PDFIO_ENCRYPTION_AES_256 // 256-bit AES encryption (PDF 2.0)
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} pdfio_encryption_t;
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typedef enum pdfio_filter_e // Compression/decompression filters for streams
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{
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PDFIO_FILTER_NONE, // No filter
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@ -78,6 +86,20 @@ typedef ssize_t (*pdfio_output_cb_t)(void *ctx, const void *data, size_t datalen
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// Output callback for pdfioFileCreateOutput
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typedef const char *(*pdfio_password_cb_t)(void *data, const char *filename);
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// Password callback for pdfioFileOpen
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enum pdfio_permission_e // PDF permission bits
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{
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PDFIO_PERMISSION_NONE = 0, // No permissions
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PDFIO_PERMISSION_PRINT = 0x0004, // PDF allows printing
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PDFIO_PERMISSION_MODIFY = 0x0008, // PDF allows modification
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PDFIO_PERMISSION_COPY = 0x0010, // PDF allows copying
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PDFIO_PERMISSION_ANNOTATE = 0x0020, // PDF allows annotation
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PDFIO_PERMISSION_FORMS = 0x0100, // PDF allows filling in forms
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PDFIO_PERMISSION_READING = 0x0200, // PDF allows screen reading/accessibility (deprecated in PDF 2.0)
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PDFIO_PERMISSION_ASSEMBLE = 0x0400, // PDF allows assembly (insert, delete, or rotate pages, add document outlines and thumbnails)
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PDFIO_PERMISSION_PRINT_HIGH = 0x0800, // PDF allows high quality printing
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PDFIO_PERMISSION_ALL = ~0 // All permissions
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};
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typedef unsigned pdfio_permission_t; // PDF permission bitfield
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typedef struct pdfio_rect_s // PDF rectangle
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{
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double x1; // Lower-left X coordinate
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@ -174,6 +196,7 @@ extern size_t pdfioFileGetNumObjs(pdfio_file_t *pdf) _PDFIO_PUBLIC;
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extern size_t pdfioFileGetNumPages(pdfio_file_t *pdf) _PDFIO_PUBLIC;
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extern pdfio_obj_t *pdfioFileGetObj(pdfio_file_t *pdf, size_t n) _PDFIO_PUBLIC;
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extern pdfio_obj_t *pdfioFileGetPage(pdfio_file_t *pdf, size_t n) _PDFIO_PUBLIC;
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extern pdfio_permission_t pdfioFileGetPermissions(pdfio_file_t *pdf) _PDFIO_PUBLIC;
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extern const char *pdfioFileGetProducer(pdfio_file_t *pdf) _PDFIO_PUBLIC;
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extern const char *pdfioFileGetSubject(pdfio_file_t *pdf) _PDFIO_PUBLIC;
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extern const char *pdfioFileGetTitle(pdfio_file_t *pdf) _PDFIO_PUBLIC;
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@ -183,6 +206,7 @@ extern void pdfioFileSetAuthor(pdfio_file_t *pdf, const char *value) _PDFIO_PUB
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extern void pdfioFileSetCreationDate(pdfio_file_t *pdf, time_t value) _PDFIO_PUBLIC;
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extern void pdfioFileSetCreator(pdfio_file_t *pdf, const char *value) _PDFIO_PUBLIC;
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extern void pdfioFileSetKeywords(pdfio_file_t *pdf, const char *value) _PDFIO_PUBLIC;
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extern bool pdfioFileSetPermissions(pdfio_file_t *pdf, pdfio_permission_t permissions, pdfio_encryption_t encryption, const char *owner_password, const char *user_password) _PDFIO_PUBLIC;
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extern void pdfioFileSetSubject(pdfio_file_t *pdf, const char *value) _PDFIO_PUBLIC;
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extern void pdfioFileSetTitle(pdfio_file_t *pdf, const char *value) _PDFIO_PUBLIC;
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