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https://github.com/rg3/libbcrypt.git
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d4bac5883f
This is irrelevant for the dynamic library thanks to -fvisibility=hidden, but it can be important to avoid symbol name collisions in the static library.
52 lines
1.6 KiB
C
52 lines
1.6 KiB
C
/*
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* Simple base64 encoding implementation, with explicit index calculation.
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*/
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#include <assert.h>
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#include <string.h>
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#include "base64.h"
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static char base64_table[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
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static void base64_block(const unsigned char *in, size_t len, char *out);
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static void base64_block(const unsigned char *in, size_t len, char out[4])
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{
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unsigned char padded_in[3] = { '\0', '\0', '\0' };
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assert(len >= 1 && len <= 3);
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memmove(padded_in, in, len);
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/* 3 bytes are grouped as 4 6-bit blocks and interpreted as indexes. */
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unsigned int index[4];
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index[0] = ((padded_in[0] >> 2) & 0x3f);
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index[1] = (((padded_in[0] & 0x3) << 4) | ((padded_in[1] >> 4) & 0xf));
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index[2] = (((padded_in[1] & 0xf) << 2) | ((padded_in[2] >> 6) & 0x3));
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index[3] = (padded_in[2] & 0x3f);
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out[0] = base64_table[index[0]];
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out[1] = base64_table[index[1]];
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/* Equal signs are used to indicate padding was applied. */
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out[2] = ((len == 1)?'=':base64_table[index[2]]);
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out[3] = ((len <= 2)?'=':base64_table[index[3]]);
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}
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void bcrypt_base64_calc(const unsigned char *in, size_t len, char *out)
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{
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size_t i, used, output_used, remaining;
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/* The code could have an integer overflow bug if len was very big, when
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* calculating used and output_used. In our code, len should always be 64 (a
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* 512-bit message digest). */
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for (i = 0; ; ++i)
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{
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used = i*3;
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output_used = i*4;
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if (used >= len)
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{
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out[output_used] = '\0';
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break;
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}
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remaining = len - used;
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base64_block(in + used, ((remaining < 3)?remaining:3), out + output_used);
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}
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}
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